Please refer to Our Environment Class 10 Science Important Questions with answers below. These solved questions for Chapter 15 Our Environment in NCERT Book for Class 10 Science have been prepared based on the latest syllabus and examination guidelines issued by CBSE, NCERT, and KVS. Students should learn these solved problems properly as these will help them to get better marks in your class tests and examinations. You will also be able to understand how to write answers properly. Revise these questions and answers regularly. We have provided Notes for Class 10 Science for all chapters in your textbooks.

Important Questions Class 10 Science Chapter 15 Our Environment

All Our Environment Class 10 Science Important Questions provided below have been prepared by expert teachers of Standard 10 Science. Please learn them and let us know if you have any questions.

Very Short Answer Questions

Question. If in the following food chain, 100 J of energy is available to the lion, how much energy was available to the producer? Plants Deer -> Lion
Answer : 10,000 J.

Question. Why are green plants called producers ?
Answer : Producers are the organisms which prepare their own food in the presence of sunlight and chlorophyll.
Therefore green plants are called producers as they prepare their own food.

Question. Which compounds are responsible for the depletion of ozone layer?
Answer : Compounds which depletes ozone layer are:
(i) Chlorofluorocarbons (CFCs) and fluorocarbons.
(ii) Free chlorine.
(iii) Aerosols.

Question. Give one protective function of forests.
Answer : Forests reduce atmospheric pollution.

Question. Flow of energy is unidirectional. Name the first two components of the environment involved in this flow of energy from the sun.
Answer : Producers and primary consumers.

Question. Mention one negative effect of our affluent lifestyle on the environment.
Answer : Our activities to maintain an affluent lifestyle pollute the environment.

Question. Name two gases which have replaced CFCs.
Answer :
(i) Isobutane (ii) Perfluorocarbon (PFC)

Question. The first trophic level in a food chain is always a green plant. Why?
Answer : Plants can only utilize the radiant energy of the sun and transform it to chemical form during photosynthesis.

Question. Which of the following are always at the second trophic level of food chains? Carnivores, Autotrophs, Herbivores.
Answer : Herbivores.

Question. What is the function of ozone in the upper atmosphere?
Answer : Ozone shields the surface of the earth from ultraviolet rays from the Sim.

Question. Why should use of Chlorofluorocarbons be reduced?
Answer : Chlorofluorocarbons [CFCs] are res¬ponsible for depletion of ozone layer.

Question. Mention two ways to make our environment clean of garbage?
Answer :
a. Reduce the use of plastics
b. Recycle waste paper, plastic, glass and metal items.

Question. The following organisms form a food chain. Which of this will have the highest concentration of nonbiodegradable chemicals? Name the phenomenon associated with it.
Insects, Hawk, Grass, Snake, Frog
Answer : 
(i) Hawk (ii) Biomagnification

Question. What will be the amount of energy available to the organisms of the 2nd trophic level of a food chain, if the energy available at the first trophic level is 10,000 joules?
Answer : 1000 joules.

Question. In an ecosystem, rats feed on grains. Name the trophic level to which the rats belong.
Answer : Second trophic level.

Question. Draw a food chain which operates in a forest ecosystem.
Answer : Grass$ Deer$ Tiger.

Question. Give the full form of CFC.
Answer : CFC stands for Chlorofluorocarbon compounds.

Question. What is the physical environment of an ecosystem called? Give one example. 
Answer : Physical environment of an ecosystem is called as the abiotic or non-living component of an ecosystem. This includes physical factors like temperature, rainfall, wind, soil and minerals. (any one)

Question. How does concentration of a pesticide change once it enters a food chain? 
Answer : Concentration of pesticide gets accumulated progressively at each trophic level once it enters a food chain.

Question. Draw the conclusion if all the herbivores are removed from the grassland. 
Answer : If all the herbivores are removed from the grassland, carnivores will not be able to survive and the autotrophs will increase in number.

Question. What is ozone? How does it form?
Answer : Ozone layer forms due to combination of molecular and elemental form of oxygen in the presence of UV rays. O3 or ozone is a deadly poison formed from oxygen O2, due to the effect of UV rays of sun.

Question. Accumulation of harmful chemicals in our body can be avoided. Explain how this can be achieved.
Answer :
Accumulation of chemicals in our body can be avoided by:
a. Washing vegetables and fruits properly with water.
b. Soak vegetables and fruits in salt water for few minutes before cooking.
c. Most vegetables should be boiled.
d. ‘Organic subtances’ should be used for cultivation.

Question. What would happen if number of carnivores decreases in an ecosystem?
Answer :
a. Population of herbivores will increase beyond control.
b. Autotrophs will disappear from earth due to overgrazing done by herbivores.
c. Both these factors may disturb food chains thus affecting the ecosystem.

Question. State the direction of flow of energy in food chain.
Can food and energy from a trophic level move back to the previous level? Give reason for your answer.
Answer :
a. Energy flows from producer to top carnivores.
b. No, because flow of energy is unidirectional. It is from lower to higher level.

Question. What will happen if all the deers are removed in the given food chain?
Plants$ Deers $ Tigers
Answer :
If all deers are removed from the given food chain, then
a. Tigers will not survive.
b. Plants will increase in number.

Question. How will food chain be affected if we hunt all the tigers in a forest?
Answer :
Tiger is the top Consumer or Top Carnivore.
Eliminating it from food chain through hunting would lead to leaving the organism at trophic level below it to multiply without control. Since there are large herbivores like deer, they will eat up the producers (grass, plants) and make the soil without vegetation.
No vegetation in soil would cause desertification, soil erosion, floods, drought etc. Less vegetation means less rainfall and disruption of water cycle. It will be a vicious cycle.
Thus this act can lead to ecological balance as well as climatic problems.

Question. Mention the differences between food habits of organisms belonging to the first and third trophic level. Give one example of each of them.
Answer : (Table 82)

Question. Food web increases the stability of an ecosystem. Justify.
Answer :
Food web depicts feeding connection in an ecological community. It consists of many food chains. Thus, if any of the organism becomes endangered or extinct, the one who is dependent on it has an alternative option available to him for its survival. In this way, food web increases stability in an ecosystem.

Question. State with reason any two possible consequences of elimination of decomposers from the earth.
Answer : Two possible consequences of elimination of decomposers from the earth are:
a. Increase of complex organic substances causes land, water and air pollution.
b. It may disturb ecosystem as without decomposition, soil will not be replenished, which is essential for ‘plants’, which forms the basis of an ecosystem.

Question. Differentiate between the food habits I of organisms belonging to the first and second trophic level.
Answer : First trophic level : Producer/autotroph Second trophic level: Primary consumer/ herbivore.

Question. Give one example from your daily life where the household wastes can be effectively reused and recycled respectively.
Answer : To reuse paper envelope To recycle-plastic mug.

Question. Why did United Nations act to reduce the levels of chloroflurocarbons used in refrigerators?
Answer : UN wanted to check the depletion of ozone layer.

Question. Write the appropriate names of the trophic levels Z and X in the figure given

(Image 16)

Answer : Tertiary consumers, X : Primary consumers.

Question. What is meant by biological magnification?
Answer : Accumulation of non-biodegradable chemicals progressively at each trophic level in a food chain is called biological magnification.

Question. Give one example each from your daily life where the domestic waste can be reused and recycled.
Answer : Waste paper, boxes, envelopes, plastic and glass bottles.

Question. Select one item which is made up of biodegradable material – plastic bag, leather bag, nylon rope, kettle
Answer : Leather bag.

Question. In the food chain given below identify the trophic level in which the number of organisms available would be minimum?
Grass$ grasshopper$ Frog$ Snake$ Peacock
Answer : Peacock.

Question. Mention the role of microorganisms like bacteria and fungi in the ecosystem.
Answer : To breakdown the dead remains and waste product of organisms.

Question. In the following food chain, grass provides 4000 J of energy to the grasshopper. How much energy will be available to snake and frog?
Grass, Grasshopper, Frog, Snake.
Answer : Grass$ Grasshopper$ Frog$ Snake
(4000 J) (400 J) (40 J) (4 J)
So, for snake and frog, 4 J and 40 J energy will be available by 10 % law respectively.

Question. Identify the biodegradable pollutant from the following: Sewage, agricultural waste, fertilizers and pesticide.
Answer : Sewage.

Short Answer Questions

Question. Why Amrita Devi Bishnoi national award for wildlife conservation has been instituted?
Answer : Amrita Devi Bishnoi gave her life while saving wild life and forest trees in her locality. This award is given for those who show major contribution in conservation and protection of wild life.

Question. Government of India is imposing ban on the use of polythene bags for shopping. List four advantages of using cloth or jute bag over polythene bags.
Answer : Four advantages of using jute/cloth bag over polythene bags:
a. It is biodegradable.
b. Does not add to the garbage and land pollution.
c. Made from renewable resources.
d. Does not block the flow of water in the drains.
e. Can be washed and reused many times.

Question. Write the aquatic organisms in order of who eats whom starting from producer and form a chain of at least three steps. What name is given to such a chain in an ecosystem and what name is given to eachst age.
Answer :
a. Phytoplankton, Zooplankton, Fish,
b. Aquatic food chain.
c. Producer, herbivore, camivore/Producer, Primary
consumer, Secondary consumer.

Question. How is depletion of ozone layer a matter of concern?
What steps should be taken to check their formation?
or
How is ozone formed in the upper atmosphere? Why is damage to ozone layer a cause of concern to us?
What causes this damage?
Answer : Depletion of Ozone layer occurs due to release of CFCs. This will result in UV radiation reaching the earth, thereby causing skin cancer, damage to eyesand im mune system.
Two steps which can be taken are alternate technology and chemicals should be used to make these appliances where CFs and CFCs are being used.
In 1987, the United Nations Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 levels.
Many countries have banned the use of CFCs.

Question. State the meaning of ‘biodiversity’. List two advantages of conserving forest and wildlife.
Answer : Biodiversity consists of various species of plants and animals. Wild life means our flora and fauna.
Two advantages of conserving forest and wildlife are:
a. To preserve bio-diversity.
b. As each species has a position in the food chain so wildlife helps in balancing the nature.

Question. We often observe domestic waste decomposing in the by lanes of residential colonies. Suggest ways to make people realise that the improper disposal of waste is harmful to the environment.
Answer :
a. Provide separate dustbins – green for wet waste and blue for recyclable dry waste at public places.
b. Resident welfare associations should insist on segregation of household waste before their disposal to outside.
c. Awareness campaigns like Swachh Bharat to disseminate the knowledge about consequences of improper disposal of wastes.

Question. List two causes of depletion of ozone layer. Mention any two harmful effects of depletion of this layer.
Answer :
Two causes of depletion of ozone layer are: i. Use of CFs (Chlorofluorocarbons) in refrigerator.
ii. Use of CFCs in fire extinguishers and aerosol sprayers.
The harmful effects of depletion of ozone layer are:
a. Due to depletion of ozone layer, UV radiations reach the earth. These UV radiations cause skin cancer, damage to eyes and immune system.
b. This depletion of ozone layer may also lead to variations.

Question. What will happen if we kill all the organism in a trophic level?
Answer : The food chain will get disrupted if we kill all the organism in a trophic level. The organism at the lower level will increase in number as there in no one to eat them and those at higher level will die of starvation.
This will cause ecological imbalance.

Question. Differentiate between biodegradable and nonbiodegradable substances with the help of one
example each. List two changes in habit that people must adopt to dispose non-biodegradable waste, for saving the environment.
Answer :
a. Biodegradable substances can be broken down into simpler substances by nature or decomposers or bacteria or saprophytes. Example: Human excreta, Vegetable peels, etc.
b. Non-biodegradable substances cannot be brokendo wn into simpler substances by nature or decomposers. Example: Plastic/glass.
Habits which people must inculcate are:
c. Use of separate dustbins for biodegradable and non-biodegradable waste..
d. Reuse of things such as poly-bags, etc.
e. Recycle of waste.
f. Use of cotton/jute bags for carrying vegetables etc.

Question. Students in a school listened to the news read in the morning assembly that the mountain of garbage in Delhi, suddenly exploded and various vehicles got buried under it. Several people were also injured and there was traffic jam all around. In the brain storming session, the teacher also discussed this issue and asked the students to find out a solution to the problem of garbage. Finally they arrived at two main points – one is self management of the garbage we produce and the second is to generate less garbage at individual level.
a. Suggest two measures to manage the garbage we produce.
b. As an individual, what can we do to generate the least garbage? Give two points.
c. List two values the teacher instilled in his students in this episode.
Answer : a. Segregation and safe disposal. Encouraging use of recycled paper, plastic and glass items.
b. Following the strategy of 3Rs:
(i) Reducing the use of packing, buying only whatever is required, taking small serving at a time.
(ii) Reusing envelops, boxes, bottles and . cans.
Old clothes can be converted into dusters, bags etc
(c) (i) Scientific attitude (ii) concern for environment.

Question. In cities garbage disposal is a major problem. How can we deal with this problem? List any two ways.
Answer : Two methods of garbage disposal are:
a. Converting organic wastes into biogas or compost.
Organic wastes like cow dung, leaves etc can be decomposed and converted into useful substance like biogas and manure.
b. Recycling plastics, glass and metals.

Question. State two methods to get rid of non-biodegradable wastes.
Answer : a. Paper bags or cloth bags should be used to carry things instead of plastic bags.
b. Non-biodegradable wastes should be sent in factories for recycling.

Question. Define food web. State its significance for ecosystem.
Answer : A system of interconnected food chains between various organisms is called a food web.
A food web maintains ecological balance by maintaining the interdependene of different organisms.

Question. Compare the advantages of cloth bags over polythene bags.
Answer : Cloth bags being biodegradable are broken down by the action of bacteria or other saprophytes, whereas polythene bags being non-biodegradable persist in the environment for a long time, causing harm to the ecosystem.

Question. You have been selected to talk on ‘ozone layer and its protection’ in the school assembly on ‘Environment Day’.
a. Why should ozone layer be protected to save the environment?
b. List any two ways you will stress in your talk to bring the awareness amongst your fellow students that would protect the ozone layer as well as the environment.
or
How is depletion of ozone layer a matter of concern?
What steps should be taken to check their formation?
Answer : Depletion of Ozone Layer due to release of CFCs. It will result in UV radiation reaching the earth, causing skin cancer, damage to eyes and immune system.
a. Two steps which can be taken are alternatete chnology and chemicals should be used to make these appliances where CFCs and CFs are being used.
b. In 1987, the United Nations Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 levels. Many countries have banned the use of
CFCs.

Long Answer Questions

Question. Some wastes in nature persist for a long time while others get decomposed in a shorter period. Explainthei r difference. State in brief two ways each in which they affect the environment.
Answer : All wastes generated are not of the same nature.
Biodegradable wastes such as plant and animal can be acted upon by decomposers in nature and broken down easily in simpler substances as they possess enzymes to do so. Example: animal excreta, fruit peels, leftover food, crop refuge and so on.
Some other wastes or materials especially the ones produced by man can not be broken down by decomposers as they do not possess enzymes to do so. They are non biodegradable wastes such as some pesticide-DDT, detergents, plastics, radioactive wastes, metals etc. These substance may be broken down by chemical and physical processes in nature
such as rusting of iron but not by biological processes.
Two ways each in which biodegradable wastes affect the environment:
a. The beauty of a place and it stinks.
b. It attracts flies, cockroaches and germs which spread diseases.
Biodegradable pollutants are agricultural waste and sewage.
Non biodegradable wastes affect our environment by entering the food chain and accumulating in the body of organisms (biomagnification).
Nitrates and phosphates entering the water bodies can result in eutrophication. Some pesticide-DDT, detergents, plastics, radioactive wastes, metals etc.

Question. Give one instance where people’s participation helped to save this natural resource? Why should forests be conserved?
Answer :
Chipko movement i.e., ‘hug the trees movement’ is one of the movements in India to conserve biodiversity and to the end the alienation of people from their forests which started in March 1973 by Sunder Lal Bahuguna in Hilly areas like Himachal Pradesh.
Two benefits are:
(i) Existing forest cover was protected reducing landslides, land erosion. It actually protected environment and maintained ecological balance.
(ii) Forest wealth could be utilized for food, fodder, fuel, fertilizers and fibers keeping in mind its conservation.
We should conserve forests as:
(i) Forests purify the air and also prevent pollution of air and regulate the climate by maintaining thelevel of rainfall necessary for their own existence.
(ii) Forests are a storehouse of biodiversity (hotspots of biodiversity).