NCERT Exemplar for Class 10 Science Chapter 15 - Our Environment (Book Solutions)

Multiple Choice Questions

1. Which one of the following is an artificial ecosystem?

(a) Pond

(b) Crop field

(c) Lake

(d) Forest

Ans: The answer is (b) Crop field. A crop field is a man-made ecosystem.

2. In a food chain, the third trophic level is always occupied by

(a) carnivores

(b) herbivores

(c) decomposers

(d) producers

Ans: The answer is (a) carnivores. The first trophic level is producers, the second trophic level is herbivores, the third trophic level is occupied by carnivores.

3. An ecosystem includes

(a) all living organisms

(b) non-living objects

(c) both living organisms and non-living objects

(d) sometimes living organisms and sometimes non-living objects

Ans: The answer is (c) both living organisms and non-living objects. An ecosystem is a complex of living and nonliving organisms and their interactions.

4. In the given food chain, suppose the amount of energy at the fourth trophic level is 5 kJ, what will be the energy available at the producer level?

Grass → Grasshopper → Frog → Snake → Hawk

(a) 5 k J

(b) 50 k J

(c) 500 k J

(d) 5000 k J

Ans: The answer is (d) 5000 k J. The amount of energy available at one trophic level is ten times that of the following trophic level. As a result, energy at the third trophic level is 50kj. The energy of the second level trophic level (Producer) is 500 KJ, whereas the energy of the first level trophic level (Producer) is 5000 KJ.

5. Accumulation of non-biodegradable pesticides in the food chain in increasing amounts at each higher trophic level is known as

(a) eutrophication

(b) pollution

(c) biomagnification

(d) accumulation

Ans: The answer is (c) bio magnification. Nutrient richness over the optimal amount is referred to as eutrophication. Runoff from the land causes eutrophication. Unwanted material is released into the environment. Pollution has a negative impact on living beings.

6. Depletion of ozone is mainly due to

(a) chlorofluorocarbon compounds

(b) carbon monoxide

(c) methane

(d) pesticides

Ans: The answer is (a) chlorofluorocarbon compounds. The contained chlorofluorocarbons are broken down by UV light in the stratosphere, releasing chlorine. The chlorine depletes the ozone layer by reacting with it. Thus, chlorofluorocarbon chemicals are the primary cause of ozone depletion.

7. Organisms that synthesize carbohydrates from inorganic compounds using radiant energy are called

(a) decomposers

(b) producers

(c) herbivores

(d) carnivores

Ans: The answer is (b) producers. Producers use solar energy to synthesize food from water and carbon-di-oxide. Plants and a few micro-organisms are the producers. Organisms that decompose organic material are called decomposers. Herbivores are the organisms that feed on plant and their products. Carnivores are the ones that feed on other organisms.

8. In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of

(a) heat energy

(b) light energy

(c) chemical energy

(d) mechanical energy

Ans: The answer is (c) chemical energy. In the form of food, energy may be transferred from one trophic level to the next. Food is a type of chemical energy.

9. Organisms of a higher trophic level that feed on several types of organisms belonging to a lower trophic level constitute the

(a) food web

(b) ecological pyramid

(c) ecosystem

(d) food chain

Ans: The answer is (a) food web. A food chain is a group of organisms through which food energy moves in an ecosystem. An ecosystem is made up of all the live creatures in a given area as well as the non-living components of their surroundings. Ecological pyramids are a visual representation of the trophic structure and energy transfer in an ecosystem. The food web is made up of higher trophic level species that feed on different sorts of lower trophic level organisms.

10. Flow of energy in an ecosystem is always

(a) unidirectional

(b) bidirectional

(c) multidirectional

(d) no specific direction

Ans: The answer is (a) unidirectional. The flow of energy is from prey to predator and it cannot be in the reverse direction. Hence the flow of energy is uni-directional.

11. Excessive exposure of humans to U V-rays results in

(i) damage to the immune system

(ii) damage to lungs

(iii) skin cancer

(iv) peptic ulcers

(a) (i) and (ii)

(b) (ii) and (iv)

(c) (i) and (iii)

(d) (iii) and (iv)

Ans: The answer is (c) (i) and (iii). The upper layer of our bodies is affected by UV radiation. UV rays cause skin cancer, and their impact on the skin has an impact on our immune system since the skin is the primary level of the immunological barrier.

12. In the following groups of materials, which group (s) contains only non-biodegradable items?

(i) Wood, paper, leather

(ii) Polythene, detergent, PVC

(iii) Plastic, detergent, grass

(iv) Plastic, bakelite, DDT

(a) (iii)

(b) (iv)

(c) (i) and (iii)

(d) (ii) and (iv)

Ans: The answer is (d) (ii) and (iv). Group i) has wood and leather which are biodegradable. Group iii) has grass that is biodegradable hence the answer is d) (ii) and (iv)

13. Which of the following limits the number of trophic levels in a food chain?

(a) Decrease in energy at higher trophic levels

(b) Sufficient food supply

(c) Polluted air

(d) Water

Ans: The answer is (a) Decrease in energy at higher trophic levels. The available energy level at one trophic level is ten times that of the following trophic level. When we reach the fourth trophic level, we have a small amount of energy from the producer.

14. Which of the statement is incorrect?

(a) All green plants and blue-green algae are producers

(b) Green plants get their food from organic compounds

(c) Producers prepare their own food from inorganic compounds

(d) Plants convert solar energy into chemical energy

Ans: The answer is (b) Green plants get their food from organic compounds. Green plants need sun energy to generate their sustenance. With the aid of inorganic components like \[CO_{2}\] and water, solar energy is utilized to make glucose.

15. Which group of organisms is not constituent of a food chain?

(i) Grass, lion, rabbit, wolf

(ii) Plankton, man, fish, grasshopper

(iii) Wolf, grass, snake, tiger

(iv) Frog, snake, eagle, grass, grasshopper

(a) (i) and (iii)

(b) (iii) and (iv)

(c) (ii) and (iii)

(d) (i) and (iv)

Ans: The answer is (c) (ii) and (iii). In option ii) plankton does not eat grass. In option iii) none of them eat grass hence option c) is the right answer.

16. The percentage of solar radiation absorbed by all the green plants for the process of photosynthesis is about

(a) 1 %

(b) 5 %

(c) 8 %

(d) 10 %

Ans: The answer is (a) 1 %. Green plants utilize 1% of the radiation absorbed by leaves and use it for photosynthesis.

17. In the given Figure 15.1 the various trophic levels are shown in a pyramid. At which trophic level is maximum energy available?

(a) T4

(b) T2

(c) T1

(d) T3

Ans: Answer is (c) T1

Producers have access to the most energy possible. An organism in the next level consumes just 10% of the energy spent at the previous level. Hence T1>T2>T3>T4

18. What will happen if deer is missing in the food chain given below? Grass → Deer → Tiger

(a) The population of tiger increases

(b) The population of grass decreases

(c) Tiger will start eating grass

(d) The population of tiger decreases and the population of grass increases

Ans: The answer is (d) The population of tiger decreases and the population of grass increases. The absence of predators will result in an increase in grass population. Due to a scarcity of food, the tiger population will decline.

19. The decomposers in an ecosystem

(a) convert inorganic material, to simpler forms

(b) convert organic material to inorganic forms

(c) convert inorganic materials into organic compounds

(d) do not breakdown organic compounds

Ans: The answer is (b) convert organic material to inorganic forms. Decomposers in an ecosystem transform organic material into inorganic forms, which are then reused by plants in the soil.

20. If a grasshopper is eaten by a frog, then the energy transfer will be from

(a) producer to decomposer

(b) producer to primary consumer

(c) primary consumer to secondary consumer

(d) secondary consumer to primary consumer

Ans: Answer is (c) primary consumer to secondary consumer. Because it eats on grass, the grasshopper is a key consumer. If a grasshopper gets devoured by a frog. The secondary consumer will be the frog.

21. Disposable plastic plates should not be used because

(a) they are made of materials with lightweight

(b) they are made of toxic materials

(c) they are made of biodegradable materials

(d) they are made of non-biodegradable materials

Ans: The answer is (d) they are made of non-biodegradable materials. Because plastics are non-biodegradable, they accumulate in nature and destroy biological species.

Short Answer Questions

22. Why is improper disposal of waste a curse to the environment?

Ans: Improper waste disposal is a curse to the environment since it pollutes the air, water, and soil, as well as has adverse impacts on living beings. For example, sewage discharge into a water body causes eutrophication, animal death, and the spread of water-borne infections.

23. Write the common food chain of a pond ecosystem.

Ans:  The common food chain of a pond ecosystem is

Phytoplanktons

↓

Small aquatic animals larvae, shrimps, Insects

↓

Fish

↓

Bird

24. What are the advantages of cloth bags over plastic bags during shopping?

Ans: The advantages of cloth bags over plastic bags during shopping are as follows

1. They can carry more weight than plastic bags

2. They are bio-degradable

3. They can be reused.

4. They do not cause environmental pollution.

25. Why are crop fields known as artificial ecosystems?

Ans: Crop fields are referred to as artificial ecosystems since they are man-made ecosystems with modified biotic and abiotic components. When they add manure to their farm, for example, they enhance the abiotic elements (nutrients) essential for plant development.

26. Differentiate between biodegradable and non-biodegradable substances. Cite examples.

Ans: The difference between biodegradable and non-biodegradable substances is

27. Suggest one word for each of the following statements/ definitions

(a) The physical and biological world where we live in

Ans: The physical and biological world where we live in an Ecosystem. An ecosystem is a collection of biotic and abiotic elements found in the natural world. 

(b) Each level of the food chain where the transfer of energy takes place

Ans: Each level of the food chain where the transfer of energy takes place is the Trophic level. The plant or the producers constitute the first trophic level. The herbivores or primary consumers form the second trophic level.

(c) The physical factors like temperature, rainfall, wind, and soil of an ecosystem.

Ans: Abiotic factors are non-living elements in an ecosystem, such as temperature, rainfall, wind, and soil.

(d) Organisms which depend on the producers either directly or indirectly for food

Ans: Organisms that depend on the producers either directly or indirectly for food is Consumers or heterotrophs

28. Explain the role of decomposers in the environment?

Ans: A community of life forms that competes with non-living components and interacts with one another is referred to as an ecosystem. Saprophytes, such as fungus and bacteria, are decomposers. They feed on dead and decaying organic substances directly. Decomposers are important for the ecology because they help recycle nutrients so that plants may utilize them again.

29. Select the mismatched pair in the following and correct it.

(a) Biomagnification — Accumulation of chemicals at the successive trophic levels of a food chain.

Ans: Biomagnification is termed as the Accumulation of chemicals at the successive trophic levels of a food chain. Therefore, it is not a mismatched pair.

(b) Ecosystem — Biotic components of the environment

Ans: Both biotic and abiotic components of the environment constitute an ecosystem. So, it is mismatched pair.

(c) Aquarium — A man-made ecosystem

Ans: Aquarium is a mam made ecosystem. Therefore, it is not a mismatched pair.

(d) Parasites — Organisms which obtain food from other living organisms

Ans: Parasites are organisms that obtain their food from other organisms. Hence, it is correctly paired.

30. We do not clean ponds or lakes, but an aquarium needs to be cleaned. Why?

Ans: An aquarium is a man-made system that is also deficient in terms of producers, food chains, and decomposers. There is no self-cleaning or recycling. A pond or lake, on the other hand, is a self-contained, natural, and complete ecosystem with perfect nutrient recycling.

Long Answer Questions

31. Indicate the flow of energy in an ecosystem. Why is it unidirectional? Justify.

Ans: The flow of energy in an ecosystem is as follows.

In a terrestrial environment, green plants collect roughly 1% of the energy that falls on their leaves and convert it into food energy.

When primary consumers eat green plants, a lot of energy is lost to the environment as heat, part of it goes into digestion and work, and the remainder goes into growth and reproduction. 10% of the food consumed is converted into its own body and made available to the next level of consumers.

As a result, 10% may be used as an average for the quantity of organic matter present at each phase before it reaches the next level of consumers.

Because the next level of consumers has so little energy, food chains are usually just three or four levels long. After four trophic levels, the energy loss is so high that there is very little useful energy left.

The lower trophic levels of an ecosystem have a higher number of people, with the producers having the highest number.

Food chains vary tremendously in length and complexity. In general, each creature is eaten by two or more other types of organisms, which are then devoured by a number of other species. Instead of a straight line food chain, the connection may be shown as a food web, which is a network of branch lines.

The energy acquired by autotrophs does not return to the solar input, and the energy passed to herbivores does not return to autotrophs, thus, the energy flow is unidirectional. It is no longer available to the previous trophic level as it progresses through the various trophic levels. Second, when energy is lost at each trophic level, the amount of energy accessible at each level diminishes.

32. What are decomposers? What will be the consequence of their absence in an ecosystem?

Ans: Bacteria and fungi are microorganisms that break down the dead remnants and waste products of species. Decomposers are microorganisms that break down complex organic chemicals into simple inorganic substances that are returned to the soil and utilized by the plants.

If decomposers are not present in the ecosystem, there will be no recycling of material in the biosphere, resulting in a build-up of dead plants and animals in the environment. Furthermore, the ecosystem would eventually be empty of all of the materials required to maintain and support life.

33. Suggest any four activities in daily life which are eco-friendly

Ans: Activities in daily life that are eco-friendly are as follows

1. Using bicycles and electrical bikes instead of vehicles run by fossil fuels.

2. Avoid using plastic bags, instead, we can use bags made of clothes and paper.

3. Plant trees in our surroundings.

4. Stop usage of old items and recycle them.

34. Give two differences between food chain and food web.

Ans:  The differences between food chain and food web are-

35. Name the wastes which are generated in your house daily. What measures would you take for their disposal?

Ans: Wastes generated in our house daily are as follows

(a) Kitchen wastes

(b) Paper wastes like newspapers, bags, envelopes

(c) Plastic bags

(d) Vegetable/fruit peels/rind Measures for disposal

Measures to take to dispose of house waste are

(a) Segregation of biodegradable and non-biodegradable wastes.

(b) Safe disposal of plastic bags.

(c) Vegetable/fruit peels can be placed near trees/plants, which on decomposition will enrich the soil with nutrients.

(d) Give paper wastes for recycling.

(e) Prepare a compost pit for kitchen wastes.

36. Suggest suitable mechanism (s) for waste management in fertilizer industries.

Ans: The following procedures must be followed to manage waste in the fertilizer industry:

Combustion equipment that can be oxidized is utilized to manage gaseous pollution. During the procedure, the contaminants are subjected to a high temperature. Adsorption equipment is used to regulate air pollutants such as specific gases and vapors, as well as combustible substances. Adsorption is a surface phenomenon that requires a big solid surface area to occur. This method effectively eliminates hazardous and odorous substances.

37. What are the by-products of fertilizer industries? How do they affect the environment?

Ans: Nitrogen and sulphur oxides are the most prevalent fertilizer industry byproducts. They disperse into the air and spread to all adjacent locations. Aside from being harmful to human beings, the gases have a corrosive impact on a variety of goods. Acid rain is also a result of them. Acid rain is extremely harmful to forests, agriculture, and aquatic life.

The most prevalent fertilizer industry by-products are nitrogen and sulphur oxides. These oxides are released into the atmosphere and spread over the area. Sulphur and nitrogen oxides corrode a variety of materials in addition to being toxic to humans. Acid rain is caused by sulphur oxides, which destroy forests, agriculture, and aquatic life.

38. Explain some harmful effects of agricultural practices on the environment.

Ans: 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: The use of synthetic fertilizers 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 shortages 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 the loss of habitat for wildlife. Thus, it also causes damage to the natural ecosystem.

Overview of NCERT Exemplar for Class 10 Science Chapter 15

This component provides you with solutions for questions in NCERT exemplar Class 10. NCERT exemplar is carefully designed by the experts after proper research of what questions are asked, weightage of different topics, previous year questions. Students are recommended to go through the following PDF provided and practice all the questions for better scores on boards. Questions similar to this model are asked in exams. Solving as many problems as possible will help you in saving time in the exam. 

Introduction to Our Environment Chapter 15

In this Chapter 15 Science - Our environment, we will be knowing about different components of the environment, how they interact with each other, how human actions affect our environment, and various changes taking place in our surroundings. This topic in exemplar contains MCQs, short and long answers. You can download it from the link given below and study it offline, students can access our material from laptops, tablets, and mobile phones.