Pages 492-499

Question 1

Speciation begins when

Answer 1

gene flow between populations is reduced or eliminated, causing genetic isolation.

Question 2

Genetic isolation

Answer 2

happens routinely when populations become geographically separated. Happens in one of two ways: dispersal or vicariance, the physical splitting of a habitat.

Question 3

allopatry

Answer 3

populations that are geographically separated.

Question 4

allopatric speciation

Answer 4

speciation that begins with geographic isolation.

Question 5

biogeography

Answer 5

the study of how species and populations are distributed geographically.

Question 6

Dispersal and colonization, followed by genetic drift and natural selection, is thought to be responsible for speciation

Answer 6

in the Galapágos finches and many other island groups.

Question 7

sister species

Answer 7

species that are each other’s closest relative.

Question 8

Geographic isolation of populations via dispersal or vicariance produces genetic isolation due to

Answer 8

the interruption of gene flow – the first requirement of speciation. When genetic isolation is accompanied by genetic divergence due to mutation, selection, and genetic drift, speciation results.

Question 9

sympatry

Answer 9

when populations or species live in the same geographic area, or at least close enough to one another to make interbreeding possible.

Question 10

sympatric speciation

Answer 10

speciation that occurs even though populations live within the same geographical area.

Question 11

Two types of events can initiate the process of sympatric speciation:

Answer 11

• External events, such as disruptive selection for extreme phenotypes based on different ecological niches.
• Internal events, such as chromosomal mutations.

Question 12

niche

Answer 12

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

Question 13

Even though sympatric populations are not geographically isolated, they may become

Answer 13

reproductively isolated by adapting to different ecological niches via disruptive selection.

Question 14

Natural selection and genetic drift are usually responsible for amplifying the effects of

Answer 14

mutation.

Question 15

polyploidy

Answer 15

occurs when an error in meiosis or mitosis results in doubling of the chromosome number – a massive mutation.

Question 16

Autopolyploid (“same-many-form”)

Answer 16

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

Question 17

Allopolyploid (“different-many-form”)

Answer 17

individuals are created when parents that belong to different species mate and produce an offspring with two different sets of chromosomes.

Question 18

Polyploidy individuals are reproductively isolated from the original diploid population

Answer 18

and thus evolutionarily independent, because breeding between diploids and tetraploids generally results in sterile offspring.

Question 19

Offspring is sterile if it has chromosomes that do not

Answer 19

pair normally during meiosis. Although, if a mutation occurs during mitosis that doubles the chromosome number in this individual before meiosis, then each chromosome gains a homolog and meiosis can proceed normally.

Question 20

Why polyploids have been so successful:

Answer 20

• Polyploids have higher levels of heterozygosity than their diploid relatives.
• Polyploids can tolerate higher levels of self-fertilization because they are not as affected by inbreeding depression as their diploid relatives.
• Genes on duplicated chromosomes can diverge independently, increasing genetic variation in a population.
• Speciation by polyploidization is virtually instantaneous.