Question 1

Why does natural selection not create a beak because birds need it?

Accepted Answer

Selection acts on genetic variation that already exists in a population. A drought or seed shortage can change which variants are favoured, but it cannot generate a needed beak in an individual.

Question 2

How do hard and soft seeds favour different finch beaks?

Accepted Answer

Deep, strong beaks can process hard and large seeds more effectively, whereas shallow beaks may be better suited to softer or smaller seeds. The favoured phenotype depends on the resources available in that environment.

Question 3

What does fitness mean in natural selection?

Accepted Answer

Fitness means relative reproductive success: how effectively an individual contributes heritable traits to the next generation. It does not necessarily mean greater body size, physical dominance, strength or lifespan.

Question 4

What is the difference between stabilising, disruptive and directional selection?

Accepted Answer

Stabilising selection favours intermediate phenotypes, disruptive selection favours both extremes at the expense of intermediates, and directional selection favours one extreme. The environment determines which pattern is operating.

Question 5

How do gene flow and genetic drift change a population?

Accepted Answer

Gene flow changes allele frequencies when migrants move alleles into or out of a population. Genetic drift changes allele frequencies through chance sampling and has a stronger effect in small populations.

Natural Selection — How Finch Beak Frequencies Shift

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