If an alien from a distant galaxy were to visit our planet

Earth, the first thing that would amaze and baffle him

would most probably be the enormous diversity of life

that he would encounter. Even for humans, the rich variety

of living organisms with which they share this planet never

ceases to astonish and fascinate us. The common man

would find it hard to believe that there are more than

20,000 species of ants, 3,00,000 species of beetles, 28,000

species of fishes and nearly 20,000 species of orchids.

Ecologists and evolutionary biologists have been trying

to understand the significance of such diversity by asking

important questions– Why are there so many species?

Did such great diversity exist throughout earth’s history?

How did this diversification come about? How and why

is this diversity important to the biosphere? Would it

function any differently if the diversity was much less?

How do humans benefit from the diversity of life?

15.1 BIODIVERSITY

In our biosphere immense diversity (or heterogeneity)

exists not only at the species level but at all levels of

biological organisation ranging from macromolecules

within cells to biomes. Biodiversity is the term popularised

by the sociobiologist Edward Wilson to describe the

CHAPTER 15

BIODIVERSITY AND

CONSERVATION

15.1 Biodiversity

15.2 Biodiversity Conservation

2015-16

planet

ffle h

of lif

variety

t never

on m

28,00

rchids.

tryin

aski

species?

history?

and why

ould it

ch less?

In our biosphere immense diversity (or heterogeneity)

exists not only at the species level but at all levels of

biological organisation ranging from macromolecule

within cells to biomes. Biodiversit

is the term

larise

the sociob

iolo

st Edward Wilson to describe t

2015-1

If an alien from a distant

alax

were to visit our

Earth, the first thing that would amaze and ba

would most probably be the enormous diversity

that he would encounter

. Even for humans, the rich

of living organisms with which they share this plane

ceases to astonish and fascinate us. The comm

eve

at t

re are mor

20,000 species of ants, 3,00,000 species of beetles,

species of fishes and nearly 20,000 species of o

Ecologists and evolutionary biologists have been

to understand the significance of such diversity by

important questions–

Why are there so many

Did such great diversity exist throughout earth’s

How did this diversification come about? How

is this diversit

rtant to the bio

her

e? W

W W

function any differently if the diversity was mu

How do humans benefit from the diversity of life

15.1 B

Biodiversity

Biodiversity Conservatio

259

BIODIVERSITY AND CONSERVATION

combined diversity at all the levels of biological organisation.

The most important of them are–

(i) Genetic diversit

y : A single species might show high diversity at

the genetic level over its distributional range. The genetic variation

shown by the medicinal plant Rauwolfia vomitoria growing in

different Himalayan ranges might be in terms of the potency and

concentration of the active chemical (reserpine) that the plant

produces. India has more than 50,000 genetically different strains

of rice, and 1,000 varieties of mango.

(ii) Species diversity : The diversity at the species level. For example,

the Western Ghats have a greater amphibian species diversity than

the Eastern Ghats.

(iii) Ecological diversity: At the ecosystem level, India, for instance,

with its deserts, rain forests, mangroves, coral reefs, wetlands,

estuaries, and alpine meadows has a greater ecosystem diversity

than a Scandinavian country like Norway.

It has taken millions of years of evolution, to accumulate this rich

diversity in nature, but we could lose all that wealth in less than two

centuries if the present rates of species losses continue. Biodiversity and

its conservation are now vital environmental issues of international concern

as more and more people around the world begin to realise the critical

importance of biodiversity for our survival and well- being on this planet.

15.1.1 How Many Species are there on Earth and How Many

in India?

Since there are published records of all the species discovered and named,

we know how many species in all have been recorded so far, but it is not

easy to answer the question of how many species there are on earth.

According to the IUCN (2004), the total number of plant and animal species

described so far is slightly more than 1.5 million, but we have no clear

idea of how many species are yet to be discovered and described. Estimates

vary widely and many of them are only educated guesses. For many

taxonomic groups, species inventories are more complete in temperate

than in tropical countries. Considering that an overwhelmingly large

proportion of the species waiting to be discovered are in the tropics,

biologists make a statistical comparison of the temperate-tropical species

richness of an exhaustively studied group of insects and extrapolate this

ratio to other groups of animals and plants to come up with a gross

estimate of the total number of species on earth. Some extreme estimates

range from 20 to 50 million, but a more conservative and scientifically

sound estimate made by Robert May places the global species diversity

at about 7 million.

2015-16

5599

BIODIVERSITY AND CONSERVATION

combined diversity at all the levels of biological organisation.

The most important of them are–

)

A single species might show high diversity at

the genetic level over its distributional range. The genetic variation

shown by the medicinal plant

Rauwolfia vomitoria

growing in

different Himalayan ranges might be in terms of the potency and

concentration of the active chemical (reserpine) that the plant

produces. India has more than 50,000 genetically different strains

(ii)

)

dive

cent

as m

15.1

Sinc

we k

easy

Acco

desc

idea

vary

taxo

than

biol

rich

ratio to other groups of animals and plants to come up with a gross

estimate of the total number of species on earth. Some extreme estimates

range from 20 to 50 million, but a more conservative and scientifically

sound estimate made by Robert May places the global species diversity

at about 7 million.

2015-1

pr g ly

of rice, and 1,000 varieties of mang

Species diversit

The diversity at the species level. For example

n Ghats have a gr

eater amphibian species diversity than

)

Ecol

ical diversit

At the ecos

tem level, India, for instance

with its deserts, rain forests, ma

roves, coral reefs, wetlands

estuaries, and a

ine meadows has a

eater ecos

tem diversit

than a Scandinavian countr

like Norwa

It has taken millions of years of evolution, to accumulate this rich

versity in nature, but we could lose all that wealth in less than two

nturies if the present rates of species losses continue. Biodiversity and

more and more

eople around the world b

in to realise the critical

rtance of biodiversi

for our survival and well- bein

on this planet.

.1.1 How Many Species are

thth

ndnd

ow Many

in India?

nce there are published records of all the species discovered and name

know how many species in all have been

ded so far

, but it is not

sy to answer the question of how many species there are on earth.

cording to the IUCN (2004), the total number of plant and animal species

scribed so far is slightly more than 1.5 million, but we have no clear

ea of how many species are yet to be discovered and described. Estimates

ry widely and many of them are only educated guesses. For many

xonomic

ecies inventories are more com

ete in tem

rate

an in tr

ical countries. Considerin

that an overwhelmi

lar

ortion of the

ecies waitin

to be discovered are in the tr

ists make a statistical co

arison of the te

erate-tr

ical s

cies

chness of an exhaustively studied group of insects and extrapolate this

tio to other groups of animals and plants to come up with a gross

260

BIOLOGY

Let us look at some interesting aspects about earth’s biodiversity based

on the currently available species inventories. More than 70 per cent of

all the species recorded are animals, while plants (including algae, fungi,

bryophytes, gymnosperms and angiosperms) comprise no more than 22

per cent of the total. Among animals, insects are the most species-rich

taxonomic group, making up more than 70 per cent of the total. That

means, out of every 10 animals on this planet, 7 are insects. Again, how

do we explain this enormous diversification of insects? The number of

fungi species in the world is more than the combined total of the species

of fishes, amphibians, reptiles and mammals. In Figure 15.1, biodiversity

is depicted showing species number of major taxa.

Figure 15.1 Representing global biodiversity: proportionate number of

species of major taxa of plants, invertebrates and vertebrates

It should be noted that these estimates do not give any figures for

prokaryotes. Biologists are not sure about how many prokaryotic species

there might be. The problem is that conventional taxonomic methods are

not suitable for identifying microbial species and many species are simply

not culturable under laboratory conditions. If we accept biochemical or

molecular criteria for delineating species for this group, then their diversity

alone might run into millions.

2015-16

BIOLOG

Let us look at so

me interesting aspects about earth’s biodiversity based

on the currently available species inventories. More than 70 per cent of

all the species recorded are animals, while plants (including algae, fungi,

bryophytes, gymnosperms and angiosperms) comprise no more than 2

per cent of the total. Among animals, insects are the most species-rich

taxonomic group, making up more than 70 per cent of the total. That

means, out of ever

10 animals on this

lanet, 7 are insects.

ain, how

do we explain this enormous diversification of insects? The number of

fungi species in the world is more than the combined total of the species

versity

mber of

ebrates

res for

species

there might be. The problem is that conventional taxonomic methods are

not suitable for identifying microbial species and many species are simply

not culturable under laboratory conditions. If we accept biochemical or

molecular criteria for delineating species for this group, then their diversity

alone might run into millions.

2015-1

226600

fungi species in the world is more than the combined total of the

of fishes, amphibians, reptiles and mammals. In Figure 15.1, biodi

is depicted showing species number

of major taxa.

gure 15.1

Representing global biodiversity: proportionate nu

species of major

of plants, invertebrates and vert

It should be noted that these estimates do not give any figu

prokaryotes. Biologists are not sure about how many prokaryotic

261

BIODIVERSITY AND CONSERVATION

Although India has only 2.4 per cent of the world’s land area, its share

of the global species diversity is an impressive 8.1 per cent. That is what

makes our country one of the 12 mega diversity countries of the world.

Nearly 45,000 species of plants and twice as many of animals have been

recorded from India. How many living species are actually there waiting

to be discovered and named? If we accept May’s global estimates, only

22 per cent of the total species have been recorded so far. Applying this

proportion to India’s diversity figures, we estimate that there are probably

more than 1,00,000 plant species and more than 3,00, 000 animal species

yet to be discover

ed and described. Would we ever be able to complete

the inventory of the biological wealth of our country? Consider the immense

trained manpower (taxonomists) and the time required to complete the

job. The situation appears more hopeless when we realise that a large

fraction of these species faces the threat of becoming extinct even before

we discover them. Nature’s biological library is burning even before we

catalogued the titles of all the books stocked there.

15.1.2 Patterns of Biodiversity

(i) Latitudinal gradients : The diversity of plants and animals is

not uniform throughout the world but shows a rather uneven

distribution. For many group of animals or plants, there are

interesting patterns in diversity, the most well- known being the

latitudinal gradient in diversity. In general, species diversity

decreases as we move away from the equator towards the poles.

With very few exceptions, tropics (latitudinal range of 23.5° N to

23.5° S) harbour more species than temperate or polar areas.

Colombia located near the equator has nearly 1,400 species of birds

while New York at 41° N has 105 species and Greenland at 71° N

only 56 species. India, with much of its land area in the tropical

latitudes, has more than 1,200 species of birds. A forest in a tropical

region like Equador has up to 10 times as many species of vascular

plants as a forest of equal area in a temperate region like the Midwest

of the USA. The largely tropical Amazonian rain forest in South

America has the greatest biodiversity on earth- it is home to more

than 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427

of mammals, 427 of amphibians, 378 of reptiles and of more than

1,25,000 invertebrates. Scientists estimate that in these rain forests

there might be at least two million insect species waiting to be

discovered and named.

What is so special about tropics that might account for their greater

biological diversity? Ecologists and evolutionary biologists have

proposed various hypotheses; some important ones are (a) Speciation

is generally a function of time, unlike temperate regions subjected

to frequent glaciations in the past, tropical latitudes have remained

relatively undisturbed for millions of years and thus, had a long

2015-16

BIODIVERSITY AND CONSERVATION

Althou

India h

as only 2.4 per cent of the world’s land area, its share

of the global species diversity is an impressive 8.1 per cent. That is what

makes our countr

one of the 12 me

diversi

countries of the world.

Nearly 45,000 species of plants and twice as many of animals have been

recorded from India. How many living species are actually there waiting

to be discovered and named? If we accept May’s global estimates, only

er cent of the total s

cies have been r

ecor

. Applying this

proportion to India’s diversity figures, we estimate that there are probably

more than 1,00,000 plant species and more than 3,00, 000 animal species

the in

trai

job.

frac

we d

cata

15.1

(i)

biol

ical diversi

Ecolo

sts and evolutiona

biolo

sts have

proposed various hypotheses; some important ones are (a) Speciation

is generally a function of time, unlike temperate regions subjected

to frequent glaciations in the past, tropical latitudes have remained

relatively undisturbed for millions of ye

ars and thus, had a long

2015-1

re than 1,00,000 plant species and more than 3,00, 000 animal species

to be discov

ould we ever be able to co

lete

inventory of the biological wealth of our country? Consider the immense

ained manpower (taxonomists) and the time required to complete the

b. The situation appears more hopeless when we realise that a large

action of these species faces the threat of becoming extinct even before

discover them. Nature’s biological library is burning even before we

talogued the titles of all the books stocked there.

.1.2 Patterns of Biodiversity

(i)

Latitudinal gradie

The diversity of plants and animals is

not uniform throughout the world but shows a rather uneven

distribution. For many group of animals or plants, there are

interesting patterns in diversity, the most well- known being the

latitudinal gradient in diversity. In general, species diversity

decreases as we move away from the equator towards the poles.

With very few exceptions, tropics (latitudinal range of 23.5° N to

23.5° S) harbour more species than temperate or polar areas.

Colombia located near the equator has near

1,400 species of birds

while New Y

ork at 41° N has 105 species and Gr

eenland at 71° N

only 56 species. India, with much of its land area in the tropical

latitudes, has more than 1,200 species of birds. A forest in a tropical

region like Equador has up to 10 times as many species of vascular

plants as a forest of equal area in a temperate region like the Midwest

of the USA. The largely tropical Amazonian rain forest in South

America has the

eatest biodiversit

on earth- it is home to more

than 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427

of mammals, 427 of amphibians, 378 of reptiles and of more than

1,25,000 invertebrates. Scientists estimate that in these rain forests

there might be at least two million insect s

cies waiti

to be

discovered and named.

What is so special about tropics that might account for their greater

biol ical div sity?

E logist d olutio biologist ha