Unit 8 Part 2

Changes in an ecosystem over a long period of time are shown in the diagram. Which BEST describes the end result of the changes occurring in the ecosystem?

• A long-term rise in environmental temperatures.

• A loss of heterotrophs that cannot be recovered.

• A stable ecosystem that can last for many years.

• A forest consisting of only producers and decomposers.

Angel was trying to explain carrying capacity to her mother. Which of the following descriptions is MOST ACCURATE?  

• The maximum number of species that can co-exist in an area.

• The maximum number of individuals that an ecosystem can sustain.

• The ability of an environment to accommodate a growing population.

• The greatest number of individuals that an area can sustain over the long term.

On remote islands, immigration and emigration usually do not have a large effect on population sizes. A bird population on a remote island remains at a relatively constant size year after year. Which of the following MOST LIKELY describes the birthrate and the death rate for this population?

• Birthrate and death rate are both zero.

• Birthrate and death rate are close to equal.

• Birthrate is significantly less than death rate.

• Birthrate is significantly greater than death rate.

Most populations introduced to a new ecosystem grow until factors such as lack of food and overcrowding limit their growth, as illustrated in the graph. What does the portion of the graph labeled B represent?

• Logistic growth

• Slowing growth

• Exponential growth

• Death rate increase

A group of science students have been studying population growth of a species of Paramecium, a single celled organism for 36 days. The students’ data is shown in the graph. Food was occasionally added to the test tube in which the paramecia were grown. According to the graph, what is the carrying capacity of the test-tube environment as long as food is added occasionally?

• About 250 paramecium.

• About 1000 paramecium.

• About 1500 paramecium.

• About 2000 paramecium.

Krakatoa was an island in the Pacific Ocean that was completely destroyed by a volcano in 1886. By 1960, the volcano had formed a new island called Surtsey. A type of lichen became the first plant life on Surtsey, followed by grass, when the seeds were dropped by birds that had passed over the island in flight. What type of ecological change does this describe?

• primary succession

• pioneer succession

• ecological turnover

• secondary succession

A population of chipmunks migrated to an environment where they had little competition. Their population quickly increased but eventually stabilized as shown in the graph. Which statement BEST explains why the population stabilized?

• The population size became limited due to factors such as availability of food.

• Interbreeding between members of the population increased the mutation rate.

• A predator species came to the area and occupied the same niche as the chipmunks.

• An increase in the chipmunk population caused an increase in the producer population.

Which of the following global issue is indirectly responsible for all of the others?

• waste disposal

• overpopulation

• poor sanitation

• resource depletion

A graph of atmospheric carbon dioxide concentration over time is shown. Scientists are investigating the cause of the large increase in atmospheric carbon dioxide concentration since about 1800. Which of the following provides the BEST explanation for the increase?

• Eruptions of large volcanoes.

• Use of fossil fuels by humans.

• Natural fluctuations of climate.

• Photosynthesis by phytoplankton.

A wheat field is cleared using a tractor, wild grasses and weeds begin growing after the field is cleared. What type of succession happened in the wheat field?

• Primary succession because pioneer species appear.

• Primary succession because there are no large trees.

• Secondary succession because soil is already present.

• Secondary succession because the field contains inorganic matter.