AP Biology Ch. 24 The Origin of Species

What is speciation?

The origin of new species.

What must evolutionary theory explain?

How new species originate and how populations evolve.

What is microevolution?

Evolutionary change within a population (changes in allele frequencies).

What is macroevolution?

Evolutionary change above the species level.

What is the biological species concept?

A species is a group of populations whose members can interbreed and produce viable, fertile offspring.

What is reproductive isolation?

Biological barriers that prevent different species from producing viable, fertile offspring.

What is a hybrid?

Offspring from the mating of two different species.

What are the two types of reproductive barriers?

Prezygotic and postzygotic barriers.

What do prezygotic barriers do?

Prevent mating or fertilization.

What is habitat isolation?

Species live in different habitats and rarely encounter each other.

What is temporal isolation?

Species breed at different times.

What is behavioral isolation?

Differences in courtship or mating behaviors prevent reproduction.

What is mechanical isolation?

Physical differences prevent mating.

What is gametic isolation?

Sperm and egg cannot fuse.

What do postzygotic barriers do?

Prevent hybrid offspring from surviving or reproducing.

What is reduced hybrid viability?

Hybrid offspring are weak or do not survive.

What is reduced hybrid fertility?

Hybrid offspring are sterile.

What is hybrid breakdown?

Hybrid offspring are viable but weak or sterile in future generations.

Why is the biological species concept limited?

It cannot be applied to fossils or asexual organisms.

What is the morphological species concept?

Defines species based on physical traits.

What is the ecological species concept?

Defines species by their ecological niche.

What is the phylogenetic species concept?

Defines species as the smallest group on a phylogenetic tree.

What are the two main types of speciation?

Allopatric and sympatric speciation.

What is allopatric speciation?

Speciation due to geographic separation.

What happens to gene flow in allopatric speciation?

It is reduced or interrupted.

What processes drive divergence in isolated populations?

Natural selection, genetic drift, and mutation.

What is sympatric speciation?

Speciation without geographic separation.

What is polyploidy?

Having more than two complete sets of chromosomes.

What is an autopolyploid?

An individual with extra chromosome sets from one species.

What is an allopolyploid?

An organism with chromosome sets from different species.

Why is polyploidy important?

It can cause instant reproductive isolation (common in plants).

What other factors can cause sympatric speciation?

Habitat differentiation and sexual selection.

What is a hybrid zone?

A region where two species meet and produce hybrids.

What is reinforcement?

Strengthening of reproductive barriers.

What is fusion?

Weakening of barriers leading to one species.

What is stability in hybrid zones?

Continued production of hybrids over time.

What is gradualism?

Slow, continuous evolutionary change.

What is punctuated equilibrium?

Long periods of little change interrupted by rapid evolution.

Who proposed punctuated equilibrium?

Niles Eldredge and Stephen Jay Gould.

What is macroevolution the result of?

Many speciation and extinction events.

How many genes may be involved in speciation?

It can involve one gene or many genes