Ecology Test

Walleyes and northern pike are both species of fish that live in freshwater lakes. Many lakes maintain large, healthy population of both of these fish species year after year. Which statement about walleyes and northern pike is most useful in explaining how they are able to live together in the same habitat?

a. The two species are adapted to eat different types of food.

Scientists have classified the sea otter as a keystone species in communities along the Pacific coast of North America. This classification depends on which property of the sea otters?

b. Sea otters act to maintain a wide variety of other populations in the community.

Which of the following describes a benefit of biodiversity to an ecosystem?

d. allows the ecosystem to withstand environmental changes

A scientist concludes that a population of bison has reached the carrying capacity of the prairie where it lives. The birthrate and death rate of the bison population are equal to each other. What can be concluded about the rates of immigration and emigration?

a. The rates of immigration and emigration are equal to each other

Which of the following best describes opportunistic, or r-strategy, organism?

b. They reach sexual maturity rapidly

A hurricane blows across a Caribbean island, the storm flattens trees and it drowns or washes away a large number of plants and animals. As a result of the storm, the carrying capacity of the island is temporarily reduced for many of the islands species. How is the storm classifying as a limiting factor?

a. The storm is density-independent limiting factor because population size and density do not alter the storms effect.

Which of the following communities is likely to be most stable?

c. One with high species diversity

In a forest ecosystem, a variety of predators compete with one another for the same prey. The predators include wolves, coyotes, foxes, and hawks. Their prey include deer, rabbits, mice, and the chickens that lives outdoors on nearby farms and backyards. Suppose that human activities such as hunting, drastically reduce the populations of the wolves, coyotes, and foxes. Which statement best explains a likely change to the hawk population?

d. The hawk population increases to a new carrying capacity that is determined by one or more limiting factors, such as the availability of food.

A frog population of 450 in a pond has a maximum annual rate of increase of 0.7. If the carrying capacity of the pond is 1,500 for this species, what is the expected population size after one year?

a. 671

In the year 2000, specimens of Caulerpa taxifolia, a green alga used in tropical aquariums were found off the coast of California. Native to the Indian Ocean, C. taxifolia is known for aggressive growth and an ability to compete with sea grasses. It is currently on an international list of invasive species. Which of the following best predicts the consequences of the introduction of C. taxifolia to the California coast?

b. Without natural herbivores or competitors, C taxifolia will grow rapidly and crowd out native species of producers.

There is strong evidence that two species of cliff-dwelling birds have nested in the same environment and fed in the same water for thousands of years, with each having stable population sizes. Based on this information which of the following statements is the best conclusion?

d. The two birds have different ecological niches that allow coexistence.

Which of the following statements correctly describes a typical trend during the initial stages of succession in a terrestrial ecosystem?

c. Diversity of plant species increases.

Which of the following statements best predicts the effect of increased cottonwood growth on the food web?

c. Increased cottonwood growth will provide more resources for cicadas, resulting in an increase in the kestrel population.

The data from the temperature-controlled experimental plots can best be used to support which of the following conclusions about cicada development?

c. Cicada nymphs mature to adults faster in warmer soil than in cooler soil.

Yellow-billed cuckoos typically hatch in mid July. Emerging cicadas are a primary food source for nesting cuckoos. Which of the following best predicts the effect of wildfires on yellow-billed cuckoo populations?

b. The yellow-billed cuckoo population will decline because the cicadas will emerge before the hatching season begins.

Wolves, once native to Yellowstone National Park, were hunted to the point of complete extinction in the park. As a result, the elk population in the park flourished, putting extra demands on the carrying capacity of the park. Many other species, such as certain trees and beavers, were negatively affected by the increase in elk. Years later, wolves were reintroduced into the park. While the elk population decreased after the wolves returned the beaver and songbird populations began to increase as did the populations of various plant species. Which of the following best explains how wolves are a keystone species in this ecosystem?

c. Wolves help balance the population sizes of other species, allowing more species to thrive in the wolves' presence than in their absence.

An overlap in the niches of two species will most frequently result in

a. interspecific competition

Which of the following observations best represents a mutualistic relationship?

d. Flowers produce nectar that bees gather to make honey, and in the process the bees pollinate the flowers

Which of the following best explains why there are seldom more than five trophic levels in a food chain?

d. Energy is lost from each trophic level.

A scientist is evaluating a proposal for raising large numbers of fish in ocean pens for human consumption. As part of the evaluation, the scientist is designing a plan for investigating how the fish in the ocean pens might affect nearby ecosystems. Which of the following is the most appropriate factor to use as the dependent variable in the experimental investigation?

c. The amount of metabolic wastes in the water where the fish are being raised

In the process of succession, which of the following is true of K-selected plant species?

b. They are usually found in climax stages of succession.

The element carbon is contained in all organic compounds. Discuss the role of photosynthesis and cellular respiration in carbon cycling in the biosphere.

Photosynthesis and cellular respiration are both processes that drive the carbon cycle to continue to move between the atmosphere and biosphere. For photoautotrophs, they remove CO2 from the atmosphere for plant growth. This creates a carbon-based food source that other organic life can use during energy transfer. For cellular respiration, living organisms break down organic molecules and release carbon back into the environment. This allows for plants to recapture that carbon dioxide and continue the carbon cycle. Without photosynthesis, there would be a build-up of CO2 and without cellular respiration, plants would have a shortage of CO2 for photosynthesis.

For THREE of the following, predict and explain the effect on the carbon cycle if:

1. decomposers were absent

2. deforestation occured

3. volcanic dust accumulated in the atmosphere

4. the average ocean temperature increased

1. Carbon would be trapped in dead organic matter & there would be a depletion of CO2 in the atmosphere. Decomposers release carbon dioxide back into the atmosphere through cellular respiration when breaking down organisms. If decomposers were absent, this process would not be available meaning plant would be prevented from continuing photosynthesis due to a lack of atmospheric carbon dioxide.

2. There would be more CO2 in the atmosphere and less carbon dioxide in organisms. Trees absorb carbon dioxide during photosynthesis which removes them from the air. Removing trees would cause a huge increasing in atmospheric carbon dioxide due to the lack of photosynthesis.

3. There would be more CO2 in the atmosphere due to a decrease in photosynthesis. When volcanic dust is accumulated in the atmosphere, it blocks the sun out and disrupts a photoautotrophs ability to perform photosynthesis. This means that they’ll take up less carbon dioxide from the atmosphere.

Explain how increased CO2 in the atmosphere results in greater acidification of oceans and describe the effect on marine organisms. Include in your discussion TWO examples of how human activity can increase atmospheric CO2.

Ocean acidification occurs because the ocean absorbs roughly a quarter of the CO2 released into the atmosphere, triggering a chemical reaction where CO2 reacts with seawater to form carbonic acid. This process increases the concentration of hydrogen ions, lowering the pH of the water and simultaneously depleting carbonate ions, which marine "calcifiers" like corals, oysters, and pteropods require to build their calcium carbonate shells and skeletons. As a result, these organisms face stunted growth or even shell dissolution, threatening the entire marine food web. This environmental shift is driven primarily by human activities such as the combustion of fossil fuels for energy and widespread deforestation, both of which release massive amounts of stored carbon into the atmosphere, intensifying the chemical pressure on our global oceans.