Question

exercise 4 (modules 36.5 - 36.6)
population growth is limited by both density - dependent (biotic) and density - independent (abiotic) environmental factors. density - dependent and density - independent factors affect birth rates and death rates in different ways. state whether each of the following words or phrases relates more to density - dependent factors (dd) or to density - independent (di) factors.

1. have more effect when the population is larger
2. have more effect when the population is smaller
3. have less effect when the population is smaller
4. effect not dependent upon density of population
5. competition for food
6. fire
7. predation
8. stress produced by crowding
9. competition for nest sites
10. storms
11. drought
12. disease
13. heat and cold
14. habitat disruption by humans
15. cause populations to stabilize in size, presumably near carrying capacity
16. cause rapid population growth followed by unpredictable crashes
17. seem to cause boom and bust cycles among predators and prey
18. limit the snowshoe hare population
19. limit the lynx population
20. effects of the nonliving environment
21. effects of organisms
22. reduce clutch size as song sparrow population grows
23. responsible for lemming boom and bust population cycles
24. cause periodic drastic declines in song sparrow population

Explanation:

Density - dependent factors (DD) are biotic and their impact varies with population density, often more significant at higher densities. Density - independent factors (DI) are abiotic and affect populations regardless of density. For example, competition for resources like food and nest sites is more intense as population grows (DD), while natural disasters like fire, storms, and drought affect populations regardless of size (DI).

1. DD: As population is smaller, resources are more available, so factors like predation or competition have less impact. As population grows, these factors become more impactful.
2. DD: Opposite of typical DD behavior. Usually DD factors have more effect as population density increases.
3. DI: By definition, density - independent factors do not depend on population density.
4. DD: More competition for food as population density increases.
5. DI: Fire affects populations regardless of their density.
6. DD: Predation rate often increases with prey population density.
7. DD: Crowding stress is higher at higher population densities.
8. DD: More competition for nest sites as population density increases.
9. DI: Storms affect populations regardless of density.
10. DI: Drought affects populations regardless of density.
11. DD: Disease spreads more easily in dense populations.
12. DI: Heat and cold affect populations regardless of density.
13. DI: Human - caused habitat disruption affects populations regardless of density.
14. DD: Factors like competition and predation stabilize populations near carrying capacity.
15. DD: Predator - prey interactions are density - dependent and can cause boom - bust cycles.
16. DD: Predator - prey relationships are density - dependent.
17. DD: Factors like predation and food availability (biotic) limit snowshoe hare population.
18. DD: Factors like availability of prey (biotic) limit lynx population.
19. DI: Effects of non - living environment are density - independent.
20. DD: Effects of organisms (biotic) are density - dependent.
21. DD: As song sparrow population grows, clutch size reduces due to density - dependent factors like resource limitation.
22. DD: Lemming population cycles are due to density - dependent factors like food availability and predation.
23. DD: Density - dependent factors like disease and competition cause periodic declines in song sparrow population.

Answer:

1. DD
2. DD
3. DI
4. DD
5. DI
6. DD
7. DD
8. DD
9. DI
10. DI
11. DD
12. DI
13. DI
14. DD
15. DD
16. DD
17. DD
18. DD
19. DI
20. DD
21. DD
22. DD
23. DD