Question 1

A small group of mice were released on an island. The island previously had no mice on it, but had abundant food and no predators. After several years of growth, the size of the new island population stabilizes. However, at this point a hurricane drastically reduces the population. How would you describe the situation?

Accepted Answer

The hurricane is an example of a density-independent factor, as it affects the population regardless of its size.

Question 2

Which of the following describe density-dependent factors?

Accepted Answer

Density-dependent factors regulate population growth by affecting birth and death rates, are crucial in K-selected populations, and involve biological interactions like intraspecific competition.

Question 3

What are characteristics of r-selected populations? (Check all that apply.)

Accepted Answer

R-selected populations are characterized by early reproduction, large brood sizes, minimal parental care, short generation times, and type III survivorship curves, which indicate high mortality rates for young individuals.

Question 4

There are three aspects of entire populations that are important and often studied. Select the best choice from the ones listed.

Accepted Answer

A population's range, the dispersal of individuals within the range, and the size that the population attains are key aspects studied in population ecology.

Question 5

During the late 1800s, cattle egrets arrived in South America from Africa and began to colonize. Their range has expanded dramatically over the years. Why were they able to do this?

Accepted Answer

The cattle egrets were able to expand their range in South America because they found suitable and unoccupied habitats that allowed them to thrive and reproduce.

Question 6

Which of the following are environmental factors that determine where an organism can live? (Check all that apply.)

Accepted Answer

These are all abiotic factors that can affect an organism's ability to survive in a particular environment.

Question 7

The figure included shows the body temperature of lizards versus air temperature in two different habitats-open and shaded forest. Which one of the following conclusions is best supported by these data.

Accepted Answer

The answer of The figure included shows the body temperature...

Question 8

Many organisms have adaptations to avoid freezing temperatures, including behaviors like migration, features like thick fur, and molecular features like antifreeze molecules. However, some organisms have a adaptation called ice nucleation, in which special proteins help ice crystals to form at warmer temperatures. What organism would be most likely to benefit from such an adaptation?

Accepted Answer

Ice nucleation would benefit a bacterial pathogen that feeds off damaged plants because it can cause ice formation at higher temperatures, leading to plant tissue damage and providing the bacteria with more access to nutrients.

Question 9

You are earning your Ph.D. in marine biology, studying the microbial ocean community. This year, you are shocked to discover that one of your study sites has become contaminated due to an industrial waste water pipe. This dumping is drastically raising the temperature and lowering the salinity of the water. What do you expect to find in your survey of the population, and what might you find in a survey years from now?

Accepted Answer

Initially, many species may decrease or disappear due to the sudden environmental changes. Over time, some species may adapt through mutations, and new species may colonize the site, leading to changes in the community composition.

Question 10

A farmer's land includes a wilderness area that is home to an endangered species of bird. He wants to sell the land to a developer, and you have been hired to evaluate the environmental concerns. "This little patch of land is not crucial for the bird species!" the farmer says, "In fact, my land is surrounded by several other wilderness patches that also have that bird." You reply: "It is possible that your land acts as the ____________ and the other areas are ___________ . If that's the case, development would be devastating to the population."

Accepted Answer

The farmer's land could be a "source" where the bird population thrives and reproduces, while the surrounding areas could be "sinks" where the population does not sustain itself without immigration from the source. Development on the source land could thus be devastating.

Question 11

An underwater volcano has erupted, and as the lava cools a new island has formed. Which types of animal species are likely to be among the first to colonize the island?

Accepted Answer

The answer of An underwater volcano has erupted, and as...

Question 12

Two populations have very similar birth rates and death rates, but the change in the growth of the populations is quite different. What other factors might account for the difference? (Check all that apply.)

Accepted Answer

Age structure affects the number of individuals capable of reproducing. Generation time influences how quickly a population can grow. Immigration can increase population size. Sex ratio affects the number of potential breeding pairs.

Question 13

A graduate student is studying the feeding behavior of a small octopus that must be laboriously collected from the shores of a remote island. Her intern wishes to do experiments to look at the octopus's mating behavior. Why might the graduate student veto this idea?

Accepted Answer

Semelparous organisms reproduce only once before dying. If the octopus is semelparous, it will die after laying eggs, making it impractical to study its mating behavior repeatedly.

Question 14

A rancher is suspected of shooting wolves near Yellowstone National Park, and you have been enlisted to go have a chat with him. The rancher doesn't see any benefit to having the wolves there. What do you say?

Accepted Answer

Wolves help control prey populations like jackrabbits, which can grow exponentially without predators. This control helps maintain ecological balance by preventing overpopulation and resource depletion.

Question 15

A population of squirrels is in a phase of exponential growth. What events would act to slow this growth? (Check all that apply.)

Accepted Answer

A forest fire, logging of nut trees, growth of the hawk population, and an increased population outstripping the food supply would all act to slow the exponential growth of the squirrel population by reducing resources or increasing predation.

Question 16

This summer, you are returning to the research station in Costa Rica to follow up on the population of butterflies you have been studying. You are disappointed to find that there are fewer this year than last. In fact, at dinner your friends studying frogs and birds are complaining about the same thing. What type of influence do you suspect?

Accepted Answer

Environmental disruptions such as weather events or habitat destruction are density-independent factors that can affect populations regardless of their size.

Quiz 33: Ecology of Populations