unit 3 progress check answers and explanations

In a given country, the population size is decreasing because there are fewer prereproductive-aged individuals in the population. Which of the age structure diagrams best illustrates the population of this country?

A A top-heavy age structure diagram, like the one for Charlotte County, Florida, as shown in the figure, illustrates a declining population size because the number of prereproductive- and reproductive-aged individuals is low.

Based on the data in the graph, when did more-developed regions first reach replacement level fertility?

1970 In 1970, the data point is just above 2 children per woman. Replacement level fertility occurs at 2.1 children per woman. Based on the data, this is the first year on the graph where the population in more-developed regions declines to replacement level.

Based on the trends shown in the table, in which of the following years was the owl population at carrying capacity?

2015 The population fluctuates between 14 and 16 owls from 2000-2015. Since owls are a K-selected species, this represents the carrying capacity of this species.

Based on the data in the graph, what was the average number of children born per woman in less-developed regions in 1975 ?

4.7 The data point on the graph for less-developed regions in 1975 is between 4 and 5 children per woman.

Based on the survivorship curves shown below, which of the following is a possible reason for the change in the shape of the curve from 1900 to 1980?

Improvements in health-care services and medical research Significant improvements in health care and medical research have increased life expectancy from an average of 45 years in 1900 to 75 years in 1980.

A country is currently in the second stage of the demographic transition. Currently the country has a birth rate of 37.9 births per 1,000 individuals and a death rate of 13.4 deaths per 1,000 individuals. Which of the following changes would indicate that the country is moving from the second stage into the third stage of the demographic transition?

The birth rate declines to 25.3 births per 1,000 individuals. The birth rate falls but does not yet match the death rate during the third stage.

Which of the following claims is best supported by the data in the table?

The black rhino is a K-selected species because it has a low number of offspring per reproductive event.

Which of the following is a characteristic of an organism that displays a Type III survivorship curve, as shown in the graph above?

The organism produces large numbers of offspring every time it reproduces. Type III organisms (including many marine invertebrates and other rr-selected species) have large numbers of offspring.

Which of the following claims is best supported by the data shown in the table above?

The owl population experienced population overshoot between 1995 and 2000 because of increased competition for resources. The population greatly exceeded carrying capacity in 1995 (30 owls) and was then followed by a dieback because of increased competition for limited food resources.

Researchers monitored the number of reindeer over time on an island off the coast of Alaska. The reindeer were introduced in year 1, and the population size was counted every 5 years. The data are shown in the table above. Which of the following claims about trends in the population size over time is best supported by the data?

The population exceeded the carrying capacity of the island, which led to a decrease in the population size following extreme resource depletion. On the island, the population overshot carrying capacity and depleted the resources. This led to a rapid decline in the population because many deer starved.

Which of the following statements best describes the pattern seen in age structure diagram C?

There is an imbalance between males and females, with a ratio of 1.5 men to every woman in the population. In this county (Bristol Bay, AK), there were approximately 150 men for every 100 women in 2000. Due to the area and the economic opportunities, there is an imbalance between males and females in the population.

Which of the following best describes the trends seen in the total fertility rates for the world population from 1950 to the projected rates in 2040 ?

Total fertility rates declined rapidly from 1960 to 2000 because women had children later in life as a result of increased educational opportunities. As more women have access to educational opportunities, they marry and reproduce later in life, leading to a decrease in the total fertility rate.

The rule of 70 can be used to determine a population's doubling time. Doubling time is a measure of the

population growth rate The rule of 70 states that dividing the number 70 by the percentage population growth rate approximates the population's doubling time.

Song sparrows are found in a variety of habitats, including marshes, grasslands, agricultural fields, and suburban areas. They feed on a variety of organisms, including beetles, caterpillars, snails, and earthworms. They also consume plants, including different types of grains and berries. The table below summarizes the reproductive data for song sparrows. Based on the description and the data table above, which of the following combinations best classifies the song sparrow?

r-strategist and generalist Song sparrows reproduce multiple times in a year and have limited parental care, traits of r-strategists. Generalists can live in a variety of habitats and have diverse diets.

The demographic transition model describes population change over time as a country becomes more developed. Age-structure diagrams describe how populations are distributed across age ranges. Which of the following age-structure diagrams best displays the age ranges in a country that is in stage 2 of the demographic transition?

An expansive pyramid age-structure diagram Stage 2 in the demographic transition has high birth rates and fairly high death rates, with a rapidly growing population. This is illustrated by high numbers of prereproductive-age individuals in the age-structure diagram, leading to a pyramid shape.

Based on current trends and patterns, which of the following statements best predicts how the human population will change over the next 50 years?

As the population density increases, there will be an increase in disease transmission, leading to increased mortality. Diseases that occurred locally will spread rapidly among a growing population with high population density.

Which of the following claims best supports the classification of bees as an organism that displays a Type II survivorship curve, as shown in the graph above?

Away from the colony, bees experience a constant probability of death per unit time as a foraging species. Type II species have a constant mortality rate throughout their lifetimes. Bees demonstrate this survivorship curve.

The graphs below show changes in a population over time. The dashed line represents the carrying capacity of the species. Which of the following graphs best shows the population size of a K-selected species over time in a stable environment?

C This graph shows a population growing to carrying capacity and remaining around carrying capacity. This is a graph for a typical K-selected population. It is smooth and the curves resemble the shape of a rollercoaster.

Which of the age structure diagrams best illustrates a county that has a stable population size and slow or no population growth?

D The column-shaped diagram indicates population stability.

A variety of plants and animals inhabit a forest ecosystem. Which statement correctly explains why certain organisms would be more likely to survive than others if a forest fire burned the area

Generalist species are more likely to survive because they can thrive in a wide variety of environmental conditions and can make use of a variety of different resources. A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources. A specialist species can thrive only in a narrow range of environmental conditions or has a limited diet. Loss of habitat leads to a loss of specialist species before a loss of generalist species.

Which of the following best describes a difference between generalist species and specialist species?

Generalists use a large range of resources, while specialists have a limited range of resources they use to survive. Generalist species can utilize a broad range of resources, while specialists utilize a much smaller range of resources.

A scientist is studying a biome that experiences large seasonal fluctuations in both temperature and precipitation patterns. Which of the following would best characterize the organisms that inhabit the biome?

Generalists would be most abundant, because the resources available would be constantly changing. Generalists have an advantage in habitats that are changing; they are capable of surviving in a wide range of conditions and use a wide range of food resources.

Which of the following density-independent factors can affect the size of a human population?

Heat waves Heat waves will affect people if there are few or many in an area; the effects are independent of population density.

Which of the following statements best describes why birth and death rates are changing in a country that is in Phase 2 of the demographic transition?

Individuals have better sanitation and access to clean drinking water In phase 2, there is rapid population growth as the result of better access to clean drinking water, food, vaccinations, and other medical care.