D 4.1 natural selection

What is natural selection?

Process where individuals with advantageous heritable traits survive and reproduce more.

What causes intraspecific competition?

Limited resources (food, water, space, light) within a species.

What is overproduction of offspring?

Organisms produce more offspring than the environment can support.

What causes variation?

Mutation + sexual reproduction.

What is “survival of the fittest”?

Individuals better adapted survive longer and reproduce more.

What leads to evolutionary change?

Heritable traits that increase survival become more common in populations.

What are selection pressures?

Environmental factors determining which traits enhance survival.

Examples of abiotic selection pressures?

Temperature, drought.

Examples of biotic selection pressures?

Competition for food, predation.

What is sexual selection?

Choosing mates with advantageous traits to increase offspring success.

What happened to guppies with no predators?

Males evolved bright colors (sexual selection).

What happened to guppies with predators?

Males evolved dull colors (natural selection).

What did Endler’s experiment show?

Different selection pressures change allele frequencies.

What is an allele?

A heritable variant of a gene.

What is a gene pool?

All alleles in a population.

Why do isolated populations evolve differently?

Different selective pressures change allele frequencies.

What is stabilizing selection?

 favors average traits instead of extreme traits

Example of stabilizing selection?

Human birth weight — extremes have higher mortality.

What is disruptive selection?

Favors extreme traits over average traits.

Example of disruptive selection?

Coho salmon — small and large males succeed; medium males fail.

What is directional selection?

Favors one extreme → shifts population traits over time.

Example of directional selection?

Gough Island mice evolved larger body size.

What does Hardy–Weinberg describe?

Conditions where allele frequencies remain constant (no evolution).

What is artificial selection?

: Humans deliberately breed organisms for desirable traits.

How does artificial selection differ from natural selection?

 because its human directed whereas natural selection is driven by environmental pressures 

Why can artificial selection cause rapid evolution?

Humans choose traits intensely and consistently.

Why do less‑adapted variants have lower survival?

Higher mortality from predation or environmental stress.

What must traits be for natural selection to act on them?

Heritable.

What increases reproductive success?

Traits that improve survival or mate attraction.

What does natural selection ultimately change?

Allele frequencies in a population over generations.