Which pattern best characterizes the history of extinctions on Earth?
A. An increasing per capita background extinction rate
B. Five major mass extinctions and several lesser episodes of heightened extinction rates
C. Three major mass extinctions and several lesser episodes of heightened extinction rates
D. Three major mass extinctions and a low background extinction rate
E. An increase in the number of mass extinctions over time
Ans: B. Five major mass extinctions and several lesser episodes of heightened extinction rates
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The ________ model is used to describe the simultaneous polymerization and depolymerization of microtubules.
Fill in the blank(s) with the appropriate word(s).
According to Lamarck, the characteristics of
organisms change because of a. chance. b. an innate drive for perfection. c. extinction of competitors. d. special acts of creation. e. genetic mutation.
Exotic species that are introduced into a non-native
habitat can a. interbreed with native species. b. drive endemic species to extinction. c. die out due to competition from native species. d. blend in with endemic species. e. create habitat islands for themselves.
The individuals that disperse as a response to high population density are
A) mostly the younger members of the population. B) more likely to survive. C) mostly females. D) usually superior competitors.