Speciation

Question 1

What is speciation?

Answer 1

The origin of new species; the key point where microevolution and macroevolution intersect.

Question 2

How many species have been described?

Answer 2

2-3 million species are known to science.

Question 3

How many species are estimated to exist?

Answer 3

5-100 million

Question 4

What does it mean for members of a biological species to be reproductively compatible?

Answer 4

They cannot interbreed with other populations.

Question 5

What is the critical issue of reproductive isolation?

Answer 5

The reduction of gene flow between populations so that populations can diverge in allele frequencies (by genetic drift or by natural selection) and become reproductively isolated.

Question 6

What is reproductive isolation?

Answer 6

The existence of biological factors (barriers) that impede two species from producing viable, fertile hybrids.

Question 7

What does the biological species concept define species as?

Answer 7

Species are groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups.

Question 8

How does temporal or habitat isolation work?

Answer 8

Potential mates do not meet, thus causing reproductive isolation.

Question 9

How does ethological, behavioral, or sexual isolation work?

Answer 9

Potential mates meet but do not mate.

Question 10

How does mechanical isolation work?

Answer 10

Copulation occurs, but there is no gamete transfer.

Question 11

How does incompatibility work?

Answer 11

Gametes are transferred, but there is no fertilization.

Question 12

How does hybrid inviability work?

Answer 12

Fertilization occurs, but F1 hybrid has reduced viability.

Question 13

How does hybrid sterility work?

Answer 13

The F1 hybrid is viable but has reduced fertility.

Question 14

How does hybrid breakdown work?

Answer 14

There is reduced viability/fertility in F2 or backcross hybrids.

Question 15

Which barriers are premating?

Answer 15

1. Temporal or habitat isolation
2. Ethological, behavioral, or sexual isolation

Question 16

Which five barriers are postmating?

Answer 16

1. Mechanical isolation
2. Incompatibility
3. Hybrid inviability
4. Hybrid sterility
5. Hybrid breakdown

Question 17

Which barriers are prezygotic (prevents zygotes from forming)?

Answer 17

1. Temporal or habitat isolation
2. Ethological, behavioral, or sexual isolation
3. Mechanical isolation
4. Incompatibility

Question 18

Which barriers are postzygotic?

Answer 18

1. Hybrid inviability
2. Hybrid sterility
3. Hybrid breakdown

Question 19

What are the limitations of the biological species concept?

Answer 19

1. Cannot be applied to fossils.
2. Cannot be applied to asexual organisms.
3. Some organisms are morphologically and ecologically distinct, yet interbreed.

Question 20

How does the morphological species concept characterize species?

Answer 20

Characterizes species by body shape and other structural features.

Question 21

How does the ecological species concept characterize species?

Answer 21

In terms of their ecological niches.

Question 22

How does the phylogenetic species concept characterize species?

Answer 22

Defines a species as the smallest group of individuals that share a common ancestor, forming one branch of the tree of life.

Question 23

What happens in allopatric speciation?

Answer 23

A population forms a new species while geographically isolated from its parent population.

Question 24

What happens in sympatric speciation?

Answer 24

A subset of a population forms a new species without geographic separation.

Question 25

What is the difference between dispersal and vicariance allopatric speciation?

Answer 25

In dispersal, organisms move to a separated land mass or area that already existed. In vicariance, some physical barrier arrives that separates the preexisting population.

Question 26

What three things can cause sympatric speciation?

Answer 26

1. Habitat differentiation
2. Polyploidy
3. Sexual selection

Question 27

What happens in autopolyploidy?

Answer 27

Some error occurs in cell division that results in polyploidy (having 4n chromosomes, for example). The gametes that form, when they recombine, may form a new species.

Question 28

What is the difference between autopolyploidy and allopolyploidy?

Answer 28

In autopolyploidy, both chromosome sets are derived from the same species. In allopolyploidy, the chromosome sets are derived from different species.