Question

an individual hydra is swept by an ocean current to an area of the ocean where no other hydras reside. the hydra asexually reproduces, as does its offspring, until there is a population of genetically identical hydra. is it possible for this population to undergo natural selection?
a. yes, all populations are capable of undergoing natural selection
b. no, natural selection does not occur in organisms that reproduce asexually
c. yes, the population will choose traits that help it adapt to the new environment
d. no, there is no genetic variation upon which natural selection can operate

Explanation:

自然选择的基础是遗传变异。该水螅种群通过无性繁殖，遗传上完全相同，没有遗传变异。自然选择需要有可遗传的变异来起作用，没有变异就无法进行自然选择。A选项说所有种群都能进行自然选择，忽略了遗传变异这个关键因素；B选项说无性繁殖的生物不发生自然选择，表述不准确，关键是有无遗传变异；C选项说种群会选择帮助适应新环境的性状，这不符合自然选择是对已有变异进行选择的原理。

Answer:

D. No, there is no genetic variation upon which natural selection can operate