CBSE Class 10 Science Our Environment Worksheet Set B

Very Short Answer Type Questions 

Question. How is ozone layer important to us?
Answer : Ozone is a pollutant at lower level of atmosphere but is very useful in shielding harmful UV rays. This layer is present in the stratosphere.
In absence of ozone layer heavy damage to organism may occur e.g. skin cancer, cataract etc.

Question. Write the two raw materials for making food, used by living organisms of first tropic level.
Answer : CO₂ and Water

Question. What are consumers in the food chain?
Answer : Those organisms which consume the food produced either directly from producers or indirectly by feeding on other organisms are called consumers.

Question. Name any two groups of producers.
Answer : Plants and blue-green algae.

Question. Name two decomposers.
Answer : Bacteria and fungi

Question. Expand UNEP
Answer : United Nations Environment Programme.

Short Answer Type Questions 

Question. Which disease is caused in human beings due to depletion of ozone layer in the atmosphere? 
Answer : Skin cancer, cataract.

Question. What are the two main components of our environment? 
Answer : Biotic (living components) ⎯⎯→ Plants, animals
Abiotic (non-living components) ⎯⎯→ Water, air

Question. Why is plastic bag called non-biodegradable while paper is not?
Answer : Plastic bag is not acted upon by decomposers as it cannot be broken down into simple components, so it is called non-biodegradable while paper gets decomposed.

Question. Pesticides are useful to farmers yet considered as pollutants. Give reasons.
Answer : Pesticides kill insects and pests thereby protecting the crops but these pesticides remain on the crops which enter the food chain and gets accumulated in the organisms and reaches the top most trophic level that causes diseases. When washed away by rain, it causes pollution of water.

Question. Differentiate between biodegradable and non biodegradable substances.
Answer : Biodegradable: These substances can be broken down by the action of saprotrophs and other agents, e.g., paper, cloth.
Non biodegradable: These substances cannot be broken down by the action of saprotrophs, e.g., glass, plastics.

Question. Which compounds are responsible for the depletion of ozone layer? 
Answer : Chlorofluorocarbons (CFC)

Question. Define an ecosystem. Explain in detail about its various components.
Answer : Ecosystem is defined as a well defined unit or area in an environment where biotic and abiotic components interact with each other to maintain balance in nature.
Biotic components – producers, consumers, saprotrophs.
Abiotic components – air, water, sunlight.

Question. State different types of consumers in an ecosystem.
Answer : The consumers are herbivores, carnivores, omnivores, parasites, saprophytes and decomposers.

Question. What is causing the damage to ozone layer?
Answer : The CFC emission due to various industrial activities has caused damage to the Ozone layer and has contributed to global warming by allowing a major portion of UV rays to reach the earth’s atmosphere through ozone holes.

Question. Define biological magnification.
Answer : The accumulation of chemicals in the bodies of the organism that belongs to the top most tropic level is called biological magnification.

Question. Differentiate between natural and artificial ecosystem.
Answer : 
Natural ecosystem     Artificial ecosystem
Naturally occurring ecosystem.
E.g., pond, grassland, forest These are man-made ecosystem.
E.g., garden, aquarium, crop-field.

Question. What is a food chain? List its characteristics features.
Answer : Food chain is defined as the phenomenon of transfer of energy through series of organisms falling on successive trophic levels.
Example: sun is the ultimate source of energy. Producers or green plants
photosynthesize and utilize solar energy. Thereafter the energy is transferred to other successive levels.
Food chain can be depicted as follows:
Plants → grasshopper → frog → snake → decomposers

Long Answer Type Questions 

Question. What are the problems caused by the non-biodegradable waste that we generate?
Answer : (i) As the non-biodegradable waste cannot be broken down into simpler forms hence they keep on accumulating in nature causing pollution.
(ii) They cause diseases.
(iii) It also causes biological magnification.

Question. What is the importance of ozone in the environment why is it depleting? What precautions are taken to preserve it?
Answer : Ozone is present in the stratosphere. It protects the earth from harmful ultraviolet radiations. UV ray causes various diseases to organisms e.g. skin cancer, cataract in human beings.
Ozone layer is depleting because of chlorides and fluorides. They act on ozone molecules and deplete it. Chlorides, fluorides are present in CFC’s which are used in refrigerants and fire extinguishers.
CFC ⎯⎯→ Chlorofluorocarbon
The precautions taken to preserve the ozone layer is to ban the use of CFC’s.

Question. What is biological magnification? Explain giving one example.
Answer : The accumulation of chemicals in the top most organism of the trophic level or food chain is called biological magnification.
Example: Farmer sprays pesticides on the crops which enters the food chain, from crops these pesticides enter into the organisms that feed on it.
grass ⎯⎯→ grasshopper ⎯⎯→ frog ⎯⎯→ snake ⎯⎯→ hawk
In this food chain the maximum amount of pesticide will be found in the top most organism i.e., in hawk the chemical keeps accumulating.

Question. What are decomposers? How are they important for the ecosystem?
Answer : Decomposers are the organisms which act on dead organisms to decompose the body so as to release all the elements back to nature.
They act as cleansing agents, hence they are important in the ecosystem.

Question. If all the waste we generate is bio-degradable, will this have no impact on the environment?
Answer : If all the waste we generate is bio-degradable and is managed in such a way that it is allowed to decompose then it will have no impact on the environment.

Question. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer : Ozone layer in the strastosphere is very helpful in shielding harmful UV rays. In absence of ozone layer heavy damage to organism may occur. It may cause diseases like skin cancer, cataract, reduced crop production etc. 
The damage is limited by UNEP (United Nations Environment Programme), it has forged an agreement to freeze for CFC production in 1986.
CFC– Chlorofluorocarbons used as refrigerants and in fire extinguishers.

Question. “Damage to the ozone layer is a cause of concern”. Justify this statement suggest any two steps to limit this damage. 
Answer : Ozone is a molecule of oxygen with 3 atoms i.e., O3. It is formed due to sunlight at higher levels with higher wavelength.
O₂ —→UV rays O + O
O₂ + O ⎯⎯→ O₃(Ozone)

Ozone is found in stratosphere shielding the earth by protecting it and by not allowing UV rays to reach the earth.
If these rays will reach the earth then many harmful diseases are caused like skin cancer, cataract, it also affects the growth of plants and vegetation.
Two steps to limit the damage of this layer are:
(i) Do not use aerosols, or any products which will release CFC (chlorofluorocarbon) in the atmosphere.
(ii) Ban on use of CFC as refrigerant and in fire extinguishers.

Question. Distinguish between biodegradable and non-biodegradable substances. List two effects of each of them on our environment.
Answer : 
Biodegradable substance Non-biodegradable substance
1. Substances can be decomposed by micro-organisms        1. Substances cannot be
2. Do not get accumulated in environment.                             2. decomposed by micro-organisms.

3. Do not cause any pollution                                                  3. It causes pollution.
It gets accumulated in environment.

Two effects on environment.

(i) Releases foul smell while decomposing in surrounding areas.  (i) It gets accumulated causing water and soil pollution and causes biological magnification.
(ii) It acts as a breeding ground for insects.                                    (ii) It disturbs the ecosystem by interfering in the food chain and killing many animals.

Question. What is the role of decomposers in the ecosystem?
Answer : Decomposers breakdown the complex organic substances like plant’s and animal’s dead body and convert them into simpler inorganic substances.
All the elements that are present in the body on which decomposers act is released back to the nature. Decomposers maintain balance in the nature and plays an important role in the environment.

Question. All eco-club students collect the vegetable peels from canteen and use them in compost pit made in their school.
(a) Name items that can be added in compost pit other than vegetable peels.
(b) What type of reaction is seen in the pit?
(c) State the values seen among eco-club members.
Answer : (a) Students can use leftover food and fruit peels, dried leaves.
(b) Fermentation i.e., anaerobic decomposition.
(c) The eco-club students show team work, collaborative work and good behaviour.

Question. What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer : The various levels or stages in a food chain at which the transfer of food takes place
is called trophic level, e.g., food chain.
Grass → Grasshopper → frog → snake → peacock
Grass — Producer — I trophic level.
Grasshopper — I Consumer (Herbivores) — II trophic level.
Frog — II Consumer (Carnivores) — III trophic level
Snake — III Consumer (Carnivores) — IV trophic level
Peacock — IV Consumer (Carnivores) — V trophic level.