Chapter 24

Question 1

speciation

Answer 1

the origin of new species, is at the focal point of evolutionary theory
-evolutionary theory must explain how new species originate and how populations evolve

Question 2

microevolution

Answer 2

consists of changes in allele frequency in a population over time

Question 3

macroevolution

Answer 3

refers to broad patterns of evolutionary change above the species level

Question 4

biological species concept

Answer 4

states that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with other populations

Question 5

reproductive isolation

Answer 5

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

Question 6

hybrids

Answer 6

offspring of crosses between different species

Question 7

prezygotic barriers

and 3 ways it occurs by

Answer 7

block fertilization from occurring by

1. impeding different species from attempting to mate
2. preventing the successful completion of mating
3. hindering fertilization if mating is successful

Question 8

habitat isolation:

Answer 8

two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers

Question 9

temporal isolation

Answer 9

species that breed at different times of the day, different seasons, or different years cannot mix their gametes

Question 10

behavioral isolation

Answer 10

courtship rituals and other behaviors unique to a species are effective barriers

Question 11

mechanical isolation

Answer 11

morphological differences can prevent successful mating

different sexual organs

Question 12

gametic isolation

Answer 12

sperm of one species may not be able to fertilize eggs of another species

Question 13

postzygotic barriers

3 preventions

Answer 13

prevent they hybrid zygote from developing into a viable, fertile adult:

1. reduced hybrid viability
2. reduced hybrid fertility
3. hybrid breakdown

Question 14

reduced hybrid viability

Answer 14

genes of the different parent species may interact and impair the hybrid’s development
ex) a mule

Question 15

reduced hybrid fertility

Answer 15

even if hybrids are vigorous, they may be sterile

Question 16

hybrid breakdown

Answer 16

some first generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterile

Question 17

the biological species concept cannot be applied to _____ or ______ organisms

Answer 17

• fossils

- asexual organisms

Question 18

the biological species concept emphasizes ________

Answer 18

absence of gene flow

Question 19

morphological species concept

Answer 19

defines a species by structural features

-applies to sexual and asexual species but relies on subjective criteria

Question 20

ecological species concept

Answer 20

views a species in terms of its ecological niche

-it applies to sexual and asexual species and emphasizes the role of disruptive selection

Question 21

phylogenetic species concept

Answer 21

defines a species as the smallest group of individuals on a phylogenetic tree
-it applies to sexual and asexual species, but it can be difficult to determine the degree of difference required for separate species

Question 22

in what two ways can speciation occur?

Answer 22

• allopatric speciation

- sympatric speciation

Question 23

allopatric speciation

Answer 23

gene flow is interrupted or reduced when a population is divided into geographic isolated subpopulations

• a population forms a new species while geographically isolated from its parent population
• -ex) the flightless cormorant of the galapagos likely originated from a flying species on the mainland

Question 24

true or false:

a definition of barrier depends on the ability of a population to disperse

Answer 24

true!

ex) a canyon may create a barrier for small rodents, but not birds, coyotes, or pollen

Question 25

separate populations may evolve independently through what three things

Answer 25

1. mutation 2. natural selection 3. genetic drift

Question 26

reproductive isolation may arise as a result of ______

Answer 26

genetic divergence

Question 27

genetic divergence

Answer 27

the process in which two or more populations of an ancestral species accumulate independent genetic changes (mutations) through time, often after the populations have become reproductively isolated for some period of time. This means that the populations of species live independently of each other long enough that they can no longer produce offspring that can survive.

Question 28

true or false: | Regions with many geographic barriers typically have more species than do regions with fewer barriers

Answer 28

true

Question 29

sympatric speciation

Answer 29

speciation takes place in geographically overlapping populations

Question 30

polyploidy

Answer 30

the presence of extra sets of chromosomes due to accidents during cell division

Question 31

true or false: | polyploidy is more common in animals than plants

Answer 31

false: polyploidy is more common in plants than animals

Question 32

what can result from the appearance of new ecological niches

Answer 32

sympatric speciation

Question 33

sexual selection can drive _____

Answer 33

sympatric speciation

Question 34

in allopatric speciation, geographic isolation restricts _____

Answer 34

gene flow between populations

Question 35

in isolated populations, reproductive isolation may arise by ____,____, or ______

Answer 35

- natural selection - genetic drift - sexual selection

Question 36

true or false: in sympatric speciation, a reproductive barrier isolates a subset of a population without geographic separation from the parent species

Answer 36

true

Question 37

sympatric speciation can result from ____, _____, or _____

Answer 37

polyploidy, natural selection, or sexual selection

Question 38

hybrid zone

Answer 38

a region in which members of different species mate and produce hybrids

Question 39

hybrids often have reduced ____ compared with parent species

Answer 39

fitness

Question 40

when closely related species meet in a hybrid zone, there are three possible outcomes

Answer 40

1. reinforcement 2. fusion 3. stability

Question 41

reinforcement

Answer 41

barriers occurs when hybrids are less fit than the parent species -over time, the rate of hybridization decreases

Question 42

if hybrids are fit as parents, there can be substantial _____ between species

Answer 42

gene flow

Question 43

Fusion.... | if gene flow is great enough, the parent species can _______

Answer 43

fuse into a single species

Question 44

Stability.... True or false: extensive gene flow from outside the hybrid zone can overwhelm selection for increased reproductive isolation inside the hybrid zone

Answer 44

true

Question 45

broad patterns in speciation can be studied using what three things

Answer 45

1. fossil record 2. morphological data 3. molecular data

Question 46

the fossil record includes examples of species that ______, ______, and then______

Answer 46

1. appear suddenly 2. persist essentially unchanged for some time 3. apparently disappear

Question 47

puncuated equilibrium

Answer 47

describe periods of apparent stasis punctuated by sudden change -contrasts with a model of gradual change in a species' existence

Question 48

true or false: | speciation may require the change of only a single allele

Answer 48

false | -may require EITHER change in only a single allele or many alleles

Question 49

macroevolution

Answer 49

the cumulative effect of many speciation and extinction events