1. Sustainable populations

2. In Kolkata, major air pollution is caused by

3. One of the greatest human impacts on natural ecosystems results from

4. Environmental pollution often decreases biodiversity by

5. Fog is a component of the

6. A keystone species

7. DDT quickly became widely used because it

8. Denitrification in sewage treatment systems requires

9. A squirrel population in the Punjab region is limited by its eagle predators, the amount of acorns produced annually, nesting sites in the trees and cold winter temperatures. Which of the following is an abiotic factor limiting this squirrel population?

10. A population would be expected to grow if

11. In a forest, deer, raccoons, squirrels and other animals eat and find shelter. A detritus food web occurs as their wastes accumulate on the forest floor. In this detritus web:

12. Heavy metals can quickly move through ecosystems because they

13. Omnivores differ from carnivores in that omnivores derive their energy from

14. Off the shore in Japan deep in the ocean where no sunlight can penetrate are found communities in which bacteria have special enzyme that allows them to form organic matter through chemosynthesis. These communities nestle around hydrothermal vents where super-heated water springs from the bottom of the ocean. These communities frequently have worms, clams, shrimp and many other organisms clustered together. Hydrothermal vent communities are unusual because

15. Most ecosystems

16. In a food chain, biomagnification is the result of

17. In general, most ecosystems in the world have

18. Because of biomagnification, the most toxic organisms in any ecosystem will be the

19. Some beetles escape from a ship and fly to a small island covered with grass but with no trees or beetle predators. A. the beetles feed, they destroy all the grasses. But with abundant food, the beetle population soars, doubling in size every month. After about a year, the population crashes as thousands of beetles have destroyed almost all of the plants and there is little left to feed the large population. This scenario best illustrates

20. A raccoon spends its week eating raspberries, grain, eggs and grasshoppers. Raccoons are therefore

21. The graphical representation of an organism's position as well as function at successive trophic levels is called

22. A stable population would remain stable if

23. Carcinogens are dangerous because they affect

24. The phenomenon of accumulation of non-biodegradable contaminants in higher trophic level is known as

25. Burning fossil fuels in a low oxygen environment will most likely produce