CBSE Class 10 Science Case Study
Chapter 13 - Our Environment
Check Point 01
Q. 1. When do we consider a given substance as waste?
Answer: Waste is something unwanted or unusable material. It is any material which is
no longer useful as it has served its purpose or at the end of the process has no further
use and it is generally discarded. For example, Garbage that we daily produce in our
home. Food that we eat goes into our body. It is then acted upon by various specific
enzymes which are needed for the breakdown of these large food molecules into
simpler small molecules which provide energy. Materials like plastic which cannot be
broken down by bacteria’s or enzymes are non-biodegradable (cause threat to human
health). Hence these products are also called waste. For example polythene bags,
metal scarps.
Q. 2. In what way can biodegradable substances be used by farmers?
Answer: Biodegradable wastes are those substances that can be broken down by
biological processes (like by enzyme or bacterial action). For Examples: cattle dung,
cotton, jute, paper, fruit and vegetable peels, leaves etc.
They can be used by farmers in various ways:
a) Cattle dung is used as natural fertilizers for crops and plants. It is also cost-free.
b) Jute can be used to prepare bags for storing grains.
c) Vegetable peels can be used as food for cattle’s. Etc.
Q. 3. Besides natural degradation by microbes, what are the other ways to
dispose of biodegradable wastes?
dispose of biodegradable wastes?
Answer: These biodegradable wastes are animal or plant matter that breaks down
naturally with exposure to microorganisms, heat, and oxygen. There are other ways
also for their decomposition:
a) Collect all the material and burn it in a pit.
b) React it with some strong acid. But both these ways are not good for nature.
c) Recycling them into a usable material which is called composting. It is done is a
sealed container (no presence of air). It will get converted into humus-like material
which is a good fertilizer for plants. This step is eco-friendly.
Q. 4. Why is plastic bag called non-biodegradable while the paper is not?
Answer: Plastic bag cannot be broken down by microorganisms. It will remain in the
environment for many years. Paper is a biodegradable material is made from other
natural products like fruits, plants etc. Hence paper can be degraded naturally by the
action of microorganisms in a few months.
Q. 5. What is the most characteristic feature of non-biodegradable wastes?
Answer: The most important characteristic features of these indecomposable products
is that they are formed from non-organic matter.
It is the material not derived from living matter. And hence will pose a threat to ecosystem.
Q. 6. Write any one effect of non-biodegradable substances.
Answer: These non-organic matters can prolong exist in the environment without
getting broken down by biological processes and will cause harm to the environment.
For example Various plastic bags, if any of them is eaten by an animal then it can choke
its digestive system. These materials can only be digested by specific enzymes, but
they are not present in the animal’s body. Hence it will lead to the death of that animal.
Check Point 02
Q. 1. From the list given below, choose an artificial ecosystem. Pond, crop field,lake, forest.
Answer: A community made up of both living and nonliving organisms forms an
ecosystem. The type of ecosystem which is made by human beings is called as artificial
ecosystem. Among the above mentioned - Pond and crop fields are manmade
ecosystem.
Q. 2. In what way, the biotic components of an ecosystem are different from
abiotic components?
Answer:
Q. 3. Producers are also referred to as the autotrophs. Why?
Answer: Organisms which can produces their own food like sugar and starch from
inorganic substances using photosynthesis in the presence of chlorophyll are called
producers. And an autotroph is also an organism that can produce its own food using
light, water, carbon dioxide, or other chemicals.
Green plants, algae, and certain bacteria are example of autotrophs that are producers.
Q. 4. Why herbivores also known as first order consumers?
Answer: Organisms which take their food prepared by plants and plants products are
called herbivores. These are the organisms that cannot make their own food. So they
depend directly on green plants for food and then are referred to as first or primary
order consumers. Herbivorous animals like elephant, camel, cow, buffalo, deer, sheep,
goat, rabbit etc. are the first order consumers.
Q. 5. Zebra, jackals, lions, goat, horse, wolves and sheep. Identify the first order
consumers from those given above. Give a reason to support your answer.
consumers from those given above. Give a reason to support your answer.
Answer: Zebra, goat, horses and sheep are all those organisms which eat producers
(green plants) for energy and hence are herbivores. They all cannot make food by
themselves hence; they feed on plants which can make food for themselves.
Q. 6. Based on their feeding habits, differentiate parasites from decomposers.
Answer: Parasites have heterotrophic mode of nutrition where a parasitic organism
lives on the body surface or inside the body of another type of organism (a host) and
gets nutrition directly from the body of the host. For Example: Plasmodium, Lice, tape
worm, round worm etc. And decomposers are organisms that get energy by decaying or
breaking down chemically the remains of dead organisms. When an organism dies,
decomposers decay the body extracting the last bit of energy from it. For example: fungi
and bacteria.
Check Point 03
Q. 1. In three words, describe the relationship of organisms working in a food
chain.
chain.
Answer: The relationship of organisms working in a food chain can be described as
“FLOW OF ENERGY”. It is from producers to consumers to decomposers. Each group
depends on each other for food and energy.
They will not be able to survive if one group were removed. In general, the flow of
energy in an ecosystem starts with sunlight (the ultimate source of all energy on Earth)
which is absorbed by the producers, goes to the consumers, then to the decomposers,
and back to the producers to start all over again.
Q. 2. Identify the members present at the bottom and top of a terrestrial food
chain.
chain.
Answer: Terrestrial food chain shows a relationship between plants and animals found
on desserts, grasslands, and forests.
The energy pyramid has a large base and becomes smaller at the top.
At the bottom or the first level are the producers. Here, the energy and the number of
organisms are very high. For each level or feeding stage, the energy and number of
organisms decrease so the pyramid becomes smaller at the top. And at the top are
carnivores like a tiger, eagle, etc.
Q. 3. Consider a food chain of the following: Fish, crab, phytoplankton, shark.
Arrange the above chain in the proper order of trophic level.
Arrange the above chain in the proper order of trophic level.
Answer:
This trophic level is a depiction of the pond ecosystem.
● The first level is represented by the producers or the autotrophs; for example,
phytoplankton and plants. They prepare their own food with the help of energy from
sunlight through the process of photosynthesis.
● The second trophic level is characterized by the presence of primary consumers such
as crabs inhabiting the pond. Organisms in this level consume the phytoplanktons or
producers.
● The third level comprises of the omnivores, especially the fish species, which can
feed on both plants.
● The fourth and the top most level is for carnivores or tertiary consumers which are
flesh eaters.
● The first level is represented by the producers or the autotrophs; for example,
phytoplankton and plants. They prepare their own food with the help of energy from
sunlight through the process of photosynthesis.
● The second trophic level is characterized by the presence of primary consumers such
as crabs inhabiting the pond. Organisms in this level consume the phytoplanktons or
producers.
● The third level comprises of the omnivores, especially the fish species, which can
feed on both plants.
● The fourth and the top most level is for carnivores or tertiary consumers which are
flesh eaters.
Q. 4. What percentage of solar radiation is absorbed by green plants for
photosynthesis?
Answer: Between 98 and 99 percent of solar energy reaching the Earth is reflected
from leaves and other surfaces and absorbed by other molecules, which convert it to
heat. Green plants capture about 1 % of the solar energy using chlorophyll in their
leaves. Photosynthesis is the chemical process by which producers capture light energy
from the sun and use it to combine water with air to form sugar or food. The chemical
equation is:
photosynthesis?
Answer: Between 98 and 99 percent of solar energy reaching the Earth is reflected
from leaves and other surfaces and absorbed by other molecules, which convert it to
heat. Green plants capture about 1 % of the solar energy using chlorophyll in their
leaves. Photosynthesis is the chemical process by which producers capture light energy
from the sun and use it to combine water with air to form sugar or food. The chemical
equation is:
Q. 5. In which form is the 10% energy available for transfer?
Answer: It is transferred in the form of chemical energy. The producers capture the
energy present in sunlight and convert it into chemical energy which is passed into onto
other trophic levels. This means that when primary consumers eat plants they are able
to turn up only 10% of food for their own body and the rest is lost in the form of heat.
And this 10% of nutrients only are available for the next level of consumers.
Answer: It is transferred in the form of chemical energy. The producers capture the
energy present in sunlight and convert it into chemical energy which is passed into onto
other trophic levels. This means that when primary consumers eat plants they are able
to turn up only 10% of food for their own body and the rest is lost in the form of heat.
And this 10% of nutrients only are available for the next level of consumers.
Q. 6. Fertilizers and other chemicals used in agriculture are harmful to us. Give
reason.Answer: Farmers use various fertilizers and pesticides (chemicals) to protect their
crops and plants from diseases. These chemicals are absorbed by the plants along with
water and minerals from the soil and are taken by aquatic plants and animals as well.
And since these chemicals are non-biodegradable, they will remain in the food chain.
Humans are the final consumers of every food chain hence, all of this chemical gets in
their body when they feed on organisms or plants of the lower trophic level. In this way,
these fertilizers can cause harm to us.
reason.Answer: Farmers use various fertilizers and pesticides (chemicals) to protect their
crops and plants from diseases. These chemicals are absorbed by the plants along with
water and minerals from the soil and are taken by aquatic plants and animals as well.
And since these chemicals are non-biodegradable, they will remain in the food chain.
Humans are the final consumers of every food chain hence, all of this chemical gets in
their body when they feed on organisms or plants of the lower trophic level. In this way,
these fertilizers can cause harm to us.
Q. 7. Identify the organisms from the following food chain which will respectively
have a maximum and minimum concentration of chemicals in its body? Peacock,
frog, snake, grasshopper.
Answer: Grasshopper will have the minimum and peacock will have the maximum
concentration of chemicals in their body.
Explanation: Among all the animals mentioned here, the grasshopper is the primary
consumes which will eat plants having chemicals so they are the first one to feed on
them. The chemicals inside the grasshoppers will start damaging his whole body and as
the food chain proceeds grasshopper will be eaten by grog, which will be eaten by a
snake. And by this time the snake’s body will also get damaged from inside with
chemicals as they cannot be degraded. Hence when peacock will feed on the snake, he
will have the maximum concentration of chemicals inside its body.
Check Point 04
Q. 1. Ozone present in the atmosphere is very important for sustenance of life on
earth. Justify.
Answer: When UV radiations from the sun reach the earth’s atmosphere which is
heavily rich in oxygen. Then these UV rays split molecular oxygen (O2) into free oxygen
(O). Afterward, this free oxygen reacts with molecular oxygen; it forms ozone (O3).
have a maximum and minimum concentration of chemicals in its body? Peacock,
frog, snake, grasshopper.
Answer: Grasshopper will have the minimum and peacock will have the maximum
concentration of chemicals in their body.
Explanation: Among all the animals mentioned here, the grasshopper is the primary
consumes which will eat plants having chemicals so they are the first one to feed on
them. The chemicals inside the grasshoppers will start damaging his whole body and as
the food chain proceeds grasshopper will be eaten by grog, which will be eaten by a
snake. And by this time the snake’s body will also get damaged from inside with
chemicals as they cannot be degraded. Hence when peacock will feed on the snake, he
will have the maximum concentration of chemicals inside its body.
Check Point 04
Q. 1. Ozone present in the atmosphere is very important for sustenance of life onearth. Justify.
Answer: When UV radiations from the sun reach the earth’s atmosphere which is
heavily rich in oxygen. Then these UV rays split molecular oxygen (O2) into free oxygen
(O). Afterward, this free oxygen reacts with molecular oxygen; it forms ozone (O3).
This ozone now protects the earth from harmful UV radiations of the sun, by allowing
only some percent of rays to fall on the earth’s surface. Ozone acts as a filter of sun
rays. These rays can cause skin cancer in human and can also affect other living
organisms.
only some percent of rays to fall on the earth’s surface. Ozone acts as a filter of sun
rays. These rays can cause skin cancer in human and can also affect other living
organisms.
Q. 2. The ultraviolet radiations are damaging to living components of the
environment. Give a reason.
Answer: When UV (ultraviolet) radiations from the sun reach earth’s atmosphere which
is heavily rich in oxygen. These high energy UV rays split molecular oxygen (O2) into
free oxygen (O). Afterward, this free oxygen reacts with molecular oxygen; it forms
ozone (O3).
These harmful UV radiations of the sun, can cause skin cancer in human and can cause
many health hazards like skin cancer, cataract, destruction of plants, etc.
environment. Give a reason.
Answer: When UV (ultraviolet) radiations from the sun reach earth’s atmosphere which
is heavily rich in oxygen. These high energy UV rays split molecular oxygen (O2) into
free oxygen (O). Afterward, this free oxygen reacts with molecular oxygen; it forms
ozone (O3).
These harmful UV radiations of the sun, can cause skin cancer in human and can cause
many health hazards like skin cancer, cataract, destruction of plants, etc.
Q. 3. Efforts are being made for substituting the chemicals like CFCs. Why?
Answer: CFCs are chlorofluorocarbons are the synthetic chemicals which are made by
humans artificially, that means they are not the natural products. Excessive use of these
CFCs in refrigerators, ACs, fire-extinguishers, etc. causes the depletion of ozone layer.
Because then UV radiations will reach the earth’s surface destructing the survival of
plants and organisms.
Answer: CFCs are chlorofluorocarbons are the synthetic chemicals which are made by
humans artificially, that means they are not the natural products. Excessive use of these
CFCs in refrigerators, ACs, fire-extinguishers, etc. causes the depletion of ozone layer.
Because then UV radiations will reach the earth’s surface destructing the survival of
plants and organisms.
Q. 4. Name the process in which wastes are burned at high temperature.
Answer: Waste Combustion is the process of burning waste at very high temperatures.
It is the simplest and earliest form of waste disposal. But this method leads to the
release of highly toxic chemicals in the environment which is harmful to the organisms.
Answer: Waste Combustion is the process of burning waste at very high temperatures.
It is the simplest and earliest form of waste disposal. But this method leads to the
release of highly toxic chemicals in the environment which is harmful to the organisms.
Q. 5. Untreated sewage being disposed of in waste bodies to lead to water
pollution. Suggest the practices that can be included for better disposal of
sewage waste.
Answer: All this untreated sewage can be processed in Sewage treatment plants. In
this, undesirable substances are removed from waste water by various physical,
chemical and biological pathways. It produces semisolid waste which is nothing but
manure. This product is more eco-friendly and biodegradable. This won’t cause any
problem with live organisms.
pollution. Suggest the practices that can be included for better disposal of
sewage waste.
Answer: All this untreated sewage can be processed in Sewage treatment plants. In
this, undesirable substances are removed from waste water by various physical,
chemical and biological pathways. It produces semisolid waste which is nothing but
manure. This product is more eco-friendly and biodegradable. This won’t cause any
problem with live organisms.
Q. 6. What can best method be used for the safe disposal of hospital wastes?
Answer: Hospital waste comprises of those biological substances that pose a threat to
living organisms. They can spread infections to the living if left untreated or just thrown
in normal dustbins. Hence the best method for their complete removal will be
combustion. Burning at a very high temperature kills all the bacteria and
microorganisms which can spread the disease.
Chapter Exercise
Q. 1. Can biodegradable wastes be harmful?Answer: Yes, sometimes biodegradable waste can be harmful also.
Because when these materials are decomposed with the help of microorganisms, then
there is a release of powerful green house gases. These greenhouse gases when
reacting with high energy UV radiations in the atmosphere leads to the depletion of the
ozone layer. This will harm the various members of the eco-system.
Q. 2. Which biological factor is responsible for poor vegetation in deserts?
Answer: In deserts, there is little water available for plants and other organisms.
Because of which desert soils are dry, and tend to have poor vegetation (plants found in
a particular area). Hence lack of water/water scarcity due to low rainfall is responsible
for poor vegetation in deserts (less growth of plants in the desert).
Answer: In deserts, there is little water available for plants and other organisms.
Because of which desert soils are dry, and tend to have poor vegetation (plants found in
a particular area). Hence lack of water/water scarcity due to low rainfall is responsible
for poor vegetation in deserts (less growth of plants in the desert).
Q. 3. Which group of organisms converts organic materials into inorganic forms?
Answer: The breakdown of organic matter and their conversion into basic inorganic
forms is called mineralization.
Decomposers are the organisms (e.g., bacteria, fungi, crabs) that breakdown organic
constituents (e.g., plant material) to release carbon and other nutrients such as nitrogen
(N) and phosphorus (P) as inorganic form.
When an organism dies, decomposers decay or breakdown his body chemically and
extract the last bit of energy from it.
Answer: The breakdown of organic matter and their conversion into basic inorganic
forms is called mineralization.
Decomposers are the organisms (e.g., bacteria, fungi, crabs) that breakdown organic
constituents (e.g., plant material) to release carbon and other nutrients such as nitrogen
(N) and phosphorus (P) as inorganic form.
When an organism dies, decomposers decay or breakdown his body chemically and
extract the last bit of energy from it.
Q. 4. Are plants actually producers of energy?
Answer: Yes, plants are the producers of energy. This is the energy absorbed by the
plant from sunlight for photosynthesis. Afterwards this energy is transferred to other
organisms by the food chain.
For example: Plant → Goat → Lion.
Energy cannot be transferred back to producers because plants cannot eat animals like
goat, insects, etc and without eating the energy cannot be transferred.
Answer: Yes, plants are the producers of energy. This is the energy absorbed by the
plant from sunlight for photosynthesis. Afterwards this energy is transferred to other
organisms by the food chain.
For example: Plant → Goat → Lion.
Energy cannot be transferred back to producers because plants cannot eat animals like
goat, insects, etc and without eating the energy cannot be transferred.
Q. 5. What do we call the various steps involved in the food chain?
Answer: A food chain is a series of organisms which eat one another. And in this food
chain at each level specific type of organisms occupy the same level. Hence, the trophic
level is the position of a group of organisms in a food chain. It refers to the mode of
nutrition at every different trophic level.
For example Plants (producers) get their nutrition from sunlight and prepare their own
food. Then comes the consumers (herbivores) they cannot prepare their own food
hence get their nutrition by feeding on plants. Then comes the secondary or tertiary
consumers (carnivores) they get energy by eating other animals. They all get the
nutrition from the organisms of lower trophic levels.
Answer: A food chain is a series of organisms which eat one another. And in this food
chain at each level specific type of organisms occupy the same level. Hence, the trophic
level is the position of a group of organisms in a food chain. It refers to the mode of
nutrition at every different trophic level.
For example Plants (producers) get their nutrition from sunlight and prepare their own
food. Then comes the consumers (herbivores) they cannot prepare their own food
hence get their nutrition by feeding on plants. Then comes the secondary or tertiary
consumers (carnivores) they get energy by eating other animals. They all get the
nutrition from the organisms of lower trophic levels.
Q. 6. Identify A and B in the given figure.
Answer: A are the producers called plants and B are the secondary consumers which
are called omnivores.
Plants make their own food with the help of sunlight through the process of
photosynthesis and hence are called the producers. They are places at first trophic
level. Secondary consumers are the organisms that can feed both on plants and
animals. They come in between primary consumers (herbivores-the plant feeders) and
the tertiary consumers (carnivores-the flesh eaters.)
are called omnivores.
Plants make their own food with the help of sunlight through the process of
photosynthesis and hence are called the producers. They are places at first trophic
level. Secondary consumers are the organisms that can feed both on plants and
animals. They come in between primary consumers (herbivores-the plant feeders) and
the tertiary consumers (carnivores-the flesh eaters.)
Q. 7. A food chain represents a unidirectional flow of X. What is X?
Answer: A food chain always represents a unidirectional flow of energy from one
trophic level to another. As a food chain proceeds from autotrophs to heterotrophs to
decomposers energy gets transferred. The flow of energy in an ecosystem starts with
sunlight (the ultimate source of all energy on Earth) which is absorbed by the producers,
goes to the consumers, then to the decomposers, and back to the producers to start all
over again.
Answer: A food chain always represents a unidirectional flow of energy from one
trophic level to another. As a food chain proceeds from autotrophs to heterotrophs to
decomposers energy gets transferred. The flow of energy in an ecosystem starts with
sunlight (the ultimate source of all energy on Earth) which is absorbed by the producers,
goes to the consumers, then to the decomposers, and back to the producers to start all
over again.
Q. 8. Why is straight line food chain not common in the natural ecosystem?
Answer: It is not common in a natural ecosystem, because during energy transfer from
one trophic level to another most of the energy is lost in the form of heat. Hence in a
natural ecosystem, we cannot see any energy transfer without a loss.
(This will be observed 1000->100->10, instead of 1000->1000->1000)
Answer: It is not common in a natural ecosystem, because during energy transfer from
one trophic level to another most of the energy is lost in the form of heat. Hence in a
natural ecosystem, we cannot see any energy transfer without a loss.
(This will be observed 1000->100->10, instead of 1000->1000->1000)
Q. 9. How many trophic levels does a food chain normally have?
Answer: A food chain normally has three trophic levels. The primary producer, plants
who will who will obtain nutrition from sunlight and prepare food for itself and for the
second trophic level organism. The secondary consumers, herbivores that will eat
plants, and at last will be the tertiary consumers called carnivores, the flesh eaters.
They will feed on secondary consumers.
Answer: A food chain normally has three trophic levels. The primary producer, plants
who will who will obtain nutrition from sunlight and prepare food for itself and for the
second trophic level organism. The secondary consumers, herbivores that will eat
plants, and at last will be the tertiary consumers called carnivores, the flesh eaters.
They will feed on secondary consumers.
Q. 10. Which trophic level has a maximum number of organisms?
Answer: The bottom most trophic level has the maximum number of organisms
because there have to be more food producers than consumers, to sustain life on earth.
Suppose if 10 producers (plants) are there and 15 animals than 5 animals will be left
hungry and will die and the eaten plants will also be not able to produce food so the
remaining 10 animals will die.
Answer: The bottom most trophic level has the maximum number of organisms
because there have to be more food producers than consumers, to sustain life on earth.
Suppose if 10 producers (plants) are there and 15 animals than 5 animals will be left
hungry and will die and the eaten plants will also be not able to produce food so the
remaining 10 animals will die.
Q. 11. How is being a vegetarian advantageous in terms of energy?
Answer: Being a vegetarian will increase the amount of energy taken up by your body.
As we know that energy decreases ate each successive trophic level. It is least
available for the last trophic level. Humans are the final (tertiary) consumers of any food
chain; hence if they skip the primary and secondary consumers and directly feed on
plants, then they can have the more amount of energy comparative to the energy if they
don’t skip.
Answer: Being a vegetarian will increase the amount of energy taken up by your body.
As we know that energy decreases ate each successive trophic level. It is least
available for the last trophic level. Humans are the final (tertiary) consumers of any food
chain; hence if they skip the primary and secondary consumers and directly feed on
plants, then they can have the more amount of energy comparative to the energy if they
don’t skip.
Q. 12. State one reason to justify the position of a man at the apex of most food
chains.
Answer: The position of the man is at the apex of most of the food chain because in a
food chain the top position is mostly taken by carnivorous animals and in a normal food
chain herbivores are the producers, some small organisms are the second consumers
and some much larger animals are the third consumers but we come at the last.
Humans can consume all most all the animals, also they are the most intelligent
organisms so they can change their position by manipulation.
chains.
Answer: The position of the man is at the apex of most of the food chain because in a
food chain the top position is mostly taken by carnivorous animals and in a normal food
chain herbivores are the producers, some small organisms are the second consumers
and some much larger animals are the third consumers but we come at the last.
Humans can consume all most all the animals, also they are the most intelligent
organisms so they can change their position by manipulation.
Q. 13. What term is given to the phenomenon where a harmful chemical enters a
food chain and starts accumulating?
Answer: The increase in the concentration of harmful chemicals (pesticides) in the
body of a living organism at each trophic level of a food chain is called biological
magnification. Its level will increase as we move from bottom to top of a food chain. For
example, when pesticides are sprayed they enter the food chain through producers
while they are absorbing nutrients from the soil. Since herbivores eat many types of
plants, therefore their body will accumulate more amounts of pesticides. Similarly,
carnivores will feed on more than one herbivore; hence it will have much more amount
of pesticide in it.
food chain and starts accumulating?
Answer: The increase in the concentration of harmful chemicals (pesticides) in the
body of a living organism at each trophic level of a food chain is called biological
magnification. Its level will increase as we move from bottom to top of a food chain. For
example, when pesticides are sprayed they enter the food chain through producers
while they are absorbing nutrients from the soil. Since herbivores eat many types of
plants, therefore their body will accumulate more amounts of pesticides. Similarly,
carnivores will feed on more than one herbivore; hence it will have much more amount
of pesticide in it.
Q. 14. Name the radiations absorbed by the ozone layer?
Answer: Ozone layer absorbs the harmful Ultraviolet (UV) radiations from sunlight.
Then these UV rays split molecular oxygen (O2) into free oxygen (O), thus keeping the
UV radiation from reaching the surface of the Earth.
Q. 15. Does change in lifestyle add waste to the environment?
Answer: No, change in lifestyle does not add waste to the environment. It helps to
reduce the amount of waste. The use of eco-friendly products and recyclable materials
will lessen the waste produced. Less use of chemical producing products, as people are
becoming more aware of the consequences of disturbing the balance of nature.
Answer: No, change in lifestyle does not add waste to the environment. It helps to
reduce the amount of waste. The use of eco-friendly products and recyclable materials
will lessen the waste produced. Less use of chemical producing products, as people are
becoming more aware of the consequences of disturbing the balance of nature.
Q. 16. Name the process by which volume of solid wastes can be reduced.
Answer: The best way to reduce the volume of solid waste is by burning waste at very
high temperatures. It is the simplest and earliest form of waste disposal. But this method
leads to the release of highly toxic chemicals in the environment which is harmful for the
organisms.
Answer: The best way to reduce the volume of solid waste is by burning waste at very
high temperatures. It is the simplest and earliest form of waste disposal. But this method
leads to the release of highly toxic chemicals in the environment which is harmful for the
organisms.
Q. 17. Give the difference between paper and glass as a waste product.
Answer:
Q. 18. List a few practices that lead to the production of non-biodegradable waste.
Answer: When we dispose of them in a garbage pile, the air, moisture, climate, or soil
cannot break them down naturally to be dissolved with the surrounding land. They are
not biodegradable.
Some practices are:
● Throwing of plastic water bottles and plastic bags.
● Metal scarps improper disposal.
● Construction waste, rubber tires, man-made fibers like nylon etc.
● Useless computer hardware like glass, CDs, DVDs, cellophane, processed woods,
cable wires, etc.
Answer: When we dispose of them in a garbage pile, the air, moisture, climate, or soil
cannot break them down naturally to be dissolved with the surrounding land. They are
not biodegradable.
Some practices are:
● Throwing of plastic water bottles and plastic bags.
● Metal scarps improper disposal.
● Construction waste, rubber tires, man-made fibers like nylon etc.
● Useless computer hardware like glass, CDs, DVDs, cellophane, processed woods,
cable wires, etc.
Q. 19. What -are the functions of an ecosystem?
Answer: Ecosystem is the interaction of living things with themselves and with the
surrounding environment. It's functions in 4 main aspects:
1. Productivity- there should be a balance between the amount of food produced and
consumed.
2. Decomposition- The dead and decay matter has to be decomposed successfully to
replenish the environment with nutrients.
3. Energy flow- the transfer of energy from one trophic level to another has to follow
10% rule to sustain life.
4. The nutrient cycling-the connection of various components of the ecosystem should
be proper to get back the depleted nutrients in the environment.
Answer: Ecosystem is the interaction of living things with themselves and with the
surrounding environment. It's functions in 4 main aspects:
1. Productivity- there should be a balance between the amount of food produced and
consumed.
2. Decomposition- The dead and decay matter has to be decomposed successfully to
replenish the environment with nutrients.
3. Energy flow- the transfer of energy from one trophic level to another has to follow
10% rule to sustain life.
4. The nutrient cycling-the connection of various components of the ecosystem should
be proper to get back the depleted nutrients in the environment.
Q. 20. Why do all food chains start with plants?
Answer: Plants are the only living organism that can consume energy from sunlight to
prepare food with the help of a process called photosynthesis. They are the primary
producers of every ecosystem. And they are always the largest in number because
there have to be more food producers than consumers, to sustain life on earth.
Answer: Plants are the only living organism that can consume energy from sunlight to
prepare food with the help of a process called photosynthesis. They are the primary
producers of every ecosystem. And they are always the largest in number because
there have to be more food producers than consumers, to sustain life on earth.
Q. 21. What do you call the organism which feeds on both plants and animals?
What is the most likely position of this organism in the food chain?
Answer: The organisms that feed on both plants, as well as animals, are called
omnivores. For example pigs, bears, mice, etc. Humans and chimpanzees are also
omnivores.
They will come to the third trophic level as they are secondary consumers. This means
they will come above herbivores (primary consumers) that can eat only plants. And
below carnivores (tertiary consumers) which feed only on flesh.
What is the most likely position of this organism in the food chain?
Answer: The organisms that feed on both plants, as well as animals, are called
omnivores. For example pigs, bears, mice, etc. Humans and chimpanzees are also
omnivores.
They will come to the third trophic level as they are secondary consumers. This means
they will come above herbivores (primary consumers) that can eat only plants. And
below carnivores (tertiary consumers) which feed only on flesh.
Q. 22. Explain the difference between the energy captured by producers and
energy transferred to consumers.
Answer: A producer is an organism that captures energy and stores it in food as
chemical energy. The producers of an ecosystem make energy available to all the other
living parts of an ecosystem.
They capture 1% of energy from sunlight and use it to produce food. Then when
consumers feed on plants the 10% rule of energy transfer is followed. In that, at each
trophic level, about 10% of the energy of previous trophic level is passed to the next
trophic level of food chain.
energy transferred to consumers.
Answer: A producer is an organism that captures energy and stores it in food as
chemical energy. The producers of an ecosystem make energy available to all the other
living parts of an ecosystem.
They capture 1% of energy from sunlight and use it to produce food. Then when
consumers feed on plants the 10% rule of energy transfer is followed. In that, at each
trophic level, about 10% of the energy of previous trophic level is passed to the next
trophic level of food chain.
The diagram is shown below:
This is how energy transfer varies between sun to plants and then plants to various
consumer levels.
consumer levels.
Q. 23. Can an organism occupy position in more than one food chain? If so, give
an example.
Answer: Yes, an organism can occupy position in more than one food chain. For
example: If we consider plants which are the primary producers, their presence is
necessary in all the food chains because they are the only organisms which can make
their own food by photosynthesis. Because of plants only ecosystem is able to exist. If
we compare forest food chain, grassland food chain, pond food chain, we will observe
that plants occupy the first trophic level of all the three food chains.
an example.
Answer: Yes, an organism can occupy position in more than one food chain. For
example: If we consider plants which are the primary producers, their presence is
necessary in all the food chains because they are the only organisms which can make
their own food by photosynthesis. Because of plants only ecosystem is able to exist. If
we compare forest food chain, grassland food chain, pond food chain, we will observe
that plants occupy the first trophic level of all the three food chains.
Q. 24. Mention the effects of ozone layer depletion on human beings.
Answer: Ozone layer depletion increases the amount of UV rays that reaches the
Earth’s surface.
● Skin Cancer- it is estimated that skin cancer rates increased due to the decrease in
stratospheric ozone (ozone layer). The most common type of skin cancer is the cause
of exposures to UV radiation from sun.
● UV rays have been linked to the development of cataracts, a clouding of the eye’s
lens.
Answer: Ozone layer depletion increases the amount of UV rays that reaches the
Earth’s surface.
● Skin Cancer- it is estimated that skin cancer rates increased due to the decrease in
stratospheric ozone (ozone layer). The most common type of skin cancer is the cause
of exposures to UV radiation from sun.
● UV rays have been linked to the development of cataracts, a clouding of the eye’s
lens.
Q. 25.A. Ultraviolet radiation from sunlight causes a reaction involving O2 as
reactant. What does that produce?
Answer: When UV radiations from the sun reaches earth’s atmosphere which is heavily
rich in oxygen. Then these UV rays split molecular oxygen (O2-reactant) into free
oxygen (O-Product). Afterwards, this free oxygen reacts with molecular oxygen; it forms
ozone (O3-Finalproduct).
Q. 25.B. What does release of phosphates and nitrates in water bodies lead to?
Answer: Phosphates and nitrates are useful nutrients but when they become too
concentrated in our water environments they can cause problems. The main sources of
phosphates coming into water bodies are drainage from farmland (fertilizers, runoff from
manure, etc.) and sewage effluent (which contains dishwasher detergents, food and
drink additives). Nitrates are used in fertilizer, which help farmers to produce more crops
which can mean lower food prices.
However, high phosphate and nitrate levels can cause eutrophication – an issue when
there is too much nutrient in a water body (e.g. rivers and lakes). This can cause
excessive growth of algae and other plants, which then affects water quality, damages
plants and animals and stops us using the water. It can cause severe illness in infants
and domestic animals.
Answer: Phosphates and nitrates are useful nutrients but when they become too
concentrated in our water environments they can cause problems. The main sources of
phosphates coming into water bodies are drainage from farmland (fertilizers, runoff from
manure, etc.) and sewage effluent (which contains dishwasher detergents, food and
drink additives). Nitrates are used in fertilizer, which help farmers to produce more crops
which can mean lower food prices.
However, high phosphate and nitrate levels can cause eutrophication – an issue when
there is too much nutrient in a water body (e.g. rivers and lakes). This can cause
excessive growth of algae and other plants, which then affects water quality, damages
plants and animals and stops us using the water. It can cause severe illness in infants
and domestic animals.
Q. 26. Give two probable damages that are caused due to ozone layer depletion.
Answer: Effects of the depletion of the ozone layer:
1.1 On human health- Skin Cancer
Today, it is estimated that skin cancer rates increased due to the decrease in
stratospheric ozone (ozone layer). The most common type of skin cancer is the cause
of exposures to UV radiation from sun.
2. Effects on aquatic ecosystems
The loss of phytoplankton, the basis of the marine food chain, has been observed as
the cause of the increase in ultraviolet radiation. For example: Under the ozone hole in
the Antarctic phytoplankton productivity decreased between 6 and 12 percent. That
disturbs the ecosystem.
Answer: Effects of the depletion of the ozone layer:
1.1 On human health- Skin Cancer
Today, it is estimated that skin cancer rates increased due to the decrease in
stratospheric ozone (ozone layer). The most common type of skin cancer is the cause
of exposures to UV radiation from sun.
2. Effects on aquatic ecosystems
The loss of phytoplankton, the basis of the marine food chain, has been observed as
the cause of the increase in ultraviolet radiation. For example: Under the ozone hole in
the Antarctic phytoplankton productivity decreased between 6 and 12 percent. That
disturbs the ecosystem.
Q. 27. How do CFCs affect ozone layer?
Answer: CFCs are manmade chemicals called chlorofluorocarbons. These substances
are found in refrigerators, ACs. Etc. Due to long life and their ability that they do not
wash in the rain, so they rise up into the ozone layer above the earth, where they
eventually breakdown by heavy exposure to ultraviolet (UV) radiations. When CFC is
broken down, it releases chlorine and bromine atoms which can destroy various ozone
molecules at once. They cause the ozone layer to breakdown faster than it can replace
itself.
Answer: CFCs are manmade chemicals called chlorofluorocarbons. These substances
are found in refrigerators, ACs. Etc. Due to long life and their ability that they do not
wash in the rain, so they rise up into the ozone layer above the earth, where they
eventually breakdown by heavy exposure to ultraviolet (UV) radiations. When CFC is
broken down, it releases chlorine and bromine atoms which can destroy various ozone
molecules at once. They cause the ozone layer to breakdown faster than it can replace
itself.
Q. 28. Disposal of waste should be done properly. Justify the statement.
Answer: It is because waste has to be disposed in such a manner that it doesn’t cause
any type of pollution. For example: When wastes are dumped into water bodies they
pollute it and also affect the marine life. If it is buried in soil, it will cause depletion of the
fertility of the soil and makes the land a waste land. Hence proper disposal of waste is
important because:
a) Garbage can be a source of diseases.
b) It can be processed to recycle useful components. So, garbage should also be
disposed at proper places.
c) Some garbage contains plastic which can harm our environment. So they should be
disposed after taking proper care.
Q. 29. (i) Why is use of disposable paper cups convenient over the use of
disposable plastic cups?
(ii) How do biodegradable wastes not cause pollution?
Answer: (i) Disposable paper cups are more convenient over disposable plastic cups
because:
a) Paper cups can decay naturally with the help of decomposers and become harmless
after sometime, but plastic cups do not.
b) They do not pollute the environment as they decay fast but plastic cups do pollute the
environment because they are non-biodegradable.
c) Plastic cups can cause health effect to the living organisms if consumed by chance.
But paper cups are made from organic products, like plants.
(ii) Biodegradable wastes are decomposed by the micro-organisms. By the process of
decomposition, mineral elements like C, N, O and P are cycled back into the biosphere.
This is done in the form of manure, etc.
Q. 30. Draw a pond ecosystem showing its different components.
Answer: A pond ecosystem refers to fresh water ecosystem where there are
communities of organism dependent on each other with the prevailing water
environment for their nutrients and survival. Usually, ponds are shallow water bodies
with a depth of 12-15 feet in which the sun rays can penetrate to the bottom promoting
the growth of plants there. It is a natural ecosystem.
The following diagram shows a pond ecosystem.
There
Answer: A pond ecosystem refers to fresh water ecosystem where there are
communities of organism dependent on each other with the prevailing water
environment for their nutrients and survival. Usually, ponds are shallow water bodies
with a depth of 12-15 feet in which the sun rays can penetrate to the bottom promoting
the growth of plants there. It is a natural ecosystem.
The following diagram shows a pond ecosystem.
There
There are two components in the pond ecosystem:
(a) Abiotic – It consists of water, dissolved minerals, oxygen and carbon dioxide.
Sunlight is the main source of energy.
(b) Biotic – It includes phytoplanktons, aquatic insects, fishes, and microbes. These
organisms are classified as producers, consumers, and decomposers. The energy flows
from producer to consumers.
(a) Abiotic – It consists of water, dissolved minerals, oxygen and carbon dioxide.
Sunlight is the main source of energy.
(b) Biotic – It includes phytoplanktons, aquatic insects, fishes, and microbes. These
organisms are classified as producers, consumers, and decomposers. The energy flows
from producer to consumers.
Q. 31. 'Man is only a consumer'. Justify the statement.
Answer: Man is an omnivore, that is, he can feed on both plants and animals. Thus, a
man can be a primary consumer when he consumes plant products such as cereals,
fruits and vegetables and he can be a secondary consumer when he consumes
herbivores such as goat and sheep (in the form of their meat). Thus, a man can be
placed at the second as well as the third trophic level of the food chain. Man cannot be
a producer because he cannot convert energy from sunlight, which is chemical energy
conversion to food. Only plants have that function to prepare food through
photosynthesis. Therefore man can only consume food and is known as a consumer.
Answer: Man is an omnivore, that is, he can feed on both plants and animals. Thus, a
man can be a primary consumer when he consumes plant products such as cereals,
fruits and vegetables and he can be a secondary consumer when he consumes
herbivores such as goat and sheep (in the form of their meat). Thus, a man can be
placed at the second as well as the third trophic level of the food chain. Man cannot be
a producer because he cannot convert energy from sunlight, which is chemical energy
conversion to food. Only plants have that function to prepare food through
photosynthesis. Therefore man can only consume food and is known as a consumer.
Q. 32. How much energy will be available to hawks in the food chain comprising
hawk, snake, paddy, and mice if 10,000 J of energy is available to paddy from the
Sun?
Answer: Paddy (rice plants) represents the producer level. Paddy plants trap only 1%
of the Sun's energy of 10,000J falling on them.
hawk, snake, paddy, and mice if 10,000 J of energy is available to paddy from the
Sun?
Answer: Paddy (rice plants) represents the producer level. Paddy plants trap only 1%
of the Sun's energy of 10,000J falling on them.
So, the energy available in paddy will be 1% of 10,000 J which will be 100 J. From
plants (paddy), the amount of energy passed to the next trophic level is 10%. As we
know paddy will be the producers, mice will be the primary consumer, and then the
snake will be the secondary consumer and at last will be a hawk, the tertiary consumer.
We can now write the food chain and apply ten percent low to it.
(Paddy100 J) → (Mice 10 J) → (Snake 1 j) → (Hawk 0.1 J)
Thus, the energy available to the hawk in the food chain will be 0.1 J.
plants (paddy), the amount of energy passed to the next trophic level is 10%. As we
know paddy will be the producers, mice will be the primary consumer, and then the
snake will be the secondary consumer and at last will be a hawk, the tertiary consumer.
We can now write the food chain and apply ten percent low to it.
(Paddy100 J) → (Mice 10 J) → (Snake 1 j) → (Hawk 0.1 J)
Thus, the energy available to the hawk in the food chain will be 0.1 J.
Q. 33. The number of trophic levels is limited to 3-4 in a food chain. Give reason.
Answer: The number of trophic levels in an ecosystem is limited and is not more than
3-4. Because the amount of energy flow decreases with successive trophic level, as
only 10% of energy is transferred from one trophic level to the next trophic level.
Explanation: At each trophic level in a food chain, a large portion of the energy is
utilized for the maintenance of organisms which occur at that trophic level and lost as
heat. As a result of this, organisms in each trophic level pass on less and less energy to
the next trophic levels, than they receive. The longer the food chain, the less is the
energy available to the final member of the food chain. Food chains generally consist of
three or four steps (three or four organisms) because after that the energy available for
the next organism will be so small that it will be insufficient to sustain the life of that
organism. There are, however, some food chains containing five steps (or five
organisms) but there are rarely more than five steps (or five organisms) in a food chain.
Answer: The number of trophic levels in an ecosystem is limited and is not more than
3-4. Because the amount of energy flow decreases with successive trophic level, as
only 10% of energy is transferred from one trophic level to the next trophic level.
Explanation: At each trophic level in a food chain, a large portion of the energy is
utilized for the maintenance of organisms which occur at that trophic level and lost as
heat. As a result of this, organisms in each trophic level pass on less and less energy to
the next trophic levels, than they receive. The longer the food chain, the less is the
energy available to the final member of the food chain. Food chains generally consist of
three or four steps (three or four organisms) because after that the energy available for
the next organism will be so small that it will be insufficient to sustain the life of that
organism. There are, however, some food chains containing five steps (or five
organisms) but there are rarely more than five steps (or five organisms) in a food chain.
Q. 34. Look at the following figures. Choose the correct one and give a reason for
your choice.
your choice.
Answer:
Correct representation of trophic levels in a food chain is shown in figure A.
The population will decrease as we move from bottom to top of a food chain. The
producers will be the highest in number in a food chain because there have to be more
food producers than consumers, to sustain life on earth. The top position is mostly taken
by carnivorous animals (tertiary consumers), omnivores being the secondary
consumers and herbivores being the primary consumers.
A food chain always represents a unidirectional flow of energy from one trophic level to
another. Each level in the pyramid represents our level in the food chain. Each level of
consumers above the producers has fewer individuals because there is less energy
available.
The population will decrease as we move from bottom to top of a food chain. The
producers will be the highest in number in a food chain because there have to be more
food producers than consumers, to sustain life on earth. The top position is mostly taken
by carnivorous animals (tertiary consumers), omnivores being the secondary
consumers and herbivores being the primary consumers.
A food chain always represents a unidirectional flow of energy from one trophic level to
another. Each level in the pyramid represents our level in the food chain. Each level of
consumers above the producers has fewer individuals because there is less energy
available.
Q. 35. Make an aquatic food chain up to the tertiary consumer level. State the
trophic level at which concentration of pesticide is maximum and why?
Answer: An aquatic food chain can go as
Phytoplankton (primary producers) ⇒ Zooplankton (primary consumer) ⇒ Small fish
(secondary consumer) ⇒ Large fish (sharks etc, tertiary consumer)
trophic level at which concentration of pesticide is maximum and why?
Answer: An aquatic food chain can go as
Phytoplankton (primary producers) ⇒ Zooplankton (primary consumer) ⇒ Small fish
(secondary consumer) ⇒ Large fish (sharks etc, tertiary consumer)