Which scenario illustrates directional selection?
a. Elk that are smaller or larger than average are easier prey for predators than elk of approximately average size.
b. Bright feathers allow birds to attract mates, dull feathers hide birds from predators, but semi-bright feathers convey no advantage.
c. Rabbits with shorter ears become more common where cattle that favor grazing on taller grass over shorter grass are introduced.
d. Wildlife living in a forest are displaced after a wildfire destroys their natural habitat.
c. Rabbits with shorter ears become more common where cattle that favor grazing on taller grass over shorter grass are introduced.
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Two frog populations (same species) living in two neighboring lakes sing slightly different courtship songs. Increased irrigation makes the land between the two lakes wetter, allowing frogs to expand their ranges to the area between the lakes
Females in both populations prefer loud frogs to quieter frogs, but do not distinguish between the two slightly different songs. Assuming that courtship song differences have a genetic basis, predict what will likely happen to the songs of the two frog populations. A) The songs will become more similar to each other. B) Males will become louder. C) Disruptive selection will cause the songs to differentiate even more. D) Genetic drift will cause the songs to differentiate even more. E) You cannot predict a change in the courtship songs at the two lakes.
In soft-bottom communities deposit feeders dominate
a. where sediments are generally muddy. b. as epifauna on worm tubes. c. as meiofauna. d. where sediments are generally sandy. e. where oxygen levels are low.
Which of the following is(are) NOT involved
in the reproduction of all viruses? a. attachment and penetration b. replication and synthesis c. assembly d. latency e. release
________ are a component of the immune system that are able to destroy cancer cells by deploying toxins into infected cells as a means of killing them. In this role they are cytotoxic—that is, "cell killing."
A) Natural killer cells B) Phagocytes C) Antibodies D) B cells