Chapter 15: Our Environment

Answer: Trophic levels are steps in a food chain where organisms obtain energy. Example: Grass (producer) → Grasshopper (primary consumer) → Frog (secondary consumer) → Snake (tertiary consumer) → Eagle (quaternary consumer).

Answer: Decomposers break down dead organic matter (plants and animals) into simpler substances, releasing nutrients back into the soil for reuse by producers. They also help in waste decomposition.

Answer: Energy flows from the sun to producers and then to consumers. At each trophic level, energy is lost as heat (due to respiration) and is not recycled back. Thus it flows in one direction.

Answer: The ecosystem balance will be disturbed. For example, if all herbivores are killed, producers will overgrow, and carnivores will starve. The entire food web may collapse.

Answer: (c) Fruit-peels, cake and lime-juice. Also (a) and (d) but (c) is fully biodegradable.

Answer: (b) Grass, goat and human.

Answer: (d) All of the above.

Answer: (Already answered in Intext Q4). It disrupts the ecosystem; populations of other trophic levels may increase or decrease drastically.

Answer: Yes. Removing producers stops all energy input; consumers die. Removing primary consumers leads to overgrowth of producers and starvation of secondary consumers. Removing top carnivores causes overpopulation of prey, disturbing the balance.

Answer: Biological magnification is the increase in concentration of harmful non-biodegradable substances (like DDT) at each successive trophic level. Yes, top consumers have the highest concentration.

Answer: (i) They persist in the environment for long periods, (ii) cause soil and water pollution, (iii) harm animals (e.g., plastic ingestion), (iv) accumulate in food chains (biomagnification), (v) take up landfill space, (vi) clog drains and cause flooding.

Answer: Even biodegradable waste, if in excess, can cause pollution. Decomposition generates foul smell, breeds pathogens, and releases methane (greenhouse gas). Overloading ecosystems beyond their capacity harms the environment.

Answer: Ozone layer protects us from harmful UV radiation. Its damage increases skin cancer, cataracts, and affects crops. Steps: Montreal Protocol banned CFCs, use of alternatives in refrigerators, aerosols, and foam.

Answer: Producers (autotrophs) produce food using sunlight (green plants). Consumers (heterotrophs) feed on others: herbivores (goat), carnivores (lion), omnivores (human), decomposers (bacteria).

Answer: Only about 10% of energy available at one trophic level is transferred to the next. Rest is lost as heat, used for metabolism, or not consumed.

Answer: An ecosystem is a community of living organisms interacting with their physical environment. Components: biotic (plants, animals, decomposers) and abiotic (soil, water, air, sunlight).