5. An African rose species varies in the density of thorns on the plants (a gene

Question

5. An African rose species varies in the density of thorns on the plants (a genetically based trait).
Roses with fewer thorns are more likely to be eaten by giraffes and other Savanna herbivores.
However, the plants with the most thorns are preferred by a weevil who lays its eggs on the
base of the plant thorns. The weevil larvae eat into the rose plant causing it to rot. Both the
giraffes and the weevils do significant damage to the plants they attack, reducing the plants
ability to reproduce. This could be categorized as an
example of:
a. Directional selection
b. Disruptive selection
c. Stabilizing selection
d. Sexual selection

6. A population of butterflies on an island varies in wing size. Some have large wings and some
have small, but they still belong to the same species. All are doing well until a meteorite hits the
island and kills many of the butterflies. More large-winged than small-winged butterflies are
killed. Which of the following should we expect if we compare the next generation to the one
that got hit?
a. Directional selection has occurred
b. Evolution has occurred
c. Sexual dimorphism has occurred
d. None of the above should occur because this was a random stochastic event

Explanation / Answer

5. An African rose species varies in the density of thorns on the plants (a genetically based trait).
Roses with fewer thorns are more likely to be eaten by giraffes and other Savanna herbivores.
However, the plants with the most thorns are preferred by a weevil who lays its eggs on the
base of the plant thorns. The weevil larvae eat into the rose plant causing it to rot. Both the
giraffes and the weevils do significant damage to the plants they attack, reducing the plants
ability to reproduce. This could be categorized as an
example of:

b. Disruptive selection


6. A population of butterflies on an island varies in wing size. Some have large wings and some
have small, but they still belong to the same species. All are doing well until a meteorite hits the
island and kills many of the butterflies. More large-winged than small-winged butterflies are
killed. Which of the following should we expect if we compare the next generation to the one
that got hit?
a. Directional selection has occurred
b. Evolution has occurred
c. Sexual dimorphism has occurred
d. None of the above should occur because this was a random stochastic event

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