Question 1

The major factor leading to the extinction of the passenger pigeon was

Accepted Answer

The passenger pigeon went extinct primarily due to overharvesting, as they were hunted extensively for food and sport in the 19th century.

Question 2

Suppose the background extinction rate of amphibians is 8 per 1,000 years and that during the twentieth century, 20 amphibians went extinct. The extinction rate of amphibians is now about how many times the background rate?

Accepted Answer

The background extinction rate is 8 per 1,000 years, so the expected number of extinctions in the twentieth century is 8 * 100 = 800. The actual number of extinctions was 20, so the extinction rate is now about 20 / 800 = 1 / 40 = 0.025 times the background rate.

Question 3

Which factor is not part of the growing taxonomic homogenization of Earth's biota?

Accepted Answer

Increases in the number of native specialist species would not contribute to taxonomic homogenization, as it would maintain or increase biodiversity rather than reduce it.

Question 4

Over the past few centuries, human populations and their levels of resource use have exploded. This has led to an increasing loss of biodiversity, but the causes of that loss have changed over the years. Which factor is a much greater threat to biodiversity in the United States in the twenty-first century than it was in the previous two centuries?

Accepted Answer

Climate change has become a much greater threat to biodiversity in the twenty-first century due to increased greenhouse gas emissions and global warming, which were not as significant in previous centuries.

Question 5

Off-road mountain vehicles and mountain bikes trample various plant species in the Santa Cruz Mountains and hills of California. Although plants still persist in the area and many species are unaffected, habitat quality for many species has declined. This is an example of habitat

Accepted Answer

Habitat degradation refers to the decline in habitat quality, which affects the ability of the environment to support certain species. In this case, the trampling by vehicles and bikes reduces the quality of the habitat for many plant species, even though the plants still persist.

Question 6

Despite the loss of the Atlantic forest habitat of Brazil, no extinctions of birds from this area have been reported. According to Brooks et al., which of the following is the most plausible explanation for the apparent lack of extinctions?

Accepted Answer

The most plausible explanation according to Brooks et al. is that there is a time lag between deforestation and extinction, meaning that the full impact of habitat loss on bird extinctions may not have been realized yet.

Question 7

Which of these is an example of an anthropogenic Allee effect?

Accepted Answer

The anthropogenic Allee effect occurs when human activities increase the value of a species as it becomes rarer, leading to increased exploitation, as seen with rhinos and poaching.

Question 8

Refer to the figure.
 The figure shows the current level of threat faced by each biome from a variety of sources. According to the figure, what is the most serious threat now facing marine ecosystems?

Accepted Answer

The answer of Refer to the figure.
 The figure shows...

Question 9

For which purpose is molecular genetic analysis not useful?

Accepted Answer

Molecular genetic analysis is not directly useful for estimating population growth rates, which are typically assessed through demographic studies rather than genetic analysis.

Question 10

Biologists can make population viability analysis (PVA) models more effective by

Accepted Answer

Checking the validity of the models against field observations ensures that the models accurately reflect real-world conditions and can be adjusted for greater accuracy.

Question 11

For which species have ex situ conservation measures been used?

Accepted Answer

Ex situ conservation measures, such as captive breeding programs, have been used for California condors to help increase their population and prevent extinction.

Question 12

Which of the following is not an axis used by biologists to determine whether, or to what extent, a species is rare?

Accepted Answer

Age structure is not typically used to determine rarity; rarity is usually assessed based on population size, habitat specificity, and geographic distribution.

Question 13

An insect has habitat requirements that overlap substantially with those of other endangered species. Because this insect is well known for its beautiful coloration, efforts to protect it have garnered much support. It is thus acting as which kind of species?

Accepted Answer

A flagship species is one that is used to attract public attention and support for conservation efforts, often because of its appealing characteristics.

Quiz 23: Conservation Biology