Question

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 _______ times the background rate.

1) 4
2) 8
3) 25
4) 40

Answer 1

Option 3.

The extinction rate of amphibians during the twentieth century is about 25 times the background rate, with the correct option being 3) 25.

Step-by-step explanation:

The question is asking to compare the background extinction rate of amphibians to the observed extinction rate during the twentieth century.

The background extinction rate is about 1 extinction per million species years (E/MSY), which means if there are about 10 million species, it is expected that 10 species would become extinct each year.

Given that 20 amphibians went extinct in the twentieth century, the yearly extinction rate can be represented as 20 extinctions per 100 years, or 0.2 extinctions per year.

Now, to calculate the number of times the twentieth-century extinction rate is of the background rate for amphibians, we take the observed rate (0.2 per year) and divide it by the expected background rate (0.008 per year, since 8 per 1000 years is equivalent to 0.008 per year).

This gives us 0.2/0.008, which equals 25.

Therefore, the extinction rate of amphibians in the twentieth century is about 25 times the background rate.

So, the correct option is 3) 25. Please mention correct option in final answer.