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genetics n evolution > evolution > Flashcards

evolution Flashcards

1
Q

Lamarck’s theory

A
  • Life had originated many times
  • Over time, lineages become more complex
  • Thus, at any one time, there are recently originated simple forms of life, and older more complex forms of life
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2
Q

Darwin and Wallace: Similarities

A
  • Evolution as a “fact”
  • Common descent
  • Gradualism
  • Population change
  • Natural selection
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3
Q

Darwin and Wallace: Differences

A

*Darwin emphasized competition between individuals of the same species to survive and reproduce
*Wallace emphasized environmental pressures on varieties and species forcing them to become adapted to their local environment.

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4
Q

Synonymous mutation

A

the AA does not change
produced amino acid sequence is not modified. This is possible because the genetic code is “degenerate”

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5
Q

Nonsynonymous mutation

A

the AA changes
there is usually an insertion or deletion of a single nucleotide in the sequence during transcription
causes a frameshift mutation

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6
Q

How often mutations occur varies:

A
  • Among regions of the genome
  • Base composition (transitions and transversions occur at different rates)
  • Position in the genome (centromeres vs chromosome tips)
  • Presence of epigenetic modifications
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7
Q

selection

A
  • Occurs when there is a difference in the survival and/or reproduction of individuals based on their phenotype
    • Survival and reproduction can be summarized as an individual’s fitness
      Selection increases the frequency of the favoured trait in the next generation
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8
Q

natural selection

A

When the difference in fitness occurs due to conditions in the biotic or abiotic environment

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9
Q

artificial selection

A

When the difference in fitness occurs due to human preference for traits (i.e., selective breeding)

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10
Q

sexual selection

A

when individuals mate preferentially with particular individuals rather than at random
- Important because individuals that survive but fail to reproduce make no contribution to the next generation = no fitness
- Thus, sexual selection has the power to favour traits that enhance chances of reproduction, even if those traits reduce chances of survival
- Limited by the need to balance survival and reproduction

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11
Q

adaptation

A

Characteristic that enhances the survival or reproduction of organisms that bear it relative to alternative character states
Process by which members of a population become better adapted to their environment over time

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12
Q

migration

A

The movement of individuals or gametes
If migrants survive and reproduce, gene flow occurs

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13
Q

gene flow

A

Gene flow changes the allele frequencies in populations in proportion to the rate and direction of migration

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14
Q

genetic drift

A

Random changes in allele frequencies from one generation to the next
* Driven by chance, not selection
Mechanisms in stable populations: Random survival
Genetic drift has larger impacts in small populations

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15
Q

population bottleneck

A

when a population is dramatically reduced in size, by chance the small number of survivors may not be representative of the original population

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16
Q

founder effect

A

when a population is started (“founded”) by a small number of individuals, they are unlikely to possess all of the alleles found in the gene pool of the source population
* Founder populations will be less variable than original
* Rare alleles are likely to be lost

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17
Q

three conditions for selection

A
  • Variation in a trait
    • Heritability of a trait
  • Differential fitness conferred by a trait
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18
Q

Qualitative versus Quantitative Traits

A
  • Qualitative traits are those that have discrete qualities often controlled by alleles at a single locus
    Quantitative traits show continuous variation can be influenced by genes at many loci as well as by the environment
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19
Q

Directional selection

A

favours one extreme value

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20
Q

Stabilizing selection

A

favours average values

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21
Q

Disruptive selection

A

favours both extreme values

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22
Q

Intra-sexually

A

competition between members of the same sex

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23
Q

Inter-sexually

A

mate choice

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24
Q

Pre-copulatory

A

acquiring mating opportunities

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25
Q

Post-copulatory

A

events that occur during and after mating

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26
Q

Frequency-dependent selection

A

the fitness of a given phenotype depends on its frequency in a population

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27
Q

negative Frequency-dependent selection

A

The less common a phenotype is, the higher its fitness

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28
Q

Heterozygote advantage

A

When different alleles are favoured under different environmental conditions heterozygous individuals may outperform homozygotes
Certain variants of the PGI gene are able better able to fly in cold conditions, while others are better able to fly in hot weather
Heterozygous individual can fly over a greater range of temperatures than either type of homozygote

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29
Q

Continental-Island model

A

One-way gene flow from a large continental mainland population to a smaller island population
Allele frequency on the island changes at a rate that depends upon the
* rate of gene flow
* difference in allele frequency between the island and the mainland

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30
Q

island model

A

Describes gene flow among many populations exchanging immigrants with one another

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31
Q

stepping stone model

A

Allow subpopulations to exchange individuals only with adjacent subpopulations in one or two or more dimensions
Two subpopulations that are far apart will experience little gene flow and will be more different that two subpopulations closer together
Probability of mating decreases with distance
* Individuals chosen from two proximate locations are more closely related then locations distributed further apart

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32
Q

types of trade offs

A
  • allocation constraints
  • functional conflicts
  • shared biochemical pathways
  • ecological circumstances
  • sexual v. natural selection
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33
Q

Macroevolution

A

Zooming out on the tree of life from populations and species to look at grand trends in evolution

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34
Q

patterns in macroevolution

A

Stasis Lineages don’t change much in outward appearance for long periods of time

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35
Q

phylogeny

A

A diagram that depicts the lines of evolutionary descent of different lineages
Shows divergence events as dichotomous branching

36
Q

Taxon (plural ‘taxa’)

A

a group of individuals that are related at any scale

37
Q

tips of the tree

A

terminal taxa or sometimes “leaves”

38
Q

nodes

A

branching points on the phylogenic tree

39
Q

clade

A

a taxon that consists of all evolutionary descendants of a common ancestor
Clades can form nested sets of taxa on a tree

40
Q

sister species

A

Two species that are each other’s closest relatives

41
Q

sister clades

A

Two clades that are each other’s closest relatives

42
Q

ancestorial traits

A

characters inherited from the common ancestor of a group

43
Q

derived traits

A

characters that are unique to specific subgroups

44
Q

homologous traits

A

A feature shared by taxa that are descended from a common ancestor

45
Q

Synapomorphy

A

Derived traits shared across all members of a group
Evidence of common ancestry

46
Q

Autapomorphy

A

A derived trait that is unique and defines that taxon

47
Q

Homoplasies

A

traits that are superficially similar but do not arise from shared ancestry
A trait that appears homologous may actually be homoplastic

48
Q

Homoplasies can arise through

A
  • Convergent Evolution
    • Independently evolved features subjected to similar selective pressures become superficially similar
    • Evolutionary Reversal
      A character reverts from a derived state back to an ancestral one
49
Q

nomenclature

A

The first name identifies the genus, the second name identifies the species

The genus name is capitalized, the specific name is not Both are always italicized NOTE: higher classifications like order or phylum are not written in italics

50
Q

Do Keep Pond Clean Or Frog Gets Sick

A

Domain
Kingdom
Phylum
Clade
Order
Family
Genus
Species

51
Q

Monophyletic groups (or clades)

A

contain all the descendants of a particular ancestor and no other organisms

52
Q

Polyphyletic groups

A

contain members of more than one recent common ancestor

53
Q

Paraphyletic groups

A

contain some, but not all, the descendants of an ancestor

54
Q

Species concept: Morphological

A
  • If two organisms look different, they are different species
    • In practice, take a selection of specimens, examine their morphology, and group specimens together into species
      Uses the judgement of the Taxonomist to decide where species boundaries lie
55
Q

Species concept: Morphological pros

A
  • Requires only a physical description (can be applied to fossils)
  • Can use statistical approaches to cluster individuals based on measurement data
56
Q

Species concept: Morphological cons

A
  • Members of a species don’t always look alike
  • Sexual dimorphism
  • Life stage
  • Different species can look really similar
57
Q

Cryptic species

A

Two or more species are morphologically indistinguishable but do not interbreed

58
Q

Species concept: Biological

A
  • Groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups
    • Proposed by Ernst Mayr (1940)
    • Implies that individuals in different species cannot successfully interbreed
      e.g. female horse Equus caballus x male donkey E. africanus = mule (sterile hybrid)
59
Q

Species concept: Biological pros

A
  • Identifies evolutionarily independent groups
60
Q

Species concept: Biological cons

A
  • What about asexually reproducing or hermaphroditic species?
  • What about geographically isolated individuals that could reproduce, but never do because of their isolation?
  • Reproductive compatibility is an ancestral character, reproductive isolation is derived
    • Can interbreed
    • Reproductively isolated
61
Q

Species concept: Ecological

A
  • Each species has a discrete ecological niche (way of living) defined in many different ways (e.g. climate, habitat, food), and different from all other species
    • The ecological niche of a species can be represented as an n-dimensional hyperspace
      Overlap in two niche dimensions resolved by a third, etc.
62
Q

Species concept: Ecological pros

A
  • Ecological data can help tease apart cryptic species
    e.g., based on their song or the time of day that they are active
63
Q

Species concept: Ecological cons

A
  • Ecological niches are extremely complicated with many possible ways that niches can differ between species
  • Gathering all the data to truly understand a given individual’s ecological niche is so much effort that it is essentially impossible
64
Q

Species concept: Phylogenetic

A
  • A group of organisms that share an ancestor (monophyly); a lineage that maintains its integrity with respect to other lineages through both time and space.
    • A species is a “tip” on a phylogeny, that is, the smallest set of organisms that share an ancestor and can be distinguished from other such sets.
      Identifies populations with no gene flow as species
65
Q

Species concept: Phylogenetic pros

A
  • Applies to all organisms (e.g., bacteria, cryptic)
  • Readily assessed using DNA
66
Q

Species concept: Phylogenetic cons

A
  • How many diagnostic characters are enough? How many genes do you have to sequence before it’s enough like
  • Application of this concept results in a LOT of species (overdiagnosis?)
67
Q

Prezygotic barrier

A

preventing mating

68
Q

Postzygotic barrier

A

preventing the development of viable offspring

69
Q

Habitat isolation

A

Populations that live in different habitats and do not meet.

70
Q

Temporal isolation

A

Mating or flowering occurs at different seasons or times of the day

71
Q

Behavioral isolation

A

There is little or no sexual attraction between females and males.

72
Q

Gametic isolation

A

Female and male gametes fail to attract each other or are unviable

73
Q

Mechanical isolation

A

Structural differences in genitalia or flowers prevent copulation or pollen transfer.

74
Q

Hybrid inviability

A

zygote fails to develop or fail to reach sexual maturity

75
Q

Hybrid sterility

A

Hybrids fail to produce functional gametes

76
Q

Hybrid breakdown

A

the offspring of hybrids have reduced viability or fertility

77
Q

How many genes need to be different for speciation to occur?

A

– as few as five and as many as 200 genes can contribute to hybrid inviability
– far fewer gene differences have been found to be sufficient in and of themselves to confer postzygotic isolation (n =4)

78
Q

Mode of Speciation: Allopatric

A

evolution of genetic reproductive barriers between populations that are geographically isolated

  • Some members of a population are separated from others by a geographic barrier.
  • Gene flow between the two populations is greatly reduced (barrier is almost impervious to gene flow)
  • The two populations evolve separately in their respective habitats
  • If the two populations come together sympatrically, they can no longer interbreed
79
Q

Mode of Speciation: Peripatric

A

new species are formed from isolated peripheral populations
* form of allopatric speciation
* linked to founder effect
* potentially more common than standard allopatric speciation.

80
Q

Mode of Speciation: Parapatric

A

occurs due to variations in mating frequency of a population within a continuous geographical area

  • Population is not split, but is large and extends over a large range.
  • Some members of the population may never interact; or change in environment across range causes differential selection pressures.
  • Gene flow between members of the population is restricted; much weaker than divergent selection.
  • Two groups evolve separately; can no longer interbreed.

Limited interaction among individuals occupying a large range can reduce gene flow

81
Q

Mode of Speciation: Sympatric

A

genetic divergence of multiple populations (from a single parent species) inhabiting the same geographic region

  • Gene flow between individuals is not restricted due to geographic barriers
  • Population may be divided by the following mechanisms
    • New niche exploitation
    • Disruptive selection
    • Polyploidy
  • New niche exploitation
  • Disruptive selection, favouring extreme phenotypes
82
Q

Autopolyploidy

A

chromosomes derived from the same species

83
Q

Allopolyploidy

A

chromosomes derived from different species

84
Q

Adaptive Radiation

A
  • Often occurs in island archipelagoes
  • Individuals of a population colonize new habitat
  • Gene flow restricted between isolated population and parent population
  • Resource environment and predator pressures different in new habitat
  • New niches available
  • Individuals in new habitat adapt accordingly, occupying new niches
  • Adaptation to the new niche drives rapid speciation
85
Q

Species Radiation

A
  • Often occurs in island archipelagoes
  • Individuals of a population colonize new habitat
  • Gene flow restricted between isolated population and parent population
  • Genetic drift and lack of geneflow result in the accumulation of differences
  • More slowly results in the formation of allopatric species
  • Adaptation is STILL HAPPENING, but not the driving force in speciation
86
Q

What is a life history?

A

An individual’s pattern of allocation, throughout life, of time and energy to various fundamental activities, such as growth, repair of cell and tissue damage, and reproduction

87
Q

Lack’s Dilemma

A

David Lack (1947) predicted that parents should be selected to attempt to raise the number of offspring that would maximize offspring production
However, it is not unusual to find birds laying fewer eggs than the Lack clutch! (tested by brood augmentation) 67% of 77 studies
Optimizing fitness in a variable and unpredictable environment
The paradox:
* Bet-hedging
* Longevity trade-off
- The hard work of raising offspring can reduce lifespan
- Parental birds foraging for food to supply offspring operate at about 4X basal metabolic rate
- Birds may be laying fewer eggs to increase odds of surviving to succeeding years
* Reproductive value
Considering not just present, but also future reproductive success
Having too many offspring at once may lead to:
* Reduced survival in the nest
* Reduced survival from fledging to the next breeding season
* Reduced probability that the parents would lay a second clutch of eggs the same year

genetics n evolution (5 decks)

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