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BIOLOGY 1210 > Microevolution > Flashcards

Microevolution Flashcards

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1
Q

what is microevolution?

A

is the study of change over time in populations

ie. the change in allele frequency in a population over time

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2
Q

what is allele frequency? instead of thinking about 2 individuals mating when it comes to allele frequency, we should think about..?

A

is a measure of how often an allele is found in a population

-think about the entire collection of gametes in a population

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3
Q

what is a gene pool a representation of? and what does allele frequency measure in this?

A

A gene pool is a representation of all the alleles that
are present in a population at a particular time
-measures how often an allele is found in a population

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4
Q

where does genetic variation in a population come from?

A
  1. mutation

2. sexual reproduction

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5
Q

what is mutation? at what 3 levels does mutation occur?

A

change in an organism’s DNA –> Ultimate source of new alleles

  1. change in chromosome number
  2. change in chromosomal structure
  3. change in DNA sequence
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6
Q

what is most genetic variation a result of?

A

the unique combination of alleles in an individual do to sexual reproduction and the fusion of gametes

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7
Q

what are 3 mechanisms that contribute to shuffling existing alleles into new combinations?

A
  1. Independent Assortment
  2. Crossing Over
  3. Fertilization
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8
Q

what is independent assortment?

A

Two equally probable arrangements of chromosomes

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9
Q

what is cross-over?

A

occurs in prophase of meiosis I and is the exchange of genetic material between two homologous chromosomes non-sister chromatids that results in recombinant chromosomes during sexual reproduction

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10
Q

what is fertilization, and how does it relate to genetic variation?

A

is the fusing of gametes (sperm and egg)

  • Any of the eggs can be fertilized by any of the sperm
  • the random nature of fertilization adds to the genetic variation arising from meiosis
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11
Q

what are 3 mechanisms of evolution?

A
  1. Genetic drift
  2. Gene flow
  3. Natural selection
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12
Q

what is genetic drift? is this process random or not?

A

-Mechanism of evolution that results in random
fluctuations in allele frequency from one generation
to the next
-Process is completely random
-Chance event causes allele frequencies to change
from one generation to the next

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13
Q

what are 2 examples of genetic drift?

A
  1. Founder Effect
    - Few individuals become isolated from larger pop.
    - Smaller group establishes new population with gene pool that differs from source population
  2. Bottleneck Effect
    - Sudden change in environment drastically reduces the size of a population
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14
Q

what kind of populations does genetic drift have a significant impact on? why?

A
  • small populations
  • Can lead to loss of genetic variation
  • can result in population changing over time (evolving) but NOT adapting to its environment
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15
Q

what is gene flow? is this process random or not?

A

-the transfer of alleles into or out of a population due to movement of fertile individuals or their gametes

-This process might be completely random or some
individuals may be more likely to move than others

-Alleles exchanged between populations, so tends to
reduce genetic differences between populations

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16
Q

what new thing can gene flow introduce to a population? what happens when this new things is introduced?

A

-new allele(s)
-Once a new allele is introduced natural selection may
cause that new allele to increase or decrease in the
population

17
Q

what is natural selection based on? what does natural selection act on? what are 3 requirements for natural selection to occur?

A
  • Based on differential success in survival and reproduction
  • Natural selection acts on individuals not on alleles
  1. Variation –> Individuals in population exhibit variations in their heritable traits
  2. Heritability –> can be passed on to offspring
  3. Differential success –> When selection is occurring some phenotypes in a population do ‘better’ than others
    -Phenotypes differ in their relative fitness in a
    particular environment
    -Those with traits that are better suited to their
    environment tend to produce more offspring than
    those with traits that are less well suited
18
Q

what is “fitness”? what are the 2 components to fitness?

A

the ability of an organism to survive and reproduce, and thus contribute offspring to the next generation

  1. Survival to reproductive age
  2. Mating success
19
Q

what does natural selection do to allele frequency? what kind of evolution does natural selection cause? what is it?

A

Results in change in allele frequency in population

-adaptive evolution –> evolution that results in a better match between organisms and their environment

20
Q

what are the 3 ways that Natural selection can alter the frequency distribution of heritable traits?

A
  1. directional selection
  2. disruptive selection
  3. stabilizing selection
21
Q

what is directional selection?

A
  • Occurs when conditions favour individuals exhibiting one extreme of a phenotypic range
  • Shifts frequency curve in one direction

eg. on a scale of white to black mouse, black fur is favorable, so white/light fur mouse die out

22
Q

what is disruptive selection?

A
  • Occurs when conditions favour individuals at both extremes of phenotypic range over individuals with intermediate phenotypes
  • makes frequency curve bimodal

eg. on a scale of white to black mouse, black fur and white fur id favorable, so brown fur dies out

23
Q

what is stabilizing selection?

A
  • occurs when conditions act against both extreme phenotypes
  • Favours intermediate phenotypes
  • Reduces phenotypic variation in a population

-eg. no white or black mice, only medium brown

24
Q

what are some barriers of natural selection?

A
  • Selection can only act on existing variation
  • Evolution is limited by historical constraints
  • Adaptations are often compromises

BIOLOGY 1210 (26 decks)

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