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IB Biology > 10.3 Gene pools and speciation > Flashcards

10.3 Gene pools and speciation Flashcards

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1
Q

What is a gene pool?

A

A gene pool represents the sum total of alleles for all genes present in a sexually reproducing population

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2
Q

What does a large gene pool indicate?

A

High amounts of genetic diversity and increasing the chances of biological fitness and survival

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3
Q

What does a small gene pool indicate?

A

Low amounts of genetic diversity and reducing biological fitness and increasing chances of extinction

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4
Q

What can gene pools be used to determine?

A

Allele frequency

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5
Q

What is allele frequency?

A

The proportion of a particular allele within a population

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6
Q

What does evolution require to happen?

A

That allele frequencies change within the gene pool of the population to reflect the evolve characteristics

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7
Q

What is evolution?

A

The cumulative change in the heritable characteristics of a population across successive generations

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8
Q

What are the five processes that can cause changes to allele frequency within a gene pool?

A

Mutation
Gene flow
Sexual reproduction
Genetic drift
Natural selection

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9
Q

How does mutation result in changes to allele frequency within a gene pool?

A

A random change in the genetic composition of an organism due to changes in the DNA base sequence

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10
Q

How does gene flow result in changes to allele frequency within a gene pool?

A

The movement of alleles into or out of a population as a result of immigration or emigration

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11
Q

How does sexual reproduction result in changes to allele frequency within a gene pool?

A

Sex can introduce new gene combinations and alter allele frequencies if mating is assortative

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12
Q

How does genetic drift result in changes to allele frequency within a gene pool?

A

The change in the composition of a gene pool as a result of a chance or random event

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13
Q

How does natural selection result in changes to allele frequency within a gene pool?

A

The change in the composition of a gene pool as a result of differentially selective environmental pressures

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14
Q

What is genetic drift?

A

The change in the composition of a gene pool as a result of chance or random event

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15
Q

When will genetic drift happen fastest and be most significant and why?

A

In smaller populations because chance events have a bigger impact on the gene pool

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16
Q

What will be less affected by random events and maintain more stable allele frequencies with low genetic drift?

A

Larger populations

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17
Q

When will allele frequencies change significantly?

A

When a large population is reduced to a small population

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18
Q

What are the two mechanisms when a large population is reduced to a small population?

A

Population bottlenecks and the founder effect

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19
Q

When do population bottlenecks occur?

A

When an event reduces population size by an order of magnitude

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20
Q

What causes population bottleneck?

A

Natural occurrences or human induced

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21
Q

What happens to the surviving population of population bottlenecks?

A

They will have less genetic variability than before and will be at a higher level of experiencing genetic drift

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22
Q

What happens to the surviving species of population bottlenecks when they repopulate?

A

The newly developing gene pool will be divergent to the original

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23
Q

When does the founder effect occur?

A

When a small group breaks away from a larger population to colonise a new territory

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24
Q

How does the founder effect differ from population bottlenecks?

A

The original population remains largely intact

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25
Q

Why is a smaller group in the founder effect subject to more genetic drift?

A

Because it does not have the same degree of diversity as a larger population

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26
Q

What happens to the smaller group in the founder effect when it increases in size?

A

Its gene pool will not be representative of the original gene pool anymore

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27
Q

What is the range of allele frequencies?

A

from 0 - 1.0

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28
Q

What can changes in allele frequencies reflect?

A

Either random processes or differential processes

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29
Q

When will the population bottlenecks and the founder effect exacerbate genetic differences?

A

Between geographically isolated populations

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30
Q

How do you compare allele frequencies?

A
  1. go to the allele frequency database
  2. type a gene name into the search parameter
  3. choose a specific gene loci
  4. Select a polymorphism
  5. Choose a frequency display format
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31
Q

What is natural selection?

A

The change in the composition of a gene pool in response to a differentially selective environmental pressure

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32
Q

What is the frequency of one particular phenotype in relation to another the product of?

A

The type of selection that is occurring

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33
Q

What is a stabilising selection?

A

When a middle phenotype is favoured at the expense of both phenotypic extremes

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34
Q

What does stabilising selection result in?

A

The removal of extreme phenotypes

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35
Q

When does stabilising selection happen?

A

When environmental conditions are stable and competition is low

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36
Q

What is an example of stabilising selection?

A

Human birth weights

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37
Q

What is directional selection?

A

When one phenotypic extreme is selected at the cost of the other phenotypic extreme

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38
Q

What does directional selection result in?

A

The phenotypic distribution clearly shift in one direction to the beneficial extreme

39
Q

When does directional selection happen?

A

In response to gradual or sustained changes in environmental conditions

40
Q

What is directional selection typically followed by and when?

A

Stabilising selection once an optimal phenotype has been normalised

41
Q

What is an example of directional selection?

A

The development of antibiotic resistance in bacterial populations

42
Q

What is disruptive selection?

A

When both phenotypic extremes are favoured at the expense of the middle phenotypic ranges

43
Q

What does disruptive selection cause?

A

The phenotypic distribution to deviate from the centre and results in a bimodal spread

44
Q

When does disruptive selection happen?

A

When fluctuating environmental conditions favour the presence of two different phenotypes

45
Q

What may happen if there is a continued separation of phenotypic variants in disruptive selection?

A

The population may split into two distinct sub populations

46
Q

What is an example of disruptive selection?

A

The proliferation of black or white moths in regions of sharply contrasting colour extremes

47
Q

When does reproductive isolation happen?

A

When barriers prevent two populations from interbreeding

48
Q

What are the two main categories of reproductive isolation barriers?

A

Prezygotic isolation and postzygotic isolation

49
Q

What is prezygotic isolation?

A

Occurs before fertilisation can occur so no offspring are produced

50
Q

What is postzygotic isolation?

A

Occurs after fertilisation where offspring are either not viable of infertile

51
Q

What are the different types of prezygotic isolation barriers?

A

Temporal
Behavioural
Geographical/Ecological
Mechanical

52
Q

What are the different types of postzygotic isolation barriers?

A

Inviability
Infertility
breakdown of hybrid organisms

53
Q

When does temporal isolation occur?

A

When two populations differ in their periods of activity or reproductive cycles

54
Q

What is an example of temporal isolation?

A

Leopard frogs and wood frogs sexually mature at different times in the spring and thus cannot interbreed

55
Q

When does behavioural isolation occur?

A

When two populations exhibit different specific courtship patterns

56
Q

What is an example of behavioural isolation?

A

Certain populations of cricket may be physically the same but only respond to specific mating songs

57
Q

When does geographic isolation occur?

A

When two populations occupy different habitats or separate niches within a common region

58
Q

What is an example of geographic isolation?

A

Lions and tigers occupy different habitats and do not interbreed

59
Q

What is hybrid inviability?

A

When hybrids are produced but fail to develop to reproductive maturity

60
Q

What is hybrid infertility?

A

Hybrids fail to produce functional gametes

61
Q

What is hybrid breakdown?

A

F1 hybrids are fertile but F2 generation fails to develop properly

62
Q

What is speciation?

A

An evolutionary process that results in the formation of a new species from a pre existing species

63
Q

When does speciation occur?

A

When reproductive isolating mechanisms prevent two breeding organisms from producing fertile viable offspring

64
Q

What are the two ways speciation can occur?

A

Allopatric and sympatric speciation

65
Q

When does allopatric speciation occur?

A

When a geographical barrier physically isolates populations of an ancestral species

66
Q

What are the reasons two populations begin to evolve in allopatric speciation?

A

Cumulative mutation
Genetic drift
Natural selection

67
Q

What eventually happens in allopatric speciation?

A

The two populations reach a degree of genetic divergence where they can no longer interbreed

68
Q

What is sympatric speciation?

A

The divergence of species within the same geographical location

69
Q

What can cause sympatric speciation?

A

The reproductive isolation of two populations as a result of genetic abnormalities

70
Q

What error typically arises during sympatric speciation and what does that cause?

A

A chromosomal error may arise which prevents successful reproduction with any organism lacking the same error

71
Q

Structurally, what can cause speciation?

A

A meiotic failure during gamete formation

72
Q

What happens if meiotic cells fail to undergo cytokinesis?

A

Chromosomal number will double in the gamete

73
Q

What is the result of offspring where the chromosomal number is double in the gamete?

A

Offspring with additional sets of chromosomes

74
Q

How can polyploid offspring cause speciation?

A

If the offspring are viable and fertile but cannot interbreed with the original parent population

75
Q

What do fertile polyploid offspring typically require?

A

Two polyploid parents

76
Q

Why do fertile polyploid offspring need two polyploid parents?

A

Because reproduction with an the original parent population results in offspring with an uneven number of chromosome sets

77
Q

Where is polyploidy more common and why?

A

Plant species as they lack separate sexes and can reproduce asexually

78
Q

Can infertile polyploids still reproduce asexually?

A

Yes via vegetative propagation

79
Q

Why do farmers develop polyploid crops? (two reasons)

A

Allows for the production of seedless fruits
Polyploid crops grow larger and demonstrate improved longevity and disease resistance

80
Q

How can farmers induce polyploidy in certain plant species?

A

By treating plants with certain drugs

81
Q

What is the genus allium comprised of?

A

Monocotyledonous flowering plants like onions, garlic, chives and leeks

82
Q

What has happened in the allium species?

A

Polyploidy resulting in reproductively isolated populations with distinct phenotypes

83
Q

What are the two ways evolution can occur?

A

Microevolution and macroevolution

84
Q

What is microevolution?

A

Within a species

85
Q

What is macroevolution?

A

Across the species barrier

86
Q

What are the two ways evolution via speciation may occur?

A

Phyletic gradualism or punctuated equilibrium

87
Q

What is the phyletic gradualism model?

A

Speciation occurs uniformly via the steady and gradual transformation of whole lineages

88
Q

What supports phyletic gradualism?

A

The fossil record of the horse as many middle forms connect to the modern equivalent

89
Q

In accordance to phyletic gradualism what type of process is speciation viewed as?

A

A smooth and continuous process

90
Q

What is the punctuated equilibrium model?

A

Species remain stable for long periods before undergoing abrupt and rapid change

91
Q

What type of process is speciation according to punctuated equilibrium?

A

A periodic process where big changes happen suddenly followed by long periods of no change

92
Q

What evidence supports the punctuated equilibrium model?

A

The general lack of transitional fossils for most species

93
Q

Apart from punctuated equilibrium what else can explain the lack of traditional fossils?

A

The rare and irregular conditions needed for fossilisation

IB Biology (57 decks)

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