Ecology Review Questions for AP Biology

Answers and Explanations

1. A—The population shown in this age structure chart is one that is growing rapidly because of the gradual increase in percentage of the population as the age approaches 0. This shows a population that has a high birth rate and a reasonable life expectancy.
2. C—CO₂ is the dominant form of carbon present in the atmosphere.
3. D—Density-dependent limiting factors show up as the population approaches and/or passes the carrying capacity. Examples of density-dependent limiting factors include availability of food resources, waste buildup, and density-induced diseases. The other four choices are examples of densityindependent factors, which affect population size regardless of how large or small it may be.
4. C—Denitrification is defined as the process by which bacteria themselves use nitrates and release nitrogen gas as a product. Bacteria also perform the necessary task of nitrogen fixation, which takes atmospheric nitrogen and converts it to NH₃. They later take this NH₃ and convert it to nitrate, which plants require for photosynthetic success. (Abiotic fixation and nitrogen turnover are terms that I made up because they sounded cool.) Chemiosynthetic autotrophs are the producers of the planet that produce energy through the movement of electrons in oxidation reactions.
5. B—At this point, the population of rabbits has declined to the point where the foxes are starting to feel the reduction in their food supply. The fox survival curve soon begins its decline that leads to the revival of the rabbits.
6. C—An ecosystem consists of all the individuals in the community and the environment in which they exist. A population is a collection of individuals of the same species living in the same area. A community is a collection of all the different populations of the various species in a geographic area. A biosphere is the collection of all the life-containing areas of the planet. A niche is a representation of all the biotic and abiotic resources a given organism requires.
7. B—An animal that is harmless copies the appearance of an animal that is dangerous as a defense mechanism to make predators think twice about attacking.
8. D—Cryptic coloration is the animal kingdom's version of army clothes. Their coloration matches that of their environment so they can blend in and hide from their predators.
9. C—Two species that are aposematically colored as an indicator of their chemical defense mechanism mimic each other's color scheme in an effort to increase the speed with which their predators learn to avoid them. This, of course, requires a predator that can learn based on experience.
10. A—This defense mechanism is warning coloration adopted by animals that possess a chemical defense mechanism. Ideally, predators will learn to avoid the species, helping the prey survive longer.
11. D—K-selected populations tend to be populations of a roughly constant size, with low reproductive rates and whose offspring require extensive postnatal care until they have sufficiently matured. R-selected populations tend to produce many offspring per birth.
12. B—Lizards follow a type II survivorship curve as illustrated in the diagram in review question 12. Humans (answer A) and whales (answer E) follow a type I curve, while oysters and fish (answers C and D) follow a type III survivorship curve.
13. D.
14. A.
15. C.
16. B.