SAT - Biology Subject Population and Community Ecology Questions and Answers

Question 1

A population of deer is introduced to a large, isolated island with abundant resources and no predators. Initially, the population grows rapidly. According to the logistic growth model, what will happen to the population's growth rate as it approaches the island's carrying capacity (K)?

Accepted Answer

The growth rate will slow down and approach zero.

Answer

In the logistic growth model, population growth is density-dependent. As the population size (N) nears the carrying capacity (K), limiting factors such as resource scarcity and increased competition cause the per capita growth rate to decrease. When N equals K, the birth rate equals the death rate, and the population growth rate becomes zero. [9, 11, 17]

Question 2

The harmless scarlet kingsnake has coloration and banding patterns that closely resemble those of the venomous eastern coral snake. Predators that have learned to avoid the coral snake will also avoid the kingsnake. This is an example of which ecological phenomenon?

Accepted Answer

Batesian mimicry

Answer

Batesian mimicry is a form of defense in which a harmless species evolves to imitate the warning signals of a harmful or unpalatable species. [7, 12, 16] The kingsnake (mimic) benefits from the predator's learned avoidance of the coral snake (model). Müllerian mimicry involves two or more harmful species resembling each other.

Question 3

Which of the following sets of characteristics is most representative of a K-selected species?

Accepted Answer

Long lifespan, extensive parental care, few offspring

Answer

K-selected species are adapted to stable environments and live at densities near the carrying capacity (K). Their life history strategy involves traits like having a long lifespan, maturing late, producing few, large offspring, and providing extensive parental care to ensure high offspring survival. [1, 2, 5, 6]

Question 4

An oyster releases millions of eggs, but the vast majority of the resulting larvae die from predation or starvation within their first few weeks of life. The few larvae that survive to adulthood have a much lower mortality rate. Which type of survivorship curve does the oyster exhibit?

Accepted Answer

Type III

Answer

A Type III survivorship curve is characterized by a very high mortality rate for the young, followed by a flatting curve indicating a much lower mortality rate for those individuals who survive to a certain age. This is typical for species that produce a large number of offspring and provide little to no parental care. [8, 23, 29, 30]

Question 5

In the coastal kelp forest ecosystems of the North Pacific, sea otters prey on sea urchins. Sea urchins, if left unchecked, will graze voraciously on kelp, destroying the forests that provide habitat for numerous other species. The sea otter's role in maintaining the structure of this community is best described as that of a(n):

Accepted Answer

Keystone species

Answer

A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. By controlling the sea urchin population, sea otters prevent the destruction of kelp forests and thereby maintain the entire community's structure and biodiversity. [4, 13, 18, 22] While they are also apex predators, the term "keystone species" specifically describes this critical ecological role.

SAT - Biology Subject Test Practice Test

SAT - Biology Subject Test Practice Test

SAT - Biology Subject Population and Community Ecology Questions and Answers