14.5.4 Population Ecology: Intraspecific Competition

Question 1

Population Ecology: Intraspecific Competition

Answer 1

• Review: K-selection and r-selection are two different population strategies found in high-density and low-density situations, respectively.
• Density-dependent factors include resources such as food or nesting sites. The magnitude of the effects of these factors depends on the population size.
• Intraspecific competition can lead to density-dependent growth in populations.
• Density-independent factors (such as weather) influence a population regardless of its size.
• A mix of density-dependent and -independent factors affects most populations.
• Interspecific interactions are interactions between two or more species.

Question 2

note

Answer 2

• Review: The logistic model of population growth shows a population whose growth rate is dependent on population size. Limited resources affect the population’s growth rate. The population growth rate increases until reaching the inflection point. It then decreases until the population reaches carrying capacity.
• The r-selected populations have life-history strategies for thriving well below carrying capacity. K-selected populations have life history strategies for remaining near carrying capacity.

Question 3

intraspecific competition

Answer 3

• The graph on the left plots density versus survivorship in a population of rhinoceros beetles (Strategus sp.). As density increases, population survivorship goes down. The phenomenon occurs because of intraspecific competition between members of the population. As the population increases, many individuals receive an insufficient amount of a particular resource and do not survive to reproduce.
• The graph illustrates an example of density-dependent factors influencing population changes.

Question 4

density independent variables

Answer 4

• The graph on the left illustrates seasonal fluctuations in a population of Australian Thrips sp. Populations increase in the spring (December in Australia), but drought decimates them in the summer. The drought affects individuals regardless of population size.

Question 5

example

Answer 5

• A classic example of interspecific interaction involves the snowshoe hare and the lynx. Populations have been tracked in the Hudson Bay area since 1850.
• Fluctuations in the hare population are followed by
  fluctuations in the lynx population. Some scientists interpret the oscillations in the hare population as evidence of a density-independent factor. Hare availability is most likely a limited resource, and therefore it is a density-dependent influence for the lynxes.
• Although these explanations seem likely, the cause of the fluctuations is still a matter of debate.

Question 6

Which of the following statements concerning K-selection and r-selection is not true?

Answer 6

• K-selected populations are so named because they typically exist well below carrying capacity.

Question 7

Which of the following factors might decrease the rate of change of the population as the logistic curve approaches the carrying capacity?

Answer 7

• intraspecific competition

- predation

Question 8

The population of Australian Thrips sp. increases dramatically in the springtime, but is decimated by drought in the summertime. This population decrease is an example of ___________ in the growth of the population.

Answer 8

• a density-independent variable

Question 9

Because of intraspecific competition, a population’s growth rate is __________.

Answer 9

• Density dependent.

Question 10

Why might women in wealthy countries reach reproductive age at a younger age than women in poorer countries?

Answer 10

• Nutrition may affect age of reproductive maturity.

Question 11

True or false?
One of the classic examples of interspecific interaction occurs between the snowshoe hare and the lynx in the Hudson Bay area. The fluctations in the snowshoe hare population are clearly due to the predation by the lynx population.

Answer 11

• false