chapter 24

What is speciation?

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

What does microevolution refer to?

Changes in allele frequency in a population over time.

What is macroevolution?

Broad patterns of evolutionary change above the species level.

How does speciation connect microevolution and macroevolution?

Speciation forms a conceptual bridge between microevolution and macroevolution.

What does the biological species concept emphasize?

Reproductive isolation among species.

What is the definition of a species according to the biological species concept?

A group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring.

What is reproductive isolation?

The existence of biological factors that impede two species from producing viable, fertile offspring.

What are hybrids?

Offspring that result from mating between different species.

What are prezygotic barriers?

Factors that prevent mating or fertilization between species.

What is gametic isolation?

When the sperm of one species may not be able to fertilize the eggs of another species.

What are postzygotic barriers?

Factors that prevent the hybrid zygote from developing into a viable, fertile adult.

What is reduced hybrid viability?

When genes of different parent species interact in ways that impair the hybrid's development or survival.

What is reduced hybrid fertility?

When meiosis fails to produce normal gametes, resulting in sterility in hybrids.

What is hybrid breakdown?

When first-generation hybrids are viable and fertile, but their offspring in the next generation are feeble or sterile.

What is a limitation of the biological species concept?

It cannot be applied to fossils or asexual organisms, including all prokaryotes.

What is allopatric speciation?

Speciation that occurs when a population is geographically isolated.

What is sympatric speciation?

Speciation that occurs in populations that live in the same geographic area.

What is polyploidy?

The presence of extra sets of chromosomes due to accidents during cell division.

What is an autopolyploid?

An individual with more than two chromosome sets derived from a single species.

How can sympatric speciation occur?

Through factors like polyploidy, sexual selection, and habitat differentiation.

What role does gene flow play in speciation?

Gene flow between populations holds a species together genetically.

What is the ecological species concept?

Defines a species in terms of its ecological niche and emphasizes the role of disruptive selection.

What is the morphological species concept?

Defines a species by structural features and applies to both sexual and asexual species.

What is an example of hybridization between distinct species?

Grizzly bears and polar bears can mate to produce 'grolar bears'.

What is the significance of the Isthmus of Panama in speciation?

It caused the divergence of sister species of snapping shrimp 3 to 9 million years ago.

What is an allopolyploid?

A species with multiple sets of chromosomes derived from different species.

Can allopolyploids interbreed with parent species?

No, allopolyploids can successfully mate with each other but cannot interbreed with either parent species.

What is the chromosome number of a diploid cell from species A if it is 2n = 6?

6 chromosomes.

What happens to a hybrid plant cell if there is a mitotic or meiotic error?

The chromosome number doubles, resulting in a viable, fertile hybrid (allopolyploid).

Name two important crops that are polyploids.

Oats and wheat.

How can plant geneticists produce new polyploid agricultural species?

By using chemicals to induce errors in cell division.

What role does sexual selection play in speciation?

It can drive sympatric speciation by favoring mates of different colors.

What is habitat differentiation in the context of sympatric speciation?

It results from the appearance of new ecological niches, allowing populations to exploit different resources.

What is a hybrid zone?

A region where members of different species mate and produce hybrids.

What can cause the relocation of existing hybrid zones?

Changes in environmental conditions.

What are the three possible outcomes if hybrids do not become reproductively isolated?

Reinforcement, fusion, and stability.

What is reinforcement in the context of hybridization?

Strengthening reproductive barriers when hybrids are less fit than parent species.

What occurs during fusion in hybridization?

Reproductive barriers weaken, and parent species can fuse into a single species if hybrids are as fit as parents.

What does stability refer to in hybrid zones?

Continued formation of hybrid individuals due to extensive gene flow from outside the hybrid zone.

What is punctuated equilibria?

A model describing periods of apparent stasis in species punctuated by sudden changes.

How can the rate of speciation be studied?

Using the fossil record, morphological data, or molecular data.

What is the significance of the sunflower Helianthus anomalus?

It was formed by hybridization followed by rapid speciation.

What is the difference between punctuated equilibrium and gradual change?

Punctuated equilibrium involves sudden changes after long periods of stasis, while gradual change is a slow, continuous process.