Question 1

Guppies from Trinidad form two distinct populations that differ in several life history traits. These traits appear to relate to the local predator populations, pike-cichlids or killifish. Which of the following experiments would best test the heritability of these traits?

Accepted Answer

Raising both populations without predators would test if the life history traits are genetically inherited (heritable) rather than solely a response to the presence of predators. If the traits persist without predators, it suggests a genetic basis.

Question 2

In terms of population dynamics, what is "boom-and-bust" cycling?

Accepted Answer

Boom-and-bust cycling refers to a pattern where a population experiences rapid growth (boom) followed by a sharp decline (bust), often due to overshooting the carrying capacity and subsequent resource depletion.

Question 3

An ecologist hypothesizes that predation by a particular owl species is the major factor controlling the population of a particular rabbit species. If this is the case, which of the following population effects could be expected in this rabbit-owl pair?

Accepted Answer

If predation by owls is the major limiting factor for the rabbit population, an increase in owl population would lead to a decrease in the rabbit population. This is because there would be more predators preying on the rabbits, leading to a decrease in their population size. Therefore, choice D is the correct answer. Choices A and B are incorrect because they are the opposite of what is expected when predation is the major factor controlling rabbit population. Choice C is also incorrect as an increase in disease in the rabbit population is not related to the owl population.

Question 4

An ecologist hypothesizes that predation by a particular owl species is the major factor controlling the population of a particular rabbit species. The first step in testing this hypothesis would be to determine

Accepted Answer

The first step in testing the hypothesis is to determine if the predation by the owl is actually happening. This can be done by observing if the owls are preying on the rabbits.

Question 5

Which of the following organisms best illustrates K-selection?

Accepted Answer

K-selection is where organisms reproduce slowly and produce few offspring, but put a lot of energy into caring and nurturing for them. Polar bears produce only one or two cubs every three years and invest significant energy into raising them, making them the best example of K-selection from the given options.

Question 6

What is the age structure of a population?

Accepted Answer

The age structure of a population refers to the proportion of individuals alive in different age-groups. It is typically shown with a pyramid-shaped graph where the youngest age groups are at the base and the oldest age groups are at the top. This can give important information about the potential for population growth, as well as the needs and demands of different age groups within the population. Options A and B are incorrect as they are not representative of the age structure of a population, and option D is not comprehensive enough as it only refers to changes in the age distribution over time, rather than the overall age structure.

Question 7

If most of the individuals of a human population are in their pre-reproductive years, you would expect the population size to ________ after 20 years.

Accepted Answer

When most individuals in a population are in their pre-reproductive years, it is expected that as they enter their reproductive years, they will contribute to population growth, leading to an increase in population size over time.

Question 8

A demographic tool used to predict a population's future growth is

Accepted Answer

Age structures provide information about the distribution of individuals within different age groups of a population, which is a key factor in determining future population growth. By analyzing the current age structure, predictions can be made about the future number of births, deaths, and overall population size. The other options are not specifically designed to predict future growth, but rather describe patterns of survival within a population.

Question 9

Which of the following statements about insecticides is true?

Accepted Answer

Prey species often have a higher reproductive rate than do predators, which means that their populations can bounce back more quickly after a control effort. This is one of the reasons why simply killing many individuals is not always the best way to reduce the size of a pest population. Additionally, biological controls and cultural methods can be used in combination with chemical insecticides to create a more effective pest management strategy.

Question 10

Which of the following statements about human population growth is true?

Accepted Answer

Demographic transition is the transition from high birth rates and high death rates to low birth rates and low death rates as a country develops economically and socially. This has been observed in many countries and is the reason for the current trend of slowing population growth rates globally. A is incorrect because human population size is not at equilibrium; it is still increasing. C is incorrect because birth rates typically drop due to improved education, health care, and economic opportunities, rather than access to contraception. D is incorrect because while there have been periods of rapid population growth in human history, such as during the agricultural and industrial revolutions, overall population growth rates have slowed in recent decades.

Question 11

In the logistic growth model, as population size increases, birth rates

Accepted Answer

In the logistic growth model, as population size approaches the carrying capacity of the environment, birth rates decline due to competition for resources. At the same time, death rates may increase due to factors such as disease, predation, or competition for resources. Therefore, the best choice is D, which states that birth rates decline and/or death rates increase as population size increases.

Question 12

Which of the following will likely decrease a population's size?

Accepted Answer

Decreasing the food supply available to the population is likely to decrease a population's size as it will lead to increased competition for limited resources and decreased reproductive success. Improving the quality or increasing the size of the habitat, and practicing sustainable resource management may actually increase the population's size by providing more resources and better living conditions.

Question 13

An r-selected species typically

Accepted Answer

r-selected species have a high reproductive rate and produce many offspring that have a low survival rate. This makes them better adapted to unstable, unpredictable environments where there are frequent disturbances, such as floods or fires. They do not offer much parental care and are usually small-bodied and short-lived.

Question 14

An ecological footprint

Accepted Answer

An ecological footprint is a tool used to measure the impact of human activities on the natural environment. It calculates the amount of land and water resources needed to sustain a specific population or activity, allowing us to understand resource availability and usage. The other options listed are not accurate descriptions of an ecological footprint.

Question 15

The age structure of the United States in 2010 shows

Accepted Answer

The age structure of the United States in 2010 shows that a greater proportion of the population is elderly now than in earlier decades. This suggests that the United States has gone through a demographic transition, as the proportion of younger individuals has decreased while the proportion of older individuals has increased. A broad base would suggest a high birth rate, but that is not evident in the age structure of the United States in 2010.

Question 16

The human population on Earth is expected to reach 9.5 billion people by

Accepted Answer

According to the United Nations, the human population on Earth is predicted to reach 9.7 billion by 2050.

Question 17

Thanks to a new conservation program, a population with only 200 individuals at the beginning of the year is growing exponentially. The population has a per capita birth rate of 0.5 per year and a death rate of 0.2 per year. What is the growth rate during the year? What will the population be at the end of the year?

Accepted Answer

The growth rate is calculated as the difference between the birth rate and the death rate multiplied by the population size. Here, it's (0.5 - 0.2) * 200 = 0.3 * 200 = 60 per year. Adding this growth to the initial population gives 200 + 60 = 260.

Question 18

The world human population

Accepted Answer

The world human population is still growing, but the rate of growth has slowed down compared to the last century. According to the United Nations, the world population reached 7.7 billion in 2019 and is projected to reach 9.7 billion by 2050. However, the rate of growth has been declining since the 1960s, and it is projected to continue to decline in the coming decades.

Question 19

Which of the following is most clearly a case of density-dependent population regulation?

Accepted Answer

Density-dependent population regulation occurs when a population's growth rate is affected by the density of the population. In the case of the dangerous new flu strain, the transmission of the virus among humans is likely to be impacted by the density of the population, as the virus can spread more quickly in crowded conditions.

Question 20

Which of the following statements about human demographic trends is true?

Accepted Answer

Delayed reproduction by women leads to a decrease in the fertility rate, which in turn slows down population growth.

Answer: D
 The demographic transition is characterized by a shift from high birth rates and high death rates to low birth rates and low death rates over time. This transition is typically associated with economic and social development.

Therefore, the correct statements are C and D. Option A is incorrect because, with the increase in status and education, women tend to have fewer children. Option B is incorrect because mortality rates have actually decreased in most developing countries since 1950.

Quiz 36: Population Ecology