Class 10 Chapter 13 Our Environment

Multiple Choice Questions

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

(a) Pond

(b) Crop field

(c) Lake

(d) Forest

Answer :  (b) Crop field:

[ A crop field is an example of an artificial ecosystem because it is created and maintained by human activities for the cultivation of crops, and it is not a naturally occurring ecosystem like a pond, lake, or forest.]

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

(a) carnivores

(b) herbivores

(c) decomposers

(d) producers

Answer : (a) carnivores:

[ The third trophic level in a food chain is typically occupied by carnivores, which are organisms that consume other animals.]

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

Answer : (c) both living organisms and non-living objects .

[ An ecosystem comprises both living organisms (biotic components) and non-living objects (abiotic components) in a specific area, interacting with each other and their environment. ]

4. In the given food chain, suppose the amount of energy at 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

Answer :  (d) 5000 kJ .

[ In a food chain, energy decreases as it moves up each trophic level due to energy loss at each step, typically around 10% efficiency. Given that the energy available at the fourth trophic level (Hawk) is 5 kJ, you can estimate the energy available at the producer level (Grass) by reversing this process:

Energy available at the fifth trophic level (Hawk) is 5 kJ.

Energy available at the fourth trophic level (Snake) is 10 times that of the Hawk, which is 5 kJ×10=50 kJ .

Energy available at the third trophic level (Frog) is 10 times that of the Snake, which is 50 kJ×10=500 kJ .

Energy available at the second trophic level (Grasshopper) is 10 times that of the Frog, which is 500 kJ×10=5000 kJ .

Energy available at the producer level (Grass) is 10 times that of the Grasshopper, which is 5000 kJ×10=50,000 kJ . ]

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

Answer :  (c) biomagnification:

[ The accumulation of non-biodegradable pesticides in increasing amounts at each higher trophic level in the food chain is known as biomagnification. ]

6. Depletion of ozone is mainly due to

(a) chlorofluorocarbon compounds

(b) carbon monoxide

(c) methane

(d) pesticides

Answer :  (a) chlorofluorocarbon compounds:

[ Depletion of ozone is mainly attributed to the release of chlorofluorocarbon (CFC) compounds into the atmosphere, which break down ozone molecules in the stratosphere.]

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

(a) decomposers

(b) producers

(c) herbivores

(d) carnivores

Answer : (b) producers

[ Organisms that synthesize carbohydrates from inorganic compounds using radiant energy (usually sunlight) through the process of photosynthesis are called producers.]

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

Answer : (c) Chemical energy.

[ In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of chemical energy stored in organic compounds, such as glucose, that make up the bodies of organisms.]

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

Answer : (a) food web.

[ Organisms of a higher trophic level that feed on several types of organisms belonging to a lower trophic level constitute a food web, which represents a complex network of interconnected food chains in an ecosystem.]

10. Flow of energy in an ecosystem is always

(a) unidirectional

(b) bidirectional

(c) multi directional

(d) no specific direction

Answer :  (a) unidirectional.

[ The flow of energy in an ecosystem is typically unidirectional, meaning it moves through the trophic levels from producers to consumers and decomposers in one direction.]

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

(i) damage to 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)

Answer : (c) (i) and (iii)

[ Excessive exposure to UV rays can result in damage to the immune system and an increased risk of skin cancer. ]

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)

Answer : (d) (ii) and (iv)

[ Polythene, detergent, PVC, plastic, bakelite, and DDT are all non-biodegradable materials, which do not easily break down in the environment.]

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

(a) Decrease in energy at higher trophic levels

(b) Dufficient food supply

(c) Polluted air

(d) Water

Answer : (a) Decrease in energy at higher trophic levels:

[ The energy available to organisms decreases as it moves up the trophic levels in a food chain. This decrease in energy limits the number of trophic levels that can be supported in an ecosystem.]

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

Answer :  (b) Green plants get their food from organic compounds.

[ This statement is incorrect. Green plants are producers that use photosynthesis to convert inorganic compounds (such as carbon dioxide and water) into organic compounds (like glucose) using solar energy.]

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)

Answer :  (c) (ii) and (iii)

[ In the given options, plankton, man, fish, and grasshopper belong to different trophic levels and do not form a direct linear sequence in a traditional food chain.]

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 %

Answer : (b) 5%

[ Approximately 5% of solar radiation is absorbed by green plants for the process of 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)      (b)        (c)      (d)

Answer :  (c)  

[ The trophic level at the base of the pyramid () typically has the maximum energy available, as it represents the primary producers (plants) that capture energy from the sun.]

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

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

[ Without deer, the tiger's primary food source is missing, leading to a decrease in the tiger population and a potential increase in the grass population.]

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

Answer : (b) convert organic material to inorganic forms.

[ Decomposers break down organic material into simpler, inorganic compounds, facilitating the recycling of nutrients in an ecosystem by returning them to the soil.]

20. If a grass hopper 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

Answer :  (b) producer to primary consumer.

[ The energy transfer occurs from the grasshopper (primary consumer) to the frog (secondary consumer), representing the flow of energy through different trophic levels in an ecosystem.]

21. Disposable plastic plates should not be used because

(a) they are made of materials with light weight

(b) they are made of toxic materials

(c) they are made of biodegradable materials

(d) they are made of non-biodegradable materials

Answer :  (d) they are made of non-biodegradable materials.

[ Non-biodegradable plastics persist in the environment for a long time, contributing to pollution and harm to wildlife. Their disposal and accumulation pose significant environmental problems.]

Short Answer Questions

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

Answer : Improper disposal of waste is a curse to the environment because it leads to pollution of land, water, and air. Waste can release harmful chemicals and toxins that contaminate soil and water sources, affecting ecosystems and human health. It also contributes to unsightly litter, encourages the spread of disease, and disrupts natural habitats, leading to long-term environmental degradation.

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

Answer :  A common food chain in a pond ecosystem is:

Phytoplankton (Producers) → Zooplankton (Primary Consumers) → Small Fish (Secondary Consumers) → Larger Fish (Tertiary Consumers)

In this chain:

Phytoplankton: Microscopic plants and algae that produce energy through photosynthesis.

Zooplankton: Small aquatic animals that feed on phytoplankton.

Small Fish: Fish that consume zooplankton.

Larger Fish: Predatory fish that eat smaller fish.

This chain illustrates the flow of energy from primary producers to top predators in a pond ecosystem.

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

Answer : Cloth bags offer several advantages over plastic bags during shopping:

(i) Cloth bags are reusable and reduce the amount of single-use plastic waste, minimizing environmental pollution and reducing landfill contributions.

(ii) Cloth bags are sturdier and can carry heavier items compared to plastic bags, which are prone to tearing.

(iii)Cloth bags help prevent harm to wildlife caused by plastic waste ingestion and entanglement.

(iv) They can be used multiple times, whereas plastic bags are often used only once before being discarded.

(v) Cloth bags are typically made from natural or recycled materials, which are more biodegradable compared to plastics that persist in the environment for hundreds of years.

(vi) Cloth bags can be cost-effective in the long run as they reduce the need for purchasing single-use plastic bags frequently.

25. Why are crop fields known as artificial ecosystems?

Answer : Crop fields are known as artificial ecosystems because they are human-made environments designed for agricultural purposes. Unlike natural ecosystems, which develop naturally, crop fields are intentionally created and managed to grow specific crops. They often lack biodiversity and rely on human intervention for irrigation, fertilization, and pest control, making them distinct from naturally occurring ecosystems.

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

Answer :  The difference between biodegradable and non-biodegradable substances :

Biodegradable	Non – Biodegradable
(i) Biodegradable substances can be broken down by natural processes, including the action of microorganisms, into simpler, non-toxic components. Examples: Food scraps, paper, wood, and natural fibers like cotton and wool.	(i) Non-biodegradable substances cannot be broken down easily by natural processes and persist in the environment for long periods. Examples: Plastics, synthetic fibers, metals, and glass.
(ii) They decompose naturally and integrate back into the environment without causing long-term pollution.	(ii) They remain in landfills or natural habitats, contributing to pollution and environmental harm.

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 food chain where 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

Answer : (a) Environment (b) Trophic (c) Abiotic (d) Consumers

28. Explain the role of decomposers in the environment?

Answer : Decomposers play a crucial role in the environment by breaking down organic matter, such as dead plants and animals, into simpler substances like carbon dioxide, water, and minerals. This process, known as decomposition, releases nutrients back into the soil, making them available for plants and other organisms. Decomposers also help in recycling nutrients and maintaining the balance of ecosystems.

29. Select the mis-matched 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

Answer : The mis-matched pair is:

(b) Ecosystem — Biotic components of environment.

Correction:

(b) Ecosystem — Interactions between biotic and abiotic components of the environment.

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

Answer : Ponds and lakes are natural ecosystems with self-regulating mechanisms, such as biological filtration by microorganisms, plants, and natural water flow, which help maintain water quality and balance. In contrast, an aquarium is a closed, artificial environment without these natural processes, so it requires regular cleaning and maintenance to prevent the buildup of waste, algae, and other pollutants, ensuring a healthy habitat for the aquatic life inside.

Long Answer Questions

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

Answer :  Flow of Energy in an Ecosystem:

Producers: Energy enters the ecosystem through primary producers (e.g., plants, algae) that convert solar energy into chemical energy via photosynthesis.

Primary Consumers: Herbivores feed on producers, transferring energy from plants to animals.

Secondary Consumers: Carnivores or omnivores that eat herbivores transfer energy further up the food chain.

Tertiary Consumers: Top predators that consume other animals occupy the highest trophic level.

Decomposers: Organisms like bacteria and fungi break down dead plants and animals, recycling nutrients back into the ecosystem.

Unidirectional Nature:

The flow of energy in an ecosystem is unidirectional because:

(i) Energy is lost at each trophic level due to metabolic processes like respiration, heat production, and waste. Only about 10% of the energy is passed to the next level, while the rest is lost.

(ii) Energy cannot be recycled in the same form through the ecosystem. Once energy is used by organisms, it cannot flow back but is instead dissipated as heat.

This one-way flow of energy drives the structure and function of ecosystems, maintaining the balance and sustainability of life forms.

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

Answer : Decomposers are organisms that break down dead plants, animals, and organic matter into simpler substances, such as nutrients and minerals, that can be reused by primary producers. They include bacteria, fungi, and some invertebrates like earthworms.

Consequences of Absence in an Ecosystem:

(i) Without decomposers, dead organic matter would accumulate, leading to a buildup of waste and detritus in the ecosystem.

(ii) Decomposers play a critical role in recycling nutrients back into the soil. Their absence would disrupt nutrient cycling, depriving plants of essential nutrients needed for growth.

(iii) The breakdown of organic matter by decomposers enriches the soil. Without them, soil fertility would decline, affecting plant health and productivity.

(iv) The lack of decomposers would lead to imbalances in the ecosystem, as plants and animals rely on the nutrient recycling provided by decomposers for survival.

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

Answer : Four eco-friendly activities in daily life are :

(i) Using reusable bags for shopping to reduce plastic waste.

(ii) Walking, biking, or using public transportation instead of driving to decrease carbon emissions.

(iii) Conserving water by fixing leaks, taking shorter showers, and using water-efficient appliances.

(iv) Recycling paper, plastic, glass, and metal to minimize waste and conserve resources.

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

Answer :  The difference between a food chain and a food web:

Aspect	Food Chain	Food Web
Definition	A linear sequence showing the flow of energy from one organism to another in a single pathway.	A complex network of interconnected food chains representing multiple feeding relationships in an ecosystem.
Complexity	Simple and linear, showing one path of energy flow.	Complex and interconnected, showing multiple paths and interactions among various organisms.

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

Answer :  Wastes generated in a household daily :

(i) Organic waste (food scraps, vegetable peels)

(ii) Paper waste (newspapers, magazines, cardboard)

(iii) Plastic waste (packaging materials, bottles, containers)

(iv) Glass waste (jars, bottles)

(v) Metal waste (aluminum cans, tin cans)

Measures for their disposal:

(i) Organic waste: Composting for soil enrichment or disposal in designated compost bins.

(ii) Paper waste: Recycling through local recycling programs or collection centers.

(iii) Plastic waste: Sorting and recycling plastics according to their types, reducing single-use plastics, and reusing plastic containers where possible.

(iv) Glass waste: Recycling through designated glass recycling bins or centers.

(v) Metal waste: Recycling metals through scrap metal collectors or recycling programs

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

Answer : In fertilizer industries, effective waste management can be achieved through the following mechanisms:

(i) Implementing processes like composting or anaerobic digestion to recover nutrients and energy from organic waste.

(ii) Adopting cleaner production techniques to reduce waste generation at the source.

(iii) Reusing by-products like gypsum or sludge in other industrial processes.

(iv) Employing chemical and biological treatment methods to neutralize hazardous waste.

(iv) Converting waste to energy through incineration or gasification to reduce landfill use and generate power.

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

Answer : By-products of Fertilizer Industries:

Ammonia: A by-product of the Haber process used to produce nitrogen fertilizers.

Nitric Acid: Produced during the synthesis of nitrogen fertilizers.

Phosphogypsum: A by-product from the production of phosphatic fertilizers.

Carbon Dioxide: Emitted during various fertilizer production processes.

Heavy Metals: Residual elements like cadmium, lead, and arsenic from phosphate rock used in fertilizers.

Environmental Impacts:

Water Pollution: Runoff containing excess fertilizers can lead to eutrophication in water bodies, causing harmful algal blooms and oxygen depletion, which adversely affects aquatic life.

Soil Degradation: Accumulation of chemical residues and heavy metals can degrade soil quality, reduce soil fertility, and harm beneficial microorganisms.

Air Pollution: Emissions of ammonia and carbon dioxide contribute to air pollution, which can lead to respiratory issues and contribute to greenhouse gas effects.

Acid Rain: Nitrogen oxides and sulfur compounds released from fertilizer production can combine with atmospheric moisture to form acid rain, which harms ecosystems and infrastructure.Top of Form

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

Answer: Agricultural practices can significantly harm the environment in several ways. Excessive use of chemical fertilizers and pesticides leads to soil degradation, water pollution, and harm to non-target species. Intensive farming can cause deforestation, loss of biodiversity, and disruption of natural habitats. Additionally, irrigation practices may deplete water resources and alter local ecosystems. The reliance on monocultures and heavy machinery contributes to soil erosion and greenhouse gas emissions, exacerbating climate change and impacting ecological balance.