All important questions at one place

1. Our Environment
Class 10

2. Q1. What are the trophic levels? Give an example of a food chain and state the different trophic levels in it.
Solution: In the food chain, the transfer of food or energy takes place at the various levels and these levels are known as trophic levels.
Example: Grass > insect > frog > snake > bird Grass > Grasshopper > bluebird > snake > owl
1. Grass represents first trophic level. 1. Grass represents the first trophic level.
2. Grasshopper represents second trophic level. 2. Grasshopper represents second trophic level.
3. Frog represents third trophic level. 3. Blue bird and snake represent third trophic level.
4. Eagle represents fourth trophic level. 4. Owl represents fourth trophic level.
Q2. What is the role of decomposers in the ecosystem?
Solution
1. Decomposers are called natural cleaning agent.
2. They act on biodegradable substances and break them into simple substances.
3. Decomposers also help in putting back the various elements of which dead plants and animals are made, back into the soil, air and water for reuse by
the producers like crop plants.
4. They help in recycling of the nutrients.
5. They decompose dead remains thereby providing space for new life to settle in the biosphere.

3. Q3. Why are some substances biodegradable and some non-biodegradable?
Solution:
Substances that are broken down by biological processes are said to be biodegradable. In our environment, many of the substances are
broken easily by decomposers (bacteria and fungi) as they possess specific enzymes for such activity. However, there are other
substances also which are not broken down in this manner and are known as non-biodegradable substances. Since these substances are
not degraded by bacteria and fungi, so they persist for a long time. These non-biodegradable substances will be acted upon by physical
processes like heat and pressure.
Q4. Give any two ways in which biodegradable substance would affect the environment.
Solution:
Following are the ways in which biodegradable substance would affect the environment:
● They keep the environment clean as they are easily decomposed.
● They can easily go through the geochemical cycle with the help of decomposers.
Q5. Give any two ways in which non-biodegradable substance would affect the environment.
Solution:
Following are the ways in which non-biodegradable substance would affect the environment:
● They cause air, soil and water pollution.
● They may cause biomagnification in the food chain resulting in the end of human.
Q6. What is ozone and how does it affect the ecosystem?
Solution Ozone is a molecule formed by three atoms of oxygen. Ozone is formed by the reaction of three molecules of oxygen in presence of
ultraviolet (UV) rays.
3O2--- UV---2O3
Ozone performs an essential function. It shields the surface of the earth from ultraviolet radiation of the sun. If this radiation enters in the

4. Q 7. How can you help in reducing the problem of waste disposal? Give any two methods.
Solution
(i) There are two types of wastes; biodegradable and non – biodegradable. We should use more and more substances that leave biodegradable
wastes.
(ii) Biodegradable wastes are converted into manure. Non – biodegradable wastes should be sent to the factories for recycling
(iii)3 R’s: By following the 3 R’s one can reduce the problem of waste disposal. The 3 R’s are reduce, recycle and reuse. Reducing the usage of their own
vehicles and opting for public transport can reduce air pollution. Recycling and reusing of plastics is also a way to reduce waste disposal.
Q8. What will happen if we kill all the organisms in one trophic level?
Solution
Each and every trophic level depends for its energy needs on its previous trophic level. If all organisms of any of the trophic levels in a food chain
are damages, the organisms of other trophic levels will also be destroyed because energy flow is stopped from one trophic level to other trophic
level. As a result animals in the higher levels will die making the growth of animals in the lower trophic level increase in an enormous way.
All of this will affect the overall balance in the ecosystem.
1. If the herbivores are killed, then the carnivores would not be able to get food and would die.
2. If carnivores are killed, then the population of herbivores would increase to unsustainable level.
3. If producers are killed, then the nutrient cycle in that area would not be completed.
Q9.What is biological magnification ? Will the levels of this magnification be different at different levels of the ecosystem ?
Solution
Biological magnification : The increase in concentration of harmful chemical substances like pesticides in the body of living organisms at each
trophic level of a food chain is called biological magnification.
Yes, levels of biomagnification would increase as the trophic level increases and would be the highest for topmost trophic level. It would affect
their biological process such as growth, reproduction, etc.
Q10. Why is improper disposal of waste a curse to environment?
Answer. Improper disposal of waste is a curse to environment because it pollutes the environment, air, water, soil and cause harmful effects on
living organisms.
For example, passage of sewage into water body cause eutrophication, killing of animals and source of water-borne pathogens.

5. Q11. Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic
level be removed without causing any damage to the ecosystem?
Solution
The impact of removing the organisms of a trophic level is different for different trophic levels. For example, if we remove plants from a
food chain, no organism will get food as plants are the primary producers in the food chain. If herbivores are removed from a food chain
then carnivores will starve and die and producers are also affected and may die due to competition for space and nutrients. If carnivores
are removed, herbivores would increase to unsustainable levels and could destroy the producers. If decomposers are removed, the dead animals
would pile up due to which the environment would become polluted. In addition to this, if dead animals will not decompose, the recycling of
nutrients in the soil will be stopped and its fertility will be reduced. As a result the green cover of the earth will be lost. Thus to maintain the
balance of the ecosystem the presence of organisms is necessary at each trophic level.It is not possible to remove a trophic level without
causing damage to the ecosystem as they are interlinked.
Q12. What are the problems caused by the non-biodegradable wastes that we generate?
Solution:
Following are the problems caused by the non-biodegradable wastes:
● These substances cannot be decomposed by the microorganisms.
● As the quantity increases, dumping becomes a problem.
● Non-biodegradable wastes like heavy metals may enter the food chain in the upper trophic levels.
● They may escape to the groundwater which causes soil infertility and disturbance in pH of the soil.
Q13.If all the waste we generate is biodegradable, will this have no impact on the environment ?
If all the waste we generate is biodegradable, it will also have impact on the environment. If it is disposed off properly, the problem of air, water
and soil pollution can be lessened to an extent. There would be less health problems and humans would be disease-free.
But if it is not disposed off properly, it will affect the environment adversely.
● As the decomposition of the biodegradable wastes are slow, they produce the awful smell and when inhaled by humans it can be harmful.

6. Q14. Why is the damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Solution
Enlargement of ozone hole will cause more ultraviolet rays to reach on the earth’s surface. This is very harmful for us, animals and
microorganisms in the following ways:
(i) Ultraviolet radiations may cause skin disease, especially skin cancer.
(ii) Plant life will be disturbed due to retarded growth and destruction of pigments.
(iii) UV – rays may kill microorganisms, decomposers and other useful microbes. It may lead to ecological imbalance.
Steps to prevent damage of ozone layer:
(i) Judicious use of aerosol sprays propellants such as fluorocarbon and chlorofluorocarbons which cause depletion or hole in ozone layer.
(ii) Limited use of supersonic planes.
(iii) Control over large scale nuclear explosions.
Q15.Why is damage to the ozone layer a cause for concern ? What steps are being taken to limit this damage ?
Solution
The damage to the ozone layer is a cause for concern because if the ozone layer in the atmosphere disappears completely, then all the
extremely harmful ultraviolet radiations coming from the sun would reach the earth. These ultraviolet radiations would cause skin cancer and
other ailments in men and animals and also damage the plants. The air pollutants like chlorofluorocarbons (CFCs) are the main reason for
the depletion of the ozone layer.
In an attempt to protect the ozone layer, the United Nations Environment Programme (UNEP) unanimously forged an agreement among its
member countries to freeze CFC production at 1986 levels.
Q16. Why are crop fields known as artificial ecosystems?
Answer. Crop fields are known as artificial ecosystems because they are man-made and some biotic and abiotic components are maintained,
nourished and reaped by human beings.
Q17. We do not clean ponds or lakes, but an aquarium needs to be cleaned. Why?
Answer. An aquarium is an artificial and incomplete ecosystem compared to pond or lakes which are natural, self-sustaining and complete
ecosystem where there is a perfect recycling of materials. Therefore, it needs to be cleaned.

7. Question 18. Name the wastes which are generated in your house daily. What measures would you take their disposal?
Answer.
Wastes which are generated in our house daily and measures for their disposal are as follows:
Raw vegetable and peels of fruits – can be disposed underground in a nearby garden which on decomposition enriches the soil with nutrients.
Paper wastes like newspaper, books etc – Can be recycled or can also be sold.
Plastic waste like polybags, plastic toys etc – Can be sold in suitable shops where they can be recycled.
Other household waste like pieces of glass, clothes etc – Should be safely dumped in garbage bins placed to collect non-biodegradable waste.
Question 19. Suggest suitable mechanism (s) for waste management in fertiliser industries.
Answer.
Chemicals and harmful gases are the main pollutants which are produced in a fertilizer factory and a suitable waste management is essential for
such industries.
These pollutants can be controlled at the point of generation within the factory or nearby treatment plant.
To control air pollution certain adsorption equipments may be fitted in chimneys of fertilizer industries which can absorb harmful pollutants
before the smoke is released into atmosphere.
Water mixed with chemicals can be sent to water bodies after treatment in treatment plants within industries. Water can also be sent to any
nearby treatment plants with the help of a suitable drainage system.
Question 20. What are the by-products of fertilizer industries? How do they affect the environment?
Answer.
The by-products of the fertiliser industries are oxides of nitrogen and sulphur i.e., SO2, CO, NOX, CO2, H2S, other solid, liquid chemicals and some
solid waste material.
These substances usually released in air or dump in river bodies or sea which causes water pollution. These substances when consumed by
plants and animals enter the food chain.
By the process of biomagnification these harmful chemicals get concentrated at each trophic level. Human being omnivore eats both plants and
animals (or aquatic animals) which is extremely harmful for health. SO2 gas released in atmosphere can cause acid rain which also effect

8. Q21. Indicate the flow of energy in an ecosystem. Why is it unidirectional? Justify.
Answer.
Flow of energy in an ecosystem is as follows:
Sun → Producer → Herbivore → Carnivore
The flow of energy in the ecosystem is unidirectional. The energy enters the plants (from the sun) through photosynthesis during the making of
food. This energy is then passed on from one organism to another in a food chain.
The energy given out by the organisms as heat is lost to the environment, it does not return to be used by the plants again. This makes the flow
of energy in ecosystem 'unidirectional'.
Q22.Explain some harmful effects of agricultural practices on the environment.
Soln:
Following are the harmful effects of agricultural practices on the environment
Soil degradation Extensive cropping causes loss of soil fertility. Also, over time it can lead to soil erosion and finally to desertification.
Pollution
Use of synthetic fertilisers and pesticides leads to soil, water and air pollution. •
Water shortage
Excess use of groundwater for agriculture lowers the water level. This results in acute water shortage at many places.
Biomagnification
The chemical pesticides, being non-biodegradable accumulate in organisms in increasing amounts at each trophic level.
Deforestation
Indiscriminate cutting of trees for agriculture has resulted in loss of habitat for wildlife. Thus, it also causes damage to the natural
ecosystem.