Exam 15: Conserving Biodiversity: Community and Ecosystem Ecology

Salmonella enteritidis causes a food-borne illness that kills 400 to 600 Americans each year. It is found mainly in poultry products. Rather than give large doses of antibiotics to poultry, some poultry producers infect the intestinal tract of hens with a harmless bacteria, resulting in a dramatic decrease of S. enteritidis found in the chickens. In this case, what principle did the producers use?

North America is currently experiencing an unprecedented and rapid loss of species. What is believed to be the main trigger of such events, either directly or indirectly?

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

How many mass extinctions were experienced on a global scale before the alarming mass extinction that's now occurring?

Which of the following would be most threatened by habitat fragmentation?

Which chemical may be recycled from ammonia in the soil and then converted to organic proteins in plants?

What is the likely cause of "colony collapse disorder" in honeybees?

The sudden loss of which organism would necessarily cause the loss of most or all of a food web?

What is the life span of a species?

Scientists have used the fossil record to estimate the average length of time that a species inhabits the Earth. How can this estimate be useful for assessing the impact of humans on the Earth's biological diversity?

At the current rate of habitat destruction, tropical rainforests will be reduced to ________ of their original size within 35 years, and ________ of species living there will go extinct.

What law was passed to address the problem of rapid species loss in the United States?

The current rapid loss of species is considered by many scientists to be another mass extinction. What may be causing this increase in extinction rate, beyond background extinction?

What phenomenon results from the runoff of fertilizers from agricultural and residential areas causing the aquatic algae in bodies of water to grow prolifically?

How many years is the average life span of a species on Earth?

Why is a species that has few individuals at greater risk of extinction than a species with a large population size?

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

At the current rate of habitat destruction, what percentage of all living species will be extinct in 50 years?

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. What description applies to this example?

What would a species that has a high number of alleles for many genes that are distributed throughout the population have?