Chapter 13: Our Environment

Q1: (d) Cake, wood and grass (all biodegradable). Q2: (b) Grass, goat and human (producer → herbivore → consumer). Q3: (d) All of the above.

The food chain is disrupted. Organisms in the next higher level lose their food and may starve/die, while the level below may overpopulate (no one to eat them). This creates an imbalance in the ecosystem.

Yes, the impact differs. Removing producers (plants) would collapse the entire ecosystem, since all life depends on them. Removing top carnivores causes herbivores to overpopulate and destroy vegetation. No trophic level can be removed without damaging the ecosystem — all levels are interdependent.

Biological magnification is the increase in concentration of harmful chemicals (like pesticides) at each successive trophic level of a food chain. The levels are different — magnification is highest at the top trophic level (e.g., humans), because these chemicals are not degraded and keep accumulating up the chain.

Q7: Non-biodegradable wastes (plastics, chemicals) do not decompose, so they accumulate — polluting soil, water and air, harming animals, clogging drains, and entering food chains (causing biomagnification). Q8: No — large amounts of biodegradable waste still cause problems: they take time to decompose, produce a foul smell and gases, and become breeding grounds for flies and germs, spreading disease.

The ozone layer protects us from the Sun's harmful UV radiation, which can cause skin cancer, cataracts and harm crops. Damage to it lets more UV reach the Earth. Steps: the Montreal Protocol (1987) was signed to ban/limit the use of CFCs and other ozone-depleting substances worldwide.

Transfer of energy between trophic levels.

Tertiary (top carnivores).

Plastic.

Reduce, Reuse, Recycle.

Each step or level in a food chain where energy transfer takes place is a trophic level.

They break down dead plants and animals, returning nutrients to the soil and keeping the ecosystem balanced.

Because at each level about 90% of energy is lost as heat, so energy decreases and flows in one direction only.

Use cloth/jute bags instead of plastic; recycle and reuse materials.

A network formed by many interconnected food chains in an ecosystem.

Energy from the sun is captured by producers (plants) during photosynthesis. It then passes to herbivores, then to carnivores. At each trophic level only about 10% of energy is transferred; the rest is lost as heat. Thus energy flows in one direction and decreases at each level, limiting food chains to 3-4 levels.

It is the increase in concentration of harmful, non-degradable chemicals (like pesticides/DDT) at each higher trophic level. For example, DDT sprayed on crops enters water, then small fish, then big fish, then humans — its concentration rising at every level, being highest in humans.

The ozone layer absorbs the Sun's harmful UV rays, protecting living beings from skin cancer and other harm. It is being damaged mainly by CFCs released from refrigerators, ACs and aerosol sprays. The Montreal Protocol limits their use to protect it.

Biodegradable substances are broken down by microbes (food waste, paper, wood). Non-biodegradable substances are not decomposed by microbes and persist for long (plastic, glass, metal, DDT), causing pollution.

It causes bad smell, breeding of flies and germs, spread of diseases, pollution of soil and water, and (with non-biodegradable waste) long-term environmental damage.

Biotic: producers (plants), consumers (herbivores like deer, carnivores like lion), decomposers (bacteria, fungi). Abiotic: air, water, soil, sunlight, temperature.