Questions in text
Q1. What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
Answer:
Trophic levels are the steps or levels in a food chain, each representing a position in the feeding hierarchy. An example of a food chain: Grass ? Grasshopper ? Frog ? Snake. The different trophic levels are: First trophic level: Producers (grass) – autotrophs that make food. Second trophic level: Primary consumers (grasshopper) – herbivores that eat producers. Third trophic level: Secondary consumers (frog) – carnivores that eat herbivores. Fourth trophic level: Tertiary consumers (snake) – larger carnivores that eat secondary consumers.
Q2. What is the role of decomposers in the ecosystem?
Answer:
Decomposers (bacteria and fungi) break down the dead remains and waste products of organisms. They convert complex organic substances into simple inorganic substances that go into the soil and are used again by plants. This natural replenishment of soil and recycling of nutrients is essential for the ecosystem to function.
Q3. Why are some substances biodegradable and some non-biodegradable?
Answer:
Substances are biodegradable if they can be broken down by biological processes, such as the action of bacteria or other saprophytes, because specific enzymes exist to decompose them. Non-biodegradable substances are not broken down by biological processes because enzymes are specific in action; many human-made materials like plastics lack the necessary enzyme systems to decompose them under ambient environmental conditions.
Q4. Give any two ways in which biodegradable substances would affect the environment.
Answer:
Two ways: (1) They can produce foul smell and attract pests if not disposed properly, leading to unhygienic conditions. (2) Their decomposition releases nutrients back into the soil, which helps in maintaining soil fertility, but if in excess, can cause pollution of water bodies through nutrient runoff.
Q5. Give any two ways in which non-biodegradable substances would affect the environment.
Answer:
Two ways: (1) They persist in the environment for a long time, leading to accumulation and causing littering and clogging of drains. (2) They can enter food chains and undergo biological magnification, causing harmful effects on organisms, especially at higher trophic levels (e.g., pesticides causing health issues).