This note is prepared for NEET examination. The living world is the first chapter under unit-1. It is very useful for students opting MBBS

1. 7/23/2021 UNIT-1
Diversity in The Living World
Dr. Ashokan Kannarath
TECHNORIUM NEW AGE
CHAPTER-1
THE LIVING WORLD

2. UNIT-1
DIVERSITY IN THE LIVING WORLD
Introduction
Biology is the study of living forms and living processes. The living world consists of
an amazing form living organisms. Our ancestors could easily differentiate animate
and inanimate things like wind, sea, fire etc, and animals and plants. A common
feature of such observation is the sense of fear that evoked. The description of living
organism begins only late in human history. The biological knowledge lag behind
because of anthropogenic views of biology. The close examination of plants and
animals later paved the birth of identification, nomenclature and classification. The
most significant observation is that living organisms share similarity among
themselves and organisms lived on the earth millions of years ago. All these
observation leads to the birth of the concept of conservation of biodiversity. The
chapters in this unit deals classification of animals and plants from the taxonomic
view.
Ernst Mayer
• This unit is dedicated to a great scientist erns Mayer.
• Mayer borne on 5th
July 1904 in Kempton, Germany
• He is an evolutionary biologist, popularly known as “Darwin of 20th
Century”.
• He was one of the 100 greatest scientists of all time.
• Mayer joined at Harvard University in 1953 and retired in 1975.
• He was titled as “Alexander Agassiz Professor of Zoology Emeritus”
• His research area was ornithology, taxonomy, zoogeography,
evolution, systematics and history and philosophy of Biology.
• He brought the concept of the species diversity in evolutionary
biology.
• Healso initiated the biological concept of species.
• He was awarded triple crown of biology- Balzan prize in 1983,
International prize for Biology in 1994 and Crafoord Prize in 1999.
• Mayer died at the age of 100 in 2004.

3. Ernst Mayer (1904-2004)
CHAPTER-01
The Living World
The living world is wonderful with wide range of amazing living organisms.
Living organisms are found every habitat like cold mountain, deciduous
forest, oceans, fresh water lakes, deserts or hot springs. The galloping
horses, migrating birds, valley of flowers or attacking shark evoke awes and
sense of wonder. The interaction between the members of population and
among populations of a community or even interaction of molecules within
the cells makes us think what life actually is? This question has two
questions hidden:’
1. What living is?
2. What is the purpose of living?
The first one is technical, and the second one is philosophical. As a science
student we try to answer the second question.
What is Living?
When we try to define ‘Living’ we may look into the characters of living
organisms, like growth, reproduction, ability to sense environments. You
may ad some other characters like metabolism, ability to self-replicate, self-
organise, interaction etc. Let us understand each one.
Growth
Increase in mass and increase in number of individuals are twin
characteristics of growth.

4. Consider Growth is increase in number
➢ A multi cellular organism grow by cell division.
➢ In plants this growth is continuous.
➢ In animals this growth is only up to a particular age.
➢ But in animals cell division occurs in certain tissue to replace lost
cells.
➢ In unicellular organism growth means multiplication one cell into two
and so on.
➢ Thus, in unicellular organisms the growth and reproduction is
inclusive process but in multicellular plants and animals both
processes are exclusive in nature.
Consider growth is increase in mass
✓ We can see that non-living things also grow as living things.
✓ But the growth of non-living things is buy deposition of matter on
outside i.e., extrinsic (Intussusception), in living things growth taken
place by increase in number of cells inside or intrinsic (accretion).
✓ Thus, both living and non-living things exhibit the character- growth,
we cannot say that growth is the defining character of living things.
✓ More over a dead organism cannot grow.
Reproduction
❖ Reproduction means production of young ones that are similar to their
parents.
❖ It may be sexual or asexual. In sexual reproduction young one shows
genetic variability from their parents.
❖ In asexual reproduction the young ones are called clones.
For examples
1. The fungi reproduce asexually by producing asexual spore.
2. In yeast and hydra asexual reproduction takes p[lace by budding.
3. In planaria (Flatworm) asexual reproduction takes place by
fragmentation i.e., the regeneration of lost part of the body.
4. In fungi, filamentous algae and protonema of mosses also reproduce
asexually by fragmentation.
1. In unicellular organisms like bacteria, unicellular algae (Yeast) and
Amoeba (protozoa) reproduction is synonymous with growth.
2. Thus, in unicellular organisms we cannot defiantly apply the term
growth and reproduction separately, both are inclusive.

5. 3. There are some organisms like mule, sterile worker bees, infertile
human couple etc do not reproduce.
4. Hence, we cannot say the reproduction is defining characters of living
things, even though non-living things do not reproduce.
Ability to sense environment
➢ This is most obvious and technically complicated feature of living
organisms.
➢ All living organisms respond to environmental stimuli of physical,
chemical or biological.
➢ Animals sense exchanges with sense organs and plants have no such
sense organs, but sense environmental factors like light, temperature,
water, other organisms, pollutants etc.
➢ Both plants and animals, the seasonal breeders show photoperiodic
effect on their reproduction.
➢ All organisms handle chemicals entering their bodies.
➢ Only human have self-consciousness.
➢ Hence, ability to sense environment and respond to it is a defining
property of living organisms.
➢ In the case of human, the fact is more confusing, for example, a man
in comma is living or dead?
Metabolism and Cellular organisation
❖ In all living organisms’ number of chemical reactions are going on.
❖ The Sum total of all the chemical reactions in an organism or cell is
called metabolism.
❖ It may be synthesising larger molecules from smaller molecule is called
anabolism or digestion of larger molecules to smaller one called
catabolism.
❖ Hence, anabolism plus catabolism is called metabolism.
❖ Metabolic reactions can be demonstrated outside the body in cell-free
system. But it is not living or non-living.
❖ Hence, metabolism is a defining character of all living organisms.
❖ Isolated reaction in a test tube is not living or non-living.
❖ Hence, Cellular organization the body is the defining feature of life
forms.
Base of the living phenomenon
➢ Interaction is the base of the living phenomenon.

6. ➢ Properties of tissue is not present in a cell, but arise as a result of
interaction between cells that form the tissues.
➢ Similarly, the properties of cellular organelles not present in the
molecules that form the organelle but arise by interaction of different
molecules to form organelle.
➢ This interaction we can see in all level’s higher organization.
➢ Therefore, we can say that living organisms are self-replicating,
evolving and self-regulating interactive system capable of responding
to external stimuli.
Diversity in the living world
If we look around, we can see different types of organisms like potted plants,
insects, birds, pets or other animals and plants. Remember, there are many
organisms that we cannot see our naked eyes, called microorganisms. If we
increase the area of observation, you can see more organisms as compared
to first. If you go a forest, you can see large number of different plants and
animals. All these animals or plants or microorganism that you see is called
species. The number of species that we know range between 1.7 -1.8 million.
This number and types of organisms present on earth is called biodiversity.
Nomenclature
The system of naming an organism is called nomenclature. It may be:
1. Vernacular nomenclature
2. Scientific nomenclature
Vernacular nomenclature
Name given to an organism in a local area by local people is known as
vernacular name. It is very confusing, because it varies from place to place
or country to country. For example, sweet potato is known in different name
at different states in India.
Scientific nomenclature
A common naming system which should be more precise and scientific, and
same all over the world is needed. This naming system is called scientific
nomenclature.
Identification
Nomenclature is possible if organism is described correctly and attached
with a name. This is called identification.

7. After a long trial by various scientists all over the world for naming organisms
which acceptable all over the world is came to exists. For plants scientific
names are based on ICBN-International Code for Botanical Nomenclature.
The same thing for animal is ICZN-International Code for Zoological
Nomenclature.
The common criteria for naming an organism are: -
Each name has two components-Generic Name and Specific Epithet. This
system of naming with two component is called binomial nomenclature. It
was proposed by Carolus Linnaeus.
For example
Mango-Mangifera indica
Mangifera is the genus name, while indica is the species epithet. Other
universal rules are: -
1. Biological names must be latinized or derived from Latin irrespective
of their origin.
2. The first name represents the genus and second indicating the species
name.
3. Both names, when writing should be under lined separately and when
print, it should be in Italics.
4. The genus name star with capital letter and the species name start
with small letter.
5. Name of the author appear at the end of the specific epithet in an
abbreviated form called citation-Mangifera Indica Lin
Classification
Classification is the process by which anything is into convenient groups
base on some easily observable characters. For example, we easily recognise
groups such as plants, animals or dog, cats, insects. When we use the terms,
we associate some characters with the organism in that group. When we
mention the word ‘DOG’ each one sees dog picture in and not cat. Similarly,
if we mention ’Alsatian’, we know that we are talking about dog. Another one
is when we say mammals, we think like animals having external ears and
body hairs. Likewise, if we say ‘wheat’ a picture appears of a wheat plant,
not a rice plant or any other plants. Hence, all these- dogs, cat, wheat, rice
etc are convenient categories we used to study organisms. The scientific term
for these categories is TAXA. Taxa indicates categories at different levels.
Animals, mammals, dogs are all taxa – but dog is mammal, mammals are

8. animals. Therefore, animals, mammals and dog represent taxa at different
levels. The classification of organisms at different taxa is called taxonomy.
Morphology, along with structure of cell, developmental process and
ecological information of organisms are necessary and forms the basis of
taxonomic studies.
Hence, Characterization, Identification, Classification and Nomenclate are
the basic to taxonomy. In the earliest day classification was based on the
use’s organisms for various purposes.
Later the branch systematics formed, because classification based on inter
relationship between the organisms originated. The word systematics means
systematic arrangement. Hence, it includes identification, nomenclature and
classification. It mainly accounts evolutionary relation ship between
organisms considered.
Taxonomic Categories
Classification is not a single step process but it involves hierarchy of steps
in which each step represents a rank or category. Each category represents
a unit of classification called tax. Hence taxa are defined as a group of
organisms that represent a concrete unit of classification. Each taxon has a
rank called category. There are 7 common categories- kingdom, phylum/
division, class, order, family, genus and species. These 7 obligatory
categories in the taxonomy. Species is the lowest category and kingdom, is
the top most category.

9. Species
Species are a group of closely related individuals which potentially interbreed
with each other.
Mangifera indica
Solanum tuberosum
Panthera leo
All the three names indica, tuberosum and leo are species epithet.
Mangifera, Solanum and Panthera are genera representing higher level of
taxon or category. Each genus may have one or more than one specific
epithet.
For example
Panthera leo-Lion
Panthera tigris-Tiger
Solanum nigrum
Solanum melongena
Scientific name of human is Homo sapiens
Genus
A group of related species together forming a higher level of
classification called genus.
Example
tuberosum (Potato)
Solanum
nigrum(brinjal)
leo (lion)
Panthera paradus (leopard)
tigris (Tiger)
Family
A group of closely related genus together forming a igher level of classification
is called family.

10. Solanum
Solanaceae Petunia
Datura
Panthera
Felidae
Felis
Order
A group of closely related family together forming a higher level of
classification called order. Solanaceae included in Polynomiales based on
floral characters
Convolvulaceae
Polynomiales
Solanaceae
Felidae
Carnivora
Canidae
Class
A group of closely related order together forming a higher level of
classification called class.
Primate
Mammalia
Carnivora
Phylum/ Division
Closely related classes together form a higher levl of classification called
phylum or division.

11. Pisces
Chordata Amphibia
Reptilia
Aves
Mamalia
Monocotyledon
Angiospermae
Dicotyledon
Kingdom
A group of closely related phylum or division together forming al higher level
of classification called kingdom.
Angiospermae
Plantae
Gymnospermae
Chordata
Animalia
Non -chordate

12. As we go higher from species to kingdom, the number of common
characteristics goes on decreasing. Lower the taxa, more are the
characteristics that the members within the taxon share. Higher the
category, greater is the difficulty of determining the relationship to other taxa
at the same level. Hence, the problem of classification becomes more
complex.
TAXONOMICAL AIDS
Biologists have established certain procedures and techniques to store and
preserve the information as well as the specimens. Some of these are
explained to help you understand the usage of these aids.
Herbarium
Herbarium is a store house of collected plant specimens that are dried,
pressed and preserved on sheets. Further, these sheets are arranged
according to a universally accepted system of classification. These
specimens, along with their descriptions on herbarium sheets, become a
store house or repository for future use. The herbarium sheets also carry a
label providing information about date and place of collection, English, local
and botanical names, family, collector’s name, etc. Herbaria also serve as
quick referral systems in taxonomical studies.
Botanical garden
These specialised gardens have collections of living plants for reference.
Plant species in these gardens are grown for identification purposes and each

13. plant is labelled indicating its botanical/scientific name and its family. The
famous botanical gardens are at Kew (England), Indian Botanical Garden,
Howrah (India) and at National Botanical Research Institute, Lucknow
(India).
Museum
Biological museums are generally set up in educational institutes such as
schools and colleges. Museums have collections of preserved plant and
animal specimens for study and reference. Specimens are preserved in the
containers or jars in preservative solutions. Plant and animal specimens may
also be preserved as dry specimens. Insects are preserved in insect boxes
after collecting, killing and pinning. Larger animals like birds and mammals
are usually stuffed and preserved. Museums often have collections of
skeletons of animals too.
Zoological Parks
These are the places where wild animals are kept in protected environments
under human care and which enable us to learn about their food habits and
behaviour. All animals in a zoo are provided, as far as possible, the
conditions similar to their natural habitats. Children love visiting these
parks, commonly called Zoos.
Key
Key is another taxonomical aid used for identification of plants and animals
based on the similarities and dissimilarities. The keys are based on the
contrasting characters generally in a pair called couplet. It represents the

14. choice made between two opposite options. This results in acceptance of only
one and rejection of the other. Each statement in the key is called a lead.
Separate taxonomic keys are required for each taxonomic category such as
family, genus and species for identification purposes. Keys are generally
analytical in nature.
Flora, manuals, monographs and catalogues are some other means of
recording descriptions. They also help in correct identification. Flora
contains the actual account of habitat and distribution of plants of a given
area. These provide the index to the plant species found in a particular area.
Manuals are useful in providing information for identification of names of
species found in an area. Monographs contain information on any one taxon.