a chapter of biology for the students of class nine.

2. INTER-RELATIONSHIP OF
ORGANISIMS AND WITH
THEIR ENVIRONMENT

3. Define the following?
Biosphere
Ecology
Habitat
Population
Community

4. BIOSPHERE
Life is
supported
on the
earth
within a
relatively
thin
envelop of
air. This life
sustaining
envelope
of earth is
called
“biosphere
.”

5. ENVIRONMENT
The surrounding in which organism lives is called its environment. It includes such non living things as light,
water, air and soil. It also includes all the other living things of the area.

6. ECOLOGY
The
relationship of
living things of
an area with
each other
and with the
non living
things of their
environment is
called
environmental
biology or
simply
“ecology.”

7. HABITAT
The are or
place
where an
organism
lives is
called its
“habitat.”

8. POPULATION
A group of
same kind of
organisms
living
together in
the same
habitat is
called the
“population.”

9. COMMUNITY
Many different
kinds of
organisms
living together
in the same
habitat make
up a
“community.”

11. Q.2 Discuss the components of a community?

12. COMPONENTS OF A COMMUNITY
The members of a community can be divided into three major groups on the basis of how they
get food.

13. PRODUCERS All the green
plants are called
producers
because they can
make their food
themselves from
water and carbon
dioxide by sun
energy.
Producers are the
primary source of
energy for other
organisms. Hence
all the members
of a community
depends, directly
or indirectly on
the producers

14. The animals and all
other organisms that
cannot make their
food are called
consumers. They
cannot use the
molecules of ‘non
living world.’ They eat
other organisms.
Consumers are of
three types:

15. Herbivores are the animals that eat plants.

16. CARNIVORES
Carnivores
are the
animals that
eat other
animals

17. OMNIVORES
Omnivores are
the animals that
eat plants and
animals both.

18. DECOMPOSERS
Many bacteria and fungi do not eat living organisms and are unable to make their food themselves. They depend
on dead organisms and extract their food by decomposing these decaying organisms . In doing so they break down
the complex organic molecules of dead plants and animals into simple inorganic substances which are returned to
environment( to water, soil and air) Green plants once again use inorganic substances, in the presence of sun light,
for manufacturing their organic food. Hence the cycle starts on.

19. Q.3 What is meant by primary consumer, secondary consumer
and tertiary consumers and predator prey relationship?

20. PRIMARY CONSUMER
As herbivores consume green plants they are called primary consumer. The primary consumers eat producers.

21. SECONDARY CONSUMER
Carnivores who feeds on primary consumers is called secondary consumer because it receives the energy from the
plants second hand via primary consumer. For example a small bird that eats a grass Hooper.

22. TERTIARY CONSUMER
An animal that
eats a secondary
consumer is
called tertiary
consumer,
Example large
bird an eagle.
The tertiary
consumers are
usually not eaten
up by other
organisms. They
after death one
however,
decomposed by
decomposers.

23. Consumer in a community
show another type of
feeding relationship called
predator prey relationship.
The two animals are
usually involved. The
animal that feeds on the
other is a predator
whereas the one that is
eaten upon is a prey.
PREDATOR PREY RELATIONSHIP

25. Q. 4 Define ecosystem, Discuss their importance and relationship?

26. ECOSYSTEM
The interdependence hence interaction of all the organisms of a community with each other and with their
nonliving environment is called ecological system or simply an ecosystem.

27. BIOTIC COMPONENTS OF ECOSYSTEM
An ecosystem may be a vast ocean, a forest, a pond, an aquarium or
even a single drop of water. The living organisms that interact in an
ecosystem make up its biotic components. These living components
include producers, all type of consumers, and the decomposers.

28. ABIOTIC COMPONENTS OF ECOSYSTEM
Abiotic components of an ecosystem are the physical aspects of its surrounding which influence the biotic
components. They may act as limiting factor. Most important abiotic components of an ecosystem are light,
temperature, water soil and air.

29. LIGHT
 Light is the most vital factor without which no life
can exist. Light coming in the form of radiant
energy from the sun is the source of energy for
every ecosystem.
 Plants by the process of photosynthesis change this
light energy into chemical energy which is needed
by every living thing.
 Distribution of plants and animals is affected by the
type, intensity and exposure time of light.
 A small amount of this light is utilized in the
photosynthesis where as rest of it maintains the
temperature of earth and atmosphere.
 Light is also necessary for vision.
 Light is necessary for the onset(start) of certain
biological processes for example flowering of
certain plants, making vitamin ”D” in human being
and migration of many animal.

30. TEMPERATURE
 Temperature is also an important factor affecting an
ecosystem.
 It influences the type of communities in different
areas.
 Temperature decreases at higher altitudes and
higher latitudes and fauna and flora changes
accordingly.
 Temperature changes during the day and night and
also varies from season to season. Its variation
affects the land animals more than the aquatic
animals where temperature changes are nominal.
 Many birds and a few mammals migrate or hibernate
in winter.
 Enzyme activities of metabolic reactions are also
altered with the change in temperature.
 Most form of life cannot survive in extreme
temperature.

31. WATER
 All the living things need
water.
 It is the major part of
protoplasm and maintains
the turgidity of the cells.
 It acts as a solvent for the
most of the metabolites.
 Inorganic substances enter
the pants with water in
dissolved form.
 It is the raw material for
photosynthesis.
 The amount of water on
land is controlled by rain
fall. The amount of water
in combination with
temperature determines
the type of vegetation of
an area.
For example:
 Thick forests grow in the warm areas which receive abundant rain fall.
 Its scarcity in the areas with extreme temperature creates desert conditions, hence it
controls the distribution of plants and animals.

32. SOIL
 Soil is the upper layer of
earth’s crust. It consists
of soil particles of varying
size where micro
organisms decompose
the dead animals and
plants to convert them
into humus.
 Humus enriches the soil
and increases its water
and air holding capacity.
 Most of the plants are
anchored in the soil and
depend on it for their
growth by absorbing
water and inorganic
substances.
 The type of soil and its
fertility determine the
flora hence, fauna of an
ecosystem.

33. AIR
 Air is a gaseous envelope which surrounds the earth. Air is a mixture of nitrogen, oxygen, carbon dioxides and
water vapors.
 It plays an important role in the smooth running of an ecosystem.
 Nitrogen is an essential constituent of proteins.
 Atmospheric nitrogen, converted into nitrates, is taken up by plant along with the nitrates of decaying
organisms for the building up of their proteins.
 Oxygen is vital for respiration of all the living beings whereas carbon dioxide is a must for photosynthesis of
carbohydrates. The organic food(plant) thus produced is taken up by animals.
 The composition of air and its velocity then thus alter abiotic factors of the environment and ultimately affect
the plant life, and the ecosystem.

34. HUMIDITY
Humidity which is
the concentration
of water vapours in
the air controls the
rate of evaporation
of water and
transpiration in
plant.

35. Q. 5 Write a note on the following?
 Energy transfer (Trophic Level)
 Food Chain
 Food web

36. TROPHIC LEVEL:(ENERGY TRANSFER)
 All the organisms in an ecosystem need energy to carry
out their life activities to stay alive.
 Its primary source is solar energy coming through the
sunlight from the sun.
 This energy is trapped by producers(the green plants) and
is converted into energy rich organic food.
 Part of this energy is transferred to primary consumer
when they eat producers.
 Primary consumer and when eaten up transfer this energy
to secondary consumers.
 Secondary consumers in turn form the meal of tertiary
consumer. Hence the energy is transferred to the next
level, the tertiary consumers.
 These steps of transfer of energy rich food are called
trophic levels.

37. FOOD CHAIN
The linkage of energy transfer from one
trophic level to another by eating or
being eaten up is called a food chain.
Energy is distributed to all organisms
through food chain. A food chain
represents one possible route for transfer
to food material and energy. Many other
routes exist .

38. FOOD WEB
 An animal does not always feed on the
same food. Most of the living thing eat
many kinds of organisms. A snake may eat a
frog, a lizard, a bird or a rat. And eagle may
eat a frog, a rabbit, a snake or another bird.
Similarly omnivores eat both plants and
animals. All these feeding relationship or
food chain in a community make up a
crisscross network of many food chains.
 This combination of many highly
interconnected food chains is called a food
web. In as food web an animal has many
option of food to eat. A food web actually
links together the different populations of a
community.

39. Q. 6 How does energy flows in an ecosystem? In what different ways ecological
pyramids are made?

40. FLOW OF ENERGY IN AN ECOSYSTEM
Energy is must to run every
ecosystem. The primary
source of energy in the
biosphere is sun. in order for
an ecosystem to stay stable
and to function properly
materials and energy must
pass through various levels
from producers up to
tertiary consumers. At each
tropic level not all but a
small amount of energy is
transferred to the next level
when it stored as plant
material or animal flesh.
More them half of the
energy is lost as heat.

41. There are three different
ways of making
pyramids.
 Pyramid of energy
 Pyramid of numbers
 Pyramid of biomass
TYPES OF PYRAMIDS

42. Q.7 What is pyramid of energy?
PYRAMID OF ENERGY
o At each tropic level not all but a small
amount of energy is transferred to the
next level where it is stored as plant
material or animal flesh.
o More than half of energy is lost as heat.
o A significant quantity is consumed at
each level by the organism itself in
carrying out its own body function like
movement, respiration, reproduction etc.
o Each stage of tropic level in a food chain
gets about 10% potential energy from its
previous level. This reduction in transfer
of energy at various levels in an
ecosystem is expressed in the form of a
pyramid called the pyramid of energy.
PYRAMID OF ENERGY

43. Q.8 What is pyramid of numbers?
PYRAMID OF NUMBERS
It is observed that the number
organisms in an ecosystem gradually
decreases at each higher tropic level.
When the number of organisms is
counted at each level it is observed that
there are always present fewer
organisms in each higher feeding level
than those in the previous one. For
example there are more mice than there
are snakes which feed on mice. This
relationship is also expressed in the
form of a pyramid known as pyramid of
numbers.
PYRAMID OF NUMBERS

44. Q.9 What is pyramid of biomass? PYRAMID OF BIOMASS
A pyramid which represents the total biomass (total mass) of dry organic matter per unit area of organism at each
trophic level is called the pyramid of biomass. It shows that each higher feeding level contains less biomass than
the previous tropic level. It results from energy loss in a food chain at each trophic level.

45. Q. 10 what are the components of pond ecosystem? Or explain a stable
ecosystem and its interaction by taking the example of afresh water pond?

46. CONPONENTS OF A POND ECOSYSTEM
There are two types of components: Abiotic components Biotic components
Abiotic components
Abiotic components include the
following:
o Water
o Sunlight
o Oxygen
o Carbon dioxide
o Nitrogen
o Calcium
o Phosphorus
o Salts
o Most of the nutrients are
available in ample quantity
particularly at the bottom of the
pond.
o Oxygen and carbon dioxide are
available in free as well as in
dissolved form and their
concentration varies due to the
photosynthesis activity of the
producers of the pond.

47. Biotic components
Biotic components include
many form of producers,
consumers and
decomposers.

48. PRODUCERS
There are two types of
producers:
MACROPHYTES:
o These include many
types of large root
bearing plants.
o They are
submerged in water
such as shrubs.
o They have large
floating leaves like
lotus or simply the
under water plants
like Hydrilla.

49. PHYTOPLANKTONS:
o These microphytes are
minute floating plant
like blue green algae,
euglena and volvox etc.
o These are distributed
throughout the pond
water wherever there is
sufficient light available
for photosynthesis.
o Phytoplankton’s
whenever present in
plenty give the water a
greenish look.

50. CONSUMERS
All major types of consumers are present in a pond ecosystem
PRIMARY CONSUMERS
These are the small herbivorous zooplankton like Euglena,
minute crustaceans like Cyclops, insects, snails, larvae of frogs
and toads and some small herbivorous fishes. They all feed
upon on pond plant.

51. SECONDARY CONSUMERS
These are the small animals which are first level carnivores and
include many beetles like insects, crustaceans, small fishes and
frogs etc.

52. TERTIARY CONSUMERS
o These are basically the large fishes.
Sometimes these are aquatic birds and
snake as well.
o The fishes in a pond occupy all the
consumer levels.
o Many small fishes are herbivorous thus
primary consumers.
o Large fishes are secondary consumers.
o The largest fishes are tertiary consumers.
o A number of bottom dwelling animals like
aquatic worms are called scavengers or
detritivores which feed on pieces of dead
organic matter falling down from the
surface water.

53. DECOMPOSERS
In pond
decomposers are
the heterotrophic
aquatic bacteria
and distributed
throughout the
pond water. They
are more common
along the bottom
where plant and
animal remains
accumulate. When
there dead
organisms are
decomposed, by
these bacteria and
fungi, nutrient
trapped in them
are released in the
soil for reuse by
plants.

54. Q.11 Write a note on Aquarium?

55. AQUARIUM o An aquarium is a simple fresh water
ecosystem usually decorated in our homes.
o Its equilibrium is to be maintained by the
curator.
o It cannot retain its good shape until and
unless all its biotic and abiotic components
are maintained in a stable form.
Example
o A regular supply of fresh water is maintained.
o Oxygen concentration is kept within limits by
an aerating pump.
o Aquatic plants are kept health.
o The minerals and fish meal is added
continually.
o Tropic levels are restricted to producer
Hydrilla like hydrophytes and one type of
consumers, the herbivorous fishes.
Decomposers are not significant, because
dead organisms are not allowed to
decompose inside the aquarium for the
cleanliness and oxygen deficiency reasons.
o Smooth running of this ecosystem needs
assistance which is provided by the aquarium
curator.

56. Q.12 What is a balanced ecosystem?
BALANCED ECOSYSTEM
o A balanced ecosystem
in actually a cycle of
energy transfer. Non
living components of
an ecosystem move
through the
environment in a
series of steps called a
cycle.
o Oxygen, carbon
dioxide, nitrogen and
water are the
essential non living
materials that and
always needed by
every ecosystem.
These are being
continuously driven in
a circular path and are
thus continuously
recycled to be used
again and again.

57. Q.13 Give an account of carbon cycle in nature? Explain with
the help of a graphic representation?

58. CARBON CYCLES
o All types of life on the earth is based on element carbon.
It is needed for the formation of proteins, carbohydrates,
fats and many other substances that make up a living
thing.
o The carbon comes from carbon dioxide which is found in
atmosphere.
o Plants take this carbon dioxide from air and convert it into
carbon dioxides by the process photosynthesis. Carbon in
this form passes into a food chain.
o Animals get carbon by eating plants and other animals.
o The amount of carbon dioxide in the air stays the same
because it is returned to the air as fast as plants take it in.
all living plants and animals respire and then exhale
carbon dioxide free from the bodies of dead organisms.
o It is also returned to the air combustion that is burning of
wood and other organic fuel like coal, petrol and gas etc.
o Two important processes the respiration and
photosynthesis helps a lot to run the carbon oxygen cycle.
o During respiration carbon dioxide is discharged and
released in the atmosphere. Photosynthesis on the other
hand consumes carbon dioxide and release oxygen and
thus the balance is maintained.

59. Q.14 Give an account of water cycle or hydrological cycle?
Explain with the help of graphic representation?

60. WATER CYCLE OR HYDROLOGICAL CYCLE
o The most common compound on the earth is water. It
plays vital role in the structure and metabolism of living
things the water recycled and used again and again.
o This water cycle is powered by the heat of the sun.
o Water evaporates in the form of water vapours from the
oceans, rivers, lakes and ice caps of the mountains.
o These water vapours move into the atmosphere this
process is called evaporation.
o When temperature of air cools water vapours condense
and form tiny drops of liquid water and fall on earth as
rain and snow, the process is called precipitation.
o Some water runs off into oceans, rivers and lakes etc. the
rest seeps into the soil.
o Some of this ground water is absorbed by the roots of the
plants.
o The plants return this water to the air, through leaves, by
transpiration.
o The water taken by animals is returned to the
environment as they urinate and perspire. They also
discharge water in the form of water vapours as they
exhale.
o In this way water cycle continues in nature.

61. Q.15 Give an account of nitrogen cycle? Explain with help of
graphic representation?

62. NITROGEN CYCLE
o Nitrogen is one of the important constituent of proteins and DNA. It
is therefore, an essential element in the structure of all the living
thins.
o Atmospheric nitrogen combines with oxygen during lightening to
make certain chemical which reach the soil with rain and form
nitrates.
o Two groups of nitrogen fixing bacteria can change atmospheric
nitrogen into nitrates, the form of N2 used by living organism.
One Group Lives in the Soil:
o Other group lives in the nodules of the roots of certain leguminous
plants.
o The conversion of atmospheric nitrogen into nitrates, for use of the
plants, is called nitrogen fixation and the bacterial performing this
function are called nitrogen fixing bacteria.
Nitrifying Bacteria:
They make nitrates from the nitrogenous wastes excreted by liing
animals and also from the decomposing bodies of dead animals and
plants. This process is called rectification. These nitrates are absorbed
by the plants and the nitrogen cycle start again.
Denitrifying Bacteria:
They are found in the soil. They break he nitrates etc. into free
nitrogen(denitrifying) which is released in the air so as to complete the
cycle and to keep the nitrogen in balance in nature.

63. Q.16 What are the biotic relationship among the organisms at
various trophic levels? Name them?

64. BIOTIC RELATIONSHIPS
Biotic relationships are common in
a community. These associations,
some how act as the limiting
factors to maintain the population
equilibrium.
Examples of these relationships are
as follows:
o Predation
o Competition
o Symbiosis
o parasitism

65. Q.17 What is Predation?
Predation
Predator
A predator is an
animal which
captures and kills
live animals for its
food.
Prey
The animal is killed
is called prey.
Predator-Prey Relationship:
o Predator-prey relationship is an important factor in which are population continually determines the population of the other.
o If prey population increase the number of predators will increase.
o When more predation will take place the prey population will be reduced.
o When prey population decreases the number of predators will decrease.
o This predator-prey cycle therefore helps in maintaining the ecosystem stable.
Example:
The population of rabbits when first introduced in Australia rapidly grew so large that its created a menace. Why? Because no
predators were present and hence there was no check on their population. Predators were introduced to counter the situation.

66. Q.18 What is competition?
Competition:
This relationship is actually a
“cold war” between the
organisms of a community
occupying the same habitat.
Purpose of Competition:
o This completion may be for
food, mate or simply for the
sake of living space.
o This competitio9n becomes a
limiting factor and aids in the
survival of the fittest and
keeps the size of community in
balance.
Types of Competition:
Intra-Specific:
Competition between the
individuals of the same species
Inter-Specific:
Competition between the
individuals of the different
species.

67. Q.19 What is symbiosis? Describe its types with examples?
SYMBIOSIS:
It is an association between the two organisms of the different species which start living together. They are mutually benefited or
at least one gets benefit but the other in neither benefited not harmed.

68. TYPES OF SYMBIOSIS:
The symbiotic associations are of two types
Mutualism:
In mutualism two different kinds of organisms get
benefit from living together. In most of the cases
they cannot live without each other.
Example 1
Termite eats wood but cannot digest its main
component the cellulose. Small unicellular
flagellate protists living in their intestine digest
this cellulose for them. The termite is thus
provided with means of digestion, in return
protists are given a safe place to live. The termites
will starve to death if these protists are removed
from their intestine.
Example 2
Another common example is of insects that
pollinate the flower as they eat nectar from them.

69. Commensalism:
It is a relationship in which one of the organisms, the commensal, gets the benefit whereas the other is neither benefited nor
harmed.
Example1.
A good example is the relationship between a sucker fish and a shark. Remora(sucker fish) is small fish which attaches itself, with
the help of its sucker, just behind the mouth opening of the shark. A fish takes a free ride and swallows the falling out pieces of
food as shark eats its prey. The shark does not benefit from this relationship, nor its skin harmed by the sucker of remora.
Example 2:
Another common example of commensals is spirochetes, a bind spiral shaped bacteria, living in between on teeth to obtain food
but causes us no harm.

70. Q.20 What is parasitism? Describe its types with examples?
PARASITISM:
o It is probably the most
famous and common
relationship in the
interaction of organisms. In
this association the parasite
lives on (Edo-parasite) or
inside the body
(Emdoparasite) of another
organism called the host.
o The parasite gets form host
the food and a place to live
and is thus benefited
whereas its host is harmed.
A successful parasite takes
out enough food from the
host to grow and reproduce.
Parasites include bacteria,
virus, insects, protozoa and
worm.

71. Example of
Ectoparasites
o Leaches who suck the blood of
cattle
o Mosquitoes who suck the
blood of human

72. Example of Endoparasites:
Plasmodium:
It is a protozoan and an endoparasite. It
lives in the human body and feeds on its
blood cells and causes him the world’s
number one disease the malaria fever.

73. Q.21 What is extreme environment? Why is life difficult in extreme environment?
What do the organisms do to cope with these adverse conditions?
EXTREME ENVIRNONMENT
The biotic factors like light, water, temperature, soil, etc. make the climate of an area. Wherever these climatic
factors are optimum, plenty of life flourishes with case but where they are at their extreme, either at their
minimum or at their maximum, the environment is said to be an extreme environment.

74. Places of Extreme Environment
These least hospitable places are:
o Ice caps of Artic and Antarctic circles (polar regions of the earth) and peaks of
high mountains which are snow coved.
o Deserts

75. Ice Caps And Peaks of High Mountains:
These are virtually incapable of supporting
life because the ground water is permanently
frozen and not available to plant roots. Soil is
almost not existent and the temperature of
the ever fast blowing air is below freezing
point almost through the year. In this harsh
environment it is very difficult for life to exist
and hence plants and animals are present in
very few numbers. It is during a short mild
summer, when some ice melts. Some lichens
and grasses grow here and there, and a few
migratory birds arrive. Permanent residents
are a few hares, arctic foxes, polar bears and
seals.
Adaptations To Cope This Environment
o They develop a thick coat of hairs on the
skin or thick insulation of fat under their
skin to conserve the body heat.
o They have broad feet and long claws
which help them in walking on ice and
occasionally swimming in water.

76. DESERTS:
Deserts have the most dry and harsh environment on the
earth. The rainfall is never more than a few centimeters per
year where as in some parts temperature varies between as
high as 70’C during the day time to as low as below freezing
point during the night. Soil is all sand with no underground
water. Decomposing activity is minimal hence nutrient content
of the soil is very low. Xerophytes Plants like cactus, camel and
nocturnal animals living in burrows are found.
Adaptations To Cope This Environment
Cactus
Cactus survives in deserts which as many modificati0ns for
maximum absorption and conservation of water.
Camel:
A familiar animal, well adapted to desert, is camel which can
survive without food and water even for a week’s time and can
cover the distance of 1000 kilometers in this condition.
Adaptive features:
o Hard skin
o Concentrated Urine
o Dry faeces
o Humps, one or two are the store houses of reserved food
o Broad and flat padded feet suit to walk on the sand
All these measures help the animal to conserve the maximum body water.

77. Survival of Fittest:
As per rule of survival of habitat,
the living things have become
modified in many ways to
become fit and to get adapted to
each and every habitat even the
least Hospitable areas including
ice caps and deserts.

78. Q.22 differentiate between a population and community? Give example?
Population Community
Definition
A group of some kind of organisms living
together in the same habitat is the
population.
Many different kinds of organisms living
together in the same habitat make up a
community.
Example
The frogs in a pond make up the frog
population, the Rohu in the same pond
makes up the Rohu population and
Hydrilla plants make up Hydrilla
population. Man is a member of human
population of his area.
A fresh water pond includes a
population of Hydrilla, a population of
frogs, insects worms, Rohu and many
other kinds of animals. Population of all
these organisms, sharing the same
habitat, constitutes the community of
that pond

79. Q.23 Difference between Autotrophs and Heterotrophs?
Autotrophs Heterotrophs
Plants which can manufacture
their own food by
photosynthesis are called
autotrophs
The animals cannot make their
own food, so they use plants
and other animals as food and
hence are called heterotrophs

80. Fill in the blanks:
1. Everything around you is our ____________
2. Area where an organism lives in nature, it ____________
3. Many populations sharing a common area is ___________
4. Green plants are called_______ because they produce food fro the entire ecosystem.
5. Organisms who cannot prepare their food are __________
6. The organisms which eater others are called ___________
7. The common decomposers in an ecosystem are________and _________
8. Steps of food and energy transfer in an ecosystem are called ____________
9. An animal has many option of food in food________
10. Living organisms of an ecosystem are called its________ components.
11. Transfer of the amount of energy in an ecosystem at various levels is expressed in the form of ______of______