Deck 50: Population Ecology

Question 1

CAUTION What is the defining feature of exponential growth?

A) The population is growing.
B) The per capita growth rate is constant.
C) The per capita growth rate increases rapidly over time.
D) The per capita growth rate is very high.

Answer 1

Growth of population is defined as an increase in the number of individuals. In a population, the overall growth rate is a function of birth rates, death rates, immigration rates, and emigration rates. Exponential growth is characterized by the increase of population at a consistent rate. Exponential growth occurs very rapidly, and is insidious.
The difference between the birth rate and death rate per individual is called per capita rate of increase. It is denoted by the symbol r. The per capita growth rate does not increase over time, and the growth rate does not alter.
Hence, the options (a), (c), and (d) are not correct.
The change in population size over time is given by the expression , where r is the per capita rate of increase and N is the initial population size. During exponential growth, the per capita growth rate remains constant irrespective of the population size. A high value of r indicates rapid increase of population size over time, whereas a low value of r indicates the slow increase of the population size.
Hence, the correct answer is option (b).

Question 2

In what populations does exponential growth tend to occur?

A) populations that colonize new habitats
B) populations that experience intense competition
C) populations that experience high rates of predation
D) populations that have surpassed their carrying capacity

Answer 2

In populations that colonize new habitats exponential growth tends to occur. Exponential population growth occurs when r does not change over time. Here r is the growth rate which is constant in exponential growth. In populations which experience intense growth or high rates of predation, the growth rate is not constant but oscillates. Exponential growth also does not occur in metapopulations.
Hence the correct option is (a) in populations that colonize new habitats.

Question 3

If most individuals in a population are young, why is the population likely to grow rapidly in the future?

A) Death rates will be low.
B) The population has a skewed age distribution.
C) Immigration and emigration can be ignored.
D) Many individuals will begin to reproduce soon.

Answer 3

If most individuals in a population are young, the population is likely to grow rapidly in the future because many individuals will begin to reproduce soon. As these populations are dominated by the young people, they will soon begin to produce children and increase the population. If the higher percentage of people in a population is old, this rapid increase will not be seen as old people will not produce children. Immigration and emigration cannot be the cause for the increase in population neither is the death rate responsible.
Hence the correct option is (d) many individuals will begin to reproduce soon.

Question 4

Why is there a trade-off between survivorship and fecundity?