Please see Chapter 10 Our Environment Exam Questions Class 10 Science below. These important questions with solutions have been prepared based on the latest examination guidelines and syllabus issued by CBSE, NCERT, and KVS. We have provided Class 10 Science Questions and answers for all chapters in your NCERT Book for Class 10 Science. These solved problems for Our Environment in Class 10 Science will help you to score more marks in upcoming examinations.
Exam Questions Chapter 10 Our Environment Class 10 Science
Very Short Answer type Questions :
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 J
Question. What is an ecosystem?
Answer : An ecosystem is a self-sustained unit which comprises of all the interacting living things together with their non-living environment.
Question. Name the organisms belonging to the second and fourth trophic levels in the food chain comprising the following:
Frogs, Plants, Snakes, Hawks, Insects
Answer : Plants → Insects → Frogs → Snakes → Hawks
The organism belonging to the second and fourth trophic levels are insects and snakes respectively.
Question. Why do producers always occupy the first trophic level on every food chain?
Answer : Producers always occupy the first trophic level on every food chain because only producers (green plants) have the ability to trap solar energy with the help of chlorophyll (Process known as photosynthesis).
Question. Give 2 examples of each:
(A) Organisms occupying the first trophic level
(B) Abiotic factors of an ecosystem
Answer : (A) Organisms occupying the first trophic level: trees, shrubs, grass.
Question. List two main components of an ecosystem.
Answer : Two main components of an ecosystem are
(1) Biotic Component
(2) Abiotic component
Question. What happens during first step of ozone formation in the the atmosphere?
Answer: O2 UV → O + O
Question. Consider a food chain consisting of wheat, rat, snakes, peacock. What will happen if all snakes are killed?
Answer: The peacock will also die. The population of rats will increase.
Question. Change one consumer each that belongs to the second and third trophic levels from the following organisms : Eagle, frog, tiger, rabbit, fox
Answer: (i) Second trophic level → Rabbit (ii) Third trophic level → Frog and fox.
Question. In the following food chain, 10 J is energy available to the hawks. How much energy would have been present for the rats? Plants → Rats → Snakes → Hawks
Answer: 1000 J.
Question. List two steps that should be taken for the maintenance of healthy environment.
Answer: (i) Controlling pollution (ii) Afforestation (iii) Proper Waste Disposal
Question. Write the appropriate names of trophic level ‘Z’ and ‘X’ in the figure given below.
Answer: ‘X’ is primary consumer, ‘Z’ is tertiary consumer in the given figure.
Question. What is depicted in the below mentioned scheme?
Answer: It depicts 10% law in food chain for energy transfer from one trophic level to another.
Question. What is the functional unit of environment?
Answer: Ecosystem is the functional unit of environment.
Question. Crop fields are called artificial ecosystem, Justify.
Answer: Crop field ecosystem is created by man and needs care like watering, supply of manure, protection from diseases. Therefore, it is an artificial ecosystem.
Question. Which of the following are not biodegradable: Wool, glass, silver foil, leather?
Answer: Glass, silver foil.
Question. What is full form of CFC and UNEP?
Answer: CFC stands for Chloroflurocarbon UNEP stands for United Nations Environment Programme.
Question. Name the radiations that are absorbed by ozone layer?
Answer: UV radiations (Ultra-Violet radiations) are absorbed by ozone layer.
Question. Why is excessive use of CFC a cause of concern?
Answer: CFC will deplete ozone layer which prevents UV radiation to reach earth. It causes skin cancer.
Question. Name the gases which have replaced CFCs.
Answer: (i) HFCs (Hydrofluorocarbons), (ii) Perfluorocarbons (PFCs) have replaced CFCs.
Question. Why should bio-degradable and non-biodegradable wastes discarded into separate dust bins?
Answer: It saves time and energy by separating them and waste disposal can be done in right way in minimum time.
Question. Name any two items which can be easily recycled but are generally thrown in the dust-bin by us.
Answer: (i) Bits of paper (ii) Plastic bottles of water or cold drinks.
Question. Why are plastics non-biodegradable substances?
Answer: It is because plastics are not decomposed by micro-organisms. (Note: Now, plastic eating enzymes has been discovered).
Short Answer type Questions :
Question. How will you create an artificial aquatic ecosystem, which is self-sustainable?
Answer : • Large jar filled with water, oxygen, food and aquatic plants and animals.
• Oxygen/oxygen pump.
• Fish food.
• Aquatic plants/Producers provide O2 during photosynthesis.
• Aquatic animals/Consumers release CO2 for the process of photosynthesis.
• Decomposers are also important for natural cleaning of the aquarium.
Question. What is a food chain? Why is the flow of energy in an ecosystem unidirectional? Explain briefly.
Answer : Food chain is a sequence of a organised some in which one the other two transfer energy.
Four example.
The flow of energy is an ecosystem is always cannot revert back the energy consume of root in environment.
Question. List two main causes of the pollution of water of the river Ganga. State how pollution and contamination of river water prove harmful for the health of the people of neighbouring areas.
Answer : Causes:
• Disposal of industrial effluents
• Human activities like bathing, washing,immersion of ashes, etc.
• Disposal of untreated sewage (any two)
Harmful effects on healths :
• Spreads water borne diseases,
• Consumptions of contaminated fishes
(or any other relevant affect)
Question. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer : 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.
Several pesticides and harmful chemicals enter our body through food chain and remain there without being decomposed. The accumulation of these harmful chemicals increases towards the higher side of the food chain that is the level or concentration of the harmful chemicals increases with increasing trophic level. So, it is different at different levels of the ecosystem.
Question. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
Answer : Ozone prevents the passage of harmful ultraviolet radiations through the atmosphere to the earth. The damage to the ozone layer is a cause of concern since in the absence of the ozone layer harmful ultraviolet radiation will reach the earth and harm organisms on the earth.
Depletion of ozone layer has been linked to chloro-floro-carbons or CFCs which are used as refrigerants. To prevent depletion of the ozone layer, use of CFCs is being restricted
and replaced by more eco-friendly refrigerants under a UNEP (United Nations Environment Programme) initiative agreed upon in1986.
Question. Why is improper disposal of waste a curse to environment?
Answer : Disposal of waste means getting rid of waste.
Improper disposal of waste can cause significant harm to human health, safety and can develop causing serious environmental problems.
(1) The accumulation of biodegradable wastes causes an obnoxious smell, which is created during the process of decomposition.
(2) There can also be a possibility of sparking an epidemic if the waste is dumped near a residential area or is allowed to contaminate the water bodies. People living in areas near
old and abandoned waste disposal sites are in a particularly vulnerable position.
(3) Improper waste storage or disposal frequently contaminates surface and groundwater supplies.
In case of non- biodegradable substances, for example, chemical fertilizers, the nutrients in the soil are destroyed which thus affects health and reduces the longevity of the
people who consume the food cooked with the produce grown in such a soil.
(4) Improper disposal of plastics prevents the seepage of rainwater underground and lead to water scarcity.
(5) If the waste is not properly segregated at some place, it might not biodegrade and simply persist in the environment for a long time or may harm the various members of
the ecosystem.
Question. (A) Construct a terrestrial food chain comprising four trophic levels.
(B) What will happen if we kill all the organisms in one trophic level?
(C) Calculate the amount of energy available to the organisms at the fourth trophic level if the energy available to the organisms at the second trophic level is 2000 J.
Answer : (A) A terrestrial food chain comprising of fourt trophic levels:
Grass → Grasshopper → Frog → Snake
(B) If we kill all the organisms in one trophic level the transfer of food energy to next level will stop. Organisms of previous trophic level will also increase.
For example: If all herbivores in an ecosystem are killed:
There will be no food available for the carnivores of that area.
Consequently they will also die or will shift to other areas.
Populations of producers will also increase in absence of herbivores causing imbalance in the ecosystem.
(C) Consider the same food chain as we have made in 19 (a):
Grass → Grass hopper → Frog → Snake
In this food chain, second trophic level is grass hopper and the energy available at this trophic level is 2000 J.
According to 10% law, 10% of energy will be available to frog (Third trophic level) which is 200 J.
The energy available to the snakes will be available as 10% of 200 J. Thus, the energy available to the snake is 20 J.
Question. Answer the following questions:
(A) To discard the household waste, we should have two separate dustbins, one for the biodegradable waste and the other for non-biodegradable waste. Justify the given statement and suggest the proper
ways of disposal of such wastes.
(B) Classify the given waste into biodegradable and non-biodegradable waste used tea leaves, leather bag, plastic bag, jute bag.
Answer : (A) First identify the waste as bioderadable and non-bioderable waste and use two different dustbins according to being biodegrable or not we can take blue for non-biodegradable
and green for biodegradable. Biodegradable waste can be composted, turned into manure and decompose by micro organisms easily.
Non-biodegradable waste should be collected and disposed off at right place so that it can be recycled.
(B)
| Biodegrable waste | Non-biodegradable waste |
| used tea leaves | plastic bag |
| leather bag | — |
| ute bag | — |
Question. Mention three harmful effects of using polythene bags on the environment. Suggest an effective alternative to these bags.
Answer : Harmful effects of using polythene bags on the environment are listed below:
(1) Plastic causes land pollution and water pollution as it is a non-biodegradable substance.
(2) Burning of plastic releases toxic gases and causes air pollution.
(3) Plastic bags cause harm to the life of animals when they consume it along with food.
(4) Plastic bags can cause blocking in sewage line.
(5) The surfaces of tiny fragments of plastic may carry disease-causing organisms and act as a vector for diseases in the environment.
Question. What are decomposers? State the role of decomposers in the environment.
Answer : The decomposers are the various organisms in the ecosystem which help in decomposing the dead bodies of plants and animals by breaking down the complex organic substances into simpler inorganic substances.
Role of decomposers in the environment:
(1) They decompose the wastes of organisms, dead plants and animals in the absence of which these would pile up leading to foul gases, diseases and deaths.
(2) They help in recycling of nutrients and thus maintain fertility of the soil.
(3) They play a maJor role in various biogeochemical cycles which are natural ways of nutrient cycling.
Question. (a) What is an ecosystem? List its two main components.
(b) We do not clean ponds or lakes, but an aquarium needs to be clean regularly, explain.
Answer: (a) Ecosystem is composed of different organisms interdependent upon each other. Biotic and abiotic components are its two main components.
(b) Pond or lake is a natural ecosystem, several organisms present in it maintain a balance in the ecosystem. Aquarium is an artificial ecosystem in which bacteria convert fish food into ammonia which is harmful for fish. Water needs to be changed regularly. Chlorine water should be dechlorinated otherwise fish will not survive. Air pump is needed to provide oxygen. Artificial ecosystem need utmost care to remain stable.
Question. Arrange the following in food chain:
(a) Frogs, Insects, Birds, grass. (b) Fish, algae, small animal, big animal.
Answer: (a) Grass → Insects → Frog → Birds
(b) Algae → Small animal → Fish → Big animal
Question. What will happen if we kill all the organisms in one trophic level?
Answer: If we kill the organisms in one trophic level.
(i) The population of organisms in previous trophic level will increase.
(ii) The population of organisms in next trophic level may decrease.
(iii) It will cause an ecological imbalance in the food chain.
Question. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?
Answer: The process in which harmful chemicals like pesticides enter the food chain and get accumulated in each trophic level is called biomagnification. The level of biomagnification will be different from different trophic level. Primary consumers will have higher concentration of pesticides than producers and secondary consumers will get pesticides by eating primary consumers and will have even higher concentration.
Question. Why are some substances biodegradable and some are non-biodegradable?
Answer: Biodegradable substances are those which are broken by micro-organisms and get decomposed. They do not persist in environment for a very long time e.g., paper.
Non-biodegradable substances are those which are not broken by micro-organisms. They persist in environment for long time. e.g. plastic, DDT.
Question. List three characteristics of energy flow in an ecosystem.
Answer: (i) The sun is the main source of energy on earth. About 1% of incident solar energy is utilized by plants during photosynthesis.
(ii) Producers [plants] convert solar energy to chemical energy of food, and then it is passed on to the consumers and to decomposers back to soil. This is in accordance with law of conservation of energy.
(iii) The energy flow is unidirectional, that is, it flows from producers through herbivores to carnivores; it cannot be transferred in the reverse direction.
(iv) The amount of energy flow decreases with successive trophic levels.
Question. What is meant by food chain? ‘The number of trophic levels in food chain is limited.’ Give reason to justify the statement.
Answer: Food chain is a sequence in which nutrients, food and energy is transferred in systematic way. Lower trophic level have maximum population because energy is available in more extent.
Primary consumers get 10% of energy of producers.
Secondary consumers get 10% of energy of primary consumers.
Tertiary consumers get 10% of energy of secondary consumers i.e. very less energy is available, that is why the trophic levels are limited. Tiger population is decreasing day by day as food is not easily available for them and forests are decreasing due to cutting of trees.
Question. Differentiate between autotrophs, heterotrophs and decomposers and give one example of each.
Answer: (i) Autotrophs. Those organisms which prepare their own food with the help of CO2, H2O and sunlight in presence of chlorophyll e.g. green plants.
(ii) Heterotrophs. Those organisms which do not prepare their own food but dependent on the other food. e.g. animals and human beings.
(iii) Decomposers. Those organisms which decompose the complex molecules present in the dead remains of plants and animals e.g. bacteria, fungi, earthworm.
Question. If all the waste we generate is biodegradable, will this have no impact on the environment?
Answer: If all waste we generate is biodegradable, the adverse effect on environment will be minimum. They will produce CO2, methane which is released in atmosphere.
Nutrients will be mixed in soil to increase the fertility of soil.
Question. Mention three methods to reduce amount of wastes produced.
Answer: (i) Recycling of non-biodegradable waste.
(ii) Reuse of waste such as newspapers can be used for making carry bags and envelopes.
(iii) Biodegradable domestic waste should be disposed in pits to form manure.
(iv) Biogas plants should be used for disposal of waste in rural areas.
Question. Construct an aquatic food chain showing four trophic levels.
Answer:
Question. What term do you use for trophic levels comprising of
(a) the organisms which make their own food
(b) animals feeding on plant matter only
(c) organisms breaking down dead plants and animals
Answer: (a) Producers (b) Herbivores (c) Decomposers
Question. How will you create an artificial aquatic ecosystem, which is self-sustainable?
Answer: • Take a large jar filled with water, oxygen, food and aquatic plants and animals.
• Oxygen/oxygen pump.
• Fish food.
• Aquatic plants/Producers provide O2 during photosynthesis.
• Aquatic animals/Consumers release CO2 for the process of photosynthesis.
• Decomposers are also important for natural cleaning of the aquarium.
Long Answer Type Questions
Question. Differentiate between biodegradable and non-biodegradable 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 : Biodegradable substances: can be broken down into simpler substances by nature / decomposers / bacteria / saprophytes / saprobionts.
Ex.- Human Excreta/Vegetable peels, etc. (any one)
Non-biodegradable substances : can’t be broken down into simpler substances by nature / decomposers.
Ex.- Plastic/ glass (or any other)
Habits:
• Use of separate dustbins for biodegradable and non biodegradable waste,
• Reuse of things such as poly-bags, etc.,
• Recycle of waste
• Use of cotton /jute bags for carrying vegetables etc.
Question. Monika was observing a lizard on the wall which chased an insect and ate it. She felt that the lizard was cruel and ugly. Suddenly, the lizard fell and was eaten by a cat. She started thinking, how are organisms connected to each other for their food?
What is a food chain? Will the world be a better place without lizards?
make a food chain of five organisms.
To which trophic level does the lizard belong?
Answer : A lizard eats an insect. When the lizard falls, it is eaten by a cat. Hence, the lizard depends on the insect for food, while the cat depends on the lizard for food. This interdependence of organisms on one another for their food is called food chain. It is very important to have a food chain in the ecosystem for maintaining the balance of nature. Hence, even though the lizard is an ugly creature, it is important for maintaining the balance of nature.
The food chain of five organisms is as follows:
Sun → Plants → Insect → Lizard → Cat
We can see that the lizard belongs to the fourth tropic level.
Question. Suggest any four activities in daily life which are eco-friendly.
Answer : Four activities in daily life which are eco-friendly:
(1) Separation of biodegradable and nonbiodegradable substances.
(2) Gardening
(3) Use of gunny bags/paper bags in place of polythene/plastic bags.
(4) Use of compost and vermicompost in place of fertilizers.
(5) Harvesting rain water.
(6) Using public transport, cycling or walking to travel.
(7) Switch off fans and lights when not in use.
(8) Use of compost and vermicompost in place of fertilizers.
Question. While teaching the chapter “Our Environment” the teacher stressed upon the harmful effects of burning of fossil fuels, plastic, paper etc.
The students noticed the extensive use of plastic and polythene in daily life, which can be avoided and the surroundings can be kept clean. They decided to make their school “plastic and polythene” free and motivated each other for its minimum use.
(A) Why should the use of polythene and plastic be reduced in daily life?
(B) In what ways the students would have avoided the use of plastic and polythene in their school?
Answer : (A) The use of polythene and plastic should be reduced in daily life because of the following reasons:
(1) They cause land pollution and water pollution as they are non-biodegradable substances.
(2) Burning of plastic and polythene releases toxic gases and causes air pollution.
(3) Plastic and polythene bags cause harm to the life of animals when they consume it along with food.
(4) Plastic and polythene bags can cause blocking in sewage line.
(5) The surfaces of tiny fragments of plastic and polythene may carry diseasecausing organisms and act as a vector for diseases in the environment.
(B) Students would have avoided use of plastic and polythene in following ways:
(1) By carrying tiffn a nd w ater i n s teel containers thereby avoiding the use of plastic.
(2) By carrying their items in cloth bags, jute bags or paper bags instead of using polythene bags.
(3) By boycotting all such items such as plastic plates and spoons, juices served in plastic cans and stationery items etc made of plastic or polythene which are sold in school canteen.
Question. Mr. Kumar, the incharge of ‘‘Eco-Club’’ of a school felt the need of organising an ‘‘Awareness Campaign’’ for the residents of the nearby areas to make them realise the necessity of segregating the biodegradable and non-biodegradable wastes. He went from door-to-door with his students and gave arguments to explain the people about the importance of disposal of their household waste judiciously. He also informed them about the prosecutional provisions in the cases where garbage is thrown at places other than the specified bins.
List two advantages of disposing the waste after segregating it in two categories.
Answer : The two advantages of disposing the waste after segregating it in two categories:
(1) The biodegradable wastes kept in a separate bin can be dumped directly in a pit for composting or for dumping in landfills.
(2) The useful part of non-biodegradable wastes kept in a different bin can be separated for recycling or reusing them.
(3) Non-useful part of wastes can be disposed off in such a way that it does not harm the people or pollute the environment in anyway.
(4) Segregated waste is cheaper to dispose of because it does not require as much manual or mechanical sorting as mixed waste.
Question. Your mother always thought that fruit juices are very healthy for everyone. One day she read in the newspaper that some brands of fruit juices in the market have been found to contain certain level of pesticides in them. She got worried as pesticides are injurious to our health.
(A) How would you explain to your mother about fruit juices getting contaminated with pesticides?
(B) It is said that when these harmful pesticides enter our body as well as in the bodies of other organisms they get accumulated and beyond a limit cause harm and damage to our orgAnswer : Name the phenomenon and write about it.
Answer : (A) Pesticides and other chemicals are sprayed on crops to protect them from diseases and pests. These chemicals are nonbiodegradable and can stick to the surfaces of fruits and vegetables. If these fruits are not washed or disinfected thoroughly before use, they will contaminate the fruit juice.
(B) The phenomenon is Biological Magnification, which refers to the process where toxic substances move up the food chain and become more concentrated at each trophic level. The pesticides and chemicals or industrial effluents are washed down into the soil or water bodies from where they are absorbed by the plants, aquatic plants or animals. This is how they enter our food chain and being non-biodegradable, their concentration increases at each trophic level. As human beings are at the top of the trophic level in any food chain, maximum concentration of these harmful chemicals get accumulated in our bodies.
Question. Give reason to justify the following:
(A) The existence of decomposers is essential in a biosphere.
(B) Flow of energy in a food chain is unidirectional.
Answer : (A) The existance of decomposers is essential in a biosphere because they breakdown complex organic substances into simple inorganic substances that can be absorbed by the plants. Thus, decomposers help in the recycling of the minerals, and also helps in removing the biodegradable waste.
(B) The flow of energy is unidirectional. The energy captured by the autotrophs does not return to the solar input and the energy which passes to the herbivores does not come back to autotrophs. Only 10% of the energy is passed on to the next level. As it moves progressively through the previous level. Hence, the energy flow is unidirectional. For Example:
