macroevolution

What is natural selection?

A mechanism of evolution where organisms with traits that improve survival and reproduction pass those traits to the next generation.

What are the key components of natural selection?

Variation exists, some traits are heritable, more offspring are produced than can survive, and traits that improve survival or reproduction become more common.

What are the three types of natural selection?

Stabilizing selection, directional selection, and disruptive selection.

What is microevolution?

Small evolutionary changes within a population across generations caused by mutation, gene flow, non-random mating, genetic drift, and natural selection.

Do individuals evolve?

No. Populations evolve over time.

What is macroevolution?

Large-scale evolutionary changes over long periods of time that result in new species and major changes in life on Earth.

What is speciation?

The formation of new and distinct species through evolution.

What is adaptive radiation?

Rapid diversification of one ancestral species into many species adapted to different environments.

How does continental drift affect evolution?

Movement of continents causes geographic isolation and climate changes that promote speciation.

What defines a species under the biological species concept?

Members can interbreed and produce fertile offspring and are reproductively isolated from other species.

What is reproductive isolation?

Mechanisms that prevent gene flow between species.

What is allopatric speciation?

Speciation that occurs when populations are geographically isolated and evolve separately.

What is sympatric speciation?

Speciation that occurs without geographic isolation, often due to genetic or behavioral changes.

What are prezygotic barriers?

Barriers that prevent mating or fertilization (habitat, temporal, behavioral, mechanical, gametic isolation).

What are postzygotic barriers?

Barriers that occur after fertilization, resulting in weak, infertile, or nonviable offspring.

Why are mules infertile?

They inherit incompatible chromosome numbers from horses and donkeys

Why are Darwin’s finches an example of adaptive radiation?

Each species evolved different beak shapes to eat different foods and no longer interbreed.

What is the gradualistic model of evolution?

Evolution occurs slowly and continuously over long periods of time.

What is punctuated equilibrium?

Long periods of little change interrupted by short bursts of rapid speciation.

What is a mass extinction?

The disappearance of a large number of species in a short period of time.

What factors contribute to mass extinctions?

Continental drift, meteor impacts, volcanic activity, and climate change.

Name two major mass extinctions.

End-Cretaceous (dinosaurs) and Permian-Triassic (largest extinction).

Is a sixth mass extinction occurring?

Scientists believe a human-caused mass extinction may be underway due to high extinction rates and climate change.

What happens after mass extinctions?

Ecosystems change, diversity takes millions of years to recover, and adaptive radiations often occur.

What are evolutionary innovations?

New traits that open new ecological niches and lead to diversification (e.g., multicellularity, flight).

Why is macroevolution important?

It explains the origin of new species, biodiversity, and major changes in life over Earth’s history.