Biology Special Notes (Question & Answer Format) - 2
Biology Special Notes (Question & Answer Format) - 2
Biology Special Notes (Question & Answer Format) - 2
1. a) Define biology
- feeding/nutrition
- Growth and development
- respiration (to produce energy)
- sensitivity/irritation/response
- excretion (getting rid of metabolic waste material)
- movement/locomotion
- reproduction
Animals Plants
All body parts grow equally(intercalary) Grow at shoot tip and root tip only
Heterotrophic Autotrophic
Cells have no cell walls Cells have cell wall made of cellulose
1
2. a) i) What is a hand lens?
- Convex lens mounted on a frame and used to magnify small objects for viewing.
-
ii) How is a hand lens used?
- For reasonably sized objects such as insect wing, leg, flower parts.
- Cannot be used for small objects such as cells, stomata.
-
iv) Explain how to calculate drawing magnification
- drawing magnification equals to length of drawing divided by length of object or image length divided
by actual length i.e. length of drawing or image length
Length of object actual length
b) i) what is classification?
- Orderly arrangement of living organisms into various groups according to their similarities.
- rhizoids(e.g. mosses)
- frond (e.g. ferns)
- roots e.g. taproot, fibrous roots, modified roots
- flowers
- leaves
- buds
- seeds
-
iii) List the external features used to classify animals
-monera
-protoctista/protista
-fungi
-plantae
-animalia
- a scientific system of naming organisms using the generic/genus and specific/species names
- e.g. for humans, Homo sapiens
- the first (generic) name should begin with a capital letter while the rest are small letters
- the two names are printed in italics and if handwritten should be underlined each separately
-
iii) Give the advantages of using binomial nomenclature
- it is the basic unit of organization of an organism i.e. the basic functional and structural unit of an
organism.
3
ii) What is cell biology?
- it magnifies and reveals the structure details of tiny objects such as the cell, that cannot be seen by
the human eye directly
-
iv) Draw a labeled sketch of a light microscope
- put the microscope on the bench with the stage facing away from you (viewer)
- turn the lower power objective to click in line with the eyepiece
- Ensure that the diaphragm/iris is fully open
- Adjust the mirror until the stage is illuminated with enough light
- Place the slide containing the specimen on the stage for magnification
- Draw the image and indicate magnification of the drawing.
ii) State the precautions that are necessary when handling a microscope
always use two hands when carrying it
never place a microscope too close to the edge of the bench or table
do not touch the mirror and lens with wet or dirty hands
clean dirty lenses using a special lens cleaning cloth
clean other parts using a soft cloth or tissue paper
low power objective must click into position before and after use.
Do not wet any part of the microscope
Clean and store well after use
d) i) What is magnification?
iii) Give the reasons for each of the following steps when preparing a cross-section of a stem or leaf
for examination under the microscope
sharp blade does not damage, deform, destroy or distort the surface of cell or tissue
it makes thin sections
5
e) i) List the parts of a cell that can be seen under a light microscope
a cell membrane
b cytoplasm
c cell wall
e nucleus
d vacuole
iii) List the parts of a cell that can be seen under an electronic microscope and state the functions of
each part.
Cell wall
found in plant cells in addition to cell membrane
made of cellulose which makes the plant tough
allows gases, water and other substances to pass through
Cell membrane
permeable/selective to control movement of materials in and out of cells
bound/encloses the cell contents
also called plasma membrane or plasmallema
Cytoplasm
fluid medium where chemical reactions occur
also where cell organelles are suspended
Nucleus
controls cell activities
Nucleolus
synthesizes DNA
6
Vacuole
sacs filled with fluid called cell sap
large in plants but small in animals
act as reservoirs for food and harmful wastes which would otherwise interfere with the metabolism
in cytoplasm
Lysosomes
store hydrolytic enzymes
destroy worn out cell organelles, cells, pathogens
digestion of food in unicellular organisms
autolysis
Golgi apparatus
processing/packaging of synthesized materials
transporting/secretion of packaged materials/cell materials e.g. glycoproteins and mucus
production of lysosomes
Ribosomes
where protein synthesis takes place
Mitochondrion
synthesis of ATP/energy
Chloroplasts
where photosynthesis takes place
Endoplasmic reticulum
transport of cell secretions
can be rough or smooth
7
f) Explain the meaning of each of the following
i) Cell
ii) Tissue
these are cells of a particular type grouped together to perform a certain function
animal tissues include epithelium, blood, nerves, muscle, skeletal and connective tissues
plant tissues include epidermal, photosynthetic, vascular, strengthening tissues
iii) Organ
tissues combine together to form organs
an organ is a complex structure with a particular function
animal examples include heart, liver, kidney, lungs, brain, blood vessels, muscles, skeleton
Plant organs include leaves, roots, flowers, and stem.
g) i) Name the structures which are present in plant cells but absent in animal cells
- Chloroplast
- Cell wall
ii) Name the structures which are present in animal cells but absent in plant cells
Lysosomes
Centrioles
Pinocytic vesicles
h) Explain how to estimate cell size
i) Materials
cell sizes are measured in units known as micrometers (my)
required is a transparent ruler marked in millimeters
1mµ = 1 mm
1000
ii) Procedure
- Click to low power
place transparent ruler with its millimeter marks on the stage
focus so that the millimeter marks can be seen as thick dark lines
estimate the diameter of field of view by counting the one millimeter spaces between the first mark
and the last one across the field of view as shown below
8
the diameter of the field of view above is estimated as 3.2 mm
convert the diameter of the field of view from millimeters to micrometers i.e. 3.2/1000
Estimate the fraction of the field of view occupied by the cell. This is done by estimating the
number of cells places end to end that would fill the diameter of the field of view as shown below
in the figure above, it is estimated that approximately six cells will occupy the diameter of the field
of view
therefore, one cell will occupy 1/6 of the field of view
its diameter is calculated as 1/6 times the diameter of the field of view
i) i) In a drawing of a giraffe, the height of the head from the ground was recorded as 10cm.
the drawing also showed a magnification of 0.02. calculate the actual height of the giraffe
ii) In a class experiment to estimate sizes of cells a student observed and obtained millimeter
marks on the field of view of a microscope as shown in the diagram below.
Millimeter marks
9
- If the student counted 40 cells on the diameter of the field of view, what was the approximate size of the
each cell in micrometers?
iii) Under which of the following light microscope magnifications would one see a larger part
of the specimen? X40 or x400? Give a reason
x40
Smaller magnification gives a wider field of view hence a larger part seen.
e.) a) i) Define cell physiology
the study of the functions of a cell in relation to their structure
semi-permeable
sensitive to changes in temperature and pH
Possesses electric charges.
c) i) What is diffusion?
d) i) What is osmosis?
Movement of water or solvent molecules from a dilute/hypotonic solution to a more
concentrated/hypertonic solution across a semi-permeable membrane.
OR
movement of solvent molecules from a region of their higher concentration to a region of their
lower concentration through a semi-permeable membrane
11
After some time they observed that the level of sugar had risen.
What was the physiological process under investigation?
Osmosis
Suggest the results that the students would obtain if they repeated the experiment using cooked
potato
The level of sugar solution will not rise.
Hypnotic
a solution whose concentration is lower than that of the cell
Isotonic
a solution whose concentration is the same as that of the cell
Hypertonic
a solution whose concentration is higher than that of the cell
Turgor pressure
As a cell gains water, its vacuole enlarges and exerts an outward pressure called turgor pressure.
12
Plasmolysis
if a plant is placed in a hypotonic solution if loses water
the protoplasm shrinks to an extent that it pulls away from the cellulose cell wall
Wilting
when a plant is turgid it can stand upright
however, if the cells lose a lot of water, turgidity is reduced
the plant then droops because the cells are flaccid
the plant is said to wilt
Haemolysis
if red blood cells are placed in distilled water, the cells take up water by osmosis, swell and burst
this is because it does not have any mechanism like the cellulose cell wall to prevent
overstretching nor any means of removing excess water
this is called haemolysis
13
e) A form one student placed red blood cells in different salt concentrations and obtained the
following
results:-
There was a gain (+) no change (0 zero) and a loss (-) in the volume of the cells as show below:-
14
2.0 ) the factors that affect the rates of the following process in living organisms.
a.) DIFFUSION.
- Diffusion gradient which refers to the difference in concentration of molecules between the region of
high concentration and the region of low concentration. Increasing the concentration gradient causes an
increase in rate of diffusion and vice versa.
-Surface area to volume ratio .is the ratio of total surface area exposed by an organism compared to its
body volume. Small sized living organisms have a large surface area to volume ratio. The larger the
surface area to volume ratio ,the high the rate of diffusion and vice versa. Small organisms like amoeba
and paramecium can hence rely on diffusion for transport of substances into and within its body and
removal of waste products
-thickness of membranes. Molecules take longer to diffuse across thick membranes than across thin
membranes hence the thin the membrane the higher the rate of diffusion.
-Temperature. Increasing temperature increases the kinetic energy of diffusing molecules making them
to spread faster. Increasing temperature increases the rate of diffusion and vice versa
-size of molecules/molecular weight.Small sized molecules/molecules of low molecular weight
move/diffuse faster hence the rate of diffusion is high where the molecules involved are small or have low
molecular weight and vice versa.
B.)OSMOSIS
-Temperature. Increasing temperature increases the kinetic energy of water molecules making them to
spread faster. Increasing temperature increases the rate of osmosis and vice versa
-concentration gradient/diffusion pressure deficit. Refers to the difference in concentration on either
side of a semi-permeable membrane. The higher the osmotic pressure difference the higher the rate of
osmosis.
15
ENZYMES INHIBITORS. They are substances which slow down (by competing with the enzyme for
the active sites in the substrate) or stop ( by blocking the active sites of the enzyme) the activity/funtioning
of enzymes .this slows down or stops respiration and so is active transport.
CONCENTRATION OF CARRIER MOLECULES IN THE CELL MEMBRANE. They are
substances that bind to the ions being transported actively and carrying them across the membrane .
increase in concentration of carrier molecules increases the rate of active transport upto a certain level and
vise versa.
5.) explain what happens when plant and animal cells are put in hypotonic and hypertonic solutions.
The concentration of the plant cell sap is hypertonic to the solution/water medium. the cell draws in water
by osmosis through the cell wall, cell membrane into the cell cytoplasm. Water enters the cell vacuole by
osmosis; it enlarges and exerts an outward pressure on the cell wall called turgor pressure. Increased
turgor pressure pushes the cell cytoplasm against the cell wall until the cell wall cannot stretch any further.
The cell becomes firm or rigid and is said to be turgid. As the cell wall is being stretched outwards, it
develops a resistant inwards pressure that is equal and opposite to the turgor pressure and this is called
wall pressure.
The plant cell sap is hypotonic to the solution medium. Water molecules are drawn out of the plant cells
by osmosis into the hypertonic solution through the semi-permiable membrane of the plant cells. As a
result the plant cell will start to shrink/less rigid and become flabby. The cell membrane/plasma
membrane is pulled away from the cell wall and the cell is said to be flaccid. this process by which a plant
cell lose water, shrink and become flaccid is called plasmolysis. However the shape of the plant cell is
maintained by the tough rigid cellulose cell wall which prevents crenation in plant cells.
The concentration of water in the cytoplasm of the plant cells is hypertonic to the solution medium in the
test. Water molecules are then drawn into the animal cell cytoplasm from the surrounding medium by
osmosis through the semipermiable membrane. the cell swells as water is drawn into them by osmosis .as
water continues to enter into the cell,the weak animal cell membrane bursts a process called lysis. in red
blood cells this process is called haemolysis. However in unicellular organisms like amoeba and
paramecium,bursting of their cells does not take place because they have specialized organelles called
contractile vacuoles for removal of exces water out of their bodies/cells.
16
ii.) animal cells in hypertonic solution.
The concentration of the animal cells cell cytoplasm is hypotonic to the solution medium in the test. the
surrounding hypertonic solution will draw water out of the animal cells by osmosis through the semi-
permeable membrane. Continued loss of water causes the cells to be smaller in size and their membranes
become wrinkled. This process will continue until the concentration of the cell sap and the surrounding
medium is equal i.e isotonic.the process by which animal cells lose water and shrink is called crenation.
It is involved in active reabsorption of glucose and mineral salts in kidney tubules during formation of
urine. it enables the absorption of digested food from the alimentary canal/small intestines into the blood
stream. Excretion of waste products from body cells for eventual removal. Involved in transmission of
nerve impulses within the nerve cells through the sodium pump which maintains a balance between
sodium and potassium ions. It facilitates accumulation of substances in the body cells to offset osmotic
pressure of organisms in dry and marine environment allowing them to absorb water by osmosis and avoid
desiccation. In plants it enables plant roots to absorb water from the soil against the concentration
gradient. It’s involved in translocation of manufactured food in the phloem tissue within the plant body.
It’s involved in the opening and closing of the stomata through the sodium-potassium pump mechanism.
i) Autotrophism
manufacturing food from simple organic substances
types are photosynthesis and chemosynthesis
ii) Heterotrophism
obtaining food from autotrophes and other organic substances
types are holozoic, saprophytic and parasitic
17
g.) a) i) Define photosynthesis
the process by which green plants build up organic compounds from carbon IV oxide and water in
the presence of sunlight
18
The leaf has a broad and flattened lamina to provide a large surface area for trapping optimum light for
photosynthesis and allow maximum gaseous exchange.
The leaf epidermis is thin ( one cell thick) to reduce the distance across which diffusion of carbon (iv)
oxide gas to palisade cells and oxygen gas from palisade cells takes place.
The leaf has numerous stomata that allows easy diffusion of gases into and out of the palisade tissue.
The leaf cuticle and epidermis are transparent to allow easy penetration of light to the photosynthetic
tissue.
The palisade cells are numerous,elongated and contain numerous chloroplasts to trapping optimum light
for photosynthesis.
The palisade tissue is just beneath the upper epidermis exposing them to trap optimum light for
photosynthesis.
The leaf has numerous leaf veins consisting of a.) xylem vessels and tracheids for transporting water and
dissolved mineral salts from the soil to the photosynthetic tissue
b.) phloem tissue for translocation of of manufactured food from the leaf to storage organs and other parts
of the plant .
Numerous and large air spaces in the spongy mesopyl layer for optimum gaseous exchange with the
photosynthetic tissue.
Phylotaxy which is regular arrangement of leaves on the stem minimizes overshadowing and overlapping
exposing all leaves to light for photosynthesis.
The prominent midrib and leaf veins reduces chances of rolling of leaves maintaining a large surface area
for trapping optimum light for photosynthesis.
19
C) Describe the structure and function of chloroplast
i) Structure
20
ii) Function
structure in which photosynthesis takes place
iii) Adaptations
has numerous/many grana to provide large surface area for packing many chlorophyll pigments
have numerous chlorophyll pigments which trap sunlight/light for photosynthesis
has stroma/third matrix which contain certain enzymes that catalyze photosynthetic reactions
Chlorophyll
The process of photosynthesis takes place in green plants allowing them to make their own food. The
process is controlled by enzymes and involves a series of reactions that take place in chloroplasts. The raw
materials required are water and carbon (iv) oxide.the process takes place in two consecutive stages i.e
21
Light reaction stage.
It’s also called the light dependent stage as it requires light energy . the reactions take place in the granna
of the chloroplast. light energy from the sun is trapped by chlorophyll in the chloroplast and converted
into chemical energy. This energy splits water molecules into hydrogen ions and oxygen atoms a process
is called photolysis. The oxygen atoms are released as aby product or used up in the process of respiration.
The hydrogen ions formed are used in the dark stage of photosynthesis.
Water hydrogen ions + oxygen atoms
2H2O 4H+ + o2 g
Some of the light enrgy is used to combine a molecule called adenosine diphosphate(ADP) with a
phosphate group to form the rich energy molecules called adenosine Tri-Phosphate(ATP)
ADP + P ATP
It’s also called the light independent stage of photosynthesis since light is not required because it can take
place both in presence and absence of light. the reactions are controlled by enzymes. the hydrogen atoms
released in the light stage are combined with carbon(iv)oxide to form simple sugars mainly glucose. The
process uses energy from ATP. This is reffered to as carbon (iv) oxide fixation. The reactions take place in
the stroma of chloroplast. The excess glucose is converted into starch or lipids for storage.
The general process of photosynthesis can be summarized by the following word and chemical equitions.
Day length. Long day length especially at high latitudes (temperate regions) provides more light for
photosynthesis causing an increase in the rate of photosynthesis.
22
Light quality. The preferred wavelengths for photosynthesis range between 400nm-700nm. the rate of
photosynthesis is higher in red and blue light and lower in all other types of light.
Concentration of carbon (iv) oxide. It’s a raw material required to combine with hydrogen ions to form
simple carbohydrate molecules. Increasing the concentration of carbon (iv) oxide increases the rate of
photosynthesis up to an optimum level beyond which other factors limit the rate of photosynthesis.
rate
of
photosynthesis
concentration of co2
f) Give the differences between the light and dark reactions during photosynthesis
proteins
carbohydrates
lipids(fats and oils)
vitamins
enzymes
nucleic acids(DNA and RNA)
23
- The elements are in the ratio of I carbon: 2 hydrogen: 1 oxygen
compounds of carbon, hydrogen and oxygen and in addition nitrogen, and sometimes sulphur and
or phosphorus
building blocks are called amino acids
essential amino acids which must be supplied in food since they body cannot synthesize them
Non-essential amino acids which body can synthesize.
first class proteins which supply all the essential amino acids
second class proteins which lack at least one amino acid
production of energy
source of metabolic water
structural compound
temperature
substrate concentration
pH of the medium
enzyme concentration
presence of inhibitors and co-factors
competitive inhibitors
non- competitive inhibitors
25
vi) What are the functions of enzymes?
i) Holozoic
Mode of feeding by animals where solid complex food substances are ingested, digested and
egested.
ii) Saprophytism
feeding on dead organic matter
iii) Parasitism
feeding from another organism but not killing it
iv) Symbiosis
an association in which organisms of different species derive mutual benefit from one another
ii) Omnivorous
omnivores are animals which feed partially on plant materials and partially on flesh e.g pigs
iii) Carnivorous
Carnivores feed on flesh alone e.g. lion
c) i) What is dentition?
Refers to the number, arrangement and kind of teeth in an animal
homodont have same kind , type, shape and size of teeth which perform similar function e.g. fish,
reptiles and amphibians
Heterodont have different kind, type, shape and size of teeth which perform different functions as
those found in mammals.
26
d) Describe the adaptations and functions of various types of mammalian teeth
Incisors
chisel shaped/wedge shaped
found in the front of the buccal cavity
used for cutting
i) Canines
next to incisors
very sharp and pointed
located at the sides of jaws
used for tearing food
ii) Premolars
next to canines but before molars
have cusps and ridges on their surface
used for crushing and grinding
iii) Molars
found at the back of the jaw
have cusps and ridges on their surface
absent in young mammals but appear later when permanent teeth grow
used for grinding and crushing
e) i)Draw a labeled diagram to represent internal structure of a mammalian tooth.
27
Root
part imbedded in the jaw below the gum
covered by substances called cement
cement is hard and bone-like
Cement
bone-like substance covering root and enamel of mammalian tooth
Neck
region at the same level with the gum
forms a junction between the crown and root
covered by enamel
Pulp cavity
at centre of tooth within dentine
has blood vessels for transporting nutrients/food and gases
has nerves for sensitivity
iii) How would one use dental formula to identify the following?
Herbivores
presence of diastema/gap between incisors and premolars
free movement of tongue
absence of incisors in upper jaw
absence of canines
presence of hard pad
closely packed molars
Carnivore
presence of canines
presence of carnassial teeth
presence of incisors in upper jaw/absence of diastema/gap between incisor and premolar
28
iv) State the functions of the following structures in mammals
Carnassials
tearing flesh from bones
Pad of gum
provides grasping surface for lower incisors
29
ii) Describe the process of digestion in the various parts of the human digestive system
Mouth
contains teeth for chewing
has tongue for mixing food with saliva
has salivary glands for chemical digestion, secretion of enzymes and mucus secretion
starch is acted on by salivary amylase enzymes to produce maltose
the tongue rolls food into a bolus which is carried into the stomach by peristalsis
peristalsis is movement of food along the gut by waves of contraction
it facilitates rapid digestion due to its mixing action
30
Oesophagus
also called gullet
forms a passage for food by peristalsis
connects the mouth to the stomach
Stomach
has gastric glands which secrete gastric juices
these juices contain hydrochloric acid(HCL), mucus, and the enzymes pepsin, rennin and lipase
HCL produces an acidic medium for enzyme action
Proteins are acted upon by pepsin to produce peptides
Caseinogen is acted upon by rennin to produce casein
Fats are acted upon by lipase to produce fatty acids and glycerol
Mucus lubricates the stomach and prevents autolysis of stomach (mucus protects stomach)
Duodenum
the first u-shaped part of the small intestine
food in the stomach is now in a semi-liquid form called chime
chime leaves the stomach by peristalsis into the duodenum
there, the liver produces bile pigments, bile salts and sodium hydrogen carbonate
the stomach is usually alkaline to neutralize chime which is acidic
bile salts emulsify fats
bile comes from the gall bladder through the bile duct
sodium hydrogen carbonate provides the correct pH/alkaline
pancreatic juices are released by pancreas into the duodenum
the juices contain trypsin, chemotrypsin, amylase, lipase and protease
proteins are acted upon by trypsin to form polypeptides and amino acids
starch is broken down to maltose by amylase
Ileum
- produces intestinal juices
- Intestinal juice contains maltase, sucrase, lactase, erepsin, lipase, and several other peptidases
- Maltose is broken down to glucose and galactose by lactase
- Sucrose is acted upon by sucrase to glucose
Polypeptides are broken down into amino acids by erepsin
- Mucus secretion is to protect the ileum wall from digestion/autolysis
Colon
- Commonly called the large intestine
- Wider than the ileum
- has several mucus-producing cells
Highly folded for water absorption
- Also prepares food for egestion
- egestion is the process by which the insoluble parts of food are discharged from the body in form of
faeces.
31
Rectum
- Muscular and enlarged
- it produces mucus
- used for storage and removal of faeces
Anus
e) i) What is assimilation?
- The process by which digested food is taken up by cells and used in the body for various purposes.
32
f) Name the types of food substances in the food that do not undergo digestion in human digestive
system
mineral salts
water
roughage
vitamins
k.) Explain the importance of the following food substances in human nutrition
Vitamins
are organic chemical compounds essential for a healthy body
are obtained from fresh fruits and vegetables
some are synthesized in the body e.g. vitamin K
they are destroyed by overcooking food
they protect the body against diseases, play regulatory mechanisms in the body and act as co-
enzymes
insufficient amounts lead to deficiency diseases e.g. rickets, scurvy, beriberi
a) Mineral salts
are important in organic compounds containing elements which are essential for normal body
metabolism
those required in large quantities are called macro-nutrients while those required in small
quantities are called micro-nutrients or trace elements
They are used in bone and teeth formation. In osmotic balance and neurotransmission
insufficient amounts lead to anaemia, rickets, goiter
Excess amounts lead to high blood pressure, and dental disorders.
b) Roughage
composed of cellulose and plant fibers
digested by cellulose contained by gut microorganisms
provides grip essential for peristalsis
lack of roughage leads to slow movement of food leading to constipation
roughage adds bulk to food for peristalsis to take place
c) Water
used in transport in the body, universal solvent, hydrolysis
insufficient leads to dehydration
33
b) Occupation
means activity occurring everyday
everyday activity determines energy requirement
People doing heavy work like digging require more energy than office workers.
c) Age
children carry out many activities and also have more cell division than adults
their BMR is therefore higher than for adults
as they grow older, they become less active and their energy requirements decrease
d) Body size
small bodied people have a large surface area to volume ratio
their bodies lose more heat energy to the surrounding
they therefore require more energy-giving foods
this is the opposite for big bodied people
e) Sex
most males are more muscular than females
they also do heavier work than females hence require more energy
females do lighter work hence require less energy
f) Climate
in warm climate the body requires less energy
in low temperatures the body requires more energy to maintain body temperature
34
FORM TWO TOPICS
1. a) i) Define transport
ii) State ways in which the root hairs are adapted to their functions
the root hair is long/narrow/numerous to increase surface area for absorption of water and mineral
salts
many mitochondria in cytoplasm to supply energy for active transport of mineral salts
are thin walled to speed up rate of absorption of water and mineral salts
Monocot root
35
ii) State the similarities and differences between a dicotyledonous and monocotyledonous root
Similarities
both used for anchorage and absorption of water and mineral salts
both have root hairs, epidermis, pericycle, cortex, endodermis and vascular bundles (xylem and
phloem)
both may be used to store food/storage organs
Differences
Monocotyledonous Dicotyledonous
phloem and xylem are arranged in phloem lies between radial rays of
ring form alternately central xylem(star shaped)
pith present pith absent
Monocotyledonous Dicotyledonous
Differences
Monocotyledonous Dicotyledonous
vascular bundles are many and vascular bundles are few and
scattered arranged in a concentric ring near
some have hollow pith or pith is the epidermis
absent pith large and well developed
no cambium layer therefore cannot presence of cambium therefore
undergo secondary growth undergoes secondary growth
very little cortex cortex has several layers of cells
36
v) State the differences between the internal structure of a root and a stem.
Root Stem
ii) State the ways in which xylem vessels are adapted to their function
ii) Describe the movement of water from the soil to the leaves of a tall plant
Soil
water exists as a thin film in the soil, between soil particles
the concentration of cell sap of root hair is greater than that of the surrounding solution in the soil,
thus drawing the water molecules across the cell wall and cell membrane into the root hair by
osmosis
water drawn into the root hair cell dilutes the cell sap making it less concentrated than that in the
adjacent cortex cells of the root
due to osmotic gradient water moves from the root hair cells into the cortex by osmosis, from cell
to cell by osmosis, across the endodermis by active transport into xylem vessels of the root that
conduct water into xylem vessels of the stem into xylem vessels of the leaves
Stem
Once in the stem water moves up the plant aided by the narrowness of the xylem vessels
(capillary), root pressure, attraction of water molecules to each other (cohesion). Attraction of
water molecules to the walls (adhesion)
37
from the stem water enters the xylem of leaves
water moves in the xylem vessels of the stem in a continuous (uninterrupted) water column up to
the tree leaves
Leaves
once in the leaves water moves into the mesophyll cells by osmosis
as water vaporizes from the spongy mesophyll cells their sap becomes more concentrated than the
adjacent cells
as the result water flows into the cell from other surrounding cells which in turn takes in water
from xylem vessels within the leaf veins
this creates a pull(suction force) called transpiration pull that pulls a stream of water from xylem
vessels in the stem and roots
The transpiration pull maintains a continuous column of water from the roots to the leaves.
iii) Name the process by which mineral salts enter into a plant
active transport
diffusion
vi) Explain the forces that make water and mineral salts move through a plant
mineral salts are taken up due to diffusion because of the concentration gradient between the
mineral ions in sap and those in soil solution
active transport involves energy in form of ATP due to respiration which forces mineral salts
through a plant against a concentration gradient
water moves by osmosis through a semi-permeable membrane of root hairs and between cells of
stem
in stem water moves by cohesion(attraction of water molecules to each other)
it also moves by adhesion(attraction of water molecules to walls)
capillarity is due to narrowness of xylem vessels
transpiration pull occurs when water vapour evaporates from sub-stomatal chambers into the air
root pressure is a force that pushes water up the stem from the roots and causes guttation
/exudation
e) i) What is transpiration?
loss of water from plant to the atmosphere
ii) Name the sites through which transpiration takes place in a plant
stomata (stomatal transpiration)
lenticels (lenticular transpiration)
cuticle(cuticular transpiration)
38
iii) State the importance of transpiration to plants
v) Explain the structural factors that affect the rate of transpiration in plants
number of stomata i.e. the more the stomata the higher the rate and vice versa
turgidity of the guard cells which control the opening and closing of stomata when they are open
transpiration rate is high
size of leaves where the larger the surface area the higher the rate of transpiration
leaf fall leads to lower rate of transpiration and also drying of leaves reduces rate of transpiration
Thin cuticle reduces distance through which water vaporizes hence increase transpiration rate.
Absence of cuticle also increase rate of transpiration
vi) explain the environmental factors that affect rate of transpiration in plants
high temperature increases rate of transpiration and low temperature reduces the rate
humidity when high increases rate and when low reduces the rate
transpiration rate is higher in moving air (wind) than in still air
high light intensity increases internal temperature hence higher rate of evaporation leading to
higher rate of transpiration
availability of water in the soil leads to more absorption hence more loss to the atmosphere
atmospheric pressure when high leads to more evaporation and when low leads to low rate
evaporation of water
vii) State the structural differences between xylem vessels and sieve tubes
sieve tubes have cross wall while xylem vessels have none
xylem vessels are lignified while sieve tubes are not
Sieve tubes have cytoplasm elements while xylem vessels have none.
viii) State the adaptations of plants which enable them to reduce water loss
thick waxy cuticle
reduced leaf size/thorns/spines
shedding of leaves
Sunken stomata. Water vapour accumulates in the depression of stomata lowering the water
vapour concentration gradient leading to lower rate of evaporation
rolling of leaves
ix) State the factors that cause increase in the rate of transpiration from leaves
increased light intensity
low relative humidity
temperature
39
x) Explain how drooping of leaves on a hot sunny day is advantageous to a plant
reduces surface area exposed to sun reducing cuticular transpiration
f) Explain how aquatic and terrestrial plants are adapted to deal with problems of
transpiration
a. Mesophytes
they grow in soils with enough water
water loss is perfectly balanced by absorption of more from the soil
no special adaptations
b. Xerophytes
they grow in dry conditions
root grow very deep to absorb water
succulent/fleshy leaves to store water
few stomata which are sunken
thickened waxy cuticle
leaves are hairy and often folding
some leaves are needle-like/spines or scales
leaf surfaces are reduced i.e. small leaves
all these adaptations are to reduce water loss
c. Hydrophytes
plants that grow in water
presence of sclereids
leaves are broad
leaves have many stomata on upper side only (none on the lower surface)
some leaves float on water
absence or reduced leaf cuticle
large air spaces
some leaves are submerged
poorly developed or reduced vascular bundles
g) i) What is translocation
transfer of manufactured food substances to the parts where they are required
ii) Name the tissue which is responsible for translocation of manufactured food in flowering plants
phloem tissue
iii) Name the processes that bring about the translocation of manufactured food
-active transport
Diffusion
Mass flow
Cytoplasmic streaming
40
iv) Draw a labeled diagram to represent phloem tissue
translocation
Companion cell
supply nutrients to sieve tube element
supply energy for translocation
regulates activities of tube cells/elements
Sieve tubes element
conduct food down the stem
41
Describe an experiment you would carry out in order to demonstrate that phloem transports
manufactured food substances in a plant
a. Ringing experiment
cut a ring in the bark including the phloem from the stem of a woody plant
phloem is found next to or just beneath the bark
observe daily for some time(more than three weeks)
a swelling of the bark appears above the ring
this is due to accumulation of food from leaves
the bark of a second similar plant is removed carefully leaving the phloem intact
a swelling does not appear
h) Describe an experiment you would carry out to demonstrate that xylem transports water
i. Either
cut a stem of a young plant or twig of a tree under water
or else uproot a young herbaceous plant and wash the soil gently
put some water in a beaker and add a dye i.e. eosin or red ink and place the cut stem or young plant
in a beaker
leave for time e.g. between 20 minutes and one hour
cut a thin section of stem or leaf
mount it on a slide and examine under a microscope
observe and note the distribution of the dye or ink
the dye appears only in the xylem vessels
ii. OR
use radio-active tracers, C14 in form of carbon
ring a plant then put it in a container containing radio-active phosphorous solution
The radio-active phosphorus is later detected in the leaves.
42
2. a) i)List the components of animal transport systems
system of blood vessels in which materials are circulated round the body
blood, a fluid medium which contains dissolved substances and cells
the heart, a pumping mechanism which keeps blood in circulation
closed system has blood vessels through which blood moves eg vertebrates
open system has no blood vessels hence blood is in direct contact with tissues e.g arthropoda
iii) What are the advantages of the closed circulatory system over open circulatory system?
Closed system has continuous vessels hence able to generate high pressure
Circulates blood over longer distance
Circulates blood at a faster rate
Efficient transport of nutrients and waste products
Animals are more active
iv) Distinguish between single circulatory system and double circulatory system
Single circulatory
blood passes through the heart once in a complete circuit of the body
Double circulation
-blood enters the heart twice in a complete circulation
- Pulmonary circulation from the heart to lungs and back
- Systemic circulation from the heart to body systems and back
blood which is a fluid tissue of the body carrying food substances, oxygen, carbon IV oxide and
metabolic wastes
arteries which are elastic tubes carrying blood from the heart to cells
veins which are blood vessels carrying blood away from the cells to the heart
capillaries which are extremely numerous and are microscopic channels connecting arteries to
veins
43
44
45
the left ventricles is the most powerful and has the thickest walls
this is because it is the chamber which pumps blood throughout the body
each time it contracts, blood is forced out into the elastic arteries(aorta)
blood moves on to the capillaries
from capillaries blood moves to veins and back to the heart through the vena cava
from vena cava it enters into right auricle which contracts and pumps blood into the right ventricle
right ventricle pumps blood into the lungs through the pulmonary artery
blood releases carbon IV oxide to lungs and picks oxygen then returns to left auricle
left auricle pumps blood into left ventricle
left ventricle then pumps blood into the aorta and into arteries, starting the process all over again
both auricles contract simultaneously while both
46
iii) Explain how the mammalian heart is adapted to performing its functions
the heart is made of muscles that contract and relax synchronously without requiring nervous
stimulation
nerve supply however, determine contraction strength and frequency
the heart is divided into four chambers
The right atrium is connected to the right auricle. It receives blood from the whole body.
The blood is pumped from the left atrium to the right ventricle
To avoid flow back into the right atrium, a valve is present between the two chambers – the
tricuspid valve
The right ventricle pumps blood to the lungs
This is facilitated by the presence of pulmonary artery
A valve is also present to avoid blood flowing back from the pulmonary artery to the right
ventricle
Blood from the lungs enters the heart through the pulmonary vein into the left atrium.
When the left atrium contracts, blood flows into the left ventricle
Blood will not flow back into the left atrium because of the presence of bicuspid valve(mitral)
The left ventricle is connected with the aorta and when it contracts, blood flows into the aorta for
distribution into the whole body
The heart muscle surrounding the left ventricle is thicker than that surrounding the right ventricle
to be able to generate enough pressure to push blood to the whole body
A pace-maker is present in the heart muscle to initiate and synchronise contractions.
For the heart muscle to be well nourished and be provided with enough oxygen and carbon IV
oxide removal, it is supplied with blood by the coronary arteries and drained by the coronary veins
iv) Explain why blood leaving the lungs may not be fully oxygenated
under ventilation of the lungs
blockage of alveoli (air sacs)
high cardiac frequency i.e. high rate of pumping of blood in the heart
47
iii. Veins
carry blood back to the heart
all carry deoxygenated blood except pulmonary vein that carries blood from the heart to lungs
have thinner walls than arteries
have valves to prevent backflow of blood
have wide lumen
g) i) State the ways in which the composition of blood in the pulmonary arterioles differs from
that in the pulmonary venules
ii) Give the reasons why pressure of blood is greater in the arterioles than I the veins of mammals
blood is pumped to the arteries by the heart at high pressure
blood pressure in veins is reduced by capillary resistance
arteries have narrow lumen which maintains high pressure/veins have wide lumen which reduces
pressure
arteries have more/thicker muscular walls which generate pressure/veins have less/thinner
muscular walls which reduce pressure
ii) Describe how mammalian blood components carry out their functions
Plasma
transport dissolved food substances like glucose, amino acids, fatty acids and glycerol from small
intestines to liver and other body tissues
transports hormones, enzymes from secretory glands to tissues when required
transports carbon IV oxide to lungs and urea from tissues to the kidneys
distributes heat
bathes the tissues allowing for exchange of materials
contains protein fibrinogen and pro-thrombin which take part in blood clotting
48
Red blood cells (Erythrocytes)
transports oxygen from the lungs to body tissues in form of haemoglobin
transport carbon IV oxide from body tissues to the lungs in form of bicarbonates
iii) State the ways in which the red blood cells are adapted to their functions
many per unit volume hence carry more oxygen and carbon IV oxide
biconcave in shape to provide large surface area for absorption of oxygen and carbon IV oxide
absence of nucleolus hence more haemoglobin to carry sufficient oxygen and carbon IV oxide
alter shape to be able to pass through the narrow lumen of capillaries to deliver or supply oxygen
and carry away carbon IV oxide
have haemoglobin with high affinity for uptake of oxygen and carbon IV oxide
iv) State the structural differences between a red blood cell and a white blood cell.
Red blood cells white blood cells
v) State the functional differences between a red blood cell and a white blood cell
Red blood cell White blood cell
- Transports oxygen and carbon IV oxide - protects body against harmful pathogens
vi) How does the heart increase blood flow to some parts of the body during exercise
stronger contractions
faster contractions/heartbeat
49
Explain how oxygen and carbon Iv oxide are transported in the blood
Oxygen
oxygen concentration is higher in lungs(alveoli) that in blood
oxygen in the alveoli dissolves in the film of moisture and diffuses through thin epithelial and
capillary walls into plasma and red blood cells
the oxygen combines with haemoglobin to form oxyhaemoglobin
blood then becomes oxygenated
blood from lungs then travels to all body tissues where the oxyhaemoglobin breaks down to form
oxygen and haemoglobin
haemoglobin is transported back to the lungs to collect more oxygen while the oxygen in
capillaries diffuses into body cells for respiration
respiration produces carbon IV oxide
Carbon IV oxide
carbon IV oxide produced during respiration diffuses out of cells into blood plasma and red blood
cells due to concentration gradient
carbon IV oxide and water form carbonic acid carbamino compounds with haemoglobin
in the presence of carboxyl anhydrase enzyme, hydrogen carbonate is carried in blood to the lungs
in the lungs the hydrogen carbonate dissociates to liberate carbon IV oxide which diffuses into
alveolar cavity due to concentration gradient
from alveolar space carbon IV oxide is expelled during expiration
Most carbon IV oxide is transported from tissues to lungs within the red blood cells and not in
the blood plasma. Give the advantages of this mode of transport.
- PH of blood is not altered/homeostasis is maintained
- Within the red blood cell is an enzyme, carbonic anhyrase which helps in fast loading(combining)
and offloading of carbon Iv oxide
i) i) what is blood clotting?
process in which blood components clump together to prevent loss of blood from an injured/cut
vessel
ii) Name a protein, vitamin, an enzyme and a mineral element involved in blood clotting
Protein – fibrinogen/prothrombin
Vitamin - k/quinine
Enzyme – thrombokinase/thromboplatin/thrombin
Mineral element – calcium
50
iii) describe the blood clotting process
enzyme thromboplastin produced in the platelets of damaged tissues converts plasma protein
prothrombin into thrombin in the presence of calcium ions
thrombin converts another plasma protein fibrogen into fibrin in the presence of vitamin K
fibrin is insoluble
fibrin forms fibres which form a meshwork that forms a clot
prothrombin thromboplastin thrombin
calcium ion
Fibrinogen thrombin fibrin clot
vitamin K
v) Explain why blood flowing in blood vessels does not normally clot
- Presence of anticoagulant in blood
j) i. list the major types of human blood groups
O, with neither B nor A antigen
AB, with both A and B antigens
A, with type A antigen
B, with type B antigen
iii. explain the meaning of :
Universal donor
a person who can donate blood to any other blood group without agglutination/clumping
this is usually blood group O
however this person cannot receive blood from other blood groups except group O
Universal recipient
can receive blood from all blood groups without agglutination
this is usually blood group AB
however, can only donate blood to group AB
iii) What is the difference between rhesus positive and Rhesus negative blood samples?
rhesus positive blood has the Rhesus (Rh) antigen
rhesus negative lacks the Rhesus antigen
51
vi) What is blood transfusion?
- Introduction of blood from one person to another
j) i) What is immunity?
- Resistance to disease by organisms
52
3. a) i) What is gaseous exchange?
The continous exchange of oxygen and carbon Iv oxide between the organism and environment.
iv) Name the theories suggesting the mechanism of opening and closing of stomata
interconversion of starch and sugar
pH theory
mineral ion concentration
53
During the day potassium ions concentrate in guard cells, raising their osmotic pressure and causes
then to open
In the night the concentration of potassium ions decreases increasing osmotic pressure in guard
cells therefore causes stomata to open.
vii) What is the advantage of having stomata open during daytime and having them closed
at night?
opening in the daytime allows diffusion of carbon IV into the leaf for photosynthesis to take place
and allows diffusion of oxygen out of the leaf
transpiration also takes place, thus cooling the leaf and facilitating uptake of water and mineral
slats
Closing in the night is to conserve water in the plant especially when there is not enough water
available in the soil.
c) i) State the ways in which leaves of plants are adapted to gaseous exchange
presence of stomata for faster gaseous exchange
intercellular spaces/air spaces in the leaf for movement/circulation of air
film of moisture around the surface of cells for easy diffusion
broad/flattened shape to increase surface area
thin lamina to reduce distance of diffusion
exposed to air for easy diffusion
54
iii) State the ways in which floating leaves of aquatic plants are adapted to gaseous exchange
stomata found only on upper dermis to allow efficient gaseous exchange
presence to aerenchyma tissues/large air spaces to enable it float/buoyancy/storage of air
absence of cuticle to enhance gaseous exchange
iv) How is aerenchyma tissue adapted to its function?
has large airspaces which store gases/for gaseous exchange/buoyancy
v) Explain stomatal distribution in plants of different habitats
land plants have their stomata mainly on the lower side to reduce water loss but if on both sides
then upper side has very few
water plants, floaters, have stomata on upper side to enhance water loss
in dry areas, plants have leaves with sunken stomata to reduce water loss by transpiration
Plants in wet areas have stomata equally distributed on both sides.
d) i) List the types of respiratory surfaces of animals
cell membrane in unicellular organisms e.g. amoeba
gills in fish
tracheal system
skin, buccal cavity and lungs in amphibians
lings in mammals
ii) State the characteristics of respiratory surfaces in animals
moist
thin walled/thin membrane/thin surface
Highly/richly vascularised/numerous blood vessels/well supplied with blood vessels.
Large surface area
iii) Describe gaseous exchange in protozoa
example is amoeba
small and have large surface area
oxygen diffuses into the organism and carbon IV oxide diffuses out into water
simple diffusion of gases is enough to meet its respiratory requirements
e) i) Make a labeled drawing of a fish gill
55
iii) Discuss gaseous exchange in bony fish
example is tilapia
the mouth opens and the floor of the mouth is lowered so that the volume in the mouth is increased
and pressure is lowered
water then enters into the mouth cavity
the mouth is closed and the floor of the mouth raised so that the volume is reduced
this raises the pressure, forcing water over gills and out through the operculum
As water passes over the gills oxygen diffuses due to concentration gradient (partial pressure) into
the blood stream.
In the body tissues, carbon IV oxide diffuses into the blood (due to concentration gradient, and is
transported to the gills and diffuses out into the water.
g) i) What is breathing?
Any process which speeds up the rate of gaseous exchange between an animal and its surrounding.
56
ii) Name the structures in humans that are used in gaseous exchange
nose
larynx
epiglottis
trachea
lungs
pleural membrane
pleural cavity
diaphragm muscles
iii) Describe the mechanism of gaseous exchange in a mammal
Breathing in
external intercostals muscles contract while internal intercostals muscles relax, raising the ribcage
upwards and outwards
muscles of the diaphragm contract hence it flattens
the volume of the thoracic cavity increases while pressure decreases
higher air pressure in the atmosphere forces air into lungs through the nose
Breathing out
external intercostals muscles relax while internal intercostals muscles contract, moving the ribcage
downwards and inwards
muscles of the diaphragm relax hence the diaphragm assumes dome shape
the volume of the thoracic cavity decreases while pressure increases
the higher pressure forces air out of the lungs through the nose
iv) Explain how mammalian lungs are adapted to gaseous exchange
large number of alveoli that increase surface area
moist inner surface of alveoli for dissolving oxygen/gases to facilitate exchange of gases through
alveolar cavities and blood
thin walls of alveoli to allow efficient/faster diffusion of gases
rich capillary/blood supply on alveolar surface to transport oxygen away from the lungs and
carbon IV oxide to the lungs
v) Name the features of alveoli that adapt them to their function
have large surface area/spherical shaped
numerous/many to increase surface area
one cell thick
moist surface for air to diffuse
highly vascularised/numerous capillaries
vii) How is the trachea of a mammal suited to its function?
has a ring of cartilage which keeps it open at all times
cilia that move mucus/particles to the top of the trachea i.e. into larynx for removal
mucus to trap dust, solid particles and microorganisms
hollow for passage of air
viii) State the advantages of breathing through the nose rather than through the mouth
nose has hairs to filter solid particles
it has mucus lining to trap dust particles
the nose has cells sensitive to smell for survival
it warms the air before it reaches the lungs
57
ix) Give the conditions under which the carbon iv oxide level rises above normal in
mammalian blood
vigorous exercise
emotions/stress
disease infection
x) Explain the physiological changes that occur in the body to lower the carbon iv oxide
level back to normal when it rises
heartbeat/cardiac frequency increases to pump blood faster carbon iv oxide from the tissues and
supply more oxygen
ventilation rate/rate and depth of breathing increases to take more oxygen and remove carbon iv
oxide from the lungs
arterioles to take in more oxygen and remove carbon iv oxide from the lungs
arterioles dilate leading to faster flow of blood to and from body tissues
4. a) i) Define respiration
the oxidation/breakdown of food within cells to release energy
58
ii) Explain the significance of respiration in living organisms
it yields energy (ATP)
this energy enables organisms to move, grow, excrete and reproduce
iii) Where does respiration take place?
in the mitochondria
b) i) Draw and label a mitochondrion
59
ii) State the most important function of mitochondria
to produce Adenosine triphosphate (ATP) which is the energy source of the whole cell
Outer membrane
controls what enters and what leaves mitochondrion
Cristae
also called inner membrane
increase surface are for attachment of enzymes
this is where cellular oxidation reactions occur
Matrix
enzymes are located here
other reactions occur here
ii) Name the end products of respiration in animals when there is insufficient oxygen supply
lactic acid
energy
iii) Why is there a high rate of lactic acid production during exercise?
the demand for oxygen is more than supply leading to anaerobic respiration
v) State why accumulation of lactic acid during vigorous exercise lead to an increase in heartbeat
lactic acid is poisonous to tissues and must be removed
to increase supply of oxygen to tissues
61
iv) Why does anaerobic respiration of a given substrate yield a smaller amount of energy than
aerobic respiration?
- Some energy locked up in intermediate products like ethanol in plants and lactic acid in animals
substrate is completely oxidized in aerobic respiration
Excretion
the process by which organisms get rid of waste products which result from chemical process
which occur in living cells
Secretion
the process by which organisms produce substances which are useful to the body, by glands
Egestion
removal of indigestive materials from the body
Homeostasis
maintenance of constant internal environment
62
ii) Why do plants lack complex excretory structures like those of animals?
plants have lower rates of metabolism
plants excrete non-poisonous products derived from carbohydrate metabolism unlike animals
which produce toxic wastes derived from protein metabolism
plants re-use some of their wastes like nitrogenous wastes used in protein synthesis
plants store waste products in roots, fruits and leaves
ii) State the excretory products of plants and some of their uses to humans
caffeine from tea and coffee is used in medicine and as a stimulant which is harmful to humans
quinine used for treating malaria
cocaine derived from leaves of cocoa plant used as a stimulant by addicts or as a local anesthesia,
also causes damage to the brain, may cause addiction if not well used and is an illegal drug
Tannins derived from barks of acacia (wattle bark) trees are used to make ink and tanning
(softening) of leather.
Nicotine got from leaves of tobacco plant stimulates the central nervous, may cause addiction if
much is used or consumed. It is used to make cigarettes, cigars and is poisonous. It is a precursor
of lung cancer
Cannabis sative(bhang) is used to make drugs
Gum derived from glues is used for sticking substances and making certain jellies
Rubber, a product of latex, got from rubber plant is sued to make tyres and synthetic fibres
Morphine from opium poppy plant is a narcotic and illegal drug as it causes addiction
Khat and miraa are used as stimulants
Colchicines used in inducing polyploidy, cancer therapy, treatment of gouts in small quantities
Papain used as meat tenderizer
63
d)i) Draw and label a mammalian skin
Epidermis
it is made up of three layers
the outermost layer, cornified layer is made up of dead cells that prevent entry of microorganisms,
prevent physical damage and dessication
granular layer made of living cells gives rise to cornified layer
malpighian layer is made up of actively dividing cells that give rise to new epidermal
cells/granular layer it contains melanin that protects the body against ultra violet rays(radiations)
64
Dermis
has several components
Has sweat gland which produce sweat through sweat pores on the skin and the sweat evaporates
cooling the body by lowering body temperature. When it is cold, no sweat is produced, conserving
water
sweat contains water, sodium chloride, uric acid and urea hence the skin acts as an excretory organ
Has hair. The hair stands erect to trap air when temperature is low to reduce loss/insulation. It lies
flat to allow heat loss when temperature is high.
Has nerve endings which are sensitive to stimuli such as heat, cold, pain, pressure and touch
Has subcutaneous fat/adipose fat that insulates the body against heat loss
Has arteries and capillaries (blood vessels) that supply food and oxygen and remove excretory
products. Arterioles vasodilate when temperatures are high to lose heat by radiation, and
convention. Arterioles constrict when temperatures are low to conserve heat i.e. reduce heat loss
Has sebaceous glands which secrete sebum, and antiseptic and water repellant that prevents drying
and cracking the skin by making the skin supple
65
ii) Homeostasis
regulation of blood glucose
the normal amount of glucose in blood is about 90mg/100
increase in blood sugar is detected by cells of the pancreas which secrete insulin
insulin stimulates the liver to convert excess glucose to glycogen
further excess glucose is converted to fats until the normal blood sugar level is attained
Excess glucose is oxidized to carbon IV oxide, water and energy. Excess glucose is also used in
respiration
decrease in blood sugar level below normal level is detected by the pancreas, which secretes
glucagon which stimulates the liver to convert glycogen to glucose until the normal sugar level is
attained
fats, amino acids are converted to glucose
it also leads to reduced oxidation of glucose
Deamination
excess amino acids are deaminated by the removal of amino group
the amino group is converted to ammonia
ammonia combines with carbon IV oxide to form urea
urea is excreted in urine through the kidney
Detoxification
poisonous substances are converted to less harmful compounds
Thermal regulation
maintenance of body temperature
heat is generated in the liver by chemical activities
the heat is distributed
66
67
ii) Describe how the human kidney functions
the afferent arterioles, which is a branch of the renal artery, supplies blood to the glomerulus
the afferent arteriole has a wider diameter than the efferent arteriole
this difference in diameter of afferent and efferent vessels causes high pressure leading to ultra
filtration
the walls of the blood capillaries are one cell thick hence glucose, amino acids, vitamins,
hormones, salts, cratinine, urea and water filter into Bowman’s capsule to form glomerular filtrate
white blood cells, red blood cells, plasma proteins (such as globulin) and platelets are too large to
pass through the capillary walls hence remain in blood capillary
the filtrate flows into proximal convoluted tubule where amino acids, vitamins and all glucose are
selectively reabsorbed back into the blood stream
many mitochondria provide energy for reabsorption of these substances against a concentration
gradient by active transport
the glomerular filtrate flows into the loop of Henle
water in the descending loop moves by osmosis into the blood capillaries
sodium chloride is actively pumped from the ascending arm of the loop of Henle into the blood
capillaries
the glomerular filatrate flows into the distal convoluted tubule
water and salts are reabsorbed from distal convoluted tubule into blood capillaries
the glomerular filtrate flows into collecting tubule (duct) from where more water is reabsorbed into
blood stream
antiduretic hormone influences the amount of water reabsorbed depending on osmotic pressure of
blood
the glomerular filtrate from collecting duct, now referred to as urine, is emptied into pelvis and
ureter into bladder and out of body through urethra
urine consists of excess water, slats and nitrogenous wastes
68
iv) Name the common kidney diseases
nephritis
kidney stones(renal calculi
cystitis
oedema
kidney failure
iv) Why does body temperature of a healthy person rise up to 37oC on a hot humid day?
sweat evaporation is reduced hence cooling is less therefore more heat is retained in the body
causing temperature to rise
69
v) Name the structures in the human body that detect external temperature changes
temperature receptors (end bulb corpuscles e.g. bulb of Krause (warmth) and organ of Ruffinni
(cold)
heat (thermal) receptors
vi) State the advantages that organisms with small surface area to volume ratio experience over
those with larger
heat loss slow hence their body temperature can increase to intolerable levels
Heat gain from surrounding slower hence may remain inactive for a long time.
Need specialized and complex transport system and also gaseous exchange system
Explain why individuals with smaller sizes require more energy per unit body weight than
those with larger sizes.
surface area to volume ratio is higher in smaller individuals than larger ones, therefore smaller heat
is lost faster by smaller ones than larger ones
they therefore require more energy per unit body weight to maintain body temperature
iv) Explain why some desert animals excrete uric acid rather than water
uric acid is less toxic than ammonia, hence elimination of uric acid requires less water than
ammonia therefore more water conserved
uric acid being less toxic is safer to excrete where there is less water/desert
v) Explain why eating a meal with too much salt leads to production of a small volume of
concentrated urine
the concentration of salts in the blood rises leading to production of more ADH hence higher rate
of water reabsorption by kidney tubules
70
vi) Explain how marine fish regulate their osmotic pressure
swallow plenty of sea water to increase amount of water in the body
have chloride excretory cells in their gills to remove excess salts
eliminate nitrogenous wastes in form of trimethalamine oxide which requires little water for
elimination
few/small glomeruli thus slow filtration rate in the kidneys
retain nitrogenous wastes in form of urea to raise osmotic pressure of body fluids
d) i) What is the biological significance of maintaining a relatively constant sugar level in a human
body?
body cells are surrounded by tissue fluids that are isotonic/same osmotic pressure as cytoplasm
if sugar level is high/hypertonic, cell will lose water by osmosis to the surrounding, thus increasing
the concentration of the contents
this changes the physiology of the cell
if the blood sugar is lower than the normal, the cytoplasm gains water by osmosis, diluting the cell
contents, thus altering the physiology of the cell
ii) Discuss the role of the following hormones in blood sugar control
Insulin
insulin is produced when there is increase in blood sugar concentration
it converts glucose to glycogen which is in the liver or muscle thus lowering sugar level
Glucagon
when glucose level decreases glucagon is produced, which causes the breakdown of glycogen to
glucose thus raising blood sugar level
71
g) Describe the role of the following hormones in homeostasis
i. Aldosterone
concerned with regulation of ionic balance
secreted by the cortex of adrenal glands
it increases sodium ion uptake by the gut and promotes the reabsorption of sodium ions (and
therefore water) in the kidneys)
this is accompanied by elimination of potassium ions
this raises the overall level of sodium and lowers the overall level of potassium in the blood
as sodium ions are absorbed in the blood, chlorine ions follow so as to neutralize the effect of
sodium ions
the production of aldosterone is regulated by the concentration of sodium ions which has an
inhibiting effect, and a fall in sodium ions has a stimulating effect on the adrenal cortex
the flow of aldosterone is stimulated by the adreno-cortic-tropic hormone (ACTH) produced in the
anterior of the pituitary gland
however, the main method of control is dependent on the fact that adrenal cortex itself is somehow
sensitive to the relative concentration of potassium and sodium in the blood
ii. Adrenaline
produced by adrenal glands
in high concentrations, it increases hydrolysis of glycogen and increases blood sugar
it is usually released in emergency cases to increase glucose level for respiration
this releases energy for the emergency
iii) Why does glucose not normally appear in urine even though it is filtered in the mammalian
Bowman’s capsule?
glucose molecules are actively reabsorbed in the proximal convoluted tubules
iv) When is glycogen which is stored in the liver converted into glucose and released into the blood?
after activity/when blood sugar (glucose) falls below normal
when glucagon
stimulates the liver/when glucagon is produced
after strenuous/vigorous activity
during starvation
v) How would one find out from a sample of urine whether a person is suffering from diabetes
mellitus?
test or react urine in Benedict’s solution
positive result i.e. orange or red precipitate
Positive result is an indication of diabetes mellitus.
72
FORM III TOPICS
1. a) i) What is meant by the term binomial nomenclature?
scientific system of naming organisms using the generic(genus) and specific (species) names
Bacteria
are useful in the manufacture of antibiotics
silage formation,
fermentation of cheese, butter, milk yoghurt
curing of tea, tobacco and retting flax
formation of vitamin B12 and K
enzymes such as amylase and invertase
hormones such as insulin
vinegar, acetic acid, lactic acid, citric acid
in septic tanks and modern sewage works make use of bacteria
biogas production
saprophytic bacteria are used in compost decomposition or cause decay
symbiotic bacteria are used in compost decomposition or cause decay
symbiotic bacteria in herbivores/ruminants help in digestion
some diseases in animals/humans and plants are caused by bacteria
many bacteria cause food spoilage/decay
nitrifying and nitrogen fixing bacteria increase soil fertility/make nitrates available
denitrifying bacteria reduce soil fertility/convert nitrates into nitrogen/reduce nitrates
i. Bryophyte
e.g. mosses and liverworts
presence of rhizoids
lack of vascular tissues (lack phloem and xylem)
body parts not differentiated into root, stem, leaves
capsule or seta
gametophyte generation dominant.
ii. Pteridophyta
e.g. ferns
has true roots, stems and leaves
fond with sori on under-surface
vascular tissues present
sporophyte generation is dominant
74
iii. Spermatophyte
photosynthetic
well differentiated into roots, stems and leaves
well developed vascular system
seed bearing plants
reproduce by flowers
seeds enclosed (in fruits)
flowers bisexual hence double fertilization
herbaceous
pollen grains land on stigma of pistil
xylem contains vessels
phloem contains companion cells
ovules contained in ovary
iii. Name the classes and state characteristics of angiospermae
Dicotyledonae
75
iv) State the importance of plants
balancing carbon IV oxide and oxygen in the atmosphere during photosynthesis and respiration
influence water cycle
reduce soil erosion by bind soil particles together
useful products e.g. food, medicine, timber, paper and clothing
habitat ( e.g. forests and grassland) for animals which may also be tourist attraction
earn money from sales of products
aesthetic value/beauty e.g. flowers, shade/shelter, live fences, windbreaks
Some are harmful e.g. poisons, weeds, injurious (stinging nettles, thorns), water hyacinth.
Diplopoda
the millipedes
two pairs of legs per segment
many segments
terrestrial habitat
body cylindrical and long
herbivorous
one pair of antennae
Chilopoda
the centipedes
one pair of legs per segment
many segments
terrestrial habitat
body long and ventro-dorsally flattened
carnivorous
last pair of legs pointing backwards with poison claws called maxillipedes
one pair of antennae
Insecta
three body parts i.e. head thorax, abdomen
six legs/three pairs of legs
a pair of compound eyes
presence of wings
a pair of antennae
76
Crustacean
two body parts
segmented body
have pincers (modified legs) to catch prey
have hard exoskeleton
a pair of compound eyes
Arachnida
body divided into two parts( abdomen and cephalothorax)
simple eyes
eight legs (four pairs of legs)
Beneficial effects
food supply
important in food chains
pollinators
biological control of pests and other organisms
aesthetic value
contribute to decomposition e.g. litter feeders like beetles
Harmful effects
pests
vectors
dirt and disease carriers
injurious e.g. stings and bites
77
Give the characteristics of the following classes of chordate
Pisces
presence of fins for locomotion
two chambered heart
presence of overlapping scales
presence of gills or operculum for gaseous exchange
presence of lateral line for protection
streamlined body
poikilothermic (body temperature varies with that of environment)
Amphibian
partially live in fresh water and partially on land
poikilothermic
pentadactylous with two pairs of limbs
webbed feet for locomotion in water
body streamlined
heart is three chambered
moist skin for gaseous exchange
Reptilia
scales on body
poikilothermic
homodont teeth except tortoise and turtle
all have limbs except snakes
skin is dry
oviparous (lay eggs)
no pinna (external ear)
three chambered heart 9crocodile has four chambers)
skin not glandular
no mammary glands
Aves
the birds
homoeothermic (constant body temperature)
four chambered heart
streamlined body for locomotion in air
skin dry and covered by feathers
scales on legs
hollow bones
oviparous (lay eggs)
mouths modified into beaks
78
Mammalian
hair on the body
homoeothermic
viviparous (give birth to live young) except a few
have mammary glands
glandular skin e.g. sweat glands, sebaceous glands
four chambered heart
pinna (external ear)
two pairs of pentadactyl limbs
presence of diaphragm
have salivary glands
A biological device (tool) which enables one to identify an organism by progressively opting
between two alternative observable characteristics
iv) Describe the procedure of using a dichotomous key. Make a list of major features of the
characteristics to be identified
79
iv You are provided with a specimen kale leaf. Use the dichotomous key below to identify the
taxonomic group to which the specimen belongs. Show the steps (number and letter) in the key that
you followed to arrive at the identify of the specimen
1 a) leaf broad go to 2
b) leaf narrow Araicaria
v) You have been provided with four animals labeled K (mature adult housefly), L (mature adult
grasshopper, M(maize flour beetle) and N(worker termite) use the dichotomous key below to
identify the specimens. Write down in the correct order, the steps (number and letter) in the key
that you followed to arrive at your answer.
Dichotomous key
i. Ecology
study of the interrelationships between organisms and their environment
ii. Environment
surrounding of the organism i.e. biotic or a biotic factors
iii. Habitat
A specific locality (home) of a living organism with a set of factors (conditions) in which an
organism lives.
iv. Ecological niche
Role of an organism in its habitat e.g. feeding relationship
v. Population
Number (group) of organisms of a species occupying a given habitat
vi. Community
Refers to different species of (plants and animals) organisms in a given habitat (area) co-existing
or interacting (living) with each other and the environment in which they live
vii. Ecosystem
A community of organisms interacting with one another and the environment in which they live
viii. Biosphere
The earth and its atmosphere where living organisms are found
ix. Autecology
Study of a single (individual) species of plants or animals within a community, ecosystem, habitat
or environment.
x. Synecology
Study of natural communities (plants and animals) or populations interacting within an ecosystem.
xi. Carrying capacity
maximum number of organisms an area can support without being depleted
xii. Biome
geographical area with particular climatic conditions and flora and fauna
it constitutes many ecosystems
xiii. Biomass
dry weight (mass) of a living organism in a given area
units of measurement are kg/m2/year
b) i) What are abiotic factors?
non-living components of the ecosystem
ii) Explain how abiotic factors affect living organisms
Wind
this influences rate of water evaporation from organisms
81
therefore it affects distribution of organisms e.g. wind increases rate of transpiration and
evaporation of water from the soil
wind is an agent of soil erosion, may break and uproot trees
may aid in the formation of sand dunes which can form habitats for some desert plants
wind disperses fruits, seeds, spores
wind forms waves in lakes and oceans which enhances aeration of water which replenishes oxygen
concentration necessary for life
wind is an agent of pollination
Temperature
influences rate of enzyme action in photosynthesis and other metabolic reactions in plants and
animals
organisms function within a narrow range of temperature
it affects distribution of organisms
changes in temperature affect rate of photosynthesis and biochemical reactions e.g. metabolism
and enzyme reaction
temperature increases rate of transpiration
Light
needed by green plants and photosynthetic bacteria which are primary producers
animals depend on plants directly or indirectly for food
main source of light is the sun
light is necessary for synthesis of vitamin D in certain animals
some plants need light for flowering
seeds like lettuce need light for germination
Humidity
amount of water vapour held by the air
affects the rate at which water is lost from organisms body by evaporation and stomatal
transpiration
when humidity is low the rate of transpiration increases
humidity influences distribution of organisms
PH
each plant requires a specific PH in which to grow (acidic, neutral or alkalinic)
pH affects enzyme reaction in metabolism
Salinity
some ions are needed for plant and animal nutrition
osmoregulation implants and animals is affected by salinity
Topography
altitude affects light, atmospheric pressure and light
Slope influences surface runoff, wind erosion, etc.
mountains affect distribution of organisms which differs in leeward side and windward side
mountains affect distribution of organisms which differ on lowlands and on highlands
mountains also form physical barriers to migration of organism and may cause isolation of species
background may offer camouflage to some organisms hence protection from enemies
Rainfall (water) or precipitation
amount and distribution of rainfall affect vegetation type
this consequently affects distribution of animals e.g. polar region water frozen hence only well
adapted organisms survive
fewer organisms found in deserts where rainfall is less
Water is required for seed germination, raw material for photosynthesis, solvent for mineral salts.
Provides turgidity for plant support, medium for transport, disperses fruits, seeds and spores
Pressure
82
the weight atmosphere exerts upon the earth
varies with altitude 9the higher the altitude the less the pressure
this variation implies change in density which directly means less oxygen for respiration and less
carbon iv oxide for photosynthesis and this affects distribution of organisms
Mineral salts (trace elements)
these affect distribution of plants in the soil
plants thrive best where elements are available
Plants living in soil deficient in a particular element must have special methods of obtaining it.
They harbor nitrogen fixing bacteria and others have carnivorous habit
Plant distribution influences animal distribution
c) i) What are biotic factors?
refers to living organisms in an area
biotic environment of an organism constitutes all organisms around it, which it relates or interacts
with in various ways
ii) Give examples of biotic factors affecting ecosystems
feeding relationships
predation
competition
diseases and pests
human activities
d) Discuss how the various biotic factors affect living organisms
i. Competition
organisms compete with one another for food, light, water, mates and shelter
organisms must live together for competition for available resources
those which cannot cope either structurally or behaviorally will migrate or die
those remaining, due to better adaptations will increase in population
competition between members of the same species is called intra-specific competition e.g. for
mates
Competition between members of different species is inter specific competition e.g. for food and
space.
ii. Predation
this is predator-prey relationship
predator feeds on prey hence both control the other’s population
Distribution of predator and prey is important as predator cannot survive without prey
It there is no predator the prey will increase in population beyond carrying capacity hence die due
to environment depletion
iii. Parasitism
an association where an organism lives in or on another living organism obtaining food(and other
benefits) from it, causing harm to it (without necessary killing it)
parasites may kill host
they deprive host of food
make host weak by introducing diseases
make reproductive ability of host low hence host becomes susceptible to predation
iv. Diseases and parasites
make organisms weak and susceptible to predation
kill organisms and reduce their population
83
v. Symbiotic
and association of organisms of different species where both benefit from the association i.e. there
is mutual benefit
vi. Human activities
these are human factors which have an influence on the biosphere
examples are road construction, industrialization, deforestation, agriculture, pollution, poaching,
fishing conservation, population control
affect ecosystem and balance of nature
Saprophytism
saprophytes are organisms which obtain organic matter in solution from dead and decaying tissues
of plants and animals
they include saprophytic bacteria and fungi
they make available carbon, nitrogen and other elements form dead to living organisms
they are useful in recycling nutrients in nature
iii. Nitrogen in the atmosphere cannot be directly utilized by plants. State two ways by which
this nitrogen is made available for plant use
f) i) Describe how energy flows from the sun through the various trophic levels in an ecosystem
energy from the sun is trapped by green plants during photosynthesis, producing chemical
energy9food or carbohydrates
green plants are producers and occupy the first trophic level
green plants are eaten by herbivores called primary producers as they occupy the second trophic
level
herbivores are eaten by carnivores, secondary consumers, which occupy the third trophic level
when organisms 9plant and animals) die, fungi and bacteria which are saprophytic organisms feed
on them thus causing them to decompose into simple substances e.g. mineral salts
these organisms are called decomposers and detrivores
decomposer feed on dead organic matter hence cause decomposition and decay which releases
nutrients for plants, linking biotic and a biotic components
at all levels energy is lost through respiration
Give the reasons for loss of energy from one trophic level to another in a food chain
- They utilize the energy from the sun to manufacture food for themselves and for subsequent trophic level
(consumers) and other organisms
85
Food web
complex feeding relationship where a consumer feeds on more than one type of food while several
herbivores feed on one type of plant
it is an interrelationship of many food chains
consumers are usually fewer than producers to ensure survival of both
Pyramid of numbers
this is a diagrammatic representation of numbers of organisms at each trophic level in a food chain
usually there are more producers than consumers
hence producers herbivores carnivore
the reason for the pyramid is because herbivores feed on many plants (producers) as carnivores
feed on many herbivores
sometimes this may not be true e.g. when many caterpillars feed on one tree or parasites on a
herbivore
this gives an inverted pyramid of numbers
Pyramid of biomass
refers to diagrammatic representation total dry weight of organisms at different trophic levels in a
food chain
producers have greater biomass than any level of consumers progressively
size of organisms in successive e trophic levels increases
amount of individuals decreases in successive levels
86
Account for the decrease of biomass in the successive trophic levels
fixed energy which supports living matter decreases at each successive trophic level since energy
is lost by respiration and indigested (unconverted) materials hence less biomass supported at each
level
Dispersion
spread or distribution of organisms in a habitat
Density
the number of individuals per unit area
ii) Explain how the following methods are used to estimate population of organisms
quadrat method
identify the study area
throw or mark out the quadrat in the area of study at random
identify or label the various species of plants in the quadrat
count plants of each species
record the numbers
repeat the process
work out the average per quadrat for each species
calculate the total number of different species in the area or calculate the population for the total
area of habitat
Line transect
a string is stretched along an identified area
all plants touching the string are counted
Belt transect
preliminary study of the study area to estimate size or make a sketch map
two parallel lines (strings or ropes) running for a determined distance and width
count the number of organisms in the transect
calculate the area covered by the transect
calculate the number of organisms being investigated per unit area
repeat this process at least three times in other parts of the study area
find the mean number of organisms per unit area from all the belt transects
from this figure calculate the total population of the desired organisms in the study area.
87
Capture-recapture method
e.g. grasshoppers or fish
capture the grasshoppers
count and mark using permanent ink
record
release and allow time
recapture and count the marked and unmarked
total population is equal to the number of marked and unmarked grasshoppers in the second
sample multiplied by the number of marked grasshoppers in the first sample divided by number of
grasshoppers marked in the second sample that were recaptured
i. Xerophytes
grow in areas with scarcity of water
roots grow deeply and extensively (widely spread) to ensure access to water
thick succulent stems, roots and leaves for water storage
photosynthetic stems take place of leaves which would lose a lot of water
Leaves are needle-like (reduced to spines), scaly, have sunken stomata. Some have curled (rolled)
leaves. Some have thick waxy cuticle, reduced number of stomata to reduce water loss by
transpiration
some shed leaves during dry season to reduce water loss
presence of thorns for protection
short life cycle to ensure survival
reversed stomatal rhythm
ii. Hyrophytes
grow in places with plenty of water(waterlogged)
aerenchyma a tissue (airspaces) and large intercellular spaces and long fibrous roots for buoyancy
(floating in water)
poorly developed support tissues (sclerenchyma) because water provides the necessary support
upper epidermis of leaves have more stomata than lower epidermis for gaseous exchange or for
increased rate of transpiration
poorly developed conducting tissues (xylem and phloem) because plants obtain water by diffusion
iii. Mesophytes
grow in well watered soils (common plants)
no special adaptations, but depending on particular habitat, may have some adaptations
in forests they grow fast, tall to capture light. Have climbers while some are adapted to carry out
photosynthesis in low light intensities (those that form undergrowth)
in places with adequate water they form broad leaves, thin cuticle and many stomata on both leaf
surfaces
in direr regions they possess more stomata on the lower leaf surface and are deep rooted
some are shallow rooted and develop buttress and prop roots for support
some have waxy or glossy surface to reflect sun rays and drip off rain water
88
iv. Halophytes
plants that grow in very salty soil where the salt concentration is higher than that in the plant
have root cells which concentrate a lot of salts in them and enable then to take in water by osmosis
succulent roots to store water
have pneumatophores (breathing roots) to take in oxygen
some have buttress roots for support
secrete excess salt by use of salt glands
have large airspaces in leaves and stems for buoyancy and to store air
capable of photosynthesis at low light intensities
e.g. mangrove
b) i) What is pollution?
any process which leads to adverse or harmful changes in the environment
ii) Explain the various human activities that have caused pollution
Causes and effects of air pollution
sulphur iv oxide, hydrogen sulphide, chlorine, oxides of nitrogen produced by industries, sewage,
decomposing organic matter and fumes affect gaseous exchange, makes acid rain and damage
plant leaves
aerosols, herbicides, insecticides (agrochemicals), paint spays, acaricides and CFC’s sprayed to
control diseases, pests and weeds affect respiratory organs of animals. The chemicals are residual
and persistent (not easily broken down) and bring depletion of the ozone layer
smoke and fumes produced in areas with heavy industries, motor vehicles, fires which burn fuel,
oil, wood and coal cause carbon ii oxide, poisoning affect respiratory systems and affect visibility
particles in smoke and fumes settle on leaves and stop photosynthesis
carbon iv oxide causes green house effect which causes temperature inversion as a result of heating
the lower layers of atmosphere
sound and noise produced incessantly by machines, aeroplanes and heavy vehicles affect hearing
in animals
dust from cement factories, quarries, dust roads settles on leaves limiting photosynthesis
removal of vegetation interferes with carbon cycle
radio-active emissions from nuclear reactors, mines and bombs cause cancer, mutations and death.
89
State the causes, effects and methods of controlling and prop roots for support water pollution
Causes and effects
90
iv) State the causes /effects and control methods of soil pollution
Causes and effects
Air pollutants e.g. sulphur IV oxide fumes form sulphuric acid with rain water. The acid rain alters
soil pH therefore affecting plants that cannot tolerate acidic soil
most aerosols sprayed to control pests and diseases precipitate in the soil and are taken up by
plants which make its concentration many times higher, increasing the toxicity in the plants which
absorb them
petroleum products due to spillage by oil tankers making it impossible for plant roots to obtain
oxygen in oil saturated soils, therefore plants are killed
agrochemicals and inorganic fertilizers contain heavy metals that are not used up by plants and
eventually soil microorganisms cannot inhabit the soils
organic matter slows down, life ceases and soil becomes exhausted
community, household wastes and industrial wastes disposal is a major problem in big towns and
cities. commodities packaged in metal tins, rubber, plastic containers, scrap metal, glass bottles,
different types of paper are nuisance to the environment, rendering it useless for agricultural
purposes
91
c) Describe the symptoms, mode of transmission and control of cholera, typhoid malaria and
amoebic dysentery in humans
92
d) Discuss Ascaris lumbricoides under the following sub-headings
i. Mode of transmission
through ingestion of contaminated food
live in intestines
ii. Effects of parasite on the host
inflammation of lungs
pneumonia
produce toxic substances
intestinal obstruction
iii. Adaptations
thick cuticle which protects it against digestion
lays many eggs to ensure survival
mouthparts for sucking partly digested food
lack of elaborate alimentary canal
tolerant to low oxygen concentration
two hosts to ensure survival
eggs have protective cover to ensure survival in adverse environments
iv. Control and prevention
proper sanitation
wash hand after defaecation and before eating
iii. Adaptations
has two hosts to increase chances of survival
eggs have a hook like structure which raptures the walls of intestine or bladder
lay large number of eggs to ensure survival
larvae have a sucker for attachment on human skin which it digests
larva has a tail which it swims with in search of host in water
prolonged association between male and female to ensure that fertilization takes place
adults can tolerate low oxygen concentration (in the animal tissues)
adult worm secretes chemicals against antibodies
larvae and eggs (have glands that) secrete lytic enzymes to soften the tissues that ease penetration
larvae are encysted so as to survive adverse conditions
93
iv) Control and prevention
proper use of toilet facilities
boiling water before use
avoid bathing/washing in infected water
Use of molluscicides (chemicals that kill snails/biological control/clearing water weeds on which
snails feed.
Drainage of stagnant water
Wearing gum/rubber boots
3. a) i) What is reproduction?
process by which living organisms give rise to new members of their own species which resemble
the parents
c) i) What is mitosis?
A type of cell division that occurs during growth leading to increase in number of cells
all cells maintain the same chromosome constitution i.e. the diploid state
replication of organelles
duplication of DNA
production of energy (ATP) for cell division
94
Prophase
stage of dehydration
chromosomes shorten and thicken
chromosome replicates into two chromatids
chromatids joined at centromere
formation of spindle fibers
Metaphase
chromosomes move to equator (early metaphase)
chromosomes line up at the equator
homologous chromosomes do not associate
Anaphase
chromatids separate
move to opposite ends (poles) of the cell
95
Telophase
d) i) What is meiosis?
division of diploid cells to form gametes which are haploid
Interphase
cell is in non-dividing condition
chromosomes appear threadlike
Prophase I
chromatic material shorten and thicken
double stranded chromosomes appear (bivalent)
double stranded chromosomes pair and twist round each other (synapsis)
point of contact of chromosomes is called chiasma
Metaphase I
96
paired homologous chromosomes line up at the equator
Anaphase I
paired homologous chromosomes move to the poles
Telophase I
paired homologous chromosomes reach the poles
two new nuclei are formed
Metaphase II
movement of chromosomes to equator
Anaphase II
-chromatids of each chromosome separate to the poles
Telophase II
reach the poles
four haploid daughter cells are formed
97
iv) Give the similarities between mitosis and meiosis
both take part in cells
both involve division (cell multiplication)
v) What are the differences between mitosis and meiosis?
Mitosis Meiosis
maintenance of chromosome reduction/halving of chromosomes
number (diploid) (haploid
takes place in somatic cells/growth occurs in reproductive
no crossing over/no variations cells/gonads/produces gametes
results into 2 daughter cells crossing over takes place/variation
no pairing/no synapsis/no bivalent occurs
formed results into 4 daughter cells
a one division process of four there is paring/synapsis/bivalent
stages a two division process of four
stages each
98
iii) Give the disadvantages of asexual reproduction
lack of genetic variation
lowered resistance to disease
loss of hybrid vigor
competition for resources due to overcrowding
iv) Explain how reproduction occurs by the following methods of asexual reproduction
Sporulation
formation of spores
spores are small haploid cells produced by plants
spores give rise to new haploid organisms
includes moulds, ferns, bryophytes, pteridophytes
Budding
where an outgrowth arises from a parent and drops off to develop into a new organisms
hereditary material in the daughter cell and parent are exactly the same
occurs in organisms such as hydra, jelly fish, sea anemones, yeast and some fungi
Binary fission
a cell splits into two new cells of equal size
each daughter cell grows into anew organism
Occurs in organisms such as amoeba, euglena, paramecium, some fungi and bacteria.
f) i) What is a flower?
this is the reproductive structure which bears the reproductive parts of a plant
it produces seeds and fruits
Receptacle
expanded end of stalk which bears floral parts
Calyx
consists of sepals
usually green
protect flower in bud
99
Corolla
consist of petals
often colored or scented to attract insects
Androecium
male part of flower
consist of stamens
each stamen consists of an anther containing pollen sacs
anther produces pollen grains which contain male gametes
Gynaecium
female part of flower
consists of one or more carpels
each carpel contains one or more ovules in an ovary
style bearing a stigma extends from ovary
ovary contains female gametes which when fertilized become seeds
Hermaphrodite
one with both stamen and carpel
most flowers are hermaphrodite/bisexual
Unisexual
have only one of carpel or stamen i.e. either male or female
Carpelate
also called pistilate
contains only carpels hence a female flower
Staminate
also called male flower
contains only stamens
Dioecious plants
have pistilate and staminate flowers on different plants e.g. pawpaw
Monoecius plants
have pistilate and staminate on one plant
however, pistilate and staminate occur at different plants e.g. maize
Complete flower
Has all four parts i.e. Calyx, corolla, androecium and gynoecium
100
Incomplete flower
does not have all four parts
at least one is missing
Inferior (epigynous)
other floral parts arise above ovary on the receptacle
g) i) What is pollination?
transfer of pollen grains from anther of a stamen to stigma of a flower
101
Wind pollinated flower (anemophilus)
anthers/stigma hang outside the flower to increase chances of pollination
the style/filament is long to expose stigma/anthers
stigma is hairy/feathery/branched to increase surface area over which pollen grains land/to trap
pollen grains
pollen grains are smooth/dry/light/small to be easily carried by wind
large amount of pollen grains to increase chances of pollination
anthers loosely attached to filaments to enable them to sway to release pollen grains
pollen grains may have structures which contain air to increase buoyancy
flowers have long stalks holding them out in the wind
vii) Give the characteristics that ensure cross pollination takes place in flowering plants
presence of special structures that attract agents of pollination
protandry/dichogamy
protagyny/dichogamy
monoecism
self sterility
heterostyly
h) i) What is fertilization?
- Fusion of male and female gametes to form a zygote
103
iv) Describe the main parts of a seed
Testa
also called seed coat
a tough outer covering which protects the seed from insects, bacteria etc
segment is the membrane inside the testa
Hilum
a scar
spot where the seed was attached to the fruit or pod
Micropyle
small hole through which water and air enter the seed
Radicle
embryonic root
grows into the shoot system
Cotyledons
embryonic leaves
store food for the germinating seed i.e. for plumule and radicle
when plumule and radicle grow, they use food stored in the cotyledon
in some seeds food is stored in the endosperm
j. i) What is placentation?
arrangement of ovules within the plant ovary
placenta formed at the base of the ovary with numerous ovules attached to it
Parietal
105
edges of carpels fuse together
dividing walls disappear, leaving one loculus
have numerous seeds e.g. passion fruit
placenta of each carpel appears as ridges on ovary wall
Axile
Aggregate fruits
consists a group of ovaries that appear on a common receptacle e.g. strawberry
106
Multiple (compound) fruits
formed from several flowers whose ovaries fuse together after fertilization
form a bunch e.g. pineapple, figs
are always false fruits
Drupe
only one seed
pericarp divided into three layers i.e. epicarp, mesocarp(juicy) and endocarp(hard)
e.g. mango and coconut
Pome
juicy part is swollen receptacle
is usually a false fruit
example is a pear
107
vi) Give types of dehiscent fruits
Legumes
split along two edges
are usually pods e.g. beans, peas, crotolaria
Follicle
split on one side only e.g. Sodom apple
Capsule
has several lines of weakness/sutures
open in many places e.g. castor oil, cotton
iii) Explain how seeds and fruits are adapted to various methods of dispersal
Adaptations for wind dispersal
they have wings, feathers or hair-like structures to increase surface area for wind to carry them
easily/buoyancy
seeds/fruits are loosely attached on the stalks so that they can easily be released and carried away
by wing
seeds/fruits are generally light and small sized to be easily carried by wind
some seeds/fruits have parachute-like structures to be easily carried b wind
some have censor mechanism where seeds and fruits are borne on long stalks that are loosely
attached which allows swaying so that movements of capsule by wind releases the seeds
108
Water dispersal seeds
seed/ mesocarp has air spaces thus light/buoyant to float hence carried by water
they have waterproof cover and tough pericarp protects seeds from getting soaked
fibrous and spongy mesocarp to easily float
Self dispersal/explosive
self opening seeds
they have lines of weakness called sutures for violent opening thus scattering seeds away from
parent plant
5. a) i) Distinguish between external and internal fertilization in animals
in external fertilization fusion of the male and female gametes takes place outside the body of the
female e.g. amphibians and fish
in internal fertilization union of gametes occurs inside the body of the female
109
iii) Give a reason why it is necessary for frogs to lay many eggs
to increase chances of survival/fertilization
110
111
ii) Describe how the mammalian male reproductive system is adapted to perform its functions
Penis
is highly vascularised/spongy
has a sensitive glands
becomes erect to allow entry into the vagina
Scrotum
contains the testes outside the body on whose walls the process of spermatogenesis takes place
the process is favored by lower temperature
it contains sertoli cells which nourish sperms until they are mature
Epididymis
long and coiled for the purpose of sperm storage
Vas deferens
muscular
upon contraction pushes sperms out and allows ejaculation
Gametes
produced in large numbers to increase chances of fertilization
the sperms have a tail for swimming/large number of mitochondria to provide energy/allow
swimming to reach the egg
Accessory glands
are seminal vesicle, Cowper’s gland and prostate gland
they produce seminal fluid to provide a medium/ nutrients for sperms to swim
112
113
114
ii) Describe how the various structures of the human female reproductive system are adapted to
their function
Ovaries
have several graafian follicles that develop and burst open to release/produce mature ova
secretes sex hormones)oestrogen) which initiate/control development of secondary sexual
characteristics
produce hormones oestrogen and progesterone which prepare the uterus for implantation and
subsequent nourishment of the embryo
115
Oviducts (fallopian tube)
are thin narrow and tubular to increase flowing speed of semen containing sperms
are funnel shaped on the end next to ovary which enables them to receive the ovum
their lining contains cilia which propel the ovum towards the uterus
has peristaltic muscles that enable movement of zygote/ovum to the uterus for implantation
is fairly long to increase surface area for fertilization
Uterus
is muscular for protection of developing embryo
has elastic wall that allows growth and development of foetus/embryo
has a highly vascularised endometrium that provides nutrients/gaseous exchange to developing
embryo
Cervix
has valves that close the lower end of the uterus to ensure continued pregnancy during gestation
period
is capable of dilating
has narrow entrance/neck-like entrance to uterus that enables quick swimming of sperms to uterus
has suction mechanism that draws up/pulls sperms into uterus
has a “W” shape that fits well with the glands of the penis to ensure sperms are deposited at the
right point
Vagina
is elastic and muscular to enable good accommodation or penetration of the penis thus proper
deposition of sperms and for easy parturition
allows menstrual flow
has sensitive labial walls which secrete/produce lubricating substances that ensure/enable/facilitate
good coition
capable of considerable enlargement, due to elastic muscles, to accommodate baby during
parturition
Clitoris
has sensitive cells for orgasm
116
d) i) Explain the process of fertilization
a process whereby the egg and sperm are brought together and fuse to form a zygote
occurs in the fallopian tube after copulation
sperm head penetrates the outer coat of the ovum while the tail remains outside
penetration is due to reaction of acrosome
acrosome digests the vitelline membrane
thereafter a zygote is formed
zygote which is diploid undergoes rapid cell division to form a mass of cells called blastocyst
after fertilization a membrane forms around the ovum to prevent further entry of sperms
blastocyst eventually develops into an embryo
117
118
119
i) Explain the process of implantation
this is the embedding and attaching of the embryo in the uterine wall/endometrium
implantation marks the beginning of pregnancy
sometimes implantation occurs in the oviduct wall which is abnormal and results in ectopic
pregnancy which is fatal
the outer wall of the blastocyst develops fingerlike projections which project into the uterine wall
for attachment
the projections are called villi
the villi and endometrium develop into an organ that is called the placenta
the embryo is attached to the placenta through a cord called the umbilical cord
120
121
iii)
122
State the functions of umbilical cord
it contains blood vessels umbilical artery, iliac arteries and umbilical veins)
it joins the placenta to the embryo
passage for nutrients from the mother
passage of excretory substances from foetus to mother for final discharge
gaseous exchange
passage of antibodies from mother to foetus, for protection of foetus against diseases
123
iv) State the role of placenta
exchange of gases between mother and foetus
exchange of nutrients and nitrogenous wastes
anchorage/attachment of foetus
produces hormones (oestrogen and progesterone)
Amnion
contains amniotic fluid
fluid surrounds embryo
protects embryo from mechanical injury by acting as shock absorbers
fluid also protects embryo from dehydration
distributes pressure equally over embryo
Yolk sac
surround the yolk
produces blood cells for embryo until its own liver is able to perform the task
Allantois
present only for a short time
removes and store waste material
it eventually becomes the umbilical cord
124
iv) State the reasons why later in pregnancy the ovary will b e removed without disturbing the
pregnancy
corpus luteum in the ovary secretes progesterone which maintains pregnancy and development of
foetus after conception
after four months pregnancy is maintained by progesterone from the placenta
125
Oxytocin
parturition
milk ejection
g) i) What is menstruation?
- vaginal discharge due to disintegration of endometrium
h) Explain the symptoms, methods of transmitting and prevention (control) of the following sexually
transmitted diseases
i) Gonorrhea
- caused by a bacterium called neisseria gonorrhea
- transmitted through sexual intercourse,
- infects urethra and vaginal tract (epithelia)
- Symptoms include pain, discharge of mucus and bad smell (females)
- Effects include sterility, heart diseases, blindness of foetus and arthritis
- Treatment by antibiotics
- Control and prevention by proper sexual conduct
126
ii) Herpes
notably Herpes simplex and H. genitalis
caused by virus which attacks genitalia
symptoms are painful sores in genitalia, skin lesions
transmitted in saliva, sexual intercourse and injection by drug addicts
no treatment
iii) Syphilis
caused by bacterium called Treponema palladium
symptoms are painless wounds in genitalia
attack genitalia, nervous system, lips
treated by antibiotics
iv) Trichomoniasis
caused by plasmodium called trichomonas
attacks reproductive tract
symptoms are itching and discharge of pus from the genitals
treated by antibiotics
v) Hepatitis
- Viral disease
Affects the liver
Transmitted through sexual intercourse
No known treatment
vi) Candidiasis
caused by fungus called candida albicans
transmitted through sexual intercourse
symptoms include itching urethra, and vaginal discharge (odourless)
controlled by personal hygiene, early treatment and responsible sexual behavior
vii) HIV/AIDS
caused by HIV virus
transmitted by sexual intercourse, blood transfusion, sharing piercing instruments from infected
mother to foetus, infant and baby
symptoms include fever, swollen lymph nodes, night sweating, cough, weight loss, fatigue, loss of
appetite, diarrhea, headache, a opportunistic infections and tumors
Control by responsible sexual behaviour, education, screening blood for transfusion and using
sterile piercing instruments.
6. a) Define the terms
i) Growth
an irreversible change in size of a cell, organ or whole organism
growth is due to synthesis of protoplasm or extracellular substances
ii) Development
refers to a series of changes which an organism goes through in its lie cycle
during development both qualitative and quantitative changes take place(involves differentiation)
127
iii) Differentiation
refers to changes in which the cells of the body undergo and become specialised to perform
specific functions
ii) Draw a sigmoid growth curve and explain its different phases/stages
A-lag phase
- Slow growth rate at first
Organism adapting to the environment
B-exponential phase
- organisms already adapted
- first growth due to birth rate that is higher than death rate
128
C- Stationery phase (plateau)
- Birth rate equals death rate (equilibrium)
Lack of nutrients, accumulation of toxic waste products
D-phase of decline
- due to depletion of nutrients, accumulation of toxic wastes, lack of space
- some individuals old hence not reproducing
- death rate higher than birth rate
A-growth
B-no growth
C- moulting/ecdysis
- seen in arthropods
- growth in in arthropods is intermittent(takes place during some time only because their hard
cuticles (exoskeleton) does not expand to cause growth
- the cuticle must be shed off first to allow further growth
- the shedding is called ecdysis or moulting
- when moulting has taken place animal grows but growth stops when the exoskeleton hardens again
129
iv) Give the conditions necessary to break seed dormancy
- scarification/scratching to make seed coat impermeable
- vernalisation/cold treatment in some seeds like wheat
- burning/nicking/expose to heat e.g. wattle seeds
- destruction of germination inhibitors
iii) Discuss the various conditions necessary for the germination of seeds
Water
- medium for enzymatic activity
- hydrolysis of food into simpler substances
- medium of transport
- softens the seed
- acts as a solvent
Air
- in form of oxygen
- oxygen is used for respiration/oxidation of food to release energy
Enzymes
- breakdown and subsequent oxidation of food
- conservation of hydrolyzed food products into new plant tissues
Viability
- only viable seed are able to germinate and grow
130
cotyledons are brought above the ground level during germination due to elongation of hypocotyls
Hypogeal
- the cotyledons remain below the surface during germination due to elongation of epicotyl e.g.
maize
v) Name the part of the bean seed that elongates to bring about epigeal germination
hypocotyl
vi) Account for the loss in dry weight of cotyledons in a germinating bean seed
- food stored is mobilized/used up for respiration and growth
vii) Describe the physiological changes that occur in a seed during germination
- in presence of oxygen, optimum temperature and water, food reserves in the seed are hydrolysed or
broken down into soluble diffusible form by enzymes
- soluble food diffuses to the growing embryo
- oils and carbohydrates provide energy
- simple sugars converted to cellulose to form cell wall
- amino acids make protoplasm
- seed develops plumule and radicle hence germinates
viii) Explain the biological significance of cotyledons being brought above the ground in epigeal
germination
- cotyledons have inadequate food
- they are brought above the ground to acquire chloroplasts to carry out photosynthesis before the
formation of foliage leaves to supplement food supply required for growth during germination
Secondary growth
-occurs at the cambium meristems
Increases width (girth) of the stem
131
iv) State the location and function of the following meristematic tissues
Apical meristem
- located at tips of roots and shoots
- increase length of stem and roots/primary growth
Intercalary meristem
- found at bases of internodes
- responsible for elongation of internodes and increase in leaf sheath in grasses
Lateral meristems
- found near the periphery of stem and root
- responsible for secondary growth/growth in girth of stem and root/lateral growth
- called cambium and constitute vascular and cork cambium
132
g) i) Describe one method which can be used to measure the average growth rate of a single leaf of a
plant
EITHER
- chose/identify a young leaf(just unfolded)
- use the same leaf throughout
- measure (total) length of (whole) leaf
- record
- repeat at regular intervals until no more change occurs/constant length
- average rate of growth is equal to total increase in length divided by the period taken to achieve
full length
Average rate of growth = total increase in length
period taken to achieve full length
OR
- choose/identify a young leaf(just unfolded)
- use the same leaf throughout
- trace the outline on a graph paper and work out the area
- record
- repeat at regular intervals until regular area
- average rate of growth equals to total increase in area divided by the period of time taken to
achieve full area
Average rate of growth = total increase in area
period of time taken to achieve final area
i
i) Describe how the growth of a root can be determined
Materials
- fine thread, marking ink, germinating bean seedlings, blotting paper, ruler marked in millimeters,
pins, cork, a boiling tube and moist cotton wool
Procedure
- dry seedlings using blotting paper
- place inside against the ruler marked in mm
- dip the fine thread in waterproof ink
- mark the radicle at equal intervals
- pin the seedling to the cork
- suspend the seedling into the boiling tube containing moist cotton wool
- allow the seedling to grow for two days/some
time observe the intervals with the marks
- record your observations the widest intervals are found in the region just behind the tip
indicating/showing region of greatest growth
iii) A boy hammered a nail in the bark of a tree at a height of 1.5metres above the ground.
Four years later, the nail was found at the same height although the tree had grown 3 meters taller.
Explain the above observation
The nail was hammered at a point where vertical growth had stopped/further growth was confined to
increase in width/diameter.
Vertical growth is confined to tips/apex/vertical apical meristem
133
h) i) Describe the role of hormones in growth and development of plants
indole acetic acid/IAA/ auxins
Cell division/increase in cell division
Tropic responses
Cell elongation/increases in ell elongation
Development of abscision layer
Growth of ovaries into fruits/parthenocarpy/initiates flowers
Inhibits growth of lateral buds/produces apical dominance
Stimulates adventitious/lateral roots
Gibberellins (Gibberellic acid/GA3
Cytokinnins (Kinnins/Kinnetin/Zeatin)
- breaks dormancy
- promotes flowering
- promotes cell division
- stabilizes protein and chlorophyll
- promotes root formation on a shoot
- low concentration encourages leaf senses
- normal concentration increases cell enlargement in leaves
- stimulates lateral bud development
Ethylene (ethynelC2H4)
- accelerates ripening in fruits
- encourages fruit fall/leaf fall
- induces thickening in stern/inhibits stem elongation
- promotes flowering (in pineapples)
- promotes germination in certain seeds
Traumatin
- heals wounds by callous formation
Florigen
- promotes flowering
134
ii) State the applications of plant hormones in agriculture
- induce root growth in stem cuttings
- selective weed killers
- encourage sprouting of lateral buds
- breaking seed dormancy
- induce parthenocarpy
- accelerate ripening of fruits
- promote flowering
- cause dormancy
iv) Describe the role of hormones in the growth and development of animal
somatotrophin (growth hormones)
- from anterior pituitary
- promotes cell division
- overproduction causes gigantism
- underproduction causes dwarfism
Thyroxine
- promotes growth and metamorphosis
- underproduction leads to a child becoming a cretin (mentally retarted)
Androgens
- in males
- growth of male reproductive organs
Oestrogen
- in females
- growth of female reproductive organs
Ecdysone
- in arthropods
- moulting (ecdysis)
t) i) What is metamorphosis?
- change in form during which there are changes in structure and function in body of organism
- prepares organism for life in a different habitat
iii) What is the significance of each of the four stages in complete metamorphosis?
Larval stage
- feeding takes place
- larva is quite different from adult
- larva sheds its cuticle (exoskeleton) several times to emerge as pupa
- dispersal stage avoids overcrowding
Pupa
- enclosed in a case called puparium (cocoon)
- no feeding
- organ formation takes place
Adult
- emerges from puparium
- reproductive stage of the life cycle
136
vi) State the advantages of metamorphosis in the life of insects
- the adult and larvae exploit different niches
- do not compete for food
- pupa cam survive adverse pupa can survive adverse conditions eg-feeding stage
- dispersal prevents overcrowding
137
FORM IV TOPICS
139
ii) Give an example of this law
In an experiment, Drosophila (fruit fly) with long wings were crossed with those having short
wings. Assume letter L denotes gene for wing size. The gene for long wings is dominant to that
for short wings
the genes for dominant are LL and for recessive ll.
State the expected results for the first cross
If the plants form F1 were selfed, work out the phenotype ratio for the F2 generation
140
f) i) What is a test cross?
- A cross between an individual showing a character for a dominant gene(that is homozygous or
heterozygous) with a homozygous recessive individual
OR
a cross between individual(organism) of unknown genotype with a homozygous recessive
individual
ii) State the importance of a test cross in genetics
helps in determining the genetic constitution/genotype of an organism
iii) What are multiple alleles?
a set of more than two alleles that may determine a character
example is blood group which can be determined by any two of three alleles i.e. A,B and O
Give a worked example using parents with heterozygous blood groups AO and BO
Let the gene for dominant Rh factor be R while gene for recessive be r
141
vii) How is sex determined in human beings?
there are two sex chromosomes in humans, x and y
males are xy and females are xx
in females all ova have x chromosome
in males 50% of sperms contain x chromosomes while 50% of sperms contain y chromosome
when a sperm containing x chromosome fuses with an ovum this results into a girl
when a sperm containing y chromosome fuses with an ovum the result is a boy
an example is given below
142
vi) In humans red-green colour blindness is caused by a recessive gene C, which is sex-linked. A
normal man married to a carrier woman transmits the trait to his children. Show the possible
genotypes of the children.
Let C represent the gene for normal colour vision (dominant)
Let c represent the gene for colour blindness
Parental phenotype Norman man x carrier woman
h) i) What is mutation?
sudden change in the structure of DNA at a particular locus/chromosome/gene
143
ii) Describe how mutations arise
mutations arise due to alterations in normal number of chromosomes
change in a portion of a chromosome affecting one or more genes
by chromosomal aberration e.g. dleltion/duplication/substitution/inversion/translocation/crossing
over
caused by mutagenic agents e.g. radiation (x-rays, ultra violet light, gamma rays) and chemicals
e.g. mustard gas/colchicines
Chemicals Effect
- colchicines prevents spindle formation
Cyclamate chromosome aberrations
Mustard gas chromosomes aberrations
Nitrous acid adenine in DNA is deaminated so behaves like guanine
Acridone orange addition and removal of bases of DNA
Formaldehyde
Duplication
a section of a chromosome is repeated/replicates
therefore genes are repeated
Inversion
occurs when chromatids break at 2 places and when rejoining the middle piece rotates and joins in
an inverted position
Deletion
portion of a chromosome is left out after it breaks off
alters number and sequence of genes
144
Translocation
occurs when a section of a chromatid breaks off and becomes attached to another chromatid of
another chromosome
Non-disjuntion
Failure of homologous chromosomes/sister chromatids to separate/segregate during meiosis
Polyploidy
where number of chromosomes double or triple
beneficial in plants due to the following
increased yields/hybrid vigour//heterosis
resistance to pests
early maturity
resistance to drought
resistance to diseases
Deletion
some bases/nucleotides of a gene are removed
Inversion
the order of some bases/nucleotides of a gene is reversed
Insertion
addition of a base between two existing bases
Substitution
a portion of a gene is replaced by a new portion
145
ii. Genetic engineering
genetic manipulation to produce desired characteristics
iii. Law
- legal questions of paternity knowledge of blood groups or blood transfusion
v) Others
- Pre-sex determination
Understanding human evolution and origin of other species.
ii) Differentiate organic evolution from chemical evolution as theories of origin of life
organic evolution refers to the emergence of present forms of organisms gradually from pre-
existing forms (some of which no longer exist)
chemical evolution explains the origin of life as having occurred when simple chemical
compounds reacted to form the simplest life forms
i) Fossils
fossils are remains of organisms preserved in naturally occurring materials for many years
they give evidence of types of plants/animals that existed at certain geological age/long
ago/millions of years ago
gives evidence of morphological/anatomical/structural changes that have taken place over a long
period of time e.g. human skull, leg of horse
146
Convergence is where different structures are modified to perform a similar function e.g. wings of
birds and insects/eyes of humans and octopuses. These are called analogous structures
Vestigial structures are greatly reduced in size and have ceased to function e.g. human
appendix/caecium/coccix in humans, wings of kiwi (flightless bird), presence of hind limb pad in
python, halters in insects, human hair nictitating membrane in human eye, human ear muscle,
pelvic girdle in whale and third digit of wing of bird.
v) Geographical distribution
organisms differ in various geographical regions
present continents are thought to have been a large land mass joined
together/pangea/Eurasia/Gondwanaland
present continents drifted apart from one land mass/continental drift
as a result of continental drift isolation of organisms occurred bring about different patterns of
evolution
organisms in each continent evolved along different lines hence emergence of new
species/divergence/convergence
Examples
marsupials in Australia
illama, jaguar, panther in S. America
lion, camel in Africa
tiger in Asia
c) i) State the evolutionary characteristics that adopt human beings to the environment
- Brain
- Eyes
- Upright posture/bipedal locomotion
- prehensible arm/hand
- Speech
147
ii) State the ways in which Homo sapiens differs from Homo habilis
standing upright/erect posture
intellectual capacity/higher thinking capacity/bigger brain/higher brain capacity
communication through language/speech
iv) State the ways in which sexual reproduction is important in the evolution of plants and animals
- brings about useful variations/desirable characters
- variations make offspring better adapted for survival/more resistant to diseases
- may lead to origin of new species
148
v) Explain the significance of mutation in evolution
- Mutation bring about variation which can be inherited
- Some of these variations are advantageous to the organism
- Others are disadvantageous
- The advantageous variations favour the organism to compete better in the struggle for survival
- This results into a more adapted organism to its environment or new species/varieties
- Those with disadvantageous characters will be discriminated against therefore eliminated from the
population/death/perish
vi) Plain why it is only mutations in genes of gametes that influence evolution
- gametes form the new offspring
vii) How would you prove that evolution is still taking place?
- resistance of organism to antibiotics, pesticides and drugs
- new varieties of bacteria are resistant to certain antibiotics such as penicillin
- houseflies and mosquitoes are resistant to DDT
vii) Explain why some bacteria develop resistance to a drug after they have bee subjected to it
for some time
- bacteria mutates/develops a new strain/chemical composition is altered hence is able to produce
enzymes/chemicals which degrade the drug rendering it non-susceptible to the drug
- the new strain is favoured by selection pressure/ natural selection
f) How has industrial melaninism i.e. peppered moth contributed towards the mechanism of
evolution
Stimulus
A change in the environment of organism which causes change in organism’s activity
Response
- change in activity of an organism caused by a stimulus
ii) State importance of irritability to living organisms
- Adjusting to environmental conditions. Sensitive/defect/responding
149
iii) List the examples of external stimuli to organisms
- air/oxygen (aero)
- light(photo)
- osmotic pressure (osmo)
- current (Rheo)
- chemical concentration (chemo)
- \water/moisture (hydro)
- Touch/contact (hapto/thigmo)
- Gravity/soil (geo)
- Temperature (thermo)
-
b) i) What are tactic responses?
- response in which whole organism or its motile parts move e.g. gamete
150
Geotropism
- response of roots/parts of a plant to the direction of force of gravity
- auxins grow towards the direction of force of gravity causing positive geotropism in roots while
shoot grows away from force of gravity (negatively geotrophic)
-
Thimotropism/Haptotropism
- growth response of plant when in contact with an object
- contact with support causes migration of auxins to outer side causing faster growth on the side
away from contact surface
- this causes tendrils/stem to twin around a support
-
Hydrotropism
- growth movement of roots in response to unilateral source of water/moisture
- the root grows towards the source of water/ positively hydrotropic while leaves are negatively
hydrotropic
-
chemostropism
- growth movement of parts of plant to unilateral source of chemicals
- the chemicals form a gradient between two regions e.g. pollen tube growing towards the ovary
through the style
-
iii) State the ways in which tropisms are important to plants
- expose leaves/shoots in positions for maximum absorption of sunlight for photosynthesis
- enables roots of plants to seek/look/search for water
- enables plant stems/tendrils to obtain mechanical support especially those that lack woody stems
- enables roots to grow deep into the soil for anchorage
- enables pollen tube grow to embryo sac to facilitate fertilization
d) The diagram below represents growing seedlings which were subjected to unilateral light at the
beginning of an experiment
151
i) State the results of P, Q and R after 5 days
- P will bend/grow towards light
- Q will remain straight/have little or no growth
- R will remain/grow straight/grow upwards
iii) If the tin foil were removed from the tip of seedling R, what results would be observed
after two days
- it will bend/grow towards light
iv) State the expected results after 3 day is if the box were removed
- all seedlings will grow straight/upwards
Account for the curvature of the shoot and root after the seven days
i) Shoot
- auxins accumulate on the lower side of the seedling due to gravity
- high concentration of auxins in shoot stimulates faster growth causing more elongation on the
lower side than the upper side hence curvature occurs upwards
ii) Root
- the high concentration of auxins inhibits growth hence the upper side with less auxins grows faster
than the lower side therefore the curvature occurs downwards
152
f) What is etiolation?
- phenomenon exhibited by plants when grown in darkness
- such plants are pale yellow due to absence of chlorophyll, have small leaves, long
stems/hypocotyle and slender stems
- plants exhibit etiolation to reach light/obtain light
- this is a survival response
vi) State the differences between somatic and autonomic systems of peripheral nervous system
- Somatic is concerned with controlling the conscious or voluntary actions of the body i.e. skin, bones,
joints and skeletal muscles
- the autonomic (automatic) nervous system controls involuntary actions of internal organs, digestive
system, blood vessels, cardiac muscles and glandular products.
b) i) What is a neurone?
the basic unit of the nervous system
also called nerve cell
conducts impulses
include monitor sensory and relay neurons
153
ii) Name the parts of a typical neurone and state the functions of each part
cell body/centron contains nucleus and cytoplasm
axon transmits impulses away from cell body
dendrites relays impulses across adjacent neurons
myelin sheath insulates axon and speeds up transmission of impulses
schwan cells forms myelin sheath and aid in nutrition and regeneration of axon
node of ranvier occur between schwan cells, where axon is not covered, speeds up impulse
transmission
nissils granules contain mitochondria that provide cell body with energy for metabolic process
154
ii) Describe the structure and function of sensory neurone
sensory neurone relays impulses from receptors (sense organs) to CNS
155
c) State the functions of the major parts of the human brain
i) Cerebrum
called forebrain
occupies most of the brain
consists of four lobes each with specific function
temporal lobe controls taste smell hearing learning and memory
partial lobe controls sensory output and touch
occipital lobe controls vision, motor output and speech
frontal lobe controls personality, learning thought and speech
also has parts called thalamus and hypothalamus
thalamus helps to sort sensory information
hypothalamus controls hunger, heartbeat body temperature and aggression
156
ii) Mid brain
quite small in humans
relay centre for audio and visual information
also involves in some sight, hearing and orientation responses
i) Hind brain
consists of cellebral and medulla oblongata
cerebellum is responsible for coordinating impulses, posture and balance, motor coordination and
muscle tone
medulla oblongata controls heartbeat, blood pressure breathing rate, coughing and sneezing
ii) Describe a reflex action that will lead to the withdrawal of a hand from a hot object
Receptors in the skin respond to stimuli. Are stimulated
an impulse is transmitted through the sensory neurone, across a synapse to the central nervous
system (white matter), through the relay neurone into grey matter, then to the motor neurone and
finally to the effect muscle which contracts
the hand is then withdrawn
ii) Briefly describe the transmission of a nervous impulse across a neuro-muscular junction
impulse arrives at synoptic knob and causes vesicle to move to the pre-synaptic membrane
vesicle discharges transmitter substance into synaptic cleft
transmitter substance/acetylcholine diffuses across the cleft and attaches to post-synaptic
membrane
the membrane is depolarized, generating the action potential
157
iii) What are the functions of a synapse?
allows transmission of nerve impulses from neurone to neurone
ensures nerve impulses travel in only one direction
in the brain they store information/memory
158
iii) Name the main endocrine glands, their secretions and functions in the human body
Gland Hormone Functions
Thyroid Thyroxine Increases rate of
metabolism
Parathyroid Parathyroid hormone Regulates calcium and
phosphate levels
Pituitary Hormone growth Regulate growth of body
Gonadotrophic hormone Stimulates the development
of male and female sex
organs
Lactogenic hormone Stimulates secretion of milk
(prolactin) after child birth
Thyrotropic hormone(TSH) - proper functioning of
thyroid gland/thyroxine
production
Adrenocorthicotropic - stimulates release of
hormone (ACTH) adrenal cortex hormone
Oxytocin regulates blood
pressure
stimulates smooth
muscles
stimulates
contraction of uterus
during childbirth
aids in flow of milk
from mammary
glands
Follicle stimulating causes maturation of
hormone(FSH) egg in females
stimulates sperm
production in males
Vasopressin (ADH) - regulates water balance by
Antiduretic hormone kidneys
Adrenal Adrenaline (epinephrine) for emergency
prepares body to
cope up with stress
Aldosterone - maintains balance of salt
and water in blood
Cortisone breaks down stored
proteins to amino
acids
aids in breakdown
of adipose tissue
regulates sugar level
in blood
prevents
inflammation
159
Sex hormones supplements sex
hormones produced
by gonads
promotes
development of
sexual
characteristics
Pancrease Insulin regulates level of
sugar in blood
enables liver to store
sugar
Glucagons regulates level of
sugar in blood
Ovaries Oestrogen causes sexual
secondary
characteristics in
females
prepares uterus for
pregnancy
Progesterone growth of mucus
lining of uterus
maintains uterus
during pregnancy
Testes Androgens(testosterone) causes secondary
sexual
characteristics in
males
Stomach cells Gastrin stimulates release of
gastric juice
Intestinal cells Secretin stimulate release of
pancreatic juice
iv) Give the differences between nervous and endocrine (hormonal) communication
Nervous Hormonal (endocrine)
Response confined to effector organs Response more widespread (various
(localized targets) targets)
Speed of response is rapid Response less rapid
Nervous impulse thro\\ugh nerves/nerve Hormones transferred through blood
cell/neurons
Duration of response is short Persist for long
Speed of transmission is rapid Speed of transmission is slower
Transmission is electrical Transmission is chemical
160
v) State the effects of over secretion and under secretion of adrenaline and thyroxine in humans
Hormone Over secretion Under secretion
Adrenaline thin toneless low blood pressure
muscles inability to withstand
high blood pressure stress
weak bones fatigue
obesity muscular weakness
early onset of sexual muscle wasting
development increased dark
pigmentation of skin
Thyroxine increased cretinism(retarded
metabolism growth and low
increased heartbeat mental development
physical restlessness lowered metabolism
mental restlessness low ventilation rate
protruding eyeballs of lungs
enlarged thyroid low body temperature
gland lowered mental
activity
coarse hair
puffy eyes
enlarged thyroid
gland
161
Stimulants
drugs that temporarily increase the action of the central nervous system
they create a feeling of alertness, wakefulness, a sense of self confidence and well being
used to decrease fatigue and mild depression
when abused they cause feelings of persecution, hallucination and addiction
include amphetamines, cocaine, caffeine, miraa and nicotine
h) i) List the special sense organs in mammals and the major function of each
- Eye for sight
- Ear for hearing and balance
- Nose for smell
- Skin for touch, temperature detection, pain detection
162
conjunctiva is thin/transparent/tough to allow light to pass through/to protect the eye
Sclerotic layer is made up of (collagen) fibers/fibrous. It maintains shape of the eyeball/protects
the eye
cornea is transparent/curved thus refracts light rays/allows light to pass through
Choroid is a layer of tissue with black pigment/dark pigment. Prevents internal reflection of light
in the eye/contains blood vessels that supply oxygen/nutrients/remove (metabolic) wastes from the
eye
retina has cones/rods for bright colour vision/low light vision
yellow spot has a high concentration of cones for accurate vision/visual acuity
Blind spot has no cones and rods. Place where optic nerve leaves/enters the eye
optic nerve has (sensory) nerve fibers for transmission of impulses to the brain (for interpretation)
Lens is biconvex/made up of elastic material/transparent. Adjust focus on far or near objects allow
light to pass through/for refraction of light rays
ciliary body is made up of muscle fibers/glandular which contract/relax to change shape
suspensory ligaments are inelastic to hold lens in position/attach it to ciliary body
iris(is the coloured part of the eye it) has radial and circular muscles which control size of pupil
pupil is the small hole at the centre of iris through which light passes into the eye
aqueous humor is a fluid through which oxygen/nutrients pass to the cornea/lens/maintains shape
of the eyeball/refracts light rays
vitreous humor is a fluid which maintains shape of eye/refracts light rays
iv) Explain how an eye viewing a near object adjusts to viewing a far object
ciliary muscles relax
suspensory ligaments become taut/tight
lens decreases curvature/becomes thinner
radial muscles relax
circular muscles contract
size of pupil decreases to reduce amount of light
v) What changes occur in the eye if it changes from observing an object at a distance to one at a
closer range?
- ciliary muscles contract
- Tension in suspensory ligaments reduces/relax/ slackens
- Lens bulges/thickens/increases curvature
- Radial muscles contract
- Circular muscles relax
- Size of pupil becomes large to allow in more light.
163
viii) State the changes which would take place in the eye if a person in a dark room had lights
switched on
circular muscles contract and radial muscles relax
pupil becomes small to allow less light into the eye
ix) Explain how the eye forms an image
the mammalian eye works like a camera
light rays enter the cornea pass through the pupil, aqueous humor, lens and vireous humor
light rays are refracted by the aqueous and humor and lenses
finally light falls on the retina to form an image
the image is real and inverted and smaller than object, back to front/reversed
Retina forms a fine image when light rays reach it.
x) Name the defects of the eye and state how they can be corrected
Short sight (Myopia)
eye cannot focus on far objects
image is formed in front of the retina because light rays converge in front of retina
the lens is too thick, curve and eyeball too long
corrected by wearing concave/biconcave/lenses
these lenses diverge light rays onto retina
164
Long sight (Hypermetropia)
eye lenses are unable to focus because they are flat, thin and weak hence unable to focus image on
the retina
they are unable to accommodate/change the focal length
near image is formed behind the retina but a distant one is correctly focused on the retina
corrected by wearing convex/biconvex/converging lenses
Presbyopia
occurs in old age hence called old sight
caused due to loss of elasticity of lenses, weakness of ciliary muscles hence lack of focus of light
rays
this causes long sight
corrected by wearing biconvex/convex/converging lenses
Squinting
eyeballs are uncoordinated/do not turn at the same time
eye muscles move in different directions
this makes accommodation and focusing difficult
corrected through surgery
165
Astigmatism
surface of cornea is uneven
leads to weak focus of light raise on retina
corrected by using cylindrical lenses/lenses with combined curvature
iv) How are the structures of the human ear suited to perform the function of hearing?
166
shape of the external ear/pinna allows collection of sound waves and channels them down the
auditory canal/auditory mateus
auditory canal is a tube that concentrates and directs sound waves to tympanic membrane/
tympanum/eardrum
Eardrum is thin and tight. It sets into vibration/vibrates/converts sound waves into vibrations
the vibrations are transmitted to the ear ossicles/malleus, incus and stapes that amplify the sound
vibrations
the vibrations are then transmitted to the fennestra ovalis/oval window
Oval window is a membrane which amplifies/transmits vibrations to the fluids (perilymph and
endolymph) then to cochlea.
The cochlea is coiled to occupy a small space and accommodate a large number of sensory cells
The sensory cells/hairs (in the cochlea) are set into vibrations/stimulated producing nerve impulses
in the auditory nerve
Impulses in the auditory nerve are transmitted to the brain for interpretation for hearing
Eustachian tube connects the inner ear to the throat. It equalizes air pressure in the middle ear with
the atmospheric air pressure (in outer ear)
Fennestra rotundus/round window dissipates/discharges/discards vibrations from inner ear to
middle ear
iii) Explain how the structure of the human ear performs the function of balancing
there are three semi-circular canals/utriculus/succulus/vestibular apparatus arranged in planes at
right angles to each other
at the end of each canal is a swelling called ampulla which contains receptors
the movement of the head causes movement of the fluid/endolymph in at least one canal
the fluid movement causes stimulation of the receptors/sensory hairs
sensory impulses are generated
the auditory nerve transmits the impulses to the brain for interpretation for the position of
body/posture/balance
iv) State what would happen if the auditory nerve was completely damaged
deafness
loss of body balance
impulse not transmitted to the brain
7. a) i) What is support?
to support is to carry part of the weight/mass of an organism
167
ii) What is locomotion?
progressive change in the position of an organism
iii) State the importance of support systems in living organisms
they provide a framework for the body of organisms and help to determine their shape
provide land animals with means for support to their weights against gravity
organs are attached to the skeleton for support and stability to avoid entanglement and crushing
each other
they protect very important and delicate organs whether inside or outside the body e.g. eyes, heart
in large plants the rigid trunks of trees support the greater mass of leaves and fruits
iv) State the importance of locomotion in animals
in search of food
search for mates
escaping predators
iv) Name the tissues in plants that are strengthened with lignin
sclerenchyma
xylem vessels/tracheids/xylem
vi) State the ways by which plants compensate for lack of ability to move from one place to another
ability to pollinate
response to nastic and tropic movement
ability to exploit localized nutrients
ability to disperse seed or fruit propagation
c) i) Explain the ways in which erect posture is maintained in a weak herbaceous stem
- This is the function of turgidity and presence of collencyma
Cells take in water and become turgid
168
ii) Explain how support in plants is achieved
Turgor pressure due to absorption of water keeps cells firm hence hold herbaceous plants upright
collenchyma and clerenchyma tissues are closely packed in stem and roots to provide support
inelastic cuticle on epidermis is covered by a waxy layer hence keeping shape of plant and setting
inward pressure against turgid cells and this causes a force to hold plant upright
xylem vessels and tracheids are lignified to provide support to stems, roots and leaves
climbing plants obtain mechanical support from other plants and objects
they have climbing structures like tendrils which hold on to other objects
ii) Name the different types of skeletons in animals, giving an example of an animal for each type of
skeleton named
exoskeleton e.g. arthropoda (crab, insect)
endoskeleton e.g. chordata (cat, fish)
g) i) Name the main parts of the vertebral column giving the types of bones found in each part
Axial skeleton
forms the main axis of the body
formed by the skull, sternum, ribs and vertebrae
Appendicular skeleton
composed of limbs and girdles
the forelimbs are connected to the trunk by the pectoral girdles (shoulder bones)
hind limbs are connected to the pelvic girdle (hips)
bones are scapular, clavicle, humerus, ulna, femur, tibia, fibula, metacarpals, carpals, tarsals,
metatarsals, phalanges, ilium, ischium and pubis
170
iv) State the general characteristics of vertebrae
have solid structure called centrum to support weight of body
has transverse process lateral to centrum for muscle attachment
neural spine is dorsal to centrum and provides surface area for muscle attachment
neural canal a passage for spinal cord and offers protection to it
has facets for articulation with other vertebrae
neural arch encloses neural canal
171
172
v) Name the bones of the vertebral column
- Cervical vertebra
- Thoracic vertebra
- Lumbar vertebra
- Sacral vertebra
- Caudal vertebra
173
vi) Describe how the various vertebrae are adapted to their functions
Bone Structure Function
Skull cranium and jaw attachment of
bones jaws
made of several protect brain
bones joined and other
together delicate parts
large box called
cranium and
smaller paired
boxes for eyes,
ears, nose, jaws
has large hole
called foramen
magnum for the
passage of spinal
cord
Cervical region ring shaped protect spinal
Atlas (first cervical) no Centrum cord
broad, flat attachment of
transverse muscles
processes allow nodding
vertebraterial of head
canal for passage
of vertebral
artery
facet for
articulation of
condyles of skull
Axis (second cervical) adontoid peg allows head to
projects from rotate
Centrum protects spinal
large flattened cord
neural spine provides
vertebrasterial surface for
canal muscle
small transverse attachment
process
174
Thoracid long backward forms rib cage
pointing neural articulation
spine with one end
transverse of a rib
process that protects,
points sideways spinal cord
facets for muscle
articulation of attachment
ribs
notch for spinal
nerves to pass
through
Lumbar short neural spine protect organs
long transverse of abdomen
process pointing support upper
towards abdomen part of body
large Centrum protect spinal
extra processes cord
e.g. muscle
prezygapophysis, attachment
hypapophysis,
anapophysis,
metapophysis
Sacral fused bones to protects
form sacrum alimentary
well developed canal
transverse attachment of
process of first hip girdles
vertebra protect spinal
vertebraterial cord
canals muscle
short neural spine attachment
175
vii) Describe the bones that form the appendicular skeleton
Bone Structure Function
Pectoral girdle scapular (shoulder bone) Broad i.e. Flattened Support
blade Muscle attachment
glenoid cavity to Articulates with
articulate with humerus
humerus
metacromion/acromio
n for muscle
attachment
hard to provide
support
socket with
cartilage/smooth
surface to reduce
friction
Humerus long shaft for muscle movement
attachment muscle
round head to attachment
articulate with glenoid
cavity
trochlea for
articulation with ulna
olecranon fosa to
prevent arm bending
the other way
Ulna and radius ulna longer and on movement
side of little finger muscle
has sigmoid notch and attachment
olecranon process to s
form hinge joint with
humerus
radius is smaller and
lies along thumb side
and does not join ulna
allows articulation
with wrist bones
176
Pelvic girdle(hip bone) composed of three movement
fused bones (ilium, muscle
ischium, pubis) attachment
upper end fused to support
sacrum absorbs
lower end has pressure
acetabalum for exerted by
articulation with femur ground
has abturator foramen when
for passage of nerves animal
and blood vessels moves
177
8. a) What is a joint?
the point where bones meet
v) Hinge joint
convex surface of one bone fits into the concave surface of another bone
this allows movement in only one plane/direction 180o
e.g. elbow joint and knee joint
178
ii) State the functions of synovial fluid
absorbs shock
reduces friction/gives lubrication
nourishment
distributes pressure
9. Muscles
e) i) What is a muscle?
fleshy part of body
composed of long cells enclosed in a sheath
specialized cells capable of contracting
179
g) Explain how muscles cause movement of the human arm
the muscles which bring about these movements are called biceps and triceps
biceps are attached to scapula and radius for bending
triceps are attached to scapula, humerus and ulna for stretching
when the biceps contracts, it pulls the radius (forearm) and the hand bends
the triceps relaxes at the same time
when the triceps contracts and biceps relaxes(extends) the arm is stretched
biceps flexes the arm (flexor) and triceps extend(extensor muscle) the arm
h) i) State the structural differences between skeletal muscles e.g. biceps and smooth muscles
e.g. gut muscle
Skeletal (biceps) Smooth (gut) muscle
multinucleated uninucleated
striated/stripped unstriated
long muscle fibers short muscle fibers
block/cylindrical spindle shaped
ii) Name the cartilage found between the bones of the vertebral column
intervertebral disc
iv) What are the functions of the cartilage named in (d) ii) above
acts as a cushion/absorbs shock
reduces friction
flexibility of vertebral column
END
180