NCERT Exemplar Solutions Class 10 Science Our Environment

Multiple Choice Questions........................

Question 1: Which one of the following is an artificial ecosystem?

(a) Pond

(b) Crop field

(c) Lake

(d) Forest 

Solution 1: (b) Crop field

A crop field is an artificial ecosystem.

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

(a) carnivores

(b) herbivores

(c) decomposers

(d) producers 

Solution 2: (a) carnivores

Producers are on the first trophic stage, herbivores are on the second, and carnivores are on the third.

Question 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 

Solution 3: (c) both living organisms and non-living objects

A network of living and nonliving species, as well as their relationships, makes up an ecosystem.

Question 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 

Solution 4: (d) 5000 k J

The available energy level at one trophic level is ten times that of the next trophic level. As a result, energy at the third trophic stage is 50kj. The energy of the second level trophic level (Producer) is 500 KJ, while the energy of the first level trophic level (Producer) is 5000 KJ. 

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

(a) eutrophication

(b) pollution

(c) biomagnification

(d) accumulation 

Solution 5: (c) biomagnification

• Eutrophication is described as nutrient richness that exceeds the optimum amount. Runoff from the soil causes eutrophication.
• Release of a harmful material into the atmosphere. Pollution has a negative impact on living organisms.

Question 6: Depletion of ozone is mainly due to

(a) chlorofluorocarbon compounds

(b) carbon monoxide

(c) methane

(d) pesticides 

Solution 6: (a) chlorofluorocarbon compounds 

Depletion of ozone is mainly due to chlorofluorocarbon compounds.

Question 7:  Organisms which synthesise carbohydrates from inorganic compounds using radiant energy are called

(a) decomposers

(b) producers

(c) herbivores

(d) carnivores 

Solution 7: (b) producers 

Solar energy is used by farmers to create food from water and carbon dioxide. The producers are plants and a few microorganisms.

Decomposers are organisms that decompose organic matter.

Herbivores are animals that eat plants and their byproducts.

Carnivores are animals that eat other organisms.

Question 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 

Solution 8:  (c) chemical energy 

In the form of food, energy can be transferred from one tropic stage to the next. Food is a form of chemical energy.

Question 9:  Organisms of a higher trophic level which 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 

Solution 9: (a) food web 

A food chain is a group of organisms through which food energy flows in an ecosystem. An ecosystem is made up of all the living creatures in a given area as well as the non-living elements in their surroundings. Ecological pyramids are a visual representation of the trophic structure and energy distribution in an ecosystem. The food web is made up of higher trophic level organisms that feed on different types of lower trophic level organisms.

Question 10:  Flow of energy in an ecosystem is always

(a) unidirectional

(b) bidirectional

(c) multidirectional

(d) no specific direction 

Solution 10:  (a) unidirectional 

Energy must move from prey to predator, not the other way around. As a result, there is a one-way flow of electricity.

Question 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) 

Solution 11:  (c) (i) and (iii) 

The upper surface of our bodies is affected by UV rays. UV rays cause skin cancer, and their effect on the skin has an impact on our immune system because the skin is the primary level of the immune barrier.

Question 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) 

Solution 12: (d) (ii) and (iv) 

Biodegradable wood and leather are included in Group I. Since grass in Group iii) is biodegradable, the response is d) (ii) and (iv)

Question 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 

Solution 13:  (a) Decrease in energy at higher trophic levels 

The available energy level at one trophic level is ten times that of the next trophic level. When we hit the fourth trophic stage, we have a small amount of energy from the producer.

Question 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 

Solution 14: (b) Green plants get their food from organic compounds 

Green plants use solar energy to generate their food. With the aid of inorganic substances like CO₂ and water, solar energy is used to make carbohydrate.

Question 15:  Which group of organisms are not constituents 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)  

Solution 15:  (c) (ii) and (iii)

Plankton does not eat grass in choice ii). Since none of them eat grass in option iii), option c) is the correct answer.

Question 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 % 

Solution 16: (a) 1 %

Green plants use 1% of the radiation absorbed by their leaves to perform photosynthesis.

Question 17: In the given figure below 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

Solution 17: (c) T₁ 

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

Question 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 

Solution 18:  (d) The population of tiger decreases and the population of grass increases. 

The absence of predators would result in an increase in grass population. Owing to a lack of food, the tiger population would decline. 

Question 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 

Solution 19:  (b) convert organic material to inorganic forms 

Organic material is converted to inorganic forms by decomposers in an environment.

Question 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 

Solution 20: (c) primary consumer to secondary consumer 

Since it feeds on grass, the grasshopper is a main user. If a grasshopper is devoured by a frog. The secondary client would be the frog.

Question 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 

Solution 21:  (d) they are made of non-biodegradable materials 

Disposable plastic plates should not be used because plastic when accumulated in nature starts harming the living organisms. Plastics are non-biodegradable material.

Short Answer Questions.......................

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

Solution 22:   Waste pollutes our climate, including the air, soil, and water, and has negative consequences for all living things.

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

Solution 23:  

Phytoplankton, algae

↓

Zooplankton, small fishes

↓

Fish, small shark

↓

Bird

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

Solution 24:   The following are some of the benefits of using cloth bags instead of plastic bags while shopping:

• They are re-usable.
• They should not pollute the atmosphere.
• They're made of biodegradable materials.
• They have a higher weight capacity than plastic bags.

Question 25:  Why are crop fields known as artificial ecosystems? 

Solution 25:   Crop fields are referred to as artificial habitats because they are man-made environments with manipulated biotic and abiotic components.

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

Solution 26:   Biodegradable substances are those that can be broken down into smaller parts through biological processes.

Non-biodegradable substances are those that cannot be broken down into smaller parts by biological processes.

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

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

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

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

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

Solution 27:

(a) Environment

(b) Trophic level

(c) Abiotic factors

(d) Consumers or heterotrophs

Question 28:  Explain the role of decomposers in the environment? 

Solution 28:   Decomposers aid in the nutrient recycling process by breaking down dead and rotting living matter. By removing dead stuff, the environment would be cleaned. 

Question 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

(b) Ecosystem — Biotic components of environment

(c) Aquarium — A man-made ecosystem

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

Solution 29:  (b) Ecosystem — Biotic components of environment

An ecosystem is made up of both biotic and abiotic components of the environment.

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

Solution 30:  When opposed to a pond or lake, which is a normal and complete ecosystem, an aquarium is an artificial ecosystem that is incomplete.

Long Answer Questions.......................

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

Solution 31:   The following diagram depicts the flow of energy in an ecosystem.

In a terrestrial ecosystem, green plants absorb about 1% of the energy that falls on their leaves and turn it into food energy.

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

As a result, 10% can be used as an estimate for the amount of organic matter present at each point before it reaches the next stage of consumers.

Since the next stage of customers has so little energy, food chains are usually just three or four steps long. After four trophic stages, the energy loss is so high that there is so little usable energy left.

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

Food chains vary widely in length and complexity. In general, each organism is eaten by two or three other types of species, which are then eaten by a number of other organisms.

So instead of a straight line food chain, the relationship can be shown as a series of branching lines called a food web.

Since the energy absorbed by autotrophs does not return to the solar input, and the energy passed to herbivores does not return to autotrophs, the energy flow is unidirectional. It is no longer accessible to the previous trophic stage as it progresses through the different trophic stages.

Second, as energy is lost at each trophic stage, the amount of energy available at each level diminishes.

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

Solution 32:  Bacteria and fungi are microorganisms that break down the dead remains and waste products of organisms. Decomposers are microorganisms that break down complex organic substances into simple inorganic substances that are returned to the soil and used by the plants.

If decomposers are not present in the ecosystem, there would be no recycling of material in the biosphere, resulting in an accumulation of dead plants and animals in the atmosphere. Furthermore, the world will eventually be devoid of any of the resources needed to maintain and sustain life.

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

Solution 33:  The following are some eco-friendly activities to engage in on a regular basis:

• Using motorcycles and hybrid bikes instead of fossil-fuel-powered cars.
• Instead of using plastic bags, we can use cloth and paper bags.
• Make our surroundings greener by planting trees.
• Recycle old products instead of using them.

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

Solution 34:

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

Solution 35:  The following are the daily wastes created in our home:

a)      Plastic bags.

b)      Kitchen wastes.

c)       Paper wastes like newspapers, bags, envelopes.

d)      Peels and rinds of vegetables and fruits disposal procedures.

Measure to take when disposing of household waste:

(a) Biodegradable and non-biodegradable wastes must be distinguished.

(b) Proper plastic bag disposal.

(c) Vegetable and fruit peels may be placed near plants to enrich the soil with nutrients as they decompose.

(d) Dispose of paper waste in a recycling bin.

e) Make a landfill pit for your food scraps.

Question 36:  Suggest suitable mechanism (s) for waste management in fertiliser industries. 

Solution 36:  Following steps must be taken in the fertiliser industry to manage waste:

⮚      Combustion equipment that can be oxidised is used to monitor gaseous contaminants. During the process, the pollutants are exposed to a high temperature. Adsorption equipment is used to monitor air contaminants such as some gases and vapours, as well as flammable compounds. Adsorption is a surface process that requires a broad solid surface area to occur. 

There are three options for handling effluents:

• Wastewater may be fully treated at the plant and reused or dumped directly into the receiving water supply.
• Inside the plant, control may take place at the point of production.
• Before being discharged to municipal treatment facilities, wastewater should be pre-treated.

Question 37:  What are the by-products of fertiliser industries? How do they affect the environment? 

Solution 37:  Nitrogen and sulphur oxides are the most common fertiliser industry by-products. They disperse into the air and spread to all surrounding locations. Aside from being toxic to living beings, the gases have a corrosive effect on a variety of objects. Acid rain is also a product of them. Acid rain is extremely harmful to trees, crops, and marine life.

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

Solution 38:  The following are some of the negative environmental impacts of agricultural practises:

Soil degradation

Soil productivity is lost as a result of extensive cropping. It can also contribute to soil erosion and, eventually, desertification. 

Pollution

Synthetic fertilisers and pesticides pollute the soil, water, and atmosphere. 

Water shortage

The use of groundwater for irrigation in excess depletes the water table. As a result, many areas are experiencing severe water shortages. 

Bio-magnification

Chemical pesticides accumulate in species in increasing concentrations at each trophic stage because they are non-biodegradable. 

Deforestation

The indiscriminate destruction of trees for agricultural purposes has resulted in the loss of wildlife habitat. As a result, it also harms the natural environment.