Define Biodiversity.

The term biodiversity has been derived from bio and diversity meaning ‘variety’ within a
species and among species. Biodiversity is a measure of the variety of organisms present in
different ecosystems.
Flora: The diversity of plants.
Fauna: The diversity of animals.
Diversity of any region depends:
a. Climate
b. Altitude
c. Soils
d. Presence of other Species

What is the importance of Biodiversity?

 Biodiversity provides food for humans.
 A significant proportion of drugs are derived, directly or indirectly, from biological
sources.
 It plays a part in regulating the chemistry of our atmosphere and water supply.
 A wide range of industrial materials e.g. building materials, fibres, dyes, resins, gums,
adhesives, rubber and oil are derived directly from plants.
 Biodiversity plays important role in making and maintaining ecosystems.
 Biodiversity is directly involved in recycling nutrients and providing fertile soils.
Define Classification.
Classification is the arrangement of organisms in groups and sub-groups on the basis of
similarities and differences.
Over 1.5 million types of animals and over 0.5 million types of plants are known to biologists
and these are only a small percentage of the total types estimated to live on Earth.  
What are the aims of Classification?
 To determine similarities and differences among organisms so that they can be studied
easily.
 To find evolutionary relationship among organisms.
What are the basis of Classification?
  Similarities in internal and external structures.
 Stages of development.
 Similarities and differences in DNA of two organisms which are studied.

Taxonomic Hierarchy:
The groups into which organisms are classified are known as taxonomic categories or
taxa (singular “taxon”). The taxa form a ladder, called taxonomic hierarchy. Kingdom is the
largest taxon. Other taxa are as under:
 Phylum (Division, for plants and fungi): A phylum is a group of related classes.
 Class: A class is a group of related orders.
 Order: An order is a group of related families.
 Family: A family is a group of related genera.
 Genus: A genus is a group of related species.
 Species: A species consists of similar organisms.
What do you know about species?
It can be defined as:
“A group of organisms which can interbreed freely among them and produce fertile offspring,
but are reproductively isolated from all other such groups in nature.”
 Basic unit of classification is species.
 All members of a species have same number of chromosomes in their cells. E.g. all
human belongs from same species.
 Each species possesses its own distinct structural, ecological and behavioural
characteristics.

Give biological classification of Human being and Pea plant?

Taxa Human Pea
Kingdom Animalia Plantae
Phylum Chordata Magnoliophyta
Class Mammalia Magnoliopsida
Order Primates Fabales
Family Hominidae Fabaceae
Genus Homo Pisum
 Species H. sapiens P. sativum

What are infertile offspring? Explain.

(OR) Which organism can cross breed under artificial conditions?
Two organisms related to two different but closely related species can cross-breed under
artificial conditions. In such unnatural crosses they produce infertile offspring. For example, a
cross between a male donkey and a female horse produces an infertile offspring i.e. mule.
Is there any case where the criterion of interbreeding cannot be used?
The criterion of interbreeding cannot be used for classification of organisms who reproduce
asexually and do not breed with one another. Those organisms are classified into species on the
basis of similarities in their characteristics.

Discuss in detail the history of classification systems.

Aristotle: Provided the first system of classification of organisms. He classified all living
organisms into ‘plantae’ and ‘animalia’.
Abu-Usman Umer Aljahiz: He described the characteristics of 350 species of animals in his
book. He wrote a lot about the life of ants.
Ibn Rushd (Averroes):  He translated Aristotle’s book “de Anima (On the Soul)” in Arabic.

Andrea Caesalpino Divided plants into fifteen groups and called them “genera“.
 John Ray Published important works on plants’ classification.

Augustus Rivinus Introduced the taxon of “order“.

Tournefort Introduced the taxa of “class“ and “species“.
Carolus Linnaeus Grouped species according to similar physical characteristics.

 Two-Kingdom Classification System:

It is the oldest system and classifies all organisms into two kingdoms i.e. Plantae and
Animalia.
Plant Kingdom (Plantae): All organisms that can prepare food from simple inorganic materials
and thus can store energy are autotrophs and are included in kingdom plantae. Bacteria, fungi
and algae were included in kingdom plantae.
Animal kingdom (Animalia): The organisms that cannot synthesize their food and depend on
autotrophs or others are heterotrophs and are included in kingdom animalia.
Objection: This system could not get much attention because some unicellular organisms like
Euglena have both plant-like (presence of chlorophyll) and animal-like (heterotrophic mode of
nutrition in darkness and lack of cell wall) characters. It also ignored the difference between
prokaryotic and eukaryotic cells.
 Three-Kingdom Classification System:
In 1866, Ernst Hackel solved the first objection and proposed a third kingdom i.e. Protista
to accommodate euglena-like organisms. He also included bacteria in kingdom protista.
Objection: This system did not clear the difference between prokaryotes and eukaryotes. Some
biologists disagreed about position of fungi in kingdom plantae because fungi have not cell wall
made up of cellulose, but of chitin.  
 Five-Kingdom Classification System:
In 1967, Robert Whittaker introduced the five-kingdom classification system. This system
is based on:
 The levels of cellular organization i.e. prokaryotic, unicellular eukaryotic and
multicellular eukaryotic.
 The principal modes of nutrition i.e. photosynthesis, absorption, and ingestion.
In 1988, Margulis and Schwartz modified the five-kingdom classification of Whittaker. They
considered genetics along with cellular organization and mode of nutrition in classification. 
The general characteristics of the five kingdoms are as follows:
1. Kingdom Monera: 

i. It includes prokaryotic organisms i.e. they are made of prokaryotic cells.

ii. Unicellular, although some types form chains, clusters, or colonies of cells.
iii. Most are heterotrophic but some perform photosynthesis because they have
chlorophyll in their cytoplasm.
iv. Within this kingdom, there are two different kinds of organisms i.e. bacteria and
cyanobacteria.
2. Kingdom Protista: 
i. It includes eukaryotic unicellular and simple multicellular organisms. There are
three main types of protists.
a. Algae are unicellular, colonial or simple multicellular. They resemble plant cells
with cell walls and chlorophyll in chloroplasts. Simple multicellular means that
they do not have multicellular sex organs and do not form embryos during their
life cycles.
b. Protozoans resemble animals whose cells lack chlorophyll and cell walls.
c. Some protists are fungi-like.
3. Kingdom Fungi: 

i. It includes eukaryotic multicellular heterotrophs which are absorptive in their

nutritional mode e.g. mushrooms.
ii. Most fungi are decomposers.
iii. They live on organic material, secrete digestive enzymes and absorb small
organic molecules formed by the digestion by enzymes.
4. Kingdom Plantae:

i. It includes eukaryotic multicellular autotrophs.

ii. Make their own food by photosynthesis.
iii. They have multicellular sex organs and form embryos during their life cycles.
 iv. Mosses, ferns and flowering plants are included in this kingdom.
5. Kingdom Animalia: 

i. It includes eukaryotic multicellular consumers.

ii. Live by ingesting food and digesting it within specialized cavities.
iii. They lack cell wall and show movements.

Kingdom Cell Type Nuclear Cell Wall Mode of Multi-

Envelope Nutrition Cellularity
Monera Prokaryotic Absent Non-cellulose Autotroph Absent
(polysaccharide or heterotroph
plus amino acids)
Protista Eukayrotic Present Present in some Photosynthetic Absent in most
forms, various types or heterotroph, forms
or combination.
Fungi Eukaryotic Present Chitin Absorptive Present in most
heterotroph forms
Plantae Eukaryotic Present Cellulose and other Photosynthetic Present in all
Polysaccharides forms
Animalia Eukaryotic Present Absent Ingestive Present
heterotroph

Q. describe viruses. In which kingdome viruses are included? or Status of Viruses? Justify why
viruses are are excluded from Five-kingdoome?
Viruses are at the borderline of living and nonliving. Due to their crystalline nature, they
are considered as non-living.
i. They are acellular.
ii. They do not have cellular organization yet show some characters of living organisms.
 iii. These are infectious entities which contain either RNA or DNA, normally encased in
protein coat. They reproduce only in living cells, where they cause a number of
diseases.
iv. They are not considered as organisms and thus are not included in the five-kingdom
classification system.
Prions: composed of only protein.
Viroids: Viroids are composed of circular RNA only.
Q. Define Binomial Nomenclature?
Binomial nomenclature is the method of giving scientific names to living organisms.
As the word “binomial” suggests, the scientific name of a species consists of two names:
the first is genus name and the second one is the name of species.
Q. what do you know about Carolus Linnaeus?
Ans: Swedish biologist Carolus Linnaeus (1707-1778 AD) first introduced and adopted the
system of binomial nomenclature. His system spread rapidly and became popular. Many of his
names are in use today.
Q. Describe the aims and principles of binomial nomenclature.
Principles of binomial nomenclature:
Some of the rules which are universally adopted while suggesting and documenting
scientific names, are:
• Scientific names are usually printed in italics, such as Homo sapiens. When handwritten
they are underlined.
• The first term (generic name) always begins with capital letter, while species name is never
capitalized (even when derived from a proper name).
• The scientific name is generally written in full when it is first used. But when several species
from the same genus are being listed, it may then be abbreviated by just using an initial
for genus; for example Escherichia coli become E. coli.
Aims or Significance of binomial nomenclature:
i. In biological research, common names cause many problems. Different regions have
different names for the same organism. For example; common name of onion in Urdu
 is ‘Piyaz’ but in different regions of Pakistan it is also known as ‘ganda’ or ‘bassal’ or
‘vassal’. In other countries, it has other sets of names. In science, it is known with a
single name as Allium cepa.
ii. In some cases, different organisms are called by the same common name. For example;
the name ‘black bird’ is used for crow as well as for raven.
iii. Common names have no scientific basis. For example; a fish is a vertebrate animal with
fins and gills. But several common names of ‘silver fish’, ‘cray fish’, ‘jelly fish’, and ‘star
fish’ do not fit the biologist’s definition of a fish.
iv. To avoid all these confusions, organisms are given scientific names by using binomial
nomenclature.
v. In binomial nomenclature, every species can be unambiguously identified with just two
words. Same name can be used all over the world, in all languages, avoiding difficulties
of translation.

Examples:

Common Name Scientific Name

Onion Allium cepa

Common sea star (starfish) Asterias rubens

House crow Corvus splendens