Biology Knowledge Organisers

Unit 1: Cells Revision technique: Read,

Unit 2: Organisation cover, write, check,
Unit 3: Infectious Diseases repeat!
Unit 4: Bioenergetics Read your notes.
(Photosynthesis and Cover your notes up and
Respiration) write down as much as
Unit 5: Homeostasis you can remember.
Unit 6: Genetics, Variation Check how you did. Did
and Inheritance you miss any information
out?
Unit 7: Ecology
Repeat the whole process.

TIPS: Only try and do a few of the squares at

a time.
Biology Exam 1: Units 1-4
Don’t keep doing the ones you know well.
Biology Exam 2: Unit 4-7 Keep repeating the ones you struggle to
remember.
AQA BIOLOGY UNIT 1: CELLS
Cells Eukaryotic cells Magnification Specialised Cells – Cells that have differentiated

Fraction of a metre Unit Symbol

• Long and thin.
Nucleus • Have a myelin sheath to prevent
Controls cell loss of impulse.
One thousandth = 0.001 = 1/1000 = 10-3 millimetre mm Neurone • Form connections with other
Ribosomes neurones.
Protein • Can carry electrical impulses in
One millionth = 0.000001 = 1/1000 000 = 10-6 micrometre μm one direction.
synthesis
• Contain digestive enzymes for
One thousand millionth = 0.000 000 001 = nanometre
Cell Membrane 1/1000 000 000 = 10-9
nm breaking down the outer layer of
Controls what goes in Sperm an egg cell.
and out the cell To calculate actual size: • Many mitochondria.
• Have long tail.
1. Measure the organelle with a ruler.
Mitochondria
2. Multiply this by 1000 to get a value in micrometres • Large surface area.
Respiration 3. Divide this by the magnification Red • Small diameter.
Blood • No nucleus.
Chloroplast e.g. The diagram below is a drawing of an organelle from a • Contain haemoglobin.
Photosynthesis Prokaryotic cells – no membrane bound organelles ciliated cell as seen with an electron microscope.
(loose DNA)
Cytoplasm • Found close to xylem
A B
Root
Where chemical Calculate the actual length of the organelle as shown • Thin membrane.
by the line AB in the diagram. Express your answer Hair • Large surface area.
reactions occur to the nearest micrometre (µm).
1. Measure it in mm = 40mm
2. Multiply by 1000 = 40000µm • Outer segment filled with visual
× 20 000 3. Divide by magnification 40000 / 20000 = 2µm pigment that changes chemically in
coloured light.
Cone • Lots of mitochondria so that you
Magnification is the number of times larger an image is compared with the real Cells constantly see in colour.
size of the object.
• Specialised synapses connecting to
the optic nerve.
Resolution is the ability to distinguish between 2 separate points.

Chromosomes Mitosis and Meiosis – cell division Diffusion

Mitosis (in humans) Movement of particles from a high concentration to a
Humans have 23 pairs of chromosomes (46 in total) in all
• Occurs all over the low concentration (down a concentration gradient)
adult cells.
body
• Makes new cells with To increase rate of diffusion:
Chromosomes 23 = sex chromosomes (XY = male XX = female) 23 pairs of
chromosomes • Increase temperature
Karyotype – visual appearance of our chromosomes. • Cells divide once • Increase surface area
• Makes new body • Increase concentration gradient
What are the cells.
• Shorten distance
differences?
Interphase: DNA copies Large organisms have a small surface area:volume so require
1. 47 instead of specialised exchange surfaces with large surface area so
46 Different stages of mitosis: Meiosis (in humans) diffusion is fast enough.
2. Extra Prophase – chromosomes condense
• Occurs in testes and ovaries
chromosome 21 Metaphase – chromosomes line up in the • Makes cells with 23 Small Intestine: Villi increase surface area
middle chromosomes Blood flow maintains conc. Gradient
(called Trisomy- • Cells divide twice
21 (Down’s Anaphase – chromosomes pulled apart
• Makes gametes (sperm and Thin wall 1 cell thick
by spindle fibres
Syndrome)) egg)
3. Normally 21 Telophase – 2 new nuclei form Lungs:
should be 2 Advantages: Alveoli increase
chromosomes Stem Cells - These are • Treat blindness surface area
undifferentiated cells • Organ transplants
• Treat paralysis
Bacteria multiply by binary fission. • Embryonic – can make any type of cell Blood flow and
• Tissue-specific – can only make cells Disadvantages: thin walls like
from specific parts of the body • Ethical issues with embryos
Growth is exponential i.e. 1  2  4  8  16  32  64… • Religious issues
the villi
Osmosis Active Transport REQUIRED PRACTICAL: Growing Bacteria
Water travels from a dilute solution (high water
This is the opposite of diffusion.
concentration) to a more concentrated solution
(low water concentration).
• Flame the loop – sterilises it
Substances move from an area of low concentration to high
The water moves across a partially permeable
membrane. concentration, against the concentration gradient. • Lift lid slightly – prevent airborne bacteria
getting into it
Isotonic means the amount of dissolved solutes is the same on the outside of the It requires ATP (energy) – this means it need mitochondria.
cell as the inside, so there is no difference in concentration of water. The ATP is used to change the shape of protein channels in
the cell membrane. • Seal with 2 bits of tape – allows air to get in
Hypotonic means there are more solutes inside the cell than outside, therefore High Concentration
inside the cell has a lower concentration of water. but keeps lid on for safety
Hypertonic means there are more solutes on the outside of the cell than on the
inside. So there is a lower concentration of water on the outside of the cell. This happens at the • Incubate at 25oC – prevents pathogens
• Turgid – When a cell fills with water (plant cell wall protects cell from Low
end of small intestine
where there are less
growing
bursting) Concentration nutrients than in the
• Flaccid – When a cell loses water blood but we don’t
want to waste them.
The solution is isotonic Root hair cells have Antibiotics on bacteria
where the line crosses the more minerals than
on the jelly.
the soil but still
x-axis i.e. 0.3 mol/dm3. needs them. Active
transport is used for
Potato gains mass in a uptake of these Big space around disk =
minerals.
hypotonic solution but loses most bacteria killed
mass in a hypertonic Root hair cells
solution. therefore have lots
of mitochondria.

AQA BIOLOGY UNIT 2: ORGANISATION

Tissues and Organs Enzymes – biological catalyst made from protein in ribosomes Digestive Enzymes

Tissues: cells working together • Enzymes have an active site (shape) Large sugars
• Active site fits a substrate and breaks it down Carbohydrase
(starch) Salivary glands, pH7-8
• Ribosomes – make enzymes and hormones (e.g. amylase)
 pancreas,
Glandular Simple sugars Small intestine 37oC
• Vesicles to store enzymes and hormones

↔ ↔ (glucose)
Animal

• Long, thin cells contracts

Muscular Stomach
• Lots of mitochondria for energy Protein Stomach
Protease = pH1-2
(e.g. pepsin)
 Pancreas
• Goblet cells make mucus
Epithelial Amino acids Small intestine
• Cells have cilia enzyme enzyme 37oC
enzyme-reactant
+ ↔ complex ↔ +
• Lots of chloroplasts Lipase Fats
Mesophyll products Stomach pH 7-8
• Photosynthesis reactant (e.g. 
Pancreas
pancreatic Fatty acids
lipase) Small intestine 37oC
Epidermal • Thin and translucent to allow light through and glycerol
Denature: Active site changes
Plant

No longer recognises substrate Commercial Use – speed up reactions, increase yields but need to
Xylem • Transports water monitor temperature and pH.
• Temperature – too cold too slow
Phloem • Transports sugars Industry Function of Enzymes
- optimum = 37oC
- too hot = denatures change glucose into fructose, which is sweeter so less is
Organs: tissues working together Diet foods
needed and is used in 'slimming' foods (isomerase).

• pH – enzymes only work at specific pH Baby food start off digestion of food (proteases and lipases)
Stomach: Glandular: Makes enzymes and acid
- stomach enzymes need pH 1-2 (acid)
Epithelial: mucus protects lining Biological
- intestinal enzymes need pH 7-8 (bile) detergent
break down stains (proteases and lipases).
Muscular: contracts, churns food
REQUIRED PRACTICAL: Food Tests The Heart Double circulation CHD and Other Heart Defects
Type of
Food
Name of Test Positive Result Negative Result Right = lungs for gas Procedure How they work Advantages Disadvantages

exchange
Starch Iodine Blue/Black Brown Drugs that lower blood Cheap
Can cause side
Statins cholesterol levels
effects
Glucose
Benedict’s (must Green  Yellow 
Blue
Left = Rest of body preventing plaque forming Preventative
be heated) Brick red

Protein Biuret Lilac Blue Needed because humans Insert a balloon and wire
mesh to artery. Inflate Invasive
Anticoagulant drugs
are needed which
are more active and Stents
balloon and leave wire in Minor surgery prevents blood
Lipids Emulsion Cloudy precipitate Clear place clotting
lungs are very delicate
Health and Risk Factors so blood can’t be at a
Piece of vein is grafted Expensive
high pressure but must Bypass
from leg to bypass the
Permanent
Scars
• Communicable disease: Any disease transmitted from one person or animal to Surgery solution
another, also called contagious disease. be to go round the rest blocked coronary artery Major surgery

• Non Communicable disease: Medical condition or disease that is non- of the body.
infectious or non-transmissible. Mechanical
Synthetic valve used to Need anticoagulant
Valve Last longer
Risk Factors: Replacement
replace faulty one. drugs
• Cardiovascular disease: diet/obesity, age, genetics and exercise. What could happen if our coronary arteries narrow?
• Lung disease: smoking and cleanliness of the environment.
Plaque (fatty deposit) builds on the walls of the blood vessel.
• Liver disease: alcohol, diet/obesity, genetics, drugs and viral infection Biological
Animal valve used to No drugs
• Type 2 diabetes: genetics, diet/obesity and exercise Valve Only lasts 15 years
The blood vessel can become blocked or in some cases the blood Replacement
replace faulty one needed
Cancer pressure increases causing some plaque to break away.
When our cells divide, mutations can occur in Surgical procedure
the DNA which lead to abnormal cells. The plaque blocks narrower vessels causing blood clots and a lack of Device used to trigger Keeps heart
Can stop working
Malignant cancer can spread to other parts of oxygen to tissue and organs. Pacemaker the heart to beat in its beating
near machinery and
normal rhythm properly
electronic devices
the body. We call this metastasis.
• Lack of oxygen
A cancer cell can detach from the tumour and
be carried by the blood to other parts of the • Lack of glucose Major surgery
body. The cancer cell can become stuck in a • For respiration Heart Donor heart used to Permanent Rejection
Transplant replace patient’s heart solution Immunosuppressant
capillary by an organ and then begin growing • No energy for contraction of cardiac muscle drugs needed
until it has invaded that organ too. • Heart stops (cardiac arrest)

Blood Vessels Plants and Photosynthesis Transpiration and Translocation

• Uptake of water and minerals Phloem
Blood Type of
Diagram Pressure Special Features • Large surface area due to root hair cells
Vessel Blood
Roots • Phloem vessels are made of long, thin-walled cells that form tubes.
• Protein channels for active transport
• Meristems – plant stem cells • Sugars and amino acids dissolved in sap are transported in the
phloem by a process called translocation.
Thick muscular elastic walls • The ends of the phloem tubes are called sieve plates and they have
Artery Oxy High • Hold leaves in position
Smaller lumen • Waxy epidermis to prevent water loss small holes in them to allow transport in both directions.
Stem • Phloem cells have no nuclei. They have companion cells next to them
• Xylem – transports water
• Phloem – transports sugars to control them which are filled with mitochondria.
Xylem
1 cell thick walls for fast • Broad, flat to increase surface area
Capillary Both Med
diffusion • Contain 4 types of tissue to carry out photosynthesis (see • Xylem tubes are made from long cells with thick, reinforced walls
below) made from lignin.
Leaves
• Guard cells close stomata at night to prevent water loss by • The vessel has a large hollow lumen for water and minerals to flow
transpiration through in one direction.
Large lumen • Waxy epidermis to prevent water loss • The cell walls are waterproof which makes the cells die which
Vein Deoxy Low results in wood in trees!
Valves to prevent back flow How is the leaf adapted for
of blood
efficient photosynthesis? Transpiration Stream
• Sun hits palisade cells at top 1. Higher concentration of water in soil than in
Blood roots
• Palisade – lots of chloroplasts
2. Water moves into roots by osmosis
• Red Blood Cells – haemoglobin carries oxygen, biconcave • Spongy mesophyll allows gas 3. Higher concentration of water in roots than
disk increases surface area, no nucleus to fit in more movement in leaves
haemoglobin. 4. Water moves up the xylem by osmosis to the
• Xylem brings water leaves
• White blood cells – fight pathogens • Phloem maintains concentration 5. Water lost through stomata and used for
gradient by removing glucose photosynthesis maintains concentration
• Plasma – transports dissolved substances gradient.
• Guard cells open to allow carbon 6. This causes more water to be drawn in by the
• Platelets – bits of cytoplasm used to form blood clots dioxide to diffuse into the leaf. roots. This is called the transpiration stream
AQA BIOLOGY UNIT 3: INFECTIOUS DISEASES
Pathogens – microorganisms that cause disease White Blood Cells
Name of Type of Transmission/how
Symptoms Treatments • Phagocytes – Engulf (phagocytosis, non-specific)
disease pathogen to prevent spread
Bacteria Virus Fungi • Lymphocytes - Make antibodies (specific proteins that bind to antigens)
• Lymphocytes - Make antitoxins (counteract toxins made by bacteria)
Uncooked poultry,
Size 1000nm 20-40nm 2-10μm dirty work surfaces Vaccines
Nausea,
Salmonella Bacteria Antibiotics
diarrhoea
Invade host They release Cook food Contain dead or inactive pathogens
thoroughly
Method of Grow then cells and tell spores which
reproduction divide in two nucleus to make travel through 1. White blood cells make antibodies
copies the air Unprotected sex Discharge, 2. Antibodies remove dead/inactive pathogen
Gonorrhoea Bacteria painful Antibiotics 3. If exposed to real pathogen, antibodies are made quickly before they can
Produce toxins Wear condoms genitals multiply.
How they
that travel Make cells Produce toxic MMR Vaccine = Measles, Mumps and Rubella
make you
around the burst open chemicals
feel ill Mosquito bites
body
Tired, Drug Trials
Malaria Protist Mosquito nets, headache, N/A
drain pools, vomiting Stage 1: Tested on animals, cells and tissue
Malaria chloroquine Check for toxicity
Stage 2: Tested on human volunteers
Caused by a protist called Plasmodium. Vector = mosquito Check dosage and side effects
Blood contact,
exchange of bodily
Symptoms Stage 3: Tested on patients to see if it is effective
1. Mosquito bite injects sporozoites into blood. from various
sexual fluids,
2. Sporozoites invade liver cells. HIV Virus sharing needles
diseases
N/A Double blind - no one knows who gets the real drug
3. Sporozoites turn into merozoites and burst open liver cells. caused by
developing - no bias
4. Merozoites invade red blood cells, digest haemoglobin, replicate and burst Condoms, don’t do
AIDs Placebo – fake drug (looks same, taken same way) It is a control.
open red blood cells. heroin
5. Merozoites taken back up into mosquito.
Thalidomide
Prevention: Droplet infection, Painkillers • Tested as sleeping pill
• Eggs laid in stagnant water – drain pools, spray them with insecticide, spray sneezes Red rash on to reduce
Measles Virus
skin the • Not tested on pregnant women
with oil to prevent oxygen getting to the eggs, MMR vaccine symptoms • Given to pregnant women for morning sickness
• Mosquito nets and repellant spray. • Babies have limb deformities
• Chloroquine • Only given now for leprosy

Medicines - A drug is a chemical that alters how the body works. Monoclonal Antibodies Plant Diseases
They alter the normal chemical reactions in the body. TRIPLE TRIPLE
Monoclonal antibodies are identical copies of Some plant diseases are caused by bacteria,
Antibiotics - kill bacteria or prevent them antibodies that have been made in
ONLY fungi and also by vectors e.g. aphids. ONLY
from multiplying.
laboratories.
THEY DON”T KILL VIRUSES
Name of Type of Prevention/
because viruses live inside cells. • Pregnancy test kits to
disease pathogen
How it is spread Symptoms
Treatment
identify the small levels of
Painkillers – relieve the symptoms only a hormone called hCG,
which is present in the
Antivirals – target specific viruses and slow down replication. urine of pregnant women. Direct contact Mosaic pattern
Field
Tobacco with diseased damaging cells
Virus hygiene and
Mosaic Virus plant material preventing
• Locate blood clots as they and by insects photosynthesis
pest control
Antibiotic Resistance bind to clots.
1. Mutation occurs when bacteria multiply
• Diagnose and then treat Remove and
2. Mutation makes bacteria resistant to antibiotic Spores carried Purple spots on
burn
3. Antibiotic kills all the others some cancers. They can Rose Black
Fungi
by wind and leaves, dead
affected
bind to the cancerous cells Spot spread by rain leaves, poor
4. No competition for food or space leaves,
from leaf to leaf flowers
5. New colony of resistant bacteria grows and help the person’s fungicides
immune system attack
e.g. MRSA them. Aphids – penetrate phloem and take products of photosynthesis.
Causes: Incorrect use of antibiotics Advantages: Monoclonal antibodies only bind to the specific cancer Also act as vectors transferring pathogens to the plants.
Not completing the full course of antibiotics
cells that need treatment. Healthy cells are not affected at all. In
Over-sterile environments e.g. hospitals
A contrast conventional drug treatment is carried all around the body in Mineral Deficiencies – Soil lacking nitrates = less protein so less
10.1
the blood and can have a devastating effect on healthy cells as well as growth.
To calculate clear zone: ∏r2 mm cancer cells. - Soil lacking magnesium = chlorosis = less
D B
chlorophyll so less photosynthesis – yellow
Disadvantages: Monoclonal antibodies create more side effects, the leaves
Resistant: 6mm or less 18.5
mm
3.4
mm most common being an allergic reaction to the drug. An allergic Detecting Diseases
Intermediate: 7-11 mm C reaction can include these symptoms: chills, fever, an itchy rash, • Fast detection – discoloration, visible pests, stunted growth.
Susceptible: 12 mm or more 7.7 feeling sick, breathlessness, wheezing, headaches, flushes and • Compare growth with normal plants or data online
mm
faintness, changes in blood pressure. • DNA analysis to identify pathogens (monoclonal antibodies)
AQA BIOLOGY UNIT 4: BIOENERGETICS
Photosynthesis Limiting factors REQUIRED PRACTICAL: Photosynthesis
Carbon + Water  Glucose + Oxygen • Light
Dioxide • Carbon dioxide concentration
6CO2 + 6H2O  C6H12O6 + 6O2 • Temperature

• Gases diffuse
through stomata

• Palisade cells have

lots of
chloroplasts

• Xylem brings Something else limits the

Controlled by enzymes that
water rate (temperature, CO2,
are too slow when cold and
amount of chlorophyll)
• Spongy to allow denature when too hot In the experiment above:
gases to move Greenhouses
through leaf. 1. Pondweed is in water with sodium carbonate
+ Control the conditions (heat, CO2, water, light, pests, weeds) solution (to provide CO2 for photosynthesis)
Uses of glucose: + Grow plants all year round
+ Grow plants not native to certain countries
2. Move light bulb different distances and count
• Respiration – energy – growth + Increased crop yields
the bubbles of oxygen that are produced per
• Starch – storage - Costs to maintain conditions
minute.
• Protein – glucose + nutrients from the soil - Conditions need to be monitored
• Fats – stored in seeds The closer the light, the more oxygen is made
Hydroponics: Plants grown in mineral solution rather than water –
• Cellulose – cell walls control nutrients, no fungal infections from soil. because the rate of photosynthesis increases.
Starch Testing a Variegated Leaf Respiration – energy RELEASE not made (exothermic) Metabolic Rate: The speed of chemical reactions in the
body.
We test for the presence of starch in leaves in order to Aerobic: Glucose + Oxygen  Carbon Dioxide + Water
determine that photosynthesis has occurred. Glucose is rapidly C6H12O6 + 6O2  6CO2 + 6H2O • Older = slower
converted into starch for storage in the chloroplast and cytoplasm. • Female = slower
• Occurs in mitochondria Some microorganisms
De-starching is the process by which the starch reserves in a plant • High fat to muscle ratio = slower
• Needs oxygen (e.g. yeast) respire
are depleted by depriving the plant of either light or carbon anaerobically • Could be inherited
dioxide. We need to remove all traces of starch in leaves so that • Releases a lot of energy (ATP) producing ethanol and
we can provide evidence that photosynthesis takes place during the CO2. This is called
Anaerobic: Glucose  Lactic acid fermentation and is Metabolic reactions:
experiment. C6H12O6  2C3H6O3 used to make bread
and alcohol.
• Respiration – catabolic (big  smaller molecules)
• Occurs in mitochondria • Photosynthesis – anabolic (small  bigger molecules)
• No oxygen • Break down of proteins to urea in liver – catabolic
• Leads to oxygen debt (which is why you breathe • Enzymes breaking down food – catabolic
heavily after sport to pay it back) • Combining glucose with nitrate ions to form amino acids
and then protein – anabolic
• Very little energy is released.
• Boiling ethanol breaks down cellulose and removes chlorophyll. Anabolic reactions require energy from cellular respiration.
• Iodine solution turns blue/black where starch is present i.e. Exercise effect on HR and BR
where photosynthesis has taken place.
Heart Rate increases – more oxygen to muscle Carbohydrates Energy

Measuring HR and BR - more glucose to muscle Protein Cell repair, growth and replacement

HR – heart rate monitor - more CO2 and water to lungs Fat Energy and insulation
BR – spirometer Breathing Rate increases – more oxygen into blood Fibre Digestion
- more CO2 and water out
Tidal volume – normal Minerals Calcium – Bones, Iron – Blood
volume breathed in and out. of the blood
Vitamins Immune system
Stored glycogen in muscle turned into glucose.
AQA BIOLOGY UNIT 5: HOMEOSTASIS
Reflexes – Prevent harm, avoid conscious parts of the brain (faster) Homeostasis - the maintenance of a constant internal
environment. The pituitary gland is
1. Stimulus e.g. stand on nail often referred to as the
2. Receptor pain The main things we need to control in the body are:
master gland because it
3. Sensory neurone electrical impulse • Temperature (thermoregulatory centre in the brain)
stimulates other glands in
4. Relay neurone (CNS) CNS • Blood glucose (pancreas)
5. Motor neurone electrical impulse the body e.g. TSH
• Water (kidneys)
6. Effector muscles stimulates the thyroid,
• Mineral ions/salts (kidneys)
FSH and LH stimulate the
Synapse – Gap between two neurones • Urea (waste) (liver and kidneys)
ovaries.
1. Electrical impulse Endocrine System – the glands of the body – secrete
arrives at synapse hormones
2. Neurotransmitter
diffuses across
synapse
3. Bind to receptors on
2nd neurone
4. Electrical impulse
passed on
REQUIRED PRACTICAL
Independent Variable:
• Number of practices
Dependent Variable:
• Reaction time (distance where ruler is
caught converted into a time)
Control Variables:
• Ruler dropped from same height
• Use weaker hand each time
• Same mass of ruler
• Same thickness of ruler

Glucose Regulation – Prevent nerve and brain damage Menstrual Cycle – 28 days (ovulation day 14) Negative Feedback (HT) – Prevent nerve and brain damage
Thyroxine – Metabolism, growth, brain development in children
• From pituitary gland
FSH
• Egg matures in ovary

• From ovaries
• Stops FSH
Oestrogen
• Thickens uterus lining
• Stimulates LH

• From pituitary gland

LH
• Egg released (ovulation day 14)

Progesterone • Maintains thick uterus lining

Contraception
• Hormonal methods (pill, patch, implant, injection) contain
oestrogen and/or progesterone to prevent FSH release so no
egg matures.
Adrenaline – This is positive feedback.
• Barrier methods (condoms, diaphragm, cap) can also help prevent
spread of STDs.
• Intrauterine devices (coils) prevent implantation of embryo.

Type 1 Diabetes Type 2 Diabetes IVF (HT ONLY)

IVF Downsides
• Born with it • Brought on by bad diet/obesity 1. Give fertility drugs (FSH and LH)
Expensive, poor success
• Don’t make insulin • Body desensitized to insulin 2. Remove mature eggs from ovaries
rate, multiple
Treatment Treatment 3. Mix with sperm in petri dish
pregnancies (low birth-
• Insulin injected daily • Careful diet 4. Incubate until it is an embryo
weight babies)
• Pancreas transplant • Exercise 5. Insert into woman’s uterus
AQA BIOLOGY UNIT 5: HOMEOSTASIS TRIPLE ONLY

Brain Thermoregulation – receptors in thermoregulatory centre in the

hypothalamus along with temperature receptors in the skin detect small changes
in body temperature.

How can we find out how the brain works?

• Study people with brain damage
• Electrically stimulate different parts of
the brain
• MRI scans
• Problems with the brain
Eyes
Ciliary Muscle Sclera Myopia - you can see close objects clearly but distant objects look blurred.
• short-sighted.
• The light is focussed in front of the retina - lens is too curved or the eyeball
Iris
Retina
is too long.
• Treatment- concave lens in front of the eye to diverge the light rays before
they hit the cornea.
Hyperopia – people can see distant objects
Waste Products
Pupil
Blind Spot but close up objects appear blurry.
• Long sighted.
• The lens is too flat and thin or because • Carbon Dioxide – produced during respiration, removed along
Cornea the eyeball is too short - light rays are concentration gradient by lungs (causes uncontrollable release of
not refracted enough so they focus water when we breathe out)
Lens beyond the retina.
• Urea – deamination in liver
Optic Nerve • Treatment - convex lens is used to
Suspensory diverge the light rays before they hit Excess
Ligament Ammonia Urea
the cornea. Amino Acids

Kidneys Kidney Failure Plant Hormones

Glucose, mineral ions, urea and Infections, accidents or inheritance can lead to kidney failure. Toxins
water move out of the blood
Auxin – builds up to
would build up, pH levels would change, cells would be damaged,
along a concentration cause growth in shoots
enzymes would denature.
gradient. The larger cells and (opposite effect in
proteins are too big to fit Treatment: roots)
through the cell membranes.
• Transplant - Tissue match to ensure antigens are similar
All the glucose is reabsorbed
Phototropism – growth to
- Immunosuppressant drugs are given for the rest of
but mineral ions and water are your life to decrease the activity of the immune light (shoots)
selectively reabsorbed system. Geotropism /
depending on the needs of the - Transplanted organs need replacing on average
body. Geotropism – growth to
every 9 years.
gravity (roots)
Water balance is controlled by a negative feedback system monitored • Dialysis
closely by the pituitary gland in the brain
Why do plant shoots grow towards the Sun?
1. Auxin builds up on shaded side.
2. Shaded side grows faster
3. Plant grows in direction of sunlight
Auxin is used as a rooting powder when taking cuttings of plants.
Also given to weeds to disrupt their growth.
Other plant hormones include:
Gibberellins
• Brewing industry to speed up seed germination
The fluid in the dialysis machine on the other side of the partially
• Promote all year round flowering
permeable membrane has no urea, a normal glucose concentration
• Increase fruit size
and a normal ion concentration.
Ethene
Downsides: 8hrs a few times per week, controlled diet, tired,
Control fruit ripening for easier transport and longer lasting fruit.
unwell, expensive, can cause fistulas.
AQA BIOLOGY UNIT 6: GENETICS, VARIATION AND INHERITANCE
Variation DNA – Instructions to make an organism. Genetic Crosses
Gene – a section of
• Genetic – inherited e.g. eye colour, hair colour • Double helix polymer e.g. A heterozygous brown eyed dog
mates with a homozygous blue eyed dog. DNA that codes
• Environmental – scars, tattoos, piercings • Sugar phosphate backbone
Brown eyes is dominant. for 1
• Nucleotides made up of 4 bases
• Both – skin colour (tan), hair style (naturally curly that pair up A-T and G-C. characteristic
but straightened) • Every 3 base pairs is the 1. Write genotype of parents
instructions given to a ribosome to
Allele – different
Chromosome – long strands of DNA (23 pairs in make an amino acid. These are Bb x bb forms of a gene
normal cells, 23 in sex cells (gametes)) combined to make proteins.
2. Draw punnet square, write parents on Genotype –
DNA – double helix, all info to make an organism Sections of coding parts of DNA are top and side and fill in the boxes Symbols used to
called genes. Non-coding sections of show genes for 1
Sexual Reproduction Asexual Reproduction DNA can turn on and off different characteristic e.g.
b b
• Fertilisation • No fertilisation genes to make different proteins.
Bb
• Gametes • No gametes Mutation -= change (mistake) in DNA
• Genetic variation in Mutations in coding = change to characteristic Phenotype –
• Identical clones are made
offspring • E.g. runners in plants
Mutations in non-coding = bigger changes to the
organism B Bb Bb Description of
genes e.g. Brown
eyes
Gender Determination
XX = female Genome– All genes of an organism b bb bb Homozygous – Both
XY = male Human Genome Project - map out all 21000 genes genes are the same
During meiosis, 1 sex chromosome goes i.e. BB or bb
3. Write out the possible phenotypes
into one gamete, and the other goes into Advantages of HGP Issues and Concerns with HGP of the offspring Heterozygous –
a second gamete.
50% chance heterozygous brown eyed Both genes are
The punnet square shows there is a • Cancer diagnosis • Genetic discrimination
Forensics Re-engineer human species 50% chance homozygous blue eyed different i.e. Bb
50% chance of having a boy or a girl • •
• Evidence for evolution • Very expenisive or a 1:1 chance of brown : blue
every time.

Genetic Diseases Genetic Engineering – adding wanted characteristics Natural Selection

to organisms.
• Polydactyly – dominant allele – extra finger or toe 1. Variation occurs naturally within a species due to
• Cystic Fibrosis – recessive allele – excess mucus e.g. Making Insulin mutations
2. Some organisms have adaptations increasing their
1. Remove wanted insulin gene using enzymes chances of survival
2. Take a plasmid from a bacteria (vector) 3. These organisms are more likely to reproduce
3. Open plasmid and insert insulin gene with DNA 4. The genes responsible for the adaptation are passed on
ligase to their offspring.
4. Put plasmid back in bacteria Reasons why people didn’t believe Darwin at first:
5. Incubate to allow bacteria to grow and make • Against religious beliefs
insulin. • They didn’t know about genes or mutations at the time
so Darwin couldn’t explain why some organisms had more
GM Crops useful characteristics
+ Resistant to insects, viruses, fungi • Not enough evidence
+ Grow bigger, taste better, more nutritious Selective Breeding
+ Crops can be grown all over the World
Humans breed animals/plants to gain desirable
+ Increased crop yield characteristics in offspring (takes many generations).
Rob and Jane must be Ff (where f means has CF) e.g. disease resistance, increased milk production,
- Worries over long term effects
behaviour, scented flowers etc.
- Reduced biodiversity
Ff x Ff F f 25% chance of CF - Could develop allergies to the food Downsides – Reduces variation limiting success of survival if
conditions change, new diseases might wipe out every
F - Herbicide resistant gene could spread to weeds
FF Ff member of the same species, inbreeding in animals leads to
making superweeds! defects.
f Ff ff
AQA BIOLOGY UNIT 6: GENETICS, VARIATION AND INHERITANCE
Fossils Extinction - Living things become extinct because: History of Genetics TRIPLE ONLY
• Habitat changes – not adapted to survive
These can be made from: • New predator – not adapted to get away or hide
• Mendel studied pea plants and discovered that characteristics
• Disease – lack of immunity
• Bones and teeth are controlled by 2 ‘units’ that can be dominant or recessive.
• New, more successful competitor – better adapted species will
• Minerals that have replaced bone and tissue get food, space, water etc. • In the late 19th century behaviour of chromosomes during cell
• Organisms trapped in amber or ice Classification
division was observed.
• Burrows, tracks, where organisms have laid • In the early 20th century it was observed that chromosomes and
Mendel’s factors behaved in similar ways, leading to the idea
Carl Linnaeus Carl Woese
that the factors (genes) were located on chromosomes.
Softer body parts such as tissue, muscle etc. decay
• Three-domain system • In the mid-20th century the structure of DNA was determined
if conditions are suitable. • Grouped according to • Based on new chemical analysis and the mechanism of gene function worked out.
characteristics and techniques that prove some
species aren’t as closely
Fossil record - collection of fossils that show structures that make related as once thought. Protein Synthesis
evolution of an organism over many up organisms. • Archaea – primitive
bacteria
years. • Bacteria – true bacteria 1. DNA strands unwind.
• Kingdom, Phylum, • Eukaryota – fungi,
- Usually incomplete as most organisms Class, Order, Family, animals, plants, protists
2. A corresponding
don’t become fossils, softer bodies Genus, Species • These are sub-divided into
K,P,C,O,F,G and S. template of ATGC is
decay, fossils melt underground due to made called mRNA.
Earth movement, not been found yet, Organisms are named using binomial system
(genus and species in latin) . It is used 3. This leaves the nucleus and binds to a ribosome.
worldwide regardless of language.
- Usually need to comment on changes
over time e.g. shape, length or number Evolutionary trees show common 4. With the help of tRNA, amino acids are made.
ancestors . The more recent the common
of bones. ancestor, the more closely related they 5. The protein is then released from the ribosome.
are.

Speciation – making a new species

Animal Cloning TRIPLE ONLY Evolution Theories TRIPLE ONLY TRIPLE ONLY
A new species is made by:
Adult Cell Cloning – makes copy of adult Lamarck – the more a
characteristic is used Alfred Wallace wanted to
1. Take nucleus from an adult cell publish his findings on
2. Take nucleus out of an egg cell the more developed it natural selection before
3. Put adult nucleus into empty egg cell becomes and is then Darwin which prompted
4. Electric shock passed on to offspring. the Origin of the Species.
5. When it becomes an embryo, insert into uterus (which is nonsense!) 1. Geographical isolation
Embryo Transplant – makes cloned offspring (species split by
E.g. Giraffes stretched water or mountains)
1. Sperm and egg mixed in petri dish
2. Grow into an embryo their necks to reach 2. Genetic variation in
3. Split the embryo into cells higher food and passed both groups means
on the characteristic to some are more
4. Each cell develops into an identical embryo adapted to survive in
5. Insert into host uteruses their offspring. their own conditions

Plant Cloning Darwin proposed that a 3. Natural selection –

best breed and pass
Cuttings – Cut a bit off and plant it. mutation made some on desirable genes
- Cheap and quick giraffes have longer
necks so they would be 4. Speciation – new
Tissue Culture – Cells put in growth medium with species can’t
hormones. Grown all year, can make lots, more more likely to eat, interbreed with the
expensive. survive and reproduce. other species
AQA BIOLOGY UNIT 7: ECOLOGY
Biotic and Abiotic Factors Distribution of Organisms Adaptations
Where organisms live depends on: Structural: the features of an organism’s body structure, e.g.
shape, size or colour.
• Temperature
Behavioural: how an organism behaves e.g. some species migrate to
• Amount of light
warmer climates during winter months.
• Availability of water
Functional: internal processes of an organism e.g. desert animals
• Availability of nutrients produce little sweat and small amounts of urine to conserve water.
• Availability of oxygen and carbon dioxide
Key Terms Arctic - prevent heat loss
Quadrats – To estimate a population - small SA:Vol = lose less heat
Habitat – where an organism lives - camouflage from prey
Population – all organisms of a species in a habitat 1. Throw randomly
Community – populations of different species in a habitat (prevent bias) many Desert - large SA:Vol = easily lose and gain heat
Ecosystem – the interaction of biotic and abiotic factors times - camouflage from prey
2. Count number of - no leaves
The animals and plants are usually interdependent: organisms / % - water storage
coverage - deep roots
• Animals eat plants 3. Calculate the mean
• Animals pollinate plants 4. See how many quadrats Predators – Camouflage Extremophile – organisms
• Animals eat animals fit in whole area - Mimicry with adaptations to live
- Poisons and spikes
• Animals use plants to build shelters 5. Multiply number of in harsh habitats to
- Warning colours
• Plants use nutrients from animal droppings quadrats by the mean reduce competition.
Line/Belt Transects – To show distribution Competition
A stable community is one where all the species and
environmental factors are in balance, so population sizes 1. Lay tape along the area Plants – light, space, water, minerals
remain fairly constant e.g. tropical rainforests. 2. Place quadrat at regular intervals Animals – space, food, water, mates
3. Count number of organisms / % coverage
• Detritus feeders = worms, beetles, maggots
Decay • Decomposers = bacteria, fungi Carbon Cycle Food Chains
• They respire using waste, dead organisms etc. Grass  Rabbit  Fox
Conditions needed = WARM, MOIST and OXYGEN (producer  primary consumer  secondary consumer)
Decay puts nitrates back into the soil and carbon dioxide back into Always start with a producer (plant) as they produce their
the atmosphere. own food – they photosynthesise using the Sun’s energy to
Compost Heaps – Decay releases nutrients from dead plants and produce glucose. Some of this glucose is used to produce
animals to make fertile soil. new biological molecules in the plant, increasing its biomass
(an energy store). Some of this biomass is passed on to the
• Air holes – let oxygen in, regulate temperature. animal that eats the plant (secondary consumer). Therefore
• Warmth generated by respiring microorganisms.
• Finely shredded waste increases surface area. energy is transferred through organisms in a food chain.

Water Cycle Predator-Prey Relationships The amount of food limits

the population of a species.
If the population of prey
increases then so will the
population of predators.
But, as the number of
predators increase, the
number of prey decrease.

The predator-prey cycles are slightly out of phase with each other
Remember to follow the path of carbon e.g. because it takes a short white for a population to respond to changes
in the other.
CO2 in air taken in by plants (photosynthesis),
plants eaten by animals, animals die (decay), If the number of rabbits increase it will take a while for the foxes
to reproduce.
microorganisms respire, CO2 back in the air.
AQA BIOLOGY UNIT 7: ECOLOGY
Biodiversity a measure of the variety of all the different Pollution Deforestation & Peat Bogs
species of organisms on Earth, or within a Slash and burn
particular ecosystem. A high diversity ensures
Land • More people = more sewage which if untreated pollutes soil There are 3 main reasons for Land cleared for
• Household waste goes to landfill – toxic chemicals spread deforestation: farming, trees burnt
the stability of an ecosystem.
into the soil • Grow staple foods e.g. rice releasing CO2.
A high biodiversity reduces the dependence of one species on • Radiation e.g. at Chernobyl
another for:
• To rear more cattle
• Herbicides and pesticides can be washed into rivers and
• Food streams – become part of food chain (bioaccumulation) • To grow crops for biofuel
• Shelter Deforestation increases atmospheric carbon dioxide levels:
Water • Eutrophication
• Maintenance of the physical environment
Human population has grown due to: Fertilisers washed into rivers causes • Less trees therefore less photosynthesis removing CO2
increase in algae and plants. These from the air.
• Growing more food compete for light so die.
Decomposers use up all the oxygen in • Burning trees releases CO2.
• Treatment of diseases
• No natural predators the water when respiring lowering • Decay of dead plants by microorganisms respiring
biodiversity. releases more CO2.
As human population increases, biodiversity decreases because: Bioindicators can be used to • Trees take in lots of CO2 which is then converted into
• Land is used for building houses, shops, industry, roads. This identify low oxygen levels e.g. plant tissue. Removal of trees removes CO2 sinks.
destroys habitats. salmon, bloodworms.
• Huge areas of land is used for farming so natural animal and Often large areas are replaced by one single species. This
Air • Global dimming – smog and smoke particulates in the air reflect
plant populations cannot survive. sunlight reducing the amount reaching us lowering ground temperature. is called a monoculture.
• Quarrying for metal ores and rocks destroys habitats. • Acid rain – Fossil fuels contain sulphur and nitrogen. Combustion results
in sulphur dioxide and nitrogen dioxide released. These dissolve in
Peat bogs – Carbon store formed very slowly. Plant material
• Waste pollutes the environment and processing it takes up more
land. rainwater and form sulphuric and nitric acids lowering rain pH. that hasn’t decayed fully due to acidic conditions and a lack
Effects of Acid Rain What is being done about it?! of oxygen.
Restoring biodiversity
• Kills leaves, flowers etc and destroys roots • Low sulphur petrol • Burning the peat releases its stored carbon back into the
• Breeding programmes for endangered species Lowers pH in lakes, rivers etc until they • Clean chimney fumes from
• Protection and regeneration of habitats
• atmosphere as carbon dioxide.
cannot support life power stations
• Reintroduction of hedgerows and field margins • Acid snow – when it melts it causes major • Catalytic converters on cars • As peat is mixed in with soil it is exposed to aerobic
• Reduce deforestation and carbon dioxide emissions damage as an ‘acid flush’ • Rely more on renewable conditions and begins to decompose - which releases
Other countries are affected due to winds energy sources.
• Recycling resources – reduces landfill • carbon as carbon dioxide.

Global Warming Decomposition TRIPLE ONLY Environmental Change TRIPLE ONLY

More CO2 being released than taken in e.g. deforestation
Temperature: Decay is controlled by enzymes so too cold = too
for rice fields or cattle that both release methane (CH4) Distribution of organisms is caused by:
slow, too hot = denatured.
Greenhouse Effect
Moisture: Makes it easier for microorganisms to digest food and • Availability of water
1. Sun’s energy warms • Temperature
prevents drying out.
up the surface of the • Concentration of dissolved atmospheric gases in water.
Earth. Oxygen: For aerobic respiration – grow, reproduce etc. Aerobic
2. Most of this energy respiration results in an increase in temperature in a compost heap.
is radiated back. Daylight, amount of rainfall,
3. Layers of CO2 and Anaerobic respiration in bacteria can produce methane – Seasonal
temperature all change with the seasons.
CH4 absorb some of flammable gas (fuel) Changes
the energy. Animals migrate.
Biogas can be produced on a small scale
4. This warms up the
in a biogas generator.
atmosphere and the Changes to soil (structure and pH),
The carbohydrate-containing materials
Geographical
surface of the Earth. altitude, saltiness of water. Organisms
are fed in, and a range of bacteria Changes
The greenhouse effect is needed to maintain life but excess have adaptations to survive.
anaerobically ferment the
gases are causing an increase in temperature. carbohydrate into biogas.
Global warming could cause: Negative: Global warming, acid rain,
The remaining solids settle to the base
pollution
• Climate change – increase severe unpredictable weather, of the digester and can be run off to
be used as fertiliser for the land. Human
higher temperature sea absorbs less CO2. Interaction Positive: Maintaining rain forests,
• Rising sea levels – ice caps, glaciers The optimum temperature for biogas
reducing pollution, conservation of
• Reduced biodiversity – organisms can’t survive as habitats production is between 32oC and 35oC.
hedgerows and woodlands
change Cooler Countries – Slow respiration rate – bury generator with thick
• Changes to migration walls.
Living New predator, diseases, new
• Changes to distribution – some organisms may be able to Warmer Countries – Denatures enzymes – bury generator so ground
keeps it cool during the day. Factors competitors
survive in more places and vice versa.
AQA BIOLOGY UNIT 7: ECOLOGY TRIPLE ONLY

Biomass – mass of organism (no water) Biomass Transfers Food Security & Efficiency
Stages in a food chain are called Trophic Levels. Biomass is lost by organisms because: Food Security = Having enough food for the population
Factors threatening food security:
Issues with measuring biomass: • Faeces – Herbivores can’t digest all the plant material • Increasing birth rate – children to work land, large families in
• Kill the organism and dry it out. e.g. cellulose, carnivores can’t digest bones, hooves, some cultures, some religions don’t use contraception.
• Wet biomass is different depending on conditions, time claws. Faeces are broken down by decomposers. • Changing Diets – People look for new interesting food, deprives
of day etc. local people of traditional food, less nutritional foods take less
• Waste – Excess protein – deamination (urea production) time to cook.
Pyramid of biomass: - Respiration – glucose used by plants and animals • New pests and pathogens – Global travel, animal and plant
transfers energy to the surroundings e.g. movement, climate change = wider spread of pathogens which
movement. affects farm animals and crops.
• Environmental Changes – Global warming = droughts and flooding of
• Temperature – Mammals and birds use respiration for farm land.
body heat
• Cost – Genetic engineered crops cost more money as do irrigation
systems, fertilisers and pesticides.
• Conflicts – infrastructure damaged, people fear they can‛t feed
their families.
General Biomass Pyramid Rules
To make food production efficient:
• Producer always at the bottom. • Shorter food chains so less biomass lost
• They always look like normal pyramids • Limit movement of farm animals – less respiration more biomass
• Not all organisms or parts are eaten by the stage above (disease spreads in intensive farms)
e.g. roots, bones. • Warmer temperature – less respiration more biomass
• Most biomass taken in is usually used for respiration. • Fish bred in cages on high protein diets
• Food chains are short as so much biomass is lost at each Downsides: Ethical concerns over animal cruelty and welfare
trophic level. Cost for lighting and heating

Sustainable Food Production

Sustainable = producing foods in ways that supply the
whole human population and can continue for years.
Fishing – To prevent overfishing:
• Larger-holed nets to only catch the bigger, older fish
• Ban fishing during breeding season
• Strict fishing quotas to make sure some fishermen only
bring in a limited number of specific types of fish.

Mycoprotein (Quorn)
Produced by fungus
called fusarium (grows
fast on glucose syrup) in
a fermenter under
aerobic conditions.

Fungal biomass is
harvested and purified
and then dried and
processed to make
mycoprotein. It can be
shaped and flavoured.