Chapter 24

Question 1

What is the Biological Species Concept (BSC)?

Answer 1

Groups that actually or potentially interbreed and produce viable, fertile offspring and are reproductively isolated from other groups.

Question 2

What does ‘reproductively isolated’ mean?

Answer 2

Populations cannot successfully interbreed or produce fertile offspring.

Question 3

What is speciation?

Answer 3

The formation of new species through evolutionary divergence.

Question 4

How does speciation connect microevolution and macroevolution?

Answer 4

Microevolution changes allele frequencies; speciation turns those changes into new species (macroevolution).

Question 5

What is reproductive isolation?

Answer 5

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

Question 6

What is mechanical isolation?

Answer 6

Reproductive structures do not fit, preventing mating.

Question 7

What is temporal isolation?

Answer 7

Species breed at different times of day or year.

Question 8

What is behavioral isolation?

Answer 8

Differences in courtship behaviors prevent mating.

Question 9

What is habitat isolation?

Answer 9

Species live in different habitats and rarely encounter one another.

Question 10

What is gametic isolation?

Answer 10

Sperm and egg cannot fuse.

Question 11

What is hybrid inviability?

Answer 11

Hybrid embryos fail to develop or survive.

Question 12

What is reduced hybrid fertility?

Answer 12

Hybrids survive but are sterile.

Question 13

What is hybrid breakdown?

Answer 13

Later-generation hybrids become weak or abnormal.

Question 14

What is allopatric speciation?

Answer 14

Speciation caused by geographic isolation.

Question 15

What drives divergence in allopatric speciation?

Answer 15

Mutation, natural selection, and genetic drift.

Question 16

Examples of allopatric speciation?

Answer 16

Mosquitofish in isolated ponds; Darwin’s finches (adaptive radiation).

Question 17

What is sympatric speciation?

Answer 17

Speciation without geographic isolation.

Question 18

Mechanisms of sympatric speciation?

Answer 18

Polyploidy, local adaptation, sexual selection.

Question 19

What is polyploidy?

Answer 19

Having extra sets of chromosomes; common in plant speciation.

Question 20

Role of sexual selection in sympatric speciation?

Answer 20

Mate preferences split populations into different evolutionary paths.

Question 21

How does speciation affect biodiversity?

Answer 21

Increases biodiversity by adding new species.

Question 22

How does extinction affect biodiversity?

Answer 22

Decreases biodiversity by removing species.

Question 23

What determines overall biodiversity?

Answer 23

The balance between speciation and extinction rates.

Question 24

What is gradualism?

Answer 24

Slow, continuous evolution over long periods with many small genetic changes.

Question 25

What is punctuated equilibrium?

Answer 25

Long periods of stability interrupted by short bursts of rapid evolution.

Question 26

Which organisms speciate fastest?

Answer 26

Species with short generation times, such as microbes.

Question 27

What defines a species under BSC?

Answer 27

Reproductive compatibility, not physical appearance.

Question 28

What is required for speciation to occur?

Answer 28

Reduced or eliminated gene flow between populations.

Question 29

Allopatric vs. Sympatric (quick difference)

Answer 29

Allopatric = geographic barrier; Sympatric = no barrier.

Question 30

What do pre- and postzygotic barriers do?

Answer 30

Stop gene flow, allowing populations to diverge and form new species.