Chapter 24 - The Origin of Species

Question 1

Speciation -

Answer 1

the process by which one species splits into two species

Question 2

When one species splits into two, the species that result share many characteristics because they are descended from this common ancestor

Question 3

Microevolution -

Answer 3

changes over time in allele frequencies in a population

Question 4

Macroevolution -

Answer 4

the broad pattern of evolution above the species level

Question 5

Biological species concept -

Answer 5

defining a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring—but do not produce viable, fertile offspring with members of other such groups

Question 6

Reproductive isolation -

Answer 6

the existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offspring

Question 7

Hybrids -

Answer 7

offspring that result from an interspecific mating

Question 8

Prezygotic barriers -

Answer 8

block fertilization from occurring

Question 9

How ‘before the zygote’ barriers work:

Answer 9

one of three ways:

by impeding members of different species from attempting to mate

by preventing an attempted mating from being completed successfully

by hindering fertilization if mating is completed successfully.

Question 10

Postzygotic barriers -

Answer 10

contribute to reproductive isolation after the hybrid zygote is formed

Question 11

How ‘after the zygote’ barriers work:

Answer 11

Developmental errors may reduce survival among hybrid embryos. Or problems after birth may cause hybrids to be infertile or decrease their chance of surviving long enough to reproduce

Question 12

Speciation occurs -

Answer 12

through the evolution of reproductive isolation

Question 13

There is no way to evaluate the reproductive isolation of _______.

Answer 13

fossils

Question 14

The biological species concept also does not apply to organisms that _____________ all or most of the time, such as prokaryotes

Answer 14

reproduce asexually

Question 15

Species are designated by the ________ ___ ____ _____.

Answer 15

absence of gene flow

Question 16

The ecological species concept -

Answer 16

defining a species in terms of its ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment. This can accommodate to asexual as well as sexual species. Also emphasizing the role of disruptive natural selection as organisms adapt to different environments

Question 17

The morphological species concept -

Answer 17

defining a species by body shape and other structural features. This can be applied to asexual and sexual organisms, and it can be useful even without information on the extent of gene flow

Question 18

Allopatric speciation -

Answer 18

populations are geographically isolated and a new species forms

can also occur without geologic change, such as when individuals colonize a remote area and their descendants become geographically isolated from the parent population

may then evolve as a by-product of the genetic divergence that results from selection or drift.

Question 19

Sympatric speciation they are not

Answer 19

populations are not geographically isolated and a new species forms

occurs if gene flow is reduced by such factors as polyploidy, sexual selection, and habitat differentiation

Question 20

Polyploidy -

Answer 20

when a species has an extra set of chromosomes, (then sometimes a species may originate from this) far more common in plants

Question 21

Botanists estimate that more than ____ of the plant species alive today are descended from ancestors that formed by polyploid speciation.

Answer 21

80%

Question 22

Autopolyploid -

Answer 22

an individual that has more than two chromosome sets that are all derived from a single species

Question 23

Tetraploid -

Answer 23

4n species can produce fertile offspring by self-pollinating or by mating with other ________. In addition, _________ are reproductively isolated from 2n plants of the original population, producing the new species

Question 24

Allopolyploid -

Answer 24

are fertile when mating with each other but cannot interbreed with either parent species; thus, represent a new biological species.

Question 25

Hybrid zone -

Answer 25

a region in which members of different species meet and mate, producing at least some offspring of mixed ancestry

Question 26

Interspecific hybrids -

Answer 26

do not become reproductively isolated from their parent species

Question 27

Interspecific hybrids three common outcomes:

Answer 27

reinforcement of barriers, fusion of species, or stability

Question 28

Reinforcement

Answer 28

natural selection strengthens prezygotic barriers to reproduction, reducing the formation of unfit hybrids.

if occurring, barriers to reproduction between species should be stronger for sympatric populations than for allopatric populations.

Question 29

Fusion -

Answer 29

When barriers to reproduction are weak when two species meet in a hybrid zone, where gene flow can occur so that reproductive barriers weaken further and the gene pools of the two species become increasingly alike. Eventually, the speciation reverses, causing the two hybridizing species to fuse into a single species

Question 30

Stability -

Answer 30

Hybrids continue to be produced, sometimes because the hybrids survive or reproduce better than members of either parent species, and form a set population

Question 31

Punctuated equilibria -

Answer 31

describes periods of apparent stasis punctuated by sudden change