Population and Evolutionary Genetics Flashcards

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1
Q

Theory of Evolution (Darwin)

A
  1. Overproduction: every species tends to produce more individuals than can survive to maturity
  2. Variation: the individuals of a population have many characteristics that differ
  3. Selection: some individuals survive longer and reproduce more than others do
  4. Adaptation: the traits of those individuals that survive and reproduce will become more common in a population
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2
Q

Natural Selection

A
  • trait is favoured so survival increases for that trait
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3
Q

Why is variation important?

A
  • because the environment changes
  • the more variation within a species, the more likely it will survive
  • the more variation of types of species in a habitat, the more likely at least some will survive
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4
Q

Fitness

A
  1. individuals have variation in phenotype
  2. many of these are inherited
  3. individuals with particular phenotypes will survive to reproduce and pass genes to offspring
    - Fitness is the relative reproductive success of a genotype
    - Fitness (W) ranges from 0-1
    W = N offspring produced by genotype/N offspring produced by most prolific genotype
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5
Q

Natural Selection can be…

A
  • Directional
  • phenotypes at one or the other end of the spectrum are selected against
  • an extreme trait is selected for - shifting population toward homozygosity and phenotypes toward one extreme
  • Stabilising
  • natural selection favours an intermediate phenotype (heterozygote advantage - higher fitness) than extremes of traits
  • reduces phenotypic variation
  • Disruptive
  • selection favours extreme phenotypes over any intermediate phenotype
  • bimodal distribution
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6
Q

Sexual Selection

A
  • selection arising through preference by one sex for certain characteristics in individuals of the other sex
  • sexual dimorphism between sexes
  • demonstrate fitness
  • higher reproductive success
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7
Q

Natural vs. Sexual Selection

A
  • Natural Selection: traits become more or less common depending on an individuals ability to survive and gather resources
  • Sexual Selection: traits become more or less common depending on an individual’s ability to mate with more or better partners
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8
Q

Put this all together

A

Gene flow + Genetic drift + Mutation > Selection > Diversity

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9
Q

Applications of population genetics

A

Helps us understand genetic relationships and history
- management
- captive breeding, translocations
- anthropogenic habitat change
- landscape variability
- conservation
- individual identification

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10
Q

Subspecies

A
  • genetically and/or phenotypically distinct
  • able to interbred but often do not due to geographic isolation
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11
Q

Speciation

A
  • Cichlids in Lake Malawi
  • Finches of the Galapagos
  • Nearly 1/4 of all described species are beetles
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12
Q

Evolutionary Genetics

A
  • phylogenetic tree

Cladogenesis = the splitting of one lineage into two

Anagenesis = evolution within a lineage with the passage of time

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13
Q

Morphospecies Concept

A

similar in appearance

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14
Q

Biological Species Concept

A
  • a population or group of populations whose members can interbreed in nature and produce viable, fertile offspring

Issues
- many species are asexual and do not mate
- not applicable to fossils
difficult to test if potential species don’t have chance to interbreed naturally
- ability to intermate sometimes drops off gradually

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15
Q

Pre-zygotic barrier

A
  • gametes from different species are prevented from fusing
  • incompatible gametes
  • different habitats
  • individuals cannot meet
  • mechanical
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16
Q

Post-zygotic barrier

A
  • gametes can fuse, but cannot reproduce
  • hybrid
  • zygote does not survive
  • hybrid is sterile - mule
  • F1 are viable, F2 are sterile
17
Q

Phylogenetic Species Concept

A

Species are the smallest monophyletic groups and share an exclusive common ancestor

18
Q

Speciation

A

Allopatric speciation
- split by geographic barrier
- gene flow is blocked
Sympatric speciation
- no geographic barrier

19
Q

What is a species?

A
  • a name given to a type of organism
  • an evolutionary independent group of organisms
  • sometimes the difference is clear
20
Q

The biological species concept

A
  • first developed by ernst mayr
  • group of organisms that can interbreed - exchange genes
  • reproductively isolated from other species - evolve independantly
21
Q

Recognition Species Concept

A
  • a species is a set of organisms that can recognize each other as potential mates
  • they do not necessarily have to be able to mate
22
Q

Phenetic species concept

A
  • a species is a set of organisms that are phenotypically similar and that look different from other sets of organisms
  • phenotypic similarly is all that matters in recognizing sperate species
23
Q

Phylogenetic species concept

A
  • 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
24
Q

Phylogenetic tree

A
  • evolutionary relationship between organisms
  • nodes
  • branches
  • rooted with ‘outgroup’
25
Q

mtDNA

A
  • 1000-10,000 “identical” copies per cell
  • maternally inherited
  • advantages
  • inherited without recombination - phylogenetic reconstruction easier
  • high mutation rate - some taxa show lower mutation rate
  • analysis from “old” and “bad” samples: “ancient samples”, hairs
  • Disadvantages
  • information only about female history
26
Q

Mutation rates generally low

A

Nonsynonymous changes - change amino acids
- missense, nonsense
Synonymous changes - do not change amino acids
- silent

27
Q

Substitution rates - different parts of a gene

A
  • evolution occurs at different pace in different regions of the gene
28
Q

How quickly does evolution happen?

A
  • rate of synonymous change higher than non-synonymous change
  • why?
  • non-synonymous change alters proteins
  • may be detrimental to fitness
  • most eliminated by natural selection