NCERT Textbook: Life on the Earth | Geography for UPSC CSE PDF Download

 Page 1


LIFE ON THE EARTH
This unit deals with
• Biosphere — importance of plants and other organisms;
ecosystems, bio-geo chemical cycle and ecological balance;
biodiversity and conservation
UNIT
VI
© NCERT
not to be republished
Page 2


LIFE ON THE EARTH
This unit deals with
• Biosphere — importance of plants and other organisms;
ecosystems, bio-geo chemical cycle and ecological balance;
biodiversity and conservation
UNIT
VI
© NCERT
not to be republished
LIFE ON THE EARTH
B
y now you might have realised that all
units of this book have acquainted you
with the three major realms of the
environment, that is, the lithosphere, the
atmosphere and the hydrosphere. You know
that living organisms of the earth, constituting
the biosphere, interact with other environmental
realms.  The biosphere includes all the living
components of the earth. It consists of all plants
and animals, including all the micro-
ECOLOGY
You have been reading about ecological and
environmental problems in newspapers and
magazines. Have you ever thought what
ecology is? The environment as you know, is
made up of abiotic and biotic components. It
would be interesting to understand how the
diversity of life-forms is maintained to bring a
kind of balance. This balance is maintained in
a particular proportion so that a healthy
interaction between the biotic and the abiotic
components goes on.
The interactions of a particular group of
organisms with abiotic factors within a
particular habitat resulting in clearly defined
energy flows and material cycles on land, water
and air, are called ecological systems.
CHAPTER
Life on the earth is found almost
everywhere. Living organisms are found
from the poles to the equator, from the
bottom of the sea to several km in the
air, from freezing waters to dry valleys,
from under the sea to underground water
lying below the earth’s surface.
organisms that live on the planet earth and their
interactions with the surrounding environment.
Most of the organisms exist on the lithosphere
and/or the hydrosphere as well as in the
atmosphere. There are also many organisms
that move freely from one realm to the other.
The biosphere and its components are very
significant elements of the environment. These
elements interact with other components of the
natural landscape such as land, water and
soil. They are also influenced by the
atmospheric elements such as the temperature,
rainfall, moisture and sunlight. The
interactions of biosphere with land, air and
water are important to the growth,
development and evolution of the organism.
The term ecology is derived from the Greek
word ‘oikos’ meaning ‘house’, combined
with the word ‘logy’ meaning the ‘science
of’ or ‘the study of’. Literally, ecology is
the study of the earth as a ‘household’,
of plants, human beings, animals and
micro-organisms. They all live together
as interdependent components. A
German zoologist Ernst Haeckel, who
used the term as ‘oekologie’ in 1869,
became the first person to use the term
‘ecology’. The study of interactions
between life forms (biotic) and the
physical environment (abiotic) is the
science of ecology. Hence, ecology can be
defined as a scientific study of the
interactions of organisms with their
physical environment and with each other.
© NCERT
not to be republished
Page 3


LIFE ON THE EARTH
This unit deals with
• Biosphere — importance of plants and other organisms;
ecosystems, bio-geo chemical cycle and ecological balance;
biodiversity and conservation
UNIT
VI
© NCERT
not to be republished
LIFE ON THE EARTH
B
y now you might have realised that all
units of this book have acquainted you
with the three major realms of the
environment, that is, the lithosphere, the
atmosphere and the hydrosphere. You know
that living organisms of the earth, constituting
the biosphere, interact with other environmental
realms.  The biosphere includes all the living
components of the earth. It consists of all plants
and animals, including all the micro-
ECOLOGY
You have been reading about ecological and
environmental problems in newspapers and
magazines. Have you ever thought what
ecology is? The environment as you know, is
made up of abiotic and biotic components. It
would be interesting to understand how the
diversity of life-forms is maintained to bring a
kind of balance. This balance is maintained in
a particular proportion so that a healthy
interaction between the biotic and the abiotic
components goes on.
The interactions of a particular group of
organisms with abiotic factors within a
particular habitat resulting in clearly defined
energy flows and material cycles on land, water
and air, are called ecological systems.
CHAPTER
Life on the earth is found almost
everywhere. Living organisms are found
from the poles to the equator, from the
bottom of the sea to several km in the
air, from freezing waters to dry valleys,
from under the sea to underground water
lying below the earth’s surface.
organisms that live on the planet earth and their
interactions with the surrounding environment.
Most of the organisms exist on the lithosphere
and/or the hydrosphere as well as in the
atmosphere. There are also many organisms
that move freely from one realm to the other.
The biosphere and its components are very
significant elements of the environment. These
elements interact with other components of the
natural landscape such as land, water and
soil. They are also influenced by the
atmospheric elements such as the temperature,
rainfall, moisture and sunlight. The
interactions of biosphere with land, air and
water are important to the growth,
development and evolution of the organism.
The term ecology is derived from the Greek
word ‘oikos’ meaning ‘house’, combined
with the word ‘logy’ meaning the ‘science
of’ or ‘the study of’. Literally, ecology is
the study of the earth as a ‘household’,
of plants, human beings, animals and
micro-organisms. They all live together
as interdependent components. A
German zoologist Ernst Haeckel, who
used the term as ‘oekologie’ in 1869,
became the first person to use the term
‘ecology’. The study of interactions
between life forms (biotic) and the
physical environment (abiotic) is the
science of ecology. Hence, ecology can be
defined as a scientific study of the
interactions of organisms with their
physical environment and with each other.
© NCERT
not to be republished
FUNDAMENTALS OF PHYSICAL GEOGRAPHY 128
A habitat in the ecological sense is  the totality
of the physical and chemical factors that
constitute the general environment.  A system
consisting of biotic and abiotic components is
known as ecosystem. All these components in
ecosystem are inter related and interact with
each other. Different types of ecosystems exist
with varying ranges of environmental
conditions where various plants and animal
species have got adapted through evolution.
This phenomenon is known as ecological
adaptation.
Types of Ecosystems
Ecosystems are of two major types: terrestrial
and aquatic. Terrestrial ecosystem can be
further be classified into ‘biomes’. A biome is a
plant and animal community that covers a
large geographical area.  The boundaries of
different biomes on land are determined mainly
by climate. Therefore, a biome can be defined
as the total assemblage of plant and animal
species interacting within specific conditions.
These include rainfall, temperature, humidity
and soil conditions. Some of the major biomes
of the world are: forest, grassland, desert and
tundra biomes. Aquatic ecosystems can be
classed as marine and freshwater ecosystems.
Marine ecosystem includes the oceans,
estuaries and coral reefs. Freshwater
Figure 15.1 : Structure and functions of ecosystems
ecosystem includes lakes, ponds, streams,
marshes and bogs.
Structure and Functions of Ecosystems
The structure of an ecosystem involves a
description of the available plant and animal
species. From a structural point of view, all
ecosystems consist of abiotic and biotic factors.
Abiotic factors include rainfall, temperature,
sunlight, atmospheric humidity, soil
conditions, inorganic substances (carbon
dioxide, water, nitrogen, calcium, phosphorus,
potassium, etc.). Biotic factors include the
producers, the consumers (primary,
secondary, tertiary) and the decomposers. The
producers include all the green plants, which
manufacture their own food through
photosynthesis. The primary consumers
include herbivorous animals like deer, goats,
mice and all plant-eating animals. The
carnivores include all the flesh-eating animals
like snakes, tigers and lions. Certain carnivores
that feed also on carnivores are known as top
carnivores like hawks and mongooses.
Decomposers are those that feed on dead
organisms (for example, scavengers like
vultures and crows), and further breaking
down of the dead matter by other decomposing
agents like bacteria and various micro-
organisms.
© NCERT
not to be republished
Page 4


LIFE ON THE EARTH
This unit deals with
• Biosphere — importance of plants and other organisms;
ecosystems, bio-geo chemical cycle and ecological balance;
biodiversity and conservation
UNIT
VI
© NCERT
not to be republished
LIFE ON THE EARTH
B
y now you might have realised that all
units of this book have acquainted you
with the three major realms of the
environment, that is, the lithosphere, the
atmosphere and the hydrosphere. You know
that living organisms of the earth, constituting
the biosphere, interact with other environmental
realms.  The biosphere includes all the living
components of the earth. It consists of all plants
and animals, including all the micro-
ECOLOGY
You have been reading about ecological and
environmental problems in newspapers and
magazines. Have you ever thought what
ecology is? The environment as you know, is
made up of abiotic and biotic components. It
would be interesting to understand how the
diversity of life-forms is maintained to bring a
kind of balance. This balance is maintained in
a particular proportion so that a healthy
interaction between the biotic and the abiotic
components goes on.
The interactions of a particular group of
organisms with abiotic factors within a
particular habitat resulting in clearly defined
energy flows and material cycles on land, water
and air, are called ecological systems.
CHAPTER
Life on the earth is found almost
everywhere. Living organisms are found
from the poles to the equator, from the
bottom of the sea to several km in the
air, from freezing waters to dry valleys,
from under the sea to underground water
lying below the earth’s surface.
organisms that live on the planet earth and their
interactions with the surrounding environment.
Most of the organisms exist on the lithosphere
and/or the hydrosphere as well as in the
atmosphere. There are also many organisms
that move freely from one realm to the other.
The biosphere and its components are very
significant elements of the environment. These
elements interact with other components of the
natural landscape such as land, water and
soil. They are also influenced by the
atmospheric elements such as the temperature,
rainfall, moisture and sunlight. The
interactions of biosphere with land, air and
water are important to the growth,
development and evolution of the organism.
The term ecology is derived from the Greek
word ‘oikos’ meaning ‘house’, combined
with the word ‘logy’ meaning the ‘science
of’ or ‘the study of’. Literally, ecology is
the study of the earth as a ‘household’,
of plants, human beings, animals and
micro-organisms. They all live together
as interdependent components. A
German zoologist Ernst Haeckel, who
used the term as ‘oekologie’ in 1869,
became the first person to use the term
‘ecology’. The study of interactions
between life forms (biotic) and the
physical environment (abiotic) is the
science of ecology. Hence, ecology can be
defined as a scientific study of the
interactions of organisms with their
physical environment and with each other.
© NCERT
not to be republished
FUNDAMENTALS OF PHYSICAL GEOGRAPHY 128
A habitat in the ecological sense is  the totality
of the physical and chemical factors that
constitute the general environment.  A system
consisting of biotic and abiotic components is
known as ecosystem. All these components in
ecosystem are inter related and interact with
each other. Different types of ecosystems exist
with varying ranges of environmental
conditions where various plants and animal
species have got adapted through evolution.
This phenomenon is known as ecological
adaptation.
Types of Ecosystems
Ecosystems are of two major types: terrestrial
and aquatic. Terrestrial ecosystem can be
further be classified into ‘biomes’. A biome is a
plant and animal community that covers a
large geographical area.  The boundaries of
different biomes on land are determined mainly
by climate. Therefore, a biome can be defined
as the total assemblage of plant and animal
species interacting within specific conditions.
These include rainfall, temperature, humidity
and soil conditions. Some of the major biomes
of the world are: forest, grassland, desert and
tundra biomes. Aquatic ecosystems can be
classed as marine and freshwater ecosystems.
Marine ecosystem includes the oceans,
estuaries and coral reefs. Freshwater
Figure 15.1 : Structure and functions of ecosystems
ecosystem includes lakes, ponds, streams,
marshes and bogs.
Structure and Functions of Ecosystems
The structure of an ecosystem involves a
description of the available plant and animal
species. From a structural point of view, all
ecosystems consist of abiotic and biotic factors.
Abiotic factors include rainfall, temperature,
sunlight, atmospheric humidity, soil
conditions, inorganic substances (carbon
dioxide, water, nitrogen, calcium, phosphorus,
potassium, etc.). Biotic factors include the
producers, the consumers (primary,
secondary, tertiary) and the decomposers. The
producers include all the green plants, which
manufacture their own food through
photosynthesis. The primary consumers
include herbivorous animals like deer, goats,
mice and all plant-eating animals. The
carnivores include all the flesh-eating animals
like snakes, tigers and lions. Certain carnivores
that feed also on carnivores are known as top
carnivores like hawks and mongooses.
Decomposers are those that feed on dead
organisms (for example, scavengers like
vultures and crows), and further breaking
down of the dead matter by other decomposing
agents like bacteria and various micro-
organisms.
© NCERT
not to be republished
LIFE ON THE EARTH 129
The producers are consumed by the
primary consumers whereas the primary
consumers are, in turn, being eaten by the
secondary consumers. Further, the secondary
consumers are consumed by the tertiary
consumers. The decomposers feed on the dead
at each and every level. They change them into
various substances such as nutrients, organic
and inorganic salts essential for soil fertility.
Organisms of an ecosystem are linked together
through a foodchain (Figure 15.1). For
example, a plant eating beetle feeding on a
paddy stalk is eaten by a frog, which is, in turn,
eaten by a snake, which is then consumed by
a hawk. This sequence of eating and being
eaten and the resultant transfer of energy from
one level to another is known as the food-chain.
Transfer of energy that occurs during the
process of a foodchain from one level to
another is known as flow of energy. However,
food-chains are not isolated from one another.
For example, a mouse feeding on grain may
be eaten by different secondary consumers
(carnivores) and these carnivores may be eaten
by other different tertiary consumers (top
carnivores). In such situations, each of the
carnivores may consume more than one type
of prey. As a result, the food- chains get
interlocked with one another. This inter-
connecting network of species is known as food
web. Generally, two types of food-chains are
recognised: grazing food-chain and detritus
food-chain. In a grazing food-chain, the first
level starts with plants as producers and ends
with carnivores as consumers at the last level,
with the herbivores being at the intermediate
level. There is a loss of energy at each level
which may be through respiration, excretion
or decomposition. The levels involved in a food-
chain range between three to five and energy
is lost at each level. A detritus food-chain is
based on autotrophs energy capture initiated
by grazing animals and involves the
decomposition or breaking down of organic
wastes and dead matter derived from the
grazing food-chain.
Types of Biomes
In the earlier paragraphs, you have learnt the
meaning of the term ‘biome’. Let us now try to
identify the major biomes of the world. There
are five major biomes  — forest, desert, grassland,
aquatic and altitudinal biomes. Some features
of these biomes are given in Table 15.1.
Biogeochemical Cycles
The sun is the basic source of energy on which
all life depends. This energy initiates life
processes in the biosphere through
photosynthesis, the main source of food and
energy for green plants. During photosynthesis,
carbon dioxide is converted into organic
compounds and oxygen. Out of the total solar
insolation that reaches the earth’s surface, only
a very small fraction (0.1 per cent) is fixed in
photosynthesis. More than half is used for plant
respiration and the remaining part is
temporarily stored or is shifted to other
portions of the plant.
Life on earth consists of a great variety of
living organisms. These living organisms exist
and survive in a diversity of associations. Such
survival involves the presence of systemic flows
such as flows of energy, water and nutrients.
These flows show variations in different parts
of the world, in different seasons of the year
and under varying local circumstances. Studies
have shown that for the last one billion years,
the atmosphere and hydrosphere have been
composed of approximately the same balance
of chemical components. This balance of the
chemical elements is maintained by a cyclic
passage through the tissues of plants and
animals. The cycle starts by absorbing the
chemical elements by the organism and is
returned to the air, water and soil through
decomposition. These cycles are largely
energised by solar insolation. These cyclic
movements of chemical elements of the
biosphere between the organism and the
environment are referred to as biogeochemical
cycles. Bio refers to living organisms and geo
to rocks, soil, air and water of the earth.
There are two types of biogeochemical
cycles : the gaseous and the sedimentary cycle.
In the gaseous cycle, the main reservoir of
nutrients is the atmosphere and the ocean. In
the sedimentary cycle, the main reservoir is the
soil and the sedimentary and other rocks of
the earth’s crust.
The Water Cycle
All living organisms, the atmosphere and the
lithosphere maintain between them a
© NCERT
not to be republished
Page 5


LIFE ON THE EARTH
This unit deals with
• Biosphere — importance of plants and other organisms;
ecosystems, bio-geo chemical cycle and ecological balance;
biodiversity and conservation
UNIT
VI
© NCERT
not to be republished
LIFE ON THE EARTH
B
y now you might have realised that all
units of this book have acquainted you
with the three major realms of the
environment, that is, the lithosphere, the
atmosphere and the hydrosphere. You know
that living organisms of the earth, constituting
the biosphere, interact with other environmental
realms.  The biosphere includes all the living
components of the earth. It consists of all plants
and animals, including all the micro-
ECOLOGY
You have been reading about ecological and
environmental problems in newspapers and
magazines. Have you ever thought what
ecology is? The environment as you know, is
made up of abiotic and biotic components. It
would be interesting to understand how the
diversity of life-forms is maintained to bring a
kind of balance. This balance is maintained in
a particular proportion so that a healthy
interaction between the biotic and the abiotic
components goes on.
The interactions of a particular group of
organisms with abiotic factors within a
particular habitat resulting in clearly defined
energy flows and material cycles on land, water
and air, are called ecological systems.
CHAPTER
Life on the earth is found almost
everywhere. Living organisms are found
from the poles to the equator, from the
bottom of the sea to several km in the
air, from freezing waters to dry valleys,
from under the sea to underground water
lying below the earth’s surface.
organisms that live on the planet earth and their
interactions with the surrounding environment.
Most of the organisms exist on the lithosphere
and/or the hydrosphere as well as in the
atmosphere. There are also many organisms
that move freely from one realm to the other.
The biosphere and its components are very
significant elements of the environment. These
elements interact with other components of the
natural landscape such as land, water and
soil. They are also influenced by the
atmospheric elements such as the temperature,
rainfall, moisture and sunlight. The
interactions of biosphere with land, air and
water are important to the growth,
development and evolution of the organism.
The term ecology is derived from the Greek
word ‘oikos’ meaning ‘house’, combined
with the word ‘logy’ meaning the ‘science
of’ or ‘the study of’. Literally, ecology is
the study of the earth as a ‘household’,
of plants, human beings, animals and
micro-organisms. They all live together
as interdependent components. A
German zoologist Ernst Haeckel, who
used the term as ‘oekologie’ in 1869,
became the first person to use the term
‘ecology’. The study of interactions
between life forms (biotic) and the
physical environment (abiotic) is the
science of ecology. Hence, ecology can be
defined as a scientific study of the
interactions of organisms with their
physical environment and with each other.
© NCERT
not to be republished
FUNDAMENTALS OF PHYSICAL GEOGRAPHY 128
A habitat in the ecological sense is  the totality
of the physical and chemical factors that
constitute the general environment.  A system
consisting of biotic and abiotic components is
known as ecosystem. All these components in
ecosystem are inter related and interact with
each other. Different types of ecosystems exist
with varying ranges of environmental
conditions where various plants and animal
species have got adapted through evolution.
This phenomenon is known as ecological
adaptation.
Types of Ecosystems
Ecosystems are of two major types: terrestrial
and aquatic. Terrestrial ecosystem can be
further be classified into ‘biomes’. A biome is a
plant and animal community that covers a
large geographical area.  The boundaries of
different biomes on land are determined mainly
by climate. Therefore, a biome can be defined
as the total assemblage of plant and animal
species interacting within specific conditions.
These include rainfall, temperature, humidity
and soil conditions. Some of the major biomes
of the world are: forest, grassland, desert and
tundra biomes. Aquatic ecosystems can be
classed as marine and freshwater ecosystems.
Marine ecosystem includes the oceans,
estuaries and coral reefs. Freshwater
Figure 15.1 : Structure and functions of ecosystems
ecosystem includes lakes, ponds, streams,
marshes and bogs.
Structure and Functions of Ecosystems
The structure of an ecosystem involves a
description of the available plant and animal
species. From a structural point of view, all
ecosystems consist of abiotic and biotic factors.
Abiotic factors include rainfall, temperature,
sunlight, atmospheric humidity, soil
conditions, inorganic substances (carbon
dioxide, water, nitrogen, calcium, phosphorus,
potassium, etc.). Biotic factors include the
producers, the consumers (primary,
secondary, tertiary) and the decomposers. The
producers include all the green plants, which
manufacture their own food through
photosynthesis. The primary consumers
include herbivorous animals like deer, goats,
mice and all plant-eating animals. The
carnivores include all the flesh-eating animals
like snakes, tigers and lions. Certain carnivores
that feed also on carnivores are known as top
carnivores like hawks and mongooses.
Decomposers are those that feed on dead
organisms (for example, scavengers like
vultures and crows), and further breaking
down of the dead matter by other decomposing
agents like bacteria and various micro-
organisms.
© NCERT
not to be republished
LIFE ON THE EARTH 129
The producers are consumed by the
primary consumers whereas the primary
consumers are, in turn, being eaten by the
secondary consumers. Further, the secondary
consumers are consumed by the tertiary
consumers. The decomposers feed on the dead
at each and every level. They change them into
various substances such as nutrients, organic
and inorganic salts essential for soil fertility.
Organisms of an ecosystem are linked together
through a foodchain (Figure 15.1). For
example, a plant eating beetle feeding on a
paddy stalk is eaten by a frog, which is, in turn,
eaten by a snake, which is then consumed by
a hawk. This sequence of eating and being
eaten and the resultant transfer of energy from
one level to another is known as the food-chain.
Transfer of energy that occurs during the
process of a foodchain from one level to
another is known as flow of energy. However,
food-chains are not isolated from one another.
For example, a mouse feeding on grain may
be eaten by different secondary consumers
(carnivores) and these carnivores may be eaten
by other different tertiary consumers (top
carnivores). In such situations, each of the
carnivores may consume more than one type
of prey. As a result, the food- chains get
interlocked with one another. This inter-
connecting network of species is known as food
web. Generally, two types of food-chains are
recognised: grazing food-chain and detritus
food-chain. In a grazing food-chain, the first
level starts with plants as producers and ends
with carnivores as consumers at the last level,
with the herbivores being at the intermediate
level. There is a loss of energy at each level
which may be through respiration, excretion
or decomposition. The levels involved in a food-
chain range between three to five and energy
is lost at each level. A detritus food-chain is
based on autotrophs energy capture initiated
by grazing animals and involves the
decomposition or breaking down of organic
wastes and dead matter derived from the
grazing food-chain.
Types of Biomes
In the earlier paragraphs, you have learnt the
meaning of the term ‘biome’. Let us now try to
identify the major biomes of the world. There
are five major biomes  — forest, desert, grassland,
aquatic and altitudinal biomes. Some features
of these biomes are given in Table 15.1.
Biogeochemical Cycles
The sun is the basic source of energy on which
all life depends. This energy initiates life
processes in the biosphere through
photosynthesis, the main source of food and
energy for green plants. During photosynthesis,
carbon dioxide is converted into organic
compounds and oxygen. Out of the total solar
insolation that reaches the earth’s surface, only
a very small fraction (0.1 per cent) is fixed in
photosynthesis. More than half is used for plant
respiration and the remaining part is
temporarily stored or is shifted to other
portions of the plant.
Life on earth consists of a great variety of
living organisms. These living organisms exist
and survive in a diversity of associations. Such
survival involves the presence of systemic flows
such as flows of energy, water and nutrients.
These flows show variations in different parts
of the world, in different seasons of the year
and under varying local circumstances. Studies
have shown that for the last one billion years,
the atmosphere and hydrosphere have been
composed of approximately the same balance
of chemical components. This balance of the
chemical elements is maintained by a cyclic
passage through the tissues of plants and
animals. The cycle starts by absorbing the
chemical elements by the organism and is
returned to the air, water and soil through
decomposition. These cycles are largely
energised by solar insolation. These cyclic
movements of chemical elements of the
biosphere between the organism and the
environment are referred to as biogeochemical
cycles. Bio refers to living organisms and geo
to rocks, soil, air and water of the earth.
There are two types of biogeochemical
cycles : the gaseous and the sedimentary cycle.
In the gaseous cycle, the main reservoir of
nutrients is the atmosphere and the ocean. In
the sedimentary cycle, the main reservoir is the
soil and the sedimentary and other rocks of
the earth’s crust.
The Water Cycle
All living organisms, the atmosphere and the
lithosphere maintain between them a
© NCERT
not to be republished
FUNDAMENTALS OF PHYSICAL GEOGRAPHY 130
Table 15.1 : World Biomes
Biomes
Forest
Subtypes Regions
Climatic
Characteristics
Soil Flora and Fauna
A. Tropical
1. Equatorial
2. Deciduous
B. Temperate
C. Boreal
Desert A. Hot and Dry
desert
B. Semi arid
desert
C. Coastal
desert
D. Cold desert
Grassland A. Tropical
Savannah
B. Temperate
Steppe
A1. 10° N-S
A2. 10°- 25° N-S
B. Eastern North
America, N.E.
Asia, Western
and Central
Europe
C. Broad belt of
Eurasia and
North America
(parts of
Siberia,
Alaska,
Canada and
Scandinavia)
A. Sahara,
Kalahari,
Marusthali,
Rub-el-Khali
B. Marginal areas
of hot deserts
C. Atacama
D. Tundra climatic
regions
A. Large areas
of Africa ,
Australia,
South
America and
India
B. Parts of
Eurasia and
North America
A1. Temp. 20-25°C,
evenly distributed
A2. Temp. 25-30°C,
Rainfall, ave. ann.
1,000mm, seasonal
B. Temp. 20-30° C,
Rainfall evenly
distributed 750-
1,500mm, Well-
defined seasons
and distinct winter.
C. Short moist moder-
ately warm
summers and long
cold dry winter;
very low
temperatures.
Precipitation mostly
snowfall
400 -1,000mm
A. Temp. 20 - 45°C.
B. 21 - 38°C.
C. 15 - 35°C.
D. 2 - 25°C
A-D Rainfall is less than
50 mm
A. Warm hot
climates, Rainfall
500-1,250 mm
B. Hot summers and
cold winter.
Rainfall 500 -
900 mm
A1. Acidic,
poor in
nutrients
A2. Rich in
nutrients
B. Fertile,
en-riched
with
decaying
litter
C. Acidic and
poor in
nutrients,
thin soil
cover
Rich in
nutrients with
little or no
organic matter
A. Porous with
thin layer of
humus.
B. Thin floccu-
lated soil,
rich in bases
A1. Multi-layered
canopy tall and
large trees
A2. Less dense, trees
of medium height;
many varieties co-
exist. Insects,
bats, birds and
mammals are
common species
in both
B. Moderately dense
broad leaved trees.
With less diversity
of plant species.
Oak, Beach, Maple
etc. are some
common species.
Squirrels, rabbits,
skunks, birds,
black bears,
mountain lions etc.
C. Evergreen conifers
like pine, fur and
spruce etc. Wood
peckers, hawks,
bears, wolves,
deer, hares and
bats are common
animals
A-C. Scanty vege-
tation; few large
mammals,
insects, reptiles
and birds
D. Rabbits, rats,
antelopes
and ground
squirrels
A. Grasses; trees
and large shrubs
absent; giraffes
zebras, buffalos,
leopards, h y e n a s ,
elephants, mice,
moles, snakes
and worms etc.,
are common
animals
B. Grasses; occ-
asional trees
such as cotton-
woods, oaks and
willows; gazelles,
zebras, rhin-
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