Chapter 24 Flashcards Preview

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Flashcards in Chapter 24 Deck (49):
1

speciation

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

2

microevolution

consists of changes in allele frequency in a population over time

3

macroevolution

refers to broad patterns of evolutionary change above the species level

4

biological species concept

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

5

reproductive isolation

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

6

hybrids

offspring of crosses between different species

7

prezygotic barriers
(and 3 ways it occurs by)

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

8

habitat isolation:

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

9

temporal isolation

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

10

behavioral isolation

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

11

mechanical isolation

morphological differences can prevent successful mating
(different sexual organs)

12

gametic isolation

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

13

postzygotic barriers
(3 preventions)

prevent they hybrid zygote from developing into a viable, fertile adult:
1. reduced hybrid viability
2. reduced hybrid fertility
3. hybrid breakdown

14

reduced hybrid viability

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

15

reduced hybrid fertility

even if hybrids are vigorous, they may be sterile

16

hybrid breakdown

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

17

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

-fossils
-asexual organisms

18

the biological species concept emphasizes ________

absence of gene flow

19

morphological species concept

defines a species by structural features
-applies to sexual and asexual species but relies on subjective criteria

20

ecological species concept

views a species in terms of its ecological niche
-it applies to sexual and asexual species and emphasizes the role of disruptive selection

21

phylogenetic species concept

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

22

in what two ways can speciation occur?

-allopatric speciation
-sympatric speciation

23

allopatric speciation

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

24

true or false:
a definition of barrier depends on the ability of a population to disperse

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

25

separate populations may evolve independently through what three things

1. mutation
2. natural selection
3. genetic drift

26

reproductive isolation may arise as a result of ______

genetic divergence

27

genetic divergence

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.

28

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

true

29

sympatric speciation

speciation takes place in geographically overlapping populations

30

polyploidy

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

31

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

false: polyploidy is more common in plants than animals

32

what can result from the appearance of new ecological niches

sympatric speciation

33

sexual selection can drive _____

sympatric speciation

34

in allopatric speciation, geographic isolation restricts _____

gene flow between populations

35

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

-natural selection
-genetic drift
-sexual selection

36

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

true

37

sympatric speciation can result from ____, _____, or _____

polyploidy, natural selection, or sexual selection

38

hybrid zone

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

39

hybrids often have reduced ____ compared with parent species

fitness

40

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

1. reinforcement
2. fusion
3. stability

41

reinforcement

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

42

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

gene flow

43

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

fuse into a single species

44

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

true

45

broad patterns in speciation can be studied using what three things

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

46

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

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

47

puncuated equilibrium

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

48

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

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

49

macroevolution

the cumulative effect of many speciation and extinction events