Question 1

A random population distribution:

Accepted Answer

Random population distributions are rare, as they tend to be clustered or evenly spaced due to resource availability and interactions between individuals within a population.

Question 2

Gum bush releases a chemical from its roots that prevents any seeds from germinating in the soil above the roots. This is an example of:

Accepted Answer

The answer of Gum bush releases a chemical from its...

Question 3

Herd animals typically live in a ________ distribution pattern.

Accepted Answer

Herd animals tend to clump together, as they have a social structure and rely on safety in numbers to protect themselves from predators.

Question 4

Purple loosestrife was introduced into the Great Lakes region from Europe and sold as a garden flower. It produces thousands of seeds and has no natural predators there. It now clogs acres of wetlands and is considered a(n):

Accepted Answer

Purple loosestrife is considered an invasive species because it was introduced into an ecosystem where it has no natural predators and can outcompete native plants, leading to the degradation of wetland habitats.

Question 5

In ________ competition, one organism uses social or chemical interactions to limit the access of other individuals to resources.

Accepted Answer

In contest competition, organisms use social or chemical interactions to limit access to resources, often through direct confrontations or territorial behaviors.

Question 6

If a caterpillar eats all the seedlings in your garden, killing all of them, the caterpillar is acting as a:

Accepted Answer

A caterpillar is a herbivorous predator that feeds on plants, in this case, the seedlings in the garden. It is not a parasite because it is not relying on the seedlings for its survival, nor is it a competitor because it is not competing with the seedlings for resources. It is also not a density-independent factor because its impact on the seedlings is directly related to the number of caterpillars present. Finally, it is not a saprophyte because it does not feed on dead or decaying organic matter.

Question 7

When mosquitoes are abundant, purple martins flock to the area and feed exclusively on them. When mosquito populations are not large, purple martins are similarly scarce and feed on other insects. This is an example of:

Accepted Answer

This is an example of density-dependent regulation, as the abundance of mosquitoes directly affects the population size and feeding habits of the purple martins.

Question 8

If the individuals of a species are very likely to live until old age, that species exhibits a(n)________ survivorship curve.

Accepted Answer

A convex survivorship curve, also known as a Type I curve, indicates that individuals of a species are more likely to survive to old age, with mortality rates increasing later in life. This pattern is typical of species that invest heavily in parental care and have low juvenile mortality rates, such as humans and elephants.

Question 9

In areas that have a stable population, the number of children born in a period of time is:

Accepted Answer

In areas with stable population, birth rates tend to match or be slightly lower than the adult population, resulting in a relatively stable population size over time.

Question 10

Why do many non-native species, such as a prickly pear cactus brought to Australia from South America, rapidly become abundant when first introduced?

Accepted Answer

Non-native species often lack the natural predators and parasites that would normally control their population in their native ecosystem, allowing them to rapidly become abundant in their new site. In this case, the prickly pear cactus may not have natural predators in Australia that would keep its population in check.

Question 11

Parasites affect their hosts' population sizes in a:

Accepted Answer

Density-dependent parasites typically affect their hosts in a way that depends on the host population size. This means that as the host population increases, so does the impact of the parasite. However, these parasites do not always directly kill their hosts. For example, they may reduce the host's reproductive success or weaken the host's immune system, making it more vulnerable to other diseases or predators.

Question 12

In a population of lemmings, a sudden freeze that caused many of the lemmings to die is an example of a:

Accepted Answer

The sudden freeze is a nonliving factor because it does not involve another organism. It is density-independent because it affects the population regardless of its size or density.

Question 13

If most of the individuals of a species die when they are young, that species exhibits a(n)________ survivorship curve.

Accepted Answer

A concave survivorship curve means the species has a high mortality rate among young individuals.

Question 14

In the eighteenth and nineteenth centuries, people increased Earth's capacity to support more humans through ________ advances.

Accepted Answer

Agricultural and medical advances increased Earth's capacity to support more humans in the eighteenth and nineteenth centuries.

Question 15

What might cause a uniform population distribution?

Accepted Answer

Allelopathy can lead to a uniform distribution as plants release chemicals to inhibit the growth of others nearby, reducing competition and spacing them evenly.

Question 16

Exponential growth occurs:

Accepted Answer

Exponential growth occurs only for a limited time in natural populations because resources eventually become limited, leading to a slowdown in growth.

Question 17

In his 1798 book, An Essay on the Principle of Population, Thomas Malthus stated: "the power of [Earth's human] population [to increase] is indefinitely greater than the power in the earth to produce subsistence for man." He explained that our population increases exponentially while we can increase our food supply only linearly. In modern terminology, what did Malthus mean by "the power in the earth to produce subsistence for man"?

Accepted Answer

"The power in the earth to produce subsistence for man" refers to the carrying capacity of Earth, which is the maximum number of individuals of a species that can be sustained by an ecosystem without causing depletion of resources or damage to the environment. Malthus was suggesting that our population growth would eventually surpass Earth's carrying capacity, leading to famine, disease, and other forms of population control.

Question 18

A population of rabbits introduced into an island grew rapidly for a few years and then the growth slowed down. Why did the population become stable?

Accepted Answer

The carrying capacity refers to the maximum number of individuals that an environment can sustain without degrading or becoming unsuitable for the species. As a population continues to grow, it consumes more resources and generates more waste, causing the environment to become less suitable for the species. Eventually, the population will reach a point where it cannot grow any further because there are not enough resources to support additional individuals. This is known as the carrying capacity, and it can cause a population to stabilize or even decline if the resources that the species depends on are limited. Therefore, the most likely reason why the population of rabbits became stable is that they reached or surpassed the carrying capacity of the island.

Question 19

Which of the following is an important density-independent factor limiting population size?

Accepted Answer

Weather events such as droughts, floods, and extreme temperatures can affect all individuals in a population regardless of population density, making them density-independent factors.

Question 20

Some predators feed preferentially on the most abundant prey. This is an example of ________ predation.

Accepted Answer

Density-dependent predation occurs when the rate of predation increases as the density of the prey population increases. Predators may preferentially target the most abundant prey, leading to a decrease in the prey population until it reaches a lower density that the predator is no longer able to sustain. This type of predation is dependent on the density of the prey population and can lead to fluctuations in population size.

Quiz 26: Population Growth and Regulation