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Biology 108 > Lecture 6 & 7 Evolution II > Flashcards

Lecture 6 & 7 Evolution II Flashcards

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1
Q

what is microevolution?

A

change in allele frequencies in populations over generations

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2
Q

what is a gene/genetic locus?

A

the combination of two alleles (in diploid individuals)

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3
Q

what is a population?

A

a group of organisms that interbreed (share a gene pool) and produce fertile offspring

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4
Q

what is a gene pool?

A

all the alleles for all loci in a population

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5
Q

what are the three factors that can change allele frequency?

A
  1. natural selection
  2. genetic drift
  3. gene flow
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6
Q

which factor is the only one that can cause adaptive evolution?

A

natural selection

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7
Q

what is a phenotype?

A

a product of inherited genotype and environmental factors

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8
Q

what are discrete characters?

A
  • typically a single locus with alternative alleles
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9
Q

what are quantitative characters?

A

characters which vary along a continuum within a population

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10
Q

what is geographic variation?

A

differences between gene pools of separate populations

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11
Q

what is a cline?

A

a graded change in a trait along a geographical axis - displays geographic variation

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12
Q

what are sources of genetic variation?

A
  • mutations

- gene duplication (ex: sexual reproduction shuffling new genes)

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13
Q

what are mutations?

A

changes in an individual’s nucleotide sequence

  • can be caused by damage in DNA replication or structural damage to DNA
  • only mutations in cells that produce games can be passed to offspring
  • random
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14
Q

what are macromutations?

A
  • very large mutations
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15
Q

what is more important for sexually reproducing organisms: mutations or shuffling?

A
  • shuffling/recombination
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16
Q

what are the three types of natural selection?

A
  • directional
  • disruptive
  • stabilizing
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17
Q

what is directional selection?

A
  • extreme is favoured, variance remains the same
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18
Q

what is disruptive selevtion

A
  • favours individuals in both extremes of phenotypic range
  • results in POLYMORPHISM
  • maintains variation
19
Q

what is stabilizing selection?

A
  • favours intermediate/common variants
  • selects against extreme phenotypes
  • mean stays the same
  • variance decreases
  • little or no evolutionary change
20
Q

what is polymorphism?

A
  • 2 or more divergent phenotypes

- result of disruptive selection

21
Q

what is genetic drift?

A
  • changes in allele frequency due to chance
  • significant in small pop’ns
  • lead to a loss of genetic variation w/in populations
  • can cause harmful alleles to become fixed
  • bottleneck and founder effect
22
Q

how do allele frequencies drift?

A

from one generation to the next

23
Q

what size of populations does genetic drift affect the most?

A

small populations

24
Q

what is the bottleneck effect?

A
  • sudden reduction to pop’n size because of environmental change
  • allele frequency in next gen is different than previous
  • rare alleles more likely to be lost because of drift
25
Q

what is the founder effect?

A
  • new population is established by a few colonizers isolated from the larger population
  • small fraction of total genetic variation compared to the ancestral population – change in allele frequency
26
Q

what is gene flow?

A

the transfer of alleles between populations

  • can introduce new variation
  • tends to slow local adaptation and reduce variation among populations over time
27
Q

what does gene flow do to fitness?

A
  • both increases and decreases fitness
28
Q

what is sexual dimorphism?

A
  • marked differences between the sexes in secondary sexual characteristics
29
Q

what is sexual selection?

A
  • selection for the acquisition of more or better mates
  • category within natural selection
  • NS for mating success
30
Q

what are the two types of sexual selection?

A
  • intrasexual

- intersexual

31
Q

what is intrasexual selection?

A
  • competition among individuals of one sex for mates of the opposite sex
  • ex: large antlers in male deer for fighting
  • result of physical competition for access to mates
32
Q

what is intersexual selection?

A
  • mate choice
  • when individuals of one sex choose in mate selection
  • flashy plumage or dances
  • usually females choose males and males are flashy
33
Q

what did Darwin think about sexual selection?

A
  • separated SS and NS because it seemed like some sexually selected traits act against naturally selected ones
  • flashy plumage – predators
  • but the same is said for many traits
  • long life against faster growth
34
Q

what is another factor that brings about evolutionary change?

A

extinction

35
Q

what is neutral variation?

A
  • genetic variation that doesn’t confer a selective advantage or disadvantage
36
Q

what are seven mechanisms that maintain genetic variation in populations?

A 
mutation
recombination
independent assortment of alleles
fertilization
disruptive selection
gene flow
balancing selection
37
Q

what is balancing selection?

what does it include? (2)

A

occurs when NS maintains stable frequencies of two or more phenotypic forms in a population

  • includes heterozygote advantages
  • frequency dependent selection
38
Q

what is heterozygote advantage?

A

balancing selection
occurs when heterozygotes have a higher fitness than do both homozygotes
- NS maintains 2 or more alleles at that locus
- ex: sickle cell and malaria

39
Q

what is frequency - dependent selection?

A

balancing selection

  • fitness of phenotype declines if it becomes too common in a population
  • rare genotype has a selection advantage
40
Q

why can’t NS fashion perfect organisms?

A
  1. NS can act ONLY on existing variations
  2. evolution is limited by historical constraints
  3. adaptations are often compromises
  4. chance, NS, and the environment interact
41
Q

what are the two modes of evolution?

what is in between?

A
  • microevolution
  • macroevolution
  • in between is speciation
42
Q

what is microevolution?

A
  • evolution at the population level
  • changes allele frequency in a population over time
  • occurs mainly through selection - results in adaptation - or drift
43
Q

what is macroevolution?

A
  • evolutionary changes ABOVE species level
  • origin of complex novel characters
  • appearance of higer taxa
  • mass extinctions

Biology 108 (27 decks)

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