Scientists studied the effects of a drought on a population of seed-eating finches living on an island in the Galapagos. They assessed beak depth data prior to the drought, collected in 1976, and compared it to beak depth data recorded after the drought in 1978. Their results are shown in Figure 1 below.
Which of the following is the most likely explanation for the results shown in Figure 1?
Finches with the mean beak depth in 1976 had the greatest reproductive fitness after the period of drought.
Plants that produced smaller seeds were killed by the drought, changing the favorable beak phenotype.
The finch population in 1976 had little phenotypic variation, limiting the rate of natural selection.
The drought caused a mutation in the gene for beak length in finches, resulting in a new favorable phenotype.
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