Unit 1c. Macroevolution

What is speciation?

The process by which one species splits into two or more species.

What is macroevolution?

Evolution above the species level.

Example of macroevolution?

Formation of mammals or flowering plants.

What is the biological species concept?

A species whose members can interbreed and produce viable, fertile offspring.

What keeps a species genetically together?

Gene flow between populations.

What is reproductive isolation?

Barriers that prevent interbreeding and fertile offspring.

What is a hybrid?

Offspring from mating between different species.

When can reproductive isolation act?

Before or after fertilization.

What is a prezygotic barrier?

A barrier that prevents fertilization.

What is habitat isolation?

Species live in different places.

What is temporal isolation?

Species reproduce at different times.

What is behavioral isolation?

Different courtship behaviors.

What is mechanical isolation?

Incompatible reproductive structures.

What is gametic isolation?

Sperm and egg cannot fuse.

What is a postzygotic barrier?

A barrier after fertilization.

What is reduced hybrid viability?

Hybrids do not survive well.

What is reduced hybrid fertility?

Hybrids survive but are sterile.

What is hybrid breakdown?

Later-generation hybrids are weak or sterile.

Why can't the biological species concept be used for fossils?

Cannot test interbreeding.

Why doesn't it work for asexual organisms?

They do not interbreed.

What does the biological species concept emphasize?

Lack of gene flow.

Can gene flow occur between distinct species?

Yes, sometimes.

What is the morphological species concept?

Defines species by physical traits.

What organisms does it apply to?

Sexual and asexual organisms.

What is the ecological species concept?

Defines species by ecological niche.

What does the ecological species concept emphasize?

Disruptive selection.

What is the phylogenetic species concept?

Smallest group sharing a common ancestor.

What is a limitation of the phylogenetic species concept?

Hard to define how different is "different enough."

What is allopatric speciation?

Speciation due to geographic isolation.

What causes divergence after isolation?

Mutation, natural selection, and genetic drift.

Where is allopatric speciation more common?

Areas with many geographic barriers.

How does distance affect reproductive isolation?

Isolation increases with distance.

Is physical separation always a biological barrier?

No.

What is sympatric speciation?

Speciation without geographic separation.

What is polyploidy?

Extra sets of chromosomes.

Polyploidy is most common in what organisms?

Plants.

Why is polyploidy important?

Can create a new species in one generation.

What is habitat differentiation?

Use of different ecological niches.

Example of habitat-based sympatric speciation?

North American maggot fly.

How can sexual selection cause speciation?

Preference for certain traits leads to isolation.

What is a hybrid zone?

Area where different species mate and produce hybrids.

Where do hybrid zones usually occur?

Narrow regions where species meet.

What is reinforcement?

Selection strengthens reproductive barriers.

What is fusion?

Species merge into one hybrid species.

What restricts gene flow in allopatric speciation?

Geographic isolation.

What processes create reproductive isolation?

Natural selection, genetic drift, and sexual selection.

What happens if species remain isolated long enough?

They cannot interbreed even if contact resumes.