GRE Subject Test: Biology : Understanding Population Ecology

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #3 : Population Ecology

K-strategist species exhibit all of the following characteristics except __________.

Possible Answers:

Little time spent by parents raising offspring

Produces relatively few offspring

Relatively long life expectancies

Late age of maturity

Correct answer:

Little time spent by parents raising offspring

Explanation:

Species designated as K-strategists thrive through longevity and have a higher survival rate at birth, but produce far fewer offspring. Examples include elephants and whales. Consider an elephant; it may produce relatively few baby elephants, but these baby elephants each have the potential to live relatively long lives. On the other hand, contrast K-strategists like elephants with r-strategists like rats, locusts, and flies. These species are designated as r-strategists because in contrast, they produce numerous offspring, few of which may survive to adulthood, and each one of which reaches maturity quickly and lives a relatively short life. K-strategists in general spend more time than r-strategists caring for and raising their offspring; they have fewer offspring, so they put more care into ensuring the survival of each one. Contrast elephants with frogs to see this difference; elephants care for their young, while frogs lay their eggs and care for their offspring very little, if at all.

Example Question #5 : Organismal Ecology

A species designated as "r-strategist" is characterized by all of the following except __________.

Possible Answers:

Low age of maturity

Small size

High reproductive rate

Little time spent by parents caring for and raising offspring

Long life expectancy

Correct answer:

Long life expectancy

Explanation:

Species described as "r-strategist" have a survival strategy of producing large numbers of offspring, a short life expectancy, and typically smaller body sizes. Examples include mice, locusts, and frogs. These species survive by producing lots of offspring, since many individuals don't survive to adulthood.

Example Question #2 : Understanding Population Ecology

K-strategist populations are more commonly regulated by ____________ limiting factors, and r-strategist populations are regulated by ___________ limiting factors.

Possible Answers:

density-independent, density-dependent

none of these

density-dependent, density-independent

density-dependent, density-dependent

density-independent, density-independent

Correct answer:

density-dependent, density-independent

Explanation:

K-strategist populations are more commonly regulated by density-dependent limiting factors. Their population sizes hover around a carrying capacity that is dependent on factors that increase in severity with the density of the population. On the other hand, r-strategist populations are regulated by density-independent limiting factors. They reproduce rapidly until a density-independent factor causes many of them to die.

Example Question #2 : Carrying Capacity

What does a J curve represent on a population growth chart?

Possible Answers:

The maximum point of growth of a species

A species cycles up to carrying capacity, and then back down to the minimum

The correlation between a species and its competitors in a specific niche

A species has reached the carrying capacity but continues to grow, creating a population explosion and a competition for resources

A species has reached carrying capacity and leveled off due to limited resources

Correct answer:

A species has reached the carrying capacity but continues to grow, creating a population explosion and a competition for resources

Explanation:

Population growth can follow either a J curve trend or an S curve trend. A J curve represents exponential, or unrestricted growth. An S curve represents logistic, or restricted, growth and accounts for the carrying capacity of an environment.

In a J curve model, the population will continue to grow even when it has reached capacity. In an S curve model, the population will stagnate and stabilize at a maximum value when capacity is reached.

Example Question #1 : Understanding Population Ecology

Which of the following most accurately describes a deme?

Possible Answers:

A set of individuals geographically isolated from other groups

A group of individuals more genetically similar to each other than to other individuals, even if spatially isolated

A set of spatially disjunct populations in which some immigration still occurs

A collection of populations of organisms isolated genetically but still living in the same area and sharing many characteristics

A group of conspecific individuals separated demographically, genetically, or spatially from other groups

Correct answer:

A group of individuals more genetically similar to each other than to other individuals, even if spatially isolated

Explanation:

A deme is defined as a group of individuals more genetically similar to each other than to other individuals, even if spatially isolated. A group of conspecific individuals separated demographically, genetically, or spatially from other groups is a populationA set of spatially disjunct populations in which some immigration still occurs is a metapopulationThe other options are not well-defined in population ecology.

Example Question #2 : Understanding Population Ecology

There are several different kinds of survivorship curves for different kinds of animals. What kind of survivorship curve do organisms with little to no parental care generally exhibit?

Possible Answers:

Very old individuals

Type III: high initial mortality

An intermediate between types I and II

Type II: constant mortality rate

Type I: high advanced age mortality

Correct answer:

Type III: high initial mortality

Explanation:

Organisms with little to no parental care typically have large amounts of offspring to compensate for high mortality rates of the young, as shown in a type III survivorship curve. These include organisms like trees, which spread large numbers of seeds because the seeds rarely find a good growing spot and mature to adulthood.

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