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BIOLOGY 108 > Topic 8: Speciation > Flashcards

Topic 8: Speciation Flashcards

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1
Q

Darwin envisioned speciation as a ____ event

A

branching

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2
Q

New species arise through the process of

A

speciation

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3
Q

Speciation

A

an ancestral species splits into two or more descendant species that are genetically different from one another and can no longer interbreed

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4
Q

Macroevolution

A

broad patterns of evolutionary change above the species level over geologic time scales

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5
Q

Examples of macroevolution

A

origin of new traits like wings, new groups like flowering plants, extinction

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6
Q

Speciation occurs between

A

microevolution and macroevolution

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7
Q

Macroevolution is the cumulative event of:

A

gradual compounding of small changes, cumulative new genetic variations, and speciation and extinction events

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8
Q

What is a species

A

a group of actually (or potentially) interbreeding individuals that produce viable, fertile offspring, and are reproductively isolated from other species

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9
Q

Capacity for ______ between populations of a species holds a species together genetically

A

gene flow

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10
Q

Limits of BDC (biological species concept)

A

cannot be applied to follis or asexual organisms, emphasizes the absence of gene flow when it can still happen (think grolar bears)

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11
Q

Other definitions for species

A

ecological species, morphological species, phylogenetic species,

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12
Q

morphological species

A

defines a species by structural features.

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13
Q

ecological species concept

A

defines a species as a set of organisms adapted to a particular set of resources, called a niche, in the environment

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14
Q

phylogenic species

A

defines a species as the smallest group of individuals on a phylogenetic tree

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15
Q

EBC emphasizes reproductive _____

A

isolation

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16
Q

Reproductive isolation is caused by

A

caused by biological factors (barriers) that impede two species from interbreeding and producing viable, fertile offspring (hybrid)

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17
Q

Reproductive isolation can be caused by (two types):

A 
prezygotic barriers (before fertilization) 
postzygotic barriers (post-fertilization)
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18
Q

Ways prezygotic barriers block fertilization

A
  • impeding different species from attempting to mate
  • preventing the successful completion of mating
  • preventing fertilization if mating is successful
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19
Q

Prezygotic reproductive barriers

A

habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation

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20
Q

Habitat isolation

A

two species encounter each other rarely because they occupy different habitats even if not separated by different barriers

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21
Q

Temporal isolation

A

species that breed at different times of the day/seasons/ years

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22
Q

Behavioral isolation

A

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

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23
Q

Mechanical isolation

A

morphological differences can prevent successive mating (autonomically incompatible)

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24
Q

Gametic isolation

A

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

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25
Q

Postzygotic barriers prevent a hybrid zygote from developing into a viable fertile adult by:

A
  • reduced hybrid viability
  • reduced hybrid fertility
  • hybrid breakdown
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26
Q

Reduced hybrid viability

A

genes of the different species may interact to impair the hybrid’s development or survival (results in death)

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27
Q

reduced hybrid fertility

A

hybrids come out sterile due to chromosomes of different numbers or structure

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28
Q

hybrid breakdown

A

some 1st-generation hybrids are vigorous and fertile, but when these hybrids mate with one another or with either parent species, offspring of subsequent generations are feeble or sterile

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29
Q

Allopatric speciation

A

occurs when gene flow between geographically isolated subpopulations is interrupted

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30
Q

barrier

A

stops the ability of a population to disperse

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31
Q

geographic isolation arises by

A

dispersion and vicariance

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32
Q

dispersal

A

results in the establishment of a new and distant population

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33
Q

vicariance

A

the range of a species is split by a change in the environment creating two subpopulations

34
Q

productive isolation between subpopulations generally increases as the distance between them ____

A

increases

35
Q

Allopatric speciation

A

the evolution of a new species following geographic isolation of two or more subpopulations of an ancestral species

36
Q

As subpopulations diverge, they may evolve traits that act as:

A

prezygotic and/or postzygotic barriers to reproduction

37
Q

The majority of speciation events occur due to

A

allopatric speciation

38
Q

Sympatric speciation

A

the evolution of a new species from an ancestral species while both continue to inhabit the same geographic region

39
Q

For sympatric speciation to occur the subpopulations occupying the same geographic region must become ___ ___ from each other.

A

reproductively isolated

40
Q

Overlapping subpopulations can become reproductively isolated from each other by:

A
  • chromosomal errors during meiosis or hybridization of closely related species
  • natural selection for reproductive isolation
41
Q

Polyploid speciation

A

occurs when changes in the number of chromosomes sets create genetically distinct descendants that are reproductively isolated from parental forms

42
Q

Polyploidy is common in

A

plants

43
Q

Hybrid speciation occurs when:

A

interbreeding between two related species creates genetically distinct descendants that are reproductively isolated from the parent species

44
Q

Polyploids have different number of ____ than their parental forms

A

chromosome sets

45
Q

Polyploids can only interbreed with individuals of the same ____

A

ploidy

46
Q

polyploids arise from

A
  • hybridization of related species to form allopolyploids

- chromosomal error during meiosis forming autopolypoids

47
Q

An ____ is a species with multiple sets of chromosomes derived from the hybridization of different species

A

allopolyploid

48
Q

Allopolyploid hybrids have ____ the
number of chromosome sets than the
parent species

A

double

49
Q

Autopolyploids can arise due to:

A

by genome doubling or by fusion of 2n gametes (failure of cell division during meiosis and creates gametes with double the number of chromosomes)

50
Q

Hybridization between different taxa is a trigger for:

A

polyploidization forming allopolyploids

51
Q

Homoploid hybrid speciation

A

Hybrid speciation can also occur with no change in chromosome number (ploidy)

52
Q

Homoploids

A

arise when hybridization produces novel combinations of genes that can adapt hybrids to new habitats that cause them to be reproductively isolated from parental populations

53
Q

Habitat differentiation increases:

A

reproductive isolation between subpopulations

54
Q

Natural selection for _______ between subpopulations
can occur after the appearance of
new ecological niches

A

reproductive isolation

55
Q

Sexual selection

A

natural selection for reproductive isolation between subpopulations

56
Q

Sexual selection leads to

A

evolution of traits that increase an individual’s access to members of the opposite sex.

57
Q

Sexual selection often leads to

A

sexual dimorphism

58
Q

Sexual dimorphism

A

marked differences between the sexes in secondary sexual characteristics

59
Q

Darwin separated sexual selection

and natural selection because:

A

some sexually selected traits would act against naturally selected ones

60
Q

Sexual selection is natural selection for

_______

A

mating success.

61
Q

Sexual selection can drive:

A

sympatric speciation

62
Q

Sympatric speciation occurs when

A

a reproductive barrier isolates a subset of a population without geographic separation from the parent species

63
Q

Sympatric speciation can arise following

A
  • Chromosomal errors during meiosis or hybridization of closely related species
  • Natural selection for reproductive isolation or following habitat differentiation
64
Q

Hybrid zone

A

a region where members of a different species interbreed and produce hybrids

65
Q

Hybrids result from

A

the mating between species with incomplete reproductive barriers

66
Q

Hybridization can result in ____

A

speciation

67
Q

Outcomes of hybrid zones

A

reinforcement of hybrid barriers, stability of hybrid barriers, and fusion of hybrid barriers

68
Q

reinforcement of reproductive barriers

A

occurs when hybrids are less fit than parent species resulting in the selection for prezygotic barriers

69
Q

Where reinforcement occurs, reproductive barriers should be stronger for _____ than _____ species

A

sympatric than allopatric

70
Q

stability of hybrid barriers

A

Continuous formation of hybrid individuals

71
Q

Continuous gene flow from outside the hybrid zone can:

A

overwhelm natural selection for increased reproductive isolation inside the hybrid zone

72
Q

Fusion ____ reproductive barriers

A

weakens

73
Q

If hybrids are as fit as parents there will be ____

A

gene flow between species and possibly the parent species will fuse back to one species

74
Q

Speciation is caused by

A

accumulation of genetic differences between populations

75
Q

How genetic drift is important in allopatric speciation:

A

Genetic drift is important in allopatric speciation when a new population arises following the dispersal of a few individuals to an isolated location

76
Q

Incomplete reproductive isolation between related species allows for ______.

A

hybridization

77
Q

Selection for increased reproductive

isolation is strongest when

A

during sympatric speciation when hybrids between the sympatric populations are of lower fitness, i.e. reinforcement of reproductive barriers

78
Q

Two patterns for the rate of speciation observed in fossil records

A

gradual, punctual models

79
Q

Gradual speciation model

A

species diverge slowly by natural selection over many generations

80
Q

punctuated speciation model

A

new species diverge quickly from a parent species but change little for the remainder of their existence

81
Q

What causes speciation to happen

A
  1. gene flow between populations is interrupted
  2. population diverges genetically to become reproductively isolated
  3. there is no event that causes gene flow to resume

BIOLOGY 108 (19 decks)

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