Our Environment CBSE Class 10 Important Question and Answers

1.Why is there a need to b an the use of poly then e bags?
Ans.Polythene bags are non- biodegradable, the y are not decomposed by micro- organisms hence, cause land pollution.

2.What are the two functions of ecosystem?
Ans.Interactions of any ecosystem refers to it s functions these interactions are-
(A) Biogeochemical cycles- The cyclic transfers between the living and non- living components.
(B) Flow of energy- in a food chain, through various st eps of eating and being eaten food energy flow from one tropic level t o another.



3.What percentage of solar energy is trapped and utilized by plants?
Ans.Plants utilized only 1% of total sun’s ener gy, which is utilized by plants in the process of photosynthesis.

4.Energy transfer is said to be unidirectional wh e r e as biochemical transfer is said be cyclic. Why?
Ans.Energy flow is unidirectional because as it transfers from one trophic level to next trophic level, it reduces only 10% is available at Successive level from previous level. Nutrient flow is cyclic because nutrients re turned back into nutrient pool from the dead bodies of plants and animals by the d ecomposition of micro- organisms from nutrient pool. They are utilized aga in by plants.
5.Give difference between produc es and consumers.
Ans.

6.There are no predators for tiger or lion. Why?
Ans. Lions and tigers are at the highest trophic level. They are largest animals which feed upon the secondary carnivores like wolves etc. they are not killed and eaten by other animals.

7.What are the measures to protect ozone depletion?
Ans..Measure to protect ozone layer-
(A) Concern over increasing global ozone depletion led to international restrictions in the use and manufacture of CFCS and halons.
(B) International concern over the seriousness of the problems associated with ozone layer depletion led to the adoption of Vienna convention for the protection of the ozone layers in 1985.
(C) Promotion of an international treaty known as Montreal protocol (1987), to which over 140 countries agreed to the reduction an d eventual phasing out of the manufacture and use of most ozone depleting sub stances.

8.What are the harmful effects of acid rain?

Ans. (1) Acid rain makes the soil acidic whic h affects the growth of trees and cereal crops badly.
(2) It makes the water of lakes, po nds, etc acidic which affects the growth of aquatic plants and animals.
(3) Bacteria useful for maintaini ng soil fertility are killed.
(4) It affects the historical monum ents and building badly specially those made up of marble.

9.Differentiate between abiotic and biotic components of ecosystem.
Ans.

10.Give any two methods reducing the problem of waste disposal.
Ans. (a) Use of recycled material.
(b) Separation of biodegradable and non-biodegradable waste during disposal.

11.Give reason: “Life on the earth depends on the sun. ”
Ans. Sun is the ultimate source of energy on ea rth. Only plants can convert solar energy into chemical energy (food), which is transferred t o different organisms at various trophic levels. Energy stored in fossil fuel is als o transferred solar energy because they made up of decomposed plants and animals. Henc e, solar energy is utilized and transformed in different form which is utilized by us.

12.Describe three biotic component of ecosystem.
Ans.Biotic components of ecosystem are-
(a) Producers- All the green plants have a unique capab ility to synthesis organic substance such as sugar and starch by the p rocess of photosynthesis. Therefore, they are called producer s.
(b) Consumers- These are the living organisms which dep end directly or indirectly on plants for their food. Consumers may be herbivore, carnivores, and omnivores.
(c) Decomposers- Decomposers are the organisms which de pend upon the dead and decaying organisms their waste material. T hey form important link between living and non-living components.

13.What is the role of decompose rs in the ecosystem?
Ans. Decomposers decompose all the organic mat ter trapped in body, body parts and waste of organisms and returned back to environment . Hence, they are the important link between living and non-living compon ents of environments. They play a vital role in biochemical or nutrient cycle and removing the organic garbage from our surroundings. They play an important role in changing our surrounding.

14.What will happen if we kill all the organisms in one trophic level?
Ans.The food chain would end and ecological bal ance would be affected-
(a) If the herbivores are killed, then the carnivores w ould not able be to get food and would die.
(b) If carnivores are killed, then the population of he rbivores would increase to unsustainable level.
(c) If producers are killed, then the nutrient cycle in the area would not be completed.

15.What is Ozone ? How does it affect any ecosystem?
Ans. Ozone (O 3 ) is an isotope of oxygen i.e. it is a molecule for med by three atoms of oxygen. At the higher levels of the atmosphere, ozo ne performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiations from the sun. These radiations are highly damaging to organi sms. Ultraviolet rays can cause skin cancer.

16.Why vegetarian food habits help us in getting more energy?
Ans. A person having vegetarian food habits is closet to the producer level get maximum amount of energy as compare to the organism at higher trophic level because only 10% of energy is available at the succ essive level than previous level.

17.What is the significance of food chains?
Ans. Significance of food chain
(a) It is a means of transfer of food from one trophic level to another.
(b) It provides information about the living component of an ecosystem.
(c) It helps us in understanding the interactions and i nterdependence amongst different organism in an ecosystem.
(d) It is a pathway for the flow of energy in any ecosy stem.

18.How Garbage pollution can be controlled?
Ans. Pollution of garbage can be controll ed by-
(a) Recycling of certain wastes products like plastic a nd paper.
(b) Making use of biodegradable products as much as we can.
(c) Producing biogas from the organic wastes.
(d) Separation of biodegradable and non-bio-degradable waste during disposal.
(e) Making the compost of biodegradable wastes by buryi ng them under soil.

19.What are the components of ecosystem?
Ans. An ecosystem has two major componen ts-
(1) Biotic components- It includes producers (plants), consumers (animals) and decomposers (bacteria and fungi).
(a) Producers- Organisms which are able to photosynthes is are called producers. It includes all green plants.
(b) Consumers- Organisms which depends upon other are c alled consumers. It is of few types-
(i) Herbivores- Animals which directly depends upon pla nts.
(ii) Carnivores- These animals eat herbivores. (iii) Secondary carnivores- Animals which depends upon carnivores.
(iv) Tertiary carnivores- Largest animals which de pends upon secondary carnivores.
(c) Decomposers- These organisms depend upon dead plant s and animals. They change complex organic substances int o simple inorganic substances.
(2) Abiotic components- Non-living components. It inclu de physical and chemical factors such as light, water, soil, air te mperature, oxygen, carbon, nitrogen and other nutrients.

20.Write any three activities which are eco - friendly.
Ans. (a) Making the compost of biodegradab le wastes by burying them under soil.
(b) Use of cloth bags instead of polythene bags.
(c) Using CNG in vehicles inst ead of petrol or diesel.

21.What is meant by environment? Name its components.
Ans. The aggregate of all external conditio ns and their influences affecting the life and the development of an organism in its natural habit at is environment. It has two components-
(1) Abiotic components (non-living):- For example- air, water, soil, temperature, etc.
(2) Biotic components (living):- For example- Plant, animals and micro- organisms.

22.What is 10% law?
Ans. According to 10% law only 10% of ener gy is available at the next trophic level. For example- If energy availa ble at producer level is 1000J then at next level o nly 10% of 1000J i.e. 100J is available.

23.What is artificial ecosystem? Give two examples.
Ans.Man-made ecosystem are called artificial ec osystem. For example- Garden, Aquarium.

24.DDT that was sprayed in minute amount on food plant s was detected in high concentration in man? How did it happen? Explain.
Ans. This occurs due to biological magnifica tion. When pesticides like DDT are used to protect crops from diseases and pests. These non-bi odegradable substances enter the soil. From soil these substances are absorbed b y plants along with water and minerals. The food plants when consumed by organism s, they get accumulated at different trophic levels. As the human beings occup y the top position in any food chain, maximum concentration of such harmful chemic als get accumulated in the bodies of man.

25.Describe how ozone layer is formed?
Ans. Formation of the ozone layer-
(a) During the origin of life Earth, some of underwater micro-organisms were to photosynthesize due to molecular oxygen (O 2 ) was released in atmosphere.
(b) This oxygen is released to stratosphere where it be gan to react with ultraviolet radiations from sun to form free oxygen (O).
(c) Free oxygen combines with molecular oxygen (O 2 ) to form (O 3 )

26.Why are the some substances biodegradable and some non - biodegradable?

Ans. The micro-organisms like bacteria and other decomposers organisms (called saprophytes) present in our environment specific in their action. They break down the materials or products made from natural ma terials (paper) as they have some peculiar enzymes for this process. But as enzymes are specific in their action, these cannot break down many man-made mater ials likes plastic. These can be acted upon by physical processes but not by biological processes. Therefore these types of substances persist for lon g time and cannot be decomposed into simpler substances.

27.What is trophic level?
Ans. Various levels or steps in a food cha in in which transfer of food takes place from one organism to another are called trophic levels.

28.Energy transfer is said to be unidirectional wherea s biochemical transfer is said to be cyclic. Why?
Ans. The flow of energy is unidirectional because the energy lost as heat to the environment can’t be reutilized by plants for photo synthesis. Energy decrease at each trophic level (10% of previous level). Hence i t can’t be reused again. Whereas, biochemical transfer is cyclic because nut rients utilized by plants and animals are returned to environment after the death of organisms.

29.Why is there a need to ban the use of polythene bags?
Ans. Polythene bags need to be banned beca use they are non-biodegradable; micro- organisms are not able to decompose it. So it goes on accumulating on the land and causes land pollution.

30.What is the significance of food chain?
Ans. Significance of food chain-
(a) It is a means of transfer of food from one trophic level to another.
(b) It provides information about the living components of our ecosystem.
(c) It helps us in understanding the interactions and i nterdependence among different organisms in an ecosystem.
(d) It is a pathway for the flow of energy in any ecosy stem.

30.How would you dispose the following wastes:
(a) domestic wastes like vegetables peels
(b) industrial wastes
Ans. (a) Domestic wastes like vegetables
peels should be disposed off in a pit.
(b) Industrial wastes should be treated first to remove poisonous salts or chemicals and disposed off in water resources like river.

31.Explain why the food chain consists of few steps on ly? Write a food chain having five steps.
Ans. Food chains consist of few steps only b ecause in food chain energy decreases at each successive trophic level, due to this energy a vailable at higher trophic level reduce step by step. If a food chain has six or mor e than six steps, energy is not sufficient for the survival of organism at that tro phic level. Plants → Grasshopper → Insect → Frog → Snake

32.What is the difference between food chain and food web?
Ans.

33.What is biological magnification? Illustrate with t he help of example.
Ans. It is a process of increase in concent ration of persistent pollutant per unit weight of the organisms with the rise in trophic level.

34.What are the ill effects of ozone layer depletion?
Ans. Ill effect of ozone depletion. (1) Human health: - (a) It cause skin cancer.
(b) Eye dise ases like cataracts.
(c) Suppresi on of the immune system.
(2) Agriculture and plant life: - Growth leaf deve lopment of most plant species decrease abundantly on exposure to high concentrati on of UV radiation which are filtered by ozone layer.
(3) Marine environment: - UV radiation filtered th rough the depleted ozone layer directly damage.
(a) Photosynthesizing phytoplankton presents in th e sea which also help in reducing the global warming.
(b) Young fishes.
(c) Shrimp, crabs larvae and other small animals.
(d) Material degradation: - The lives of many plas tics have been found to be shortened due to exposure to UV radiations.