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Evolution > Evolution - lecture 16 - Important definitions > Flashcards

Evolution - lecture 16 - Important definitions Flashcards

1
Q

What is a species?

A

Smallest evolutionary independent unit.

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2
Q

What is evolutionary independence?

A

occurs when mutation, selection, gene flow, and drift operate on populations separately.

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3
Q

The essence of speciation is lack of _____ ______ when populations are in contact with each other.

A

gene flow

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4
Q

What is the morphospecies concept?

A

Careful analyses of phenotypic differences are the basis of identifying morphospecies.

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5
Q

What are the advantages of the morphospecies concept?

A

Can be applied to living/extinct individuals and in sexual/asexual organisms.

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6
Q

What are the disadvantages of the morphospecies concept?

A

1 - When not applied correctly, species definitions can become arbitrary
2 - concept is hard to apply to small organisms (don’t have easy to define morphological differences)
3 - cryptic species

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7
Q

What is speciation?

A

Lack of gene flow

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8
Q

What are cryptic species?

A

Species that are similar in morphology but strongly differ in traits like drought resistance, courtship displays and songs. Hard to say the species are different from morphology alone.
Defn: groups that are independent of one another but appear to be from the same species

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9
Q

What is the phylogenetic species concept?

A

Geneological species concept focusing on monophyly.

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10
Q

What is a monophyletic group?

A

Defined as lineages that contain all of the known descendants of a single common ancestor.

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11
Q

The rationale behind the PSC is that _______ can distinguish populations on a phylogeny only if populations have been _________ in terms of _____ _____ and have diverged __________, and possibly __________ as well.

A 
1 - traits
2 - isolated
3 - gene flow
4 - genetically
5 - morphologically
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12
Q

What are the advantages of the PSC?

A

1 - can be applied to any organism

2 - testable

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13
Q

What are the disadvantages of the PSC?

A

1 - Challenge in putting it into practice

2 - Could potentially double the number of named species

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14
Q

Recent analyses have found that the ____ often distinguishes multiple ______ ______ in populations that were formerly considered a single species.

A

1 - PSC

2 - cryptic species

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15
Q

What is the criterion for identifying evolutionary independence in the BSC?

A

reproductive isolation

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16
Q

What is reproductive isolation?

A

If populations of organisms do not hybridize regularly in nature, or if they fail to produce fertile offspring when they do, (then they are reproductively isolated and considered separate species.)

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17
Q

What are the strengths of the BSC?

A

1 - Reproductive isolation is a meaningful criterion for identifying species because is confirms lack of gene flow.

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18
Q

What are the disadvantages of the BSC?

A

1 - difficult to separate species if populations do not come into direct contact
2 - Cannot be tested in fossil form
3 - irrelevant to asexual populations

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19
Q

What is peculiar of bacteria and archea when it comes to gene flow?

A

Gene flow actually contributes to speciation whereas this prevents it in eukaryotic, sexually reproducing species.

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20
Q

What is an evolutionary significant unit?

A

If genetic diversity is correlated with phenotypic diversity, then preserving genetically distinct populations is more likely to lead to LT survival in the face of evolutionary change.
ESU = genetically distinct (if this correlates with phenotypic diversity) populations for the sake of conservation biology.

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21
Q

_________ ______ is perhaps the closes of all overfished species to being lost.

A

European skate

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22
Q

Classically, speciation has been hypothesized to be a three stage model. What are these stages?

A

1 - Isolation
2 - Divergence
3 - final phase that produces reproductive isolation (Secondary contact)
Postulated that 1 and 2 occur over time and that the populations need to geographically isolated.

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23
Q

What is secondary contact?

A

When diverged populations come back into physical contact due to migration or geographic changes and interbreed.

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24
Q

Recent evidence has modified which parts of the originally speciation 3 part model?

A

1 - Isolation and divergence can occur at the same time and place
2 - in many cases, second contact doesn’t occur

25
Q

What is isolation?

A

A reduction in gene flow between two populations.

26
Q

What are the two general methods of isolation?

A

1 - Geographical
2 - Genetic
(Physical is a possibility too)

27
Q

The speciation process begins when _____ _____ is disrupted and populations become _______ isolated.

A

1 - gene flow

2 - genetically

28
Q

Gene flow tends to ______ gene frequencies and reduce the __________ of populations.

A

1 - homogenize

2 - divergence (differentiation)

29
Q

What is allopatric speciation?

A

Physical isolation creates a barrier to gene flow. Species do not co-occur geographically.

30
Q

Geographic isolation has been an important trigger for what stage of the speciation process?

A

Second stage: ecological and genetic divergence

31
Q

What are the two mechanisms of geographic isolation?

A

1 - DISPERSAL across a physical barrier followed by colonization of a novel habitat
2 - VICARIANCE, in which an existing range is split by the appearance of a new physical barrier

32
Q

How can gene flow between populations be reduced in the absence of physical isolation?

A

Genetic isolation:
1 - Changes in ploidy
2 - Changes in chromosome number

33
Q

Speciation triggered by changes in chromosome number has been especially important in _____.

A

plants

34
Q

What are sympatric species?

A

Species that overlap geographically.

Species co-occur.

35
Q

Sympatric species are most likely to be isolated by what?

A

Genetically, through a difference in chromosome number.

36
Q

Sympatric species with matching ________ _______ are rare, likely because coexisting populations are not able to diverge into separate species without a boundary to _____ ______.

A

1 - chromosome number

2 - gene flow

37
Q

What are other examples of isolation that are not genetic or geographic in nature?

A

1 - Difference in flowering time
2 - Difference in pollinator visits
3 - physical isolation (snail shells)

38
Q

What is the most important mechanism promoting divergence between populations?

A

Natural selection

39
Q

_________ __________ can cause populations to diverge based on food preferences, habitats used, or other ecological differences.

A

natural selection

40
Q

What is assortative mating?

A

Individuals with certain traits more often choose mates that share those same traits.

41
Q

What is hybridization?

A

Occurs when recently diverged populations interbreed.

42
Q

What keeps two sympatric species separate?

A

1 - prezygotic isolation

2 - postzygotic isolation

43
Q

What is prezygotic isolation?

A

In which hybrid offspring (zygotes) are never formed.

  • this can be because separate species do not mate
  • this can be an internal mechanism preventing fertilization
44
Q

What is postzygotic isolation?

A

In which hybrid offspring suffer from inviability, sterility or reduced fitness.

45
Q

What is reinforcement?

A

Reinforcement occurs when hybrid offspring have low fitness, and natural selection leads to assortative mating and the prezygotic isolation of populations.

46
Q

Reinforcement is associated with what type of zygotic isolation?

A

Pre-zygotic isolation (since individuals should prefer to not mate in the first place)

47
Q

What is gametic isolation?

A

Phenomenon in which gametes from the same species are preferentially selected to produce zygotes.

48
Q

What is polyploid hybrid speciation?

A

When species hybridize and the resulting offspring have an increase in ploidy. Offspring can now only mate with themselves or other, similar hybrids.

49
Q

What is homoploid hybrid speciation?

A

When ploidy stays the same following hybridization.

50
Q

What are hybrid zones?

A

Region where diverged populations interbreed and hybrid offspring are common.

51
Q

Hybrid zones are more common when secondary contact occurs between species that have diverged in ________.

A

allopatry

52
Q

What s adaptive radiation?

A

When a new habitat is first explored by a certain group of organisms, an adaptive radiation occurs, in which many new species form rapidly.

53
Q

What was the ecological control for species richness for the Anolis lizard on the Caribbean Islands?

A

island size

54
Q

Species with _____ ranges and ____ dispersal are less likely to be exposed to new environments and selective pressures than those with ______ ranges.

A

1 - small
2 - low
3 - large

55
Q

How can high dispersal act as a barrier to speciation?

A

Due to continued gene flow among populations since they can disperse rather far.

56
Q

Environmental parameters such as island size that determine the speciation rates and how they change over time.

A

External ecological control on diversification

57
Q

What is an endogenous control on diversification?

A

The property of an organism, rather than of its environment, control speciation rate.

58
Q

What are the potential outcomes of hybridization?

A

reinforcement of prezygotic isolation, hybrid speciation, stable hybrid zones

59
Q

Which of the outcomes of speciation lead to an increase in species number?

A

hybrid speciation

Evolution (5 decks)

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