OUR ENVIRONMENT

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

(a) Pond

(b) Crop field

(c) Lake

(d) Forest

Answer: (b) Crop field

Explanation: A crop field is an artificial ecosystem because it is created and managed by humans. In this type of ecosystem, humans control various factors, such as the type of plants grown, soil treatment, water supply, and pest control. On the other hand, ponds, lakes, and forests are natural ecosystems that exist without human intervention.

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

(a) Carnivores

(b) Herbivores

(c) Decomposers

(d) Producers

2. Answer: (a) Carnivores

Explanation: In a food chain, the third trophic level is typically occupied by carnivores, also known as secondary consumers. The first trophic level consists of producers (plants), the second trophic level consists of herbivores (primary consumers), and the third level consists of carnivores that feed on herbivores.

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

The correct answer is:

(c) Both living organisms and non-living objects

Explanation:

An ecosystem is a community that includes both living organisms (plants, animals, bacteria, fungi, etc.) and non-living components (soil, water, air, sunlight, minerals, etc.). These components interact with each other in various ways. Living organisms depend on non-living elements for resources like water, nutrients, and shelter, while they also influence the non-living environment through processes such as decomposition, nutrient cycling, and energy flow. This dynamic interaction between biotic (living) and abiotic (non-living) factors makes up a balanced ecosystem.

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 kJ

(b) 50 kJ

(c) 500 kJ

(d) 5000 kJ

1. Question: 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?

Food Chain:

Grass → Grasshopper → Frog → Snake → Hawk

Answer:

(d) 5000 kJ

Explanation:

In an ecosystem, energy transfer follows the 10% rule, which states that only about 10% of the energy at one trophic level is passed on to the next level, with the rest being lost as heat. Given that the fourth trophic level (snake) has 5 kJ, we work backwards to estimate energy at the producer level (grass).

Fourth trophic level (Snake): 5 kJ

Third trophic level (Frog): 5 kJ × 10 = 50 kJ

Second trophic level (Grasshopper): 50 kJ × 10 = 500 kJ

First trophic level (Grass): 500 kJ × 10 = 5000 kJ

Therefore, the energy available at the producer level 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

Answer:

(c) Biomagnification

Explanation:

Biomagnification refers to the process by which non-biodegradable substances, like pesticides, accumulate in greater concentrations at each successive trophic level in a food chain. As organisms at each trophic level consume others, the concentration of these substances increases because they are not broken down or excreted efficiently. This phenomenon poses serious health risks to top predators, including humans.

Other options:

Eutrophication is the excessive enrichment of water bodies with nutrients, often leading to algal blooms and oxygen depletion.

Pollution is the introduction of harmful substances into the environment.

Accumulation is a general term for buildup but does not specifically describe biomagnification.

6. Depletion of ozone is mainly due to:

(a) Chlorofluorocarbon compounds

(b) Carbon monoxide

(c) Methane

(d) Pesticides

Answer: (a) Chlorofluorocarbon compounds

Explanation: Chlorofluorocarbons (CFCs) are chemicals that break down ozone molecules in the stratosphere, causing ozone depletion.

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

(a) Decomposers

(b) Producers

(c) Herbivores

(d) Carnivores

Answer: (b) Producers

Explanation: Producers, such as plants and algae, use photosynthesis to convert light energy into chemical energy (carbohydrates).

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

Explanation: Only about 10% of the energy from one trophic level is transferred to the next level in the form of chemical energy, stored in organic compounds.

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

Explanation: A food web represents the complex network of feeding relationships between organisms at different trophic levels.

10. Flow of energy in an ecosystem is always:

(a) Unidirectional

(b) Bidirectional

(c) Multidirectional

(d) No specific direction

Answer: (a) Unidirectional

Explanation: Energy flows in one direction—from the sun to producers, then to consumers, and finally to decomposers.

11. Excessive exposure of humans to UV 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)

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

Explanation: UV radiation can cause skin cancer and damage the immune system, but it does not typically affect the lungs or cause peptic ulcers.

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

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

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

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

14. Which of the statements is incorrect?

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

15. Which group of organisms are not constituents of a food chain?

Answer: (b) (iii) and (iv)

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

Answer: (b) 1%

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

Answer: (c) T1

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

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

Explanation: Non-biodegradable materials are those that do not break down naturally in the environment.

Group (ii): Polythene, detergent, PVC – all are synthetic, non-biodegradable materials.

Group (iv): Plastic, bakelite, DDT – all are non-biodegradable.

Group (i) contains biodegradable materials like wood and paper, and Group (iii) includes grass, which is biodegradable.

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

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

Explanation: Energy decreases as we move up trophic levels due to energy loss at each level (mostly as heat). This loss limits the number of trophic levels, as there isn’t enough energy to sustain many higher levels.

14. Which of the statements is incorrect?

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

Explanation: Green plants synthesize their food through photosynthesis, using sunlight, carbon dioxide, and water, not organic compounds. They are autotrophs, meaning they produce their own food. Organic compounds are usually consumed by heterotrophs.

15. Which group of organisms are not constituents of a food chain?

Answer: (b) (iii) and (iv)

Explanation:

Group (iii): Wolf, grass, snake, tiger – a wolf and tiger are both top carnivores, and thus unlikely to be in the same food chain.

Group (iv): Frog, snake, eagle, grass, grasshopper – eagles and snakes are both high-level predators and would not coexist in a direct chain with the other organisms.

The other groups (i) and (ii) show proper sequences that can exist in a food chain.

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

Answer: (b) 1%

Explanation: Only about 1% of the total solar energy that reaches the Earth is absorbed by plants and used for photosynthesis. The rest is either reflected, absorbed by the atmosphere, or converted into other forms of energy like heat.

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

Answer: (c) T1

Explanation: In an ecological pyramid, the first trophic level (T1) consists of producers (plants), which capture and store the most energy from the sun. As energy moves up through the trophic levels, it decreases due to the energy lost at each level, making T1 the level with the maximum energy.

12. Answer: (b) (iv)

Plastic, bakelite, DDT are all non-biodegradable materials.

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

This limits the number of trophic levels in a food chain.

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

This statement is incorrect because green plants prepare their food from inorganic compounds like CO2 and water.

15. Answer: (b) (iii and iv)

Both options (iii) and (iv) contain organisms that are not part of the same food chain.

16. Answer: (a) 1%

About 1% of solar radiation absorbed by plants is used in photosynthesis.

17. Answer: (c) T1

T1, which represents the first trophic level (producers), has the maximum energy available.

18. What will happen if the deer is missing in the food chain (Grass → Deer → Tiger)? Answer:

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

19. The decomposers in an ecosystem: Answer:

(b) Convert organic material to inorganic forms.

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

(c) Primary consumer to secondary consumer.

21. Disposable plastic plates should not be used because: Answer:

(d) They are made of non-biodegradable materials.

Short Answer Questions:

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

Answer: Improper disposal of waste leads to pollution of air, water, and soil, harms wildlife, disrupts ecosystems, and can contribute to health issues for humans.

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

Answer: A typical food chain in a pond ecosystem is: Algae → Small fish → Large fish → Birds.

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

Answer: Cloth bags are reusable, biodegradable, and do not contribute to pollution like plastic bags, which are non-biodegradable and harmful to the environment.

25. Why are crop fields known as artificial ecosystems?

Answer: Crop fields are called artificial ecosystems because they are created and maintained by humans, unlike natural ecosystems, which function on their own.

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

Answer:

Biodegradable substances are those that can be broken down by microorganisms (e.g., food waste, paper).

Non-biodegradable substances do not decompose easily and remain in the environment for long periods (e.g., plastic, glass).

27. Suggest one word for each of the following statements/definitions: (a) The physical and biological world where we live in – Biosphere

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

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

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

28. Explain the role of decomposers in the environment: Decomposers, such as bacteria and fungi, break down dead plants and animals into simpler substances. This process recycles nutrients back into the soil, making them available for producers (like plants). Decomposers play a critical role in maintaining the balance of ecosystems by aiding in the process of nutrient cycling.

29. Select the mis-matched pair in the following and correct it: (a) Biomagnification — Correct

(b) Ecosystem — Correct

(c) Aquarium — A man-made ecosystem (Correct)

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

30. We do not clean ponds or lakes, but an aquarium needs to be cleaned. Why? Ponds and lakes are natural ecosystems that have self-cleaning mechanisms through the presence of decomposers and other organisms that balance the ecosystem. Aquariums are artificial and do not have this natural balance, so they require manual cleaning to remove waste and maintain a healthy environment for the organisms living in them.

Long Answer Questions:

31. Indicate the flow of energy in an ecosystem. Why is it unidirectional? Justify. The flow of energy in an ecosystem is unidirectional because it moves from producers (plants) to primary consumers (herbivores), then to secondary consumers (carnivores), and so on. Energy is lost at each trophic level, mainly in the form of heat, and cannot be recycled. This loss of energy and the one-way transfer from one level to the next makes the flow unidirectional.

32. What are decomposers? What will be the consequence of their absence in an ecosystem? Decomposers are organisms like bacteria and fungi that break down dead organic matter and release nutrients back into the environment. If decomposers were absent, dead plants and animals would accumulate, and nutrients would not be recycled. This would disrupt the food chain and lead to nutrient depletion in the soil, eventually causing the ecosystem to collapse.

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

1. Using reusable bags instead of plastic ones.

2. Reducing water waste by fixing leaks and using water-efficient appliances.

3. Composting organic kitchen waste.

4. Using energy-efficient light bulbs and appliances.

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

1. Food Chain: Linear sequence of organisms where each is eaten by the next one in the chain.

Food Web: Complex network of interconnected food chains showing multiple feeding relationships.

2. Food Chain: Represents a single path of energy flow.

Food Web: Represents multiple pathways of energy flow.

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

Kitchen waste (vegetable peels, food leftovers)

Plastic waste (packaging, bottles)

Paper waste (newspapers, cardboard)

Electronic waste (batteries, gadgets)

Disposal measures:

Compost organic kitchen waste.

Recycle plastic, paper, and electronic waste.

Reduce use of single-use plastics by opting for reusable products.

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

Implementing waste recycling techniques to reduce hazardous waste.

Adopting pollution control technologies to minimize the release of harmful by-products.

Using sustainable raw materials and reducing the use of harmful chemicals.

37. What are the by-products of fertilizer industries? How do they affect the environment? The by-products of fertilizer industries include nitrogen oxides, phosphates, and ammonia. These chemicals can cause water pollution through runoff, leading to algal blooms and dead zones in aquatic ecosystems. They also contribute to air pollution and acid rain, which can harm plants and soil.

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

Overuse of chemical fertilizers can lead to soil degradation and water pollution.

Excessive irrigation can cause waterlogging and salinization of soil.

Pesticides can harm non-target species, including beneficial insects, and contaminate water bodies.

Monoculture farming reduces biodiversity and increases vulnerability to pests and diseases.

Here are some questions and answers based on the content of the file:

Multiple Choice Questions (MCQs):

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

(a) Pond

(b) Crop field

(c) Lake

(d) Forest

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

(a) Carnivores

(b) Herbivores

(c) Decomposers

(d) Producers

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

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 kJ

(b) 50 kJ

(c) 500 kJ

(d) 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

6. Depletion of ozone is mainly due to

(a) Chlorofluorocarbon compounds

(b) Carbon monoxide

(c) Methane

(d) Pesticides

Short Answer Questions:

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

Improper disposal of waste leads to environmental pollution, harming the air, water, and soil. It disrupts ecosystems and can cause the accumulation of harmful substances, affecting both flora and fauna.

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

Example: Phytoplankton → Zooplankton → Small fish → Large fish → Bird

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

Cloth bags are biodegradable, reusable, and environmentally friendly. Unlike plastic bags, they don't contribute to pollution or pose threats to wildlife.

4. Why are crop fields known as artificial ecosystems?

Crop fields are artificial ecosystems because they are man-made and controlled environments where humans plant crops, manage water 

supply, and use fertilizers to sustain growth.

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

Biodegradable substances: These can be broken down by microorganisms, e.g., food waste, paper.

Non-biodegradable substances: These cannot be easily decomposed, e.g., plastics, metals.