Which of these statements best describes what conservation biologists mean by 'the rapid loss of biodiversity'?

a. Introduced species, such as starlings and zebra mussels, have rapidly expanded their ranges.

b. Harvests of marine fishes, such as cod and bluefin tuna, are declining.

c. The current species extinction rate is as much as 100 times greater than at any time in the past 100,000 years.

d. Many potential medicines are being lost as plant species become extinct.

Which of the following currently poses the single greatest threat to biodiversity?

a. Invasive species

b. Overhunting

c. Habitat loss

d. Pollution

Which of the following is characteristic of endemic species?

a. They are often found in biodiversity hot spots.

b. They are distributed widely in the biosphere.

c. They require edges between ecosystems.

d. They are often keystone species whose presence helps to structure a community.

Ospreys and other top predators are most severely affected by pesticides such as PCBs because they

a. Are especially sensitive to chemicals.

b. Have very long life spans.

c. Store the pesticides in their tissues.

d. Consume prey in which pesticides are concentrated.

Movement corridors are

a. The routes taken by migratory animals.

b. Strips or clumps of habitat that connect isolated fragments of habitat.

c. Landscapes that include several different ecosystems.

d. Edges, or boundaries, between ecosystems.

With limited resources, conservation biologists need to prioritize their efforts. Of the following choices, which should receive the greatest attention for the goal of conserving biodiversity?

a. A commercially important species

b. All endangered vertebrate species

c. A declining keystone species in a community

d. All endangered species

What are the causes and possible consequences of climate change?

Why is international cooperation necessary if we are to solve this problem?

The human-generated increase in greenhouse gases (see Module 38.3) provides many opportunities to study the effects of climate change. For example, snowshoe hares are adapted to the climate of their habitat in the taiga of the high mountains and northern regions of North America. One adaptation is seasonal changes in fur color—a white winter coat that turns brown in the spring—that camouflage hares from a long list of predators. These color changes are triggered by day length. As increasing spring temperatures cause earlier snowmelt in the taiga, biologists have observed many white hares sitting on brown earth. Suggest how this natural experiment could be used to investigate the effects of climate change on populations and communities in the taiga ecosystem (assume historical data are available).

Researchers studied active and abandoned pika colonies at two sites (one in southeast Oregon and one in northwest Nevada) to understand how elevation might influence pika range (see Module 38.0 and Module 38.11). Sites were classified as old (no longer occupied) or current. How would you summarize the findings?

Does this study support the hypothesis that pika ranges are shifting to higher elevations due to climate change?

What are some limitations to describing patterns in nature as compared to doing a controlled experiment?

Will increasing atmospheric levels of CO₂ make you sneeze as well as itch?

Scientists studying the effects of rising CO₂ levels have looked at ragweed, whose pollen is the primary allergen for fall hay fever. They grew ragweed in three levels of CO₂: a pre-industrial concentration of 280 ppm, a year 2000 level of 370 ppm, and a projected level of 600 ppm. They found that pollen production increased by 131% and 320% in the plants exposed to the recent and projected CO₂ levels, respectively.

What was the hypothesis of this experiment?

Do the results support the hypothesis?

Given what you know about climate change, what other variables would you like to test, and what other measurements would you like to take?