BIO 101 Ch12 and Ch14 Evolution and Speciation

What is evolution?

A change in a populations genetics over time, driven by natural selection acting on existing variation plus chance.

What are the requirements for natural selection?

Variation in a trait, the trait is heritable, and some versions survive and reproduce more than others.

What is fitness?

How many offspring an individual leaves behind compared with others. It is about reproductive success, not strength.

What is adaptation?

A heritable trait that improves survival or reproduction in a particular environment.

Peppered moth example?

Dark moths survived better on soot-darkened trees because predators ate the light ones. Predators acted as the selecting force.

Do individuals evolve?

No. Populations evolve over generations. Individuals do not change their genes to adapt.

What is genetic drift?

Random change in allele frequencies, strongest in small populations. Chance, not selection.

What is gene flow?

Movement of alleles between populations when individuals migrate and breed.

What is the evidence for common ancestry?

Shared features across species, fossils, and similarities down to the molecular level such as DNA and the genetic code.

Homologous vs analogous structures?

Homologous structures share ancestry (human arm and whale flipper). Analogous structures have similar function but evolved separately (bird and insect wings).

What is a species?

Populations that interbreed and produce fertile offspring (biological species concept).

What is speciation?

When populations diverge enough that they no longer interbreed.

Allopatric vs sympatric speciation?

Allopatric: a geographic barrier splits a population. Sympatric: speciation happens in the same area.

What are reproductive barriers?

Prezygotic barriers stop mating or fertilization. Postzygotic barriers cause hybrids to be sterile or unfit.

How do bacterial species differ?

Speciation for bacteria looks more like environmental specialization than a sexual reproduction barrier.

What is a mass extinction?

A short period when a large share of species vanish. Survivors can diversify into open niches.

What was the Permian extinction?

The Great Dying, the largest mass extinction, which nearly erased life on Earth. Land life took much longer to recover than sea life.

What is adaptive radiation?

Rapid diversification of a lineage into many species filling different niches, often after an extinction or arrival on islands.

What does antibiotic resistance show?

Evolution by natural selection in action: resistant bacteria survive and come to dominate.

How do the island bird simulations work?

They show how selection on beak or trait variation over time can produce new species on islands.