Science Assessment III.2 - 9°

Science Assessment III.2

9° - 2020

Describing Populations

• Geographic range: The area inhabited by a population is called its geographic range.

• Density and distribution.

• Growth rate: Does the population increase, decrease, or stay the same size?

• Age structure: Age and male/female

Multiple Choice

Frank counts 56 maple trees living on a 20-acre tract of land. He calculate the (A)____ of the maple trees on the land. He observes that most of the maple trees grow closely together in groups of 6 to 8 trees, which describes the (B)_____.

• (A) population density (B) population distribution

• (A) population distribution (B) population density

• (A) age structure (B) population distribution

• (A) population density (B) age structure

Multiple Choice

Which factor might NOT contribute to an exponential growth rate in a given population?

• Lower death rates

• Higher birth rates

• Minimal immigation rates

• Huge emigration rates

Multiple Choice

The population of adult frogs in a wetlands ecosystem has increased to 1000 individuals, which is its carrying capacity. The frogs eat flies and other small animals, and they are prey for raccoons, snakes, and a variety of large birds.

Which most likely would happen if an additional 200 adult frogs immigrated to the ecosystem?

• The carrying capacity for frogs in the ecosystem would increase by 200 frogs.

• The carrying capacity for frog predators in the ecosystem would increase by 200 individuals.

• The frog population would experience a pattern of exponential growth.

• About 200 adult frogs would die because of lack of resources, or by predation or disease.

Open Ended

Compare exponential and logistic growth.

Limits to Growth

Limiting factors determine the carrying capacity of an environment for a species. There are two types of limiting factors: density-dependent and density-independent.

Density-Dependent Factors

• Density-dependent limiting factors operate strongly when population density reaches a certain level.

• Competition, parasitism and disease, stress from overcrowding, predation, and herbivory.

Density-Independent Factors

Density-independent limiting factors affect all populations regardless of population size and density.

Density-independent limiting factors include natural disasters and usual weather.

Multiple Choice

Which of the following statements describes density-independent limiting factors?

• Competition is an example.

• Parasitism and disease are examples.

• Environmental extremes, such as a hurricane or drought, are examples.

• Their effects increase as the population increases in an area.

Multiple Choice

Which would be least likely to be affected by a density-dependent limiting factor?

• A small, scattered population

• A population with a high birth rate

• A large, dense population

• A population with a high immigration rate

Multiple Choice

A population of mountain lions lives in an alpine forest. The mountain lions hunt deer, rabbits, and other prey. As the population increases, which of these events becomes more likely to occur?

• Female mountain lions raise an increasing number of pups per litter, and a greater percentage of pups survive to adulthood.

• Competition for territory and other resources acts to slow the growth rate of the population.

• A wildfire, drought, or other natural disaster acts to decrease the mountain lion population by at least 50 percent.

• A decrease in competition acts to increase the growth rate of the population

Multiple Choice

Which is an example of herbivory affecting an ecosystem?

• Tall trees block the sunlight from reaching plants on the forest floor.

• Coyotes catch slow-moving rabbits, but not the faster rabbits.

• Deer eat the stems of plants without thorns, allowing plants with thorny stems to thrive.

• Fungi break down dead organic matter, which returns nutrients to the soil.

Multiple Choice

Competition for food would probably be most severe between two ___.

• unrelated species in the same community occupying different niches

• closely related species in different niches

• closely related species in similar niches

• unrelated species in different communities

Multiple Choice

Which statement is true regarding keystone species in an environment?

• They always have the largest number of organisms in an environment.

• They promote stability in an ecosystem.

• They are non-native species that outcompete native organisms for resources.

• They reduce biodiversity within an ecosystem.