Paragraph one: Here’s another way of looking at the effect of differences betwee

Paragraph one:
Here’s another way of looking at the effect of differences between males and females on the probability that their putative offspring are truly their genetic offspring. If a female lays a fertilized egg or gives birth to a baby, this offspring will definitely have 50 percent of her genes. In contrast, a male that mated with this female may or may not be the father of that offspring. Thus, the argument goes, males have less to gain by parental behavior, and this tilts the equation in favor of nonpaternal males that seek out multiple partners rather than limiting themselves to caring for the offspring of one or a few mates. But let’s check the logic of this argument by imagining a hypothetical species in which males have a fairly low probability of siring the offspring of any given mate—say, a 40 percent chance.
Further, imagine that there are two hereditarily different male phenotypes in the population, a paternal type and a nonpaternal type. The average paternal male mates with two females (each with an average of 10 eggs), whereas the average nonpaternal male mates with five females (which enables him to fertilize a proportion of 50 eggs). In addition, let’s say that the paternal male boosts the survival chances of the eggs under his care to 50 percent versus 10 percent for the unprotected offspring of nonpaternal males.
Which behavior is adaptive here? Show your math. What point does this example make about the evolution of male parental care?
Paragraph two:
Birds are not the only animals in which intense, and sometimes fatal, sibling conflicts are known to occur. For example, spotted hyena females often give birth to twins, and the pups compete aggressively for their mother’s milk. The battles between pups sometimes lead to the death of one of the twins. Let’s say that you want to test the proposition that these cases of occasional siblicide are adaptive.
Develop one or more hypotheses and then make use of the following findings:
the total input from mothers to pairs of offspring in which siblicide eventually occurs is lower than from mothers to twins that do not commit siblicide,
females do not reduce the amount they provide after siblicide has occurred,
siblicide is more common when females have to travel great distances in search of prey, and
females sometimes separate fighting twins and may preferentially nurse the subordinate cub.