Question

Male redback spiders present themselves for consumption to female redback spiders after they have mated with the female spiders. Female spiders eat the male spiders resulting in sexual cannibalism. What is the best way to characterize the evolutionary changes in redback spider behavior that occur over time due to natural selection?

Group of answer choices:

a) The proportion of redback spiders that performed sexual cannibalism increased in a population over time.

b) Environments where food is scarce cause specific mutations for sexual cannibalism to occur in individual redback spiders.

c) A mutation resulting in sexual cannibalism occurred to meet the changing needs of the redback spider.

d) Individuals in the redback spider population increasingly perform sexual cannibalism over their lifetime.

Answer 1

Evolution by natural selection occurs when organisms with favorable traits reproduce more, thus increasing the frequency of that trait in a population gradually over time.All known red spiders perform sexual cannibalism because the proportion of redback spiders that performed sexual cannibalism increased in a population over time owing to certain fitness value provided by that behavioral trait.Therefore option a) is the right answer.

Option b) and c) are wrong because natural selection directly acts on phenotype and not on genotype.Also it is not likely that a single mutation can result in a complex behavioral trait like cannibalism in an individual.

Option d) is wrong because it does not clearly mention the increase in frequency of spiders performing sexual cannibalism in a population over a long period of time.One generation of spiders performing cannibalism in their lifetime is not enough to cause evolution by natural selection.