Ch.24: Speciation

Question 1

Speciation

Answer 1

• evolution of two or more distinct species from a single ancestral species
• results from genetic isolation and genetic divergence
• genetic isolation results from lack of gene flow
• genetic divergence results from selection, genetic drift, and mutations occurring independently in the isolated populations

Question 2

Species

Answer 2

evolutionary independent population or groups of populations

Question 3

four criteria in which species can be identified

Answer 3

the biological species concept; the morphospecies concept; the ecological species concept; and the phylogenetic species concept

Question 4

What is the key criteria to identifying a species according to the biological species concept?

Answer 4

reproductive isolation

Question 5

What are the two mechanisms of reproductive isolation?

Answer 5

pre-zygotic isolation (temporal, habitual, behavioural, mechanical, and gametic barrier) and post-zygotic isolation (hybrid sterility and hybrid viability)

Question 6

Temporal

Answer 6

populations are isolated because they breed at different times

Question 7

Habitaul

Answer 7

populations are isolated because they breed in different habitats

Question 8

Behavioural

Answer 8

populations are isolated because they differ by courtship displays

Question 9

Mechanical

Answer 9

populations are isolated because male and female reproductive structures are incompatible

Question 10

Gametic barrier

Answer 10

populations are isolated because eggs and sperms are incompatible

Question 11

Hybrid sterility

Answer 11

hybrid offspring mature but are sterile as adults

Question 12

Hybrid viability

Answer 12

hybrid offspring do not develop normally and die as embryos

Question 13

disadvantages of biological species concept

Answer 13

• the criteria of reproductive isolation cannot be applied in fossils or asexual species
• hard to apply to closely related populations that do not overlap geographically

Question 14

Hybrid breakdown

Answer 14

• hybrids are viable and fertile but their offspring is feeble and sterile

Question 15

What is the key criteria to identifying species based on the morphospecies concept?

Answer 15

differences in size, shape or other morphological features

Question 16

disadvantages of morphospecies concept

Answer 16

• cannot identify cryptic species
• may lead to naming two or more species when there is actually one polymorphic species with differing phenotypes
• morphological features are subjective

Question 17

what is the key criteria to identifying species based on the ecological species concept?

Answer 17

emphasizes on the role of natural selection

Question 18

what is the key criteria to identifying species based on the phylogenetic species concept?

Answer 18

identifies species based on evolutionary history

species is the smallest monophyletic group on the tree of life

Question 19

How are monophyletic groups identified?

Answer 19

by synamorphies

Question 20

Synamorphy

Answer 20

homologous trait that is found in a certain group of organisms and their common ancestor, but is missing in more distant ancestors

Question 21

disadvantage(s) of the phylogenetic species concept

Answer 21

few well-established phylogenies are available

Question 22

two ways in which genetic isolation can occur

Answer 22

dispersal and vicariance

Question 23

Dispersal

Answer 23

when some individuals disperse from their population and colonize a new habitat

Question 24

Vicariance

Answer 24

physical splitting of habitat

Question 25

Allopatric speciation

Answer 25

speciation that begins with physical isolation via either dispersal or vicariance

Question 26

Sympatric speciaition

Answer 26

speciation that occurs even though populations live in the same geographical area and serves as a source of new branches on the tree of life

Question 27

two types of events that can initiate the process of sympatric speciation

Answer 27

external events (ex. disruptive selection)
internal events (ex. chromosomal mutations)

Question 28

Niche

Answer 28

range of ecological resources that a species can use and the range of conditions that it can tolerate

Question 29

Example of sympatric speciation by disruptive selection

Answer 29

apple trees and hawthorn trees are next to each other. Apple maggot flies mate only on apple trees and hawthorn maggot flies mate only on hawthorn trees. Even though they live in the same geographical area they don’t mate with each other.

Question 30

Polyploidy

Answer 30

• occurs when an error in meiosis or mitosis results in a doubling of the chromosome number
• this mutation reduces gene flow between mutant and normal individuals
• occurs by autopolyploidy and allopolyploidy

Question 31

Autopolyploid

Answer 31

individuals are produced when a mutation results in a doubling of chromosome number and the chromosomes all come from the same species

Question 32

Allopolyploid

Answer 32

individuals are created when parents that belong to different species mate and produce an offspring where chromosome number doubles