Natural selection requires genetic variation, competition for limited resources, overproduction of offspring, and unequal reproductive success. Which requirement does the following sentence represent? A subset of finches that have large beaks is contained within a population of finches that mostly have small beaks.

genetic variation

competition for limited resources

overproduction of offspring

unequal reproductive success

answer

watching

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Reid WolffLv2

3 May 2019

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A population of finches lives on an island some distance from the mainland, where another population of finches of the same species resides. In both populations, the size of the birds' beaks is influenced by two alleles at the beak locus, B and b. Finches with the BB genotype have the largest beaks, bb have the smallest beaks, and Bb individuals have a beak size intermediate between the two homozygotes. On the island, the frequency of the B allele is 0.3, and the frequency of the b allele is 0.7. On the mainland, both alleles are equally frequent (0.5).

(a) If the migration rate from the mainland to the island is 0.1 (meaning that 10% of individuals in the island population migrate in from the mainland every generation), what is the change in the frequency of the B allele on the island in one generation due to migration? Assume there is no migration from the island back to the mainland.

(b) The genotypes at the beak locus have the following fitness on the island: w_BB = 0.95, w_Bb = 0.98, w_bb = 1. Which allele is the most fit? What size beak is selectively favored on the island? What do you predict will happen to the frequencies of these alleles in the long term?

(c) The island experiences a severe drought for two consecutive years, which kills a plant species on the island that makes small seeds eaten by the finches. As a consequence, the food available decreases and the average size of edible seeds on the island increases greatly. Birds with large beaks are much better able to crack large seeds and thus better able to survive the drought. Which allele is the most fit? How do you predict the allele frequencies of B and b will change during this drought?

Describe the requirements for natural selection and the process of evolution, using antibiotic resistance in bacteria as an example. In your response, address the following questions: Where does genetic variation come from? How have humans introduced an environment that selects for resistance? How do antibiotics introduce a difference in reproductive success among the bacteria?

Which statement about evolution by natural selection isfalse?

Natural selection allows organisms with higher fitness toreproduce more successfully.

Natural selection favors those traits that confer higherfitness in the environment.

Natural selection is a random change in characteristics of apopulation over generations.

Evolution by natural selection affects populations oforganisms, not individual organisms.

An organism's fitness depends on its _____.

ability to survive and reproduce

ability to swap genetic material with other organisms

physical size

ability to mutate

population

Consider the heavily armored stickleback fish population thatcolonized the lake. If all the individuals in that population weregenetically identical, what do you predict would happen when theycolonized the freshwater lake?

The population would increase, as it has increased foodresources.

The population would evolve through natural selection to bebetter adapted to its environment.

The population would decrease due to more juvenile fish beingeaten.

No answer text provided.

Which of the following are adaptations?

Thicker beaks on finches that allows them to eat large seeds,when large seeds are the most abundant.

Less armor on stickleback fish in freshwater that allows themto grow faster to avoid predation.

More armor on stickleback fish in the ocean that prevents themfrom being eaten by larger predators.

None of the above.

All of the above.