Bios 101, Problem Set 3 Please type these on separate sheets of paper. They are due in discussion. It is imperative that none of your answers have been copied directly from another student or from an outside source. 1). Green swordtails are sexually dimorphic: males have a long, swordlike projection from their tails, and females have rounded tails. In choice experiments, female swordtails greatly prefer males with elongated tails to males with tails of normal length. An experimenter decides to perform an experiment on a closely related species, a molly, in which males and females are not sexually dimorphic for tail size and shape. He glues artificial tails to half of his male subjects, and leaves the others alone. a) (one point) Describe what he should do next. b) (one point) Imagine that this experiment was conduced, and females has a strong preference for augmented males. Why might this be the case? 2). A population of Anopheles mosquitoes reaches very high densities, and is subjected to aerial spraying by DDT. The following six years, the mosquitoes are not observed at all, but the population was sprayed “just in case”. An outbreak occurs sevem years later, however, and this time, the aerial spraying with DDT is much less effective. Laboratory tests indicate that these mosquitoes are resistant to DDT, avoiding surfaces coated with it. It also seems that they have a reduced growth rate and lower fertility than mosquitoes from previous years. Field ecologists report that virtually every predatory insect has been eliminated from the regions sprayed with DDT. a) (one point) What type of evolutionary event has occurred here? What was the likely mechanism for the change in the mosquito population? b) (one point) What recommendations would you make as a mosquito control strategy for the future. 3. (one point) Research at least one study attempting to document and measure natural selection. What was the organism? What type of selection was involved? Was natural selection observed or demonstrated? Cite your source. 4. (one point) In terms of sexual selection, under what conditions would you expect female choice to be the strongest? Under what conditions would you expect males to be choosy in selecting a mating partner? Can you find an example of the latter phenomenon? Research online.5. (one point) The mutation rate to a lethal, recessive genetic illness is 10-14. Individuals die before they get a chance to reproduce. Under mutation-selection balance, what is the equilibrium frequency of the heterozygous genotype? Imagine it was discovered that, in a population of Icelanders, the frequency of this allele was .01. Come up with a likely explanation for the high frequency of the allele. 6. Several species of orchid bee live in a neotropical forest. Their habitats and ranges overlap. The species never interbreed because the male bees visit different types of orchids, and harvest different oils from these plants, thus, attracting females of their own species. An experimenter decides to play a trick on these two species of bees, by creating fake orchids with the oil glands filled with compounds from the species of orchid that the males do not normally visit. He discovers that the bees that visit these “trick” orchids attract female bees of the wrong species, and mate with them. The resulting offspring are hybrids between the two species. Female hybrids have trouble finding a mate, and males have trouble deciding which orchid to visit, and fitness of these hybrids is quite low. a) (one point) Go online and look up orchid bees. List at least three species and describe their biology. b) (one point) In this fictional example, what type of isolation mechanism is involved? 7. (one point) Go online or use whatever resources you have available to you and look up five species that have gone extinct in the last two centuries or so. List the causes, and for each one, list what measures could have been done to prevent the
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