D | Question 47 1.67 pts Case Study Darwin\'s Finches In 1977 the Galapagos had
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D | Question 47 1.67 pts Case Study Darwin's Finches In 1977 the Galapagos had abnormally low rainfall and the seed plants on which the medium ground finch, Geospiza fortis, depend produced small crops. Only 15% of the population survived the drought, and the survivors were the mostly large birds with strong beaks, because they were able to crack large seeds. The population as a whole was shifted The level of selection measured in the drought and the drastic population crash was the highest yet recorded in a vertebrate population. However, a few years later there was a particularly wet year, and enormous quantities of seeds were produced. The finches had multiple broods that year, and smaller individuals, having great numbers of small seeds available, and reaching maturity faster,raised more offspring The effect of the wet year was to shift the average body size back toward smaller size. Similar major fluctuations in climate and food supply occur on approximately a 20-year spacing in the Galapagos as El Nino and La Niña perturbs the local climate, producing dry and wet years Peter and Rosemary Grant observed the beak size of the Galapagos Finches over a few years. They noted that the average beak size in some years increased and in other years decreased signitficantly as the availability of large and small seeds changed overtime. What could expliain these changes in beak size Females change their preference for males with large beaks to males with small beaks Finches with small beaks cannot secure enough food and do not reproduce The environment changes and favors different beak sines every time Finches from other islands wene immigrating into the population Genetic drift is randomly changing the genetic composition of the population Next . 2 3 6 8Explanation / Answer
47)The environment changes and favors different beak size every time.
Extreme weather is therefore a “selection event,” a time when not every bird is equipped to survive The birds that survive are best equipped for those extreme conditions. When the conditions improve the bird that survived the hard time is not necessarily best equipped for the good times.
48) Yes because the population is getting smaller.
Since they're bottlenecked, genetic drift is occurring there, and there's also continuing selection for "island feeders." Which can feed on the seeds produced on island.
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