Chapter 8 Flashcards
How does the Red Queen hypothesis help us understand the fitness benefits of sexual reproduction?
The Red Queen Hypothesis states that sexual reproduction can increase resistance to parasites. In the roundworm (Caenorhabditis elegans), for example, researchers raised populations in the laboratory that reproduce either sexually or asexually. Then they exposed the two different types of worm populations to a bacterial parasite and observed the survival of the populations over 30 generations.
The hypothesis that sexual reproduction allows hosts to evolve at a rate that can counter the rapid evolution of parasites.
Freshwater snails exhibit both sexual and asexual reproduction. Why might natural selection favor such a mixed breeding strategy?
Natural selection might favor this strategy due to an abundance in parasites. The snail’s mode reproduction depends on the depth of water in which it lives. In the shallower regions of a lake, where a parasitic worm is more common, a higher proportion of the snails use sexual reproduction. These snails continue to evolve resistance to the parasite to avoid getting sterile. In deeper regions, where the parasite is rare, a higher proportion of the snails use asexual reproduction.
Given that self-fertilization leads to inbreeding depression, under what conditions should a hermaphrodite use self- fertilization?
Although self-fertilization may result in lower fitness than breeding with a mate, low fitness is better than the zero fitness the organism would obtain by avoiding self-fertilization altogether. Self-fertilizing will not provide as many viable offspring as outcrossing, but it might be better than not reproducing at all.
What strategies do monoecious plants use to avoid possible negative effects of inbreeding?
Self incompatibility genes meaning if an organism can produce both sperm and egg, they cant cause germination.
Monoecious species have self-incompatibility genes. Individuals with the same self-incompatibility genotype— including an individual mating with itself—cannot produce offspring.
In addition to affecting sex ratios, what other traits might be affected by the artificial selection caused by intense fishing?
Time of sexual maturation, size of mature fish, the fecundity ability (ability to produce many offspring
Turtle embryos incubated at lower temperatures typically produce males, whereas those incubated at higher temperatures produce females. In the face of global warming, how might turtles evolve to change their egg- laying behavior to maintain an even sex ratio?
They might change the materials used for the nest, turtles hatch on the beach, maybe grain size they lay the eggs will change depending how much heat the grain size holds?
Compare and contrast monogamy, polygyny, polyandry, and promiscuity
In monogamous systems, one male and one female are paired for at least one breeding season.
Polygamy refers to either one male mating with multiple females or one female mates with many males. When one male mating with multiple females, called polygyny (“many females”), the female takes responsibility for most of the parental care as the single male is not capable of providing care to that many offspring.
polyandry (“many males”), where one female mates with multiple males. Polyandry very rare because it involves sex role reversal, where females invest less in offspring while males invest more.
Promiscuous mating systems occur when females mate with multiple males, and males mate with multiple females.
Explain how extra-pair copulation has favored the evolution of mate guarding
it has led to evolution of mate guarding since the original male mate’s fitness declines due to their inability to satisfy the female in maintaining monogamy. Since the original males don’t benefit if their female mates breed with other males that might have superior genes and stronger immunity than them, they try to prevent extra-pair copulations to prevent mates from defecting to rival males, a great defensive strategy for the males.
Why might exaggerated secondary sexual characteristics in males demonstrate a superior genotype to females?
The more exaggerated the traits the more likely itll be for a female to think he has a stronger immune system and want to mate with him
How might genetic resistance against parasites be exhibited by males in ways to allow female selection?
Females will think he has resistance to parasites and want to mate with male cuz they think he has a stronger immune system and want to mate with him. Because parasites and pathogens can impair the production of secondary sex characteristics, a male bird that has an elaborate and showy plumage might communicate to females that because he has the energy to build elaborate feathers, he can resist parasites and pathogens.
