Exam 15: Conserving Biodiversity: Community and Ecosystem Ecology

A researcher returns from the Amazon River with 10 individuals of a species of fish and establishes a small breeding colony in her laboratory. She maintains the colony for several years (many fish generations), always maintaining the number of adult fish between 10 and 30. She notices that as generations of fish are bred, the reproductive rate decreases. What is the most likely reason for this?

What is the estimated "background rate" of extinction, as calculated by scientists?

The heath hen, found off the east coast of North America in the 18th century, is now extinct. What finally caused its extinction?

Cattle egrets hitch a ride on domestic cows and eat insects that are stirred up by their activity. This is an example of

A species that has a high number of alleles for many genes that are distributed throughout the population is said to have

The estimated 10 million species that exist today are thought to represent approximately ________ of the species that have ever existed on Earth.

How does the rate of extinction today compare to the rates in the past?

The lifespan of a species is the

In certain areas of the world where there's a high incidence of malaria, there's also a high incidence of sickle-cell anemia. Sickle-cell anemia results from a mutation in the gene that codes for hemoglobin. Malaria is an infectious disease carried by mosquitoes. Both malaria and sickle-cell anemia can be fatal. If an individual is homozygous for normal hemoglobin, they're more prone to malaria. If an individual is homozygous for sickle-cell hemoglobin, they'll develop sickle-cell anemia. However, if an individual is heterozygous and possesses one allele for normal hemoglobin and one allele for sickle-cell hemoglobin, they're less prone to malaria and won't develop sickle-cell disease. This is an example of how

Although most biologists believe that many species are becoming extinct each year because of the activities of humans, relatively few species actually appear on compiled lists of extinct species. What is one reason why so few species are listed as extinct?

The variety of species in an area of interest is called