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Chapter 9 questions
1. Cheetahs have been hunting gazelles in the savannahs of Africa for hundreds of thousands of years. Over time both gazellesand cheetahshave incrementally increased their speed. Explain a reason this may be occurring. What hypothesis could explain this phenomenon?
2. A downside of self-fertilizing in hermaphrodites is inbreeding depression. How does inbreeding depression impair fitness?
3. Consider a pathogen that infects a species of tree. Over many decades, how might the presence of the pathogen influence the proportion of individuals in the tree population that reproduce by self-fertilization (asexually) versus the proportion that reproduce by outcrossing (sexually)? Why?
4. What characteristics in a species are associated with monogamy? What kinds of animals have a high percentage of species utilizing a monogamous mating strategy? Are these species truly monogamous?
5. When researchers experimentally altered tail lengths of male widowbirds (Euplectes progne), they found that females chose males with longer tails even when tail length did not correlate with any tangible benefit to a male’s ability to defend territory. What are two possible reasons that females prefer longer tails?
6. You discover a new species of wasp with females that lay their eggs inside tree branches which protect their eggs from predators. After the eggs hatch, only the females possess the mouthparts needed to chew through the wood and escape. All of the males die in the nest. The young females must obtain the strength necessary for eating their way out of the branch by eating spermatophores (small packets containing sperm and nutrients) that each male releases in the nest. These spermatophores also fertilize the females. Once a male releases his spermatophore, he dies. The more spermatophores a female eats, the more likely it is that she will escape the nest.
In this wasp species, would you predict a sex ratio bias? Explain. Would this mating system be classified as promiscuity, polygyny, polyandry, or monogamy?
Chapter 10 questions
7. You discover a small reef fish species in the Great Barrier Reef off the Australian coast. You study its ecology and discover that many midsized and large predatory fish consume the new species. Further, you find that this species consumes the same prey as many other species of similar-sized fish. However, many of those other small species tend to live in large schools, whereas individuals of this newlydiscovered species live alone. Propose proximate and ultimate causes for this behavior.
8. What is a lek? How is it beneficial?
9. Why would evolution favor a social structure that relies on dominance hierarchies rather than individual territories?
10. Why would an individual in a social group of a diploid species help to rear the young of its siblings rather than reproducing itself? Describe the expected relative importance of direct and indirect fitness benefits and explain your answer.
11. What is eusociality? What evidence is therethat eusociality likely evolved independently at least several times?
12. Why does natural selection not favor spiteful behavior?