Ecosystem and Environment — Food Chains, the 10% Law, the Nutrient Cycles and the Ozone Hole Case

Environment and ecology give up the cheapest marks in the general science section. Every paper carries two or three of them, the facts do not change from year to year, and nothing here needs a formula. Students still lose these marks, and for a specific reason: the chapter is taught as vocabulary and tested as relationships.

Knowing that a frog is a carnivore earns nothing. The question asks which trophic level the frog occupies, how much of the grass's energy has reached it by then, and what happens to the whole chain if the frogs are removed. Those are three different questions built on one diagram.

So learn this chapter as a set of connected chains rather than a glossary. Four things do almost all the work: who eats whom, how much energy survives each step, how the same atoms cycle back through soil and air, and what happens when a substance enters the chain that nothing can break down. The last of those gives the two cases papers return to again and again.

1. According to the 10% law, approximately how much of the energy at one trophic level passes to the next?

2. Which group occupies the first trophic level of a food chain?

3. The ozone layer that absorbs ultraviolet radiation lies mainly in which layer of the atmosphere?

4. Which international agreement, adopted in 1987, was aimed at phasing out ozone-depleting substances?

5. Which bacterium lives in the root nodules of leguminous plants and fixes atmospheric nitrogen?

6. Which ecological pyramid is always upright, in every ecosystem?

7. Because of biomagnification, the concentration of DDT in a food chain is highest in:

8. In the food chain grass → grasshopper → frog → snake → hawk, the frog occupies which trophic level?