Two distinctly different beak sizes occur in a single...

Two distinctly different beak sizes occur in a single population of finch called the black-bellied seedcracker. These birds live in an isolated region in West Africa. The oldest inhabitants of the region remember that all these finches used to have the same length beak. This change in the population is shown by this graph. The best explanation for the change in beak length is (A) mutation (B) stabilizing selection (C) convergent evolution (D) genetic drift (E) diversifying selection

Two distinctly different beak sizes occur in a single population of finch called the black-bellied seedcracker. These birds live in an isolated region in West Africa. The oldest inhabitants of the region remember that all these finches used to have the same length beak. This change in the population is shown by this graph. The best explanation for the change in beak length is
(A) mutation
(B) stabilizing selection
(C) convergent evolution
(D) genetic drift
(E) diversifying selection

Key Concepts

Genetic Drift

Genetic drift refers to random fluctuations in allele frequencies within a population, which can lead to significant changes in traits over time, especially in small populations. Unlike natural selection, genetic drift is not driven by differences in fitness.

Natural Selection

Natural selection is the process by which environments favor individuals with certain heritable traits over others, leading to changes in the trait distribution within a population. It serves as a fundamental mechanism of evolution, guiding the adaptation of species over time.

Disruptive (Diversifying) Selection

Disruptive, or diversifying, selection is a type of natural selection that favors individuals with extreme values of a trait over those with intermediate values. This mechanism can lead to a bimodal distribution of traits in a population and is often responsible for the development of distinct subgroups.

Mutation

Mutation is a random change in the DNA sequence that introduces new genetic variation into a population. It is the source of many novel traits and forms the raw material upon which natural selection and other evolutionary processes act.

Stabilizing Selection

Stabilizing selection is a form of natural selection that favors intermediate variants by selecting against extreme phenotypes. This process reduces trait variation within a population and maintains the status quo of the prevailing phenotype.

Convergent Evolution

Convergent evolution is the process by which unrelated or distantly related organisms independently evolve similar traits as a result of having to adapt to similar environments or ecological challenges. This phenomenon illustrates how similar environmental pressures can shape similar adaptations in different lineages.

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