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biology 142 > chapter 23: evolution of populations > Flashcards

chapter 23: evolution of populations Flashcards

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1
Q

what is the smallest unit of evolution

A

natural selection acts on individuals but individuals do not evolve

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2
Q

microevolution

A

small scale view of evolution that looks at change in allele frequencies in a population over generations

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3
Q

3 mechanisms that cause allele frequency change

A
  1. natural selection
  2. genetic drift
  3. gene flow
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4
Q

which mechanism that causes allele frequency changes is the only one that improves adaptation?

A

natural selection

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5
Q

what is genetic variation?

A
  • differences among individual in the composition of genes and other dna sequences
  • average percent loci that are heterozygous
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6
Q

what can phenotypes be caused by

A
  • caused by single gene locus with different alleles for different phenotypes
  • phenotypes can be influenced by multiple genes
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7
Q

what is nucleotide variability

A

genetic variation at the molecular level of dna (little variation comes from phenotype variability)

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8
Q

where do nucleotide variations occur

A

introns (variation in exons does not change amino acid sequence)

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9
Q

what are phenotypes a combination of

A

combination of inherited genotype and environmental influences

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10
Q

can evolution occur without genetic variation

A

no

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11
Q

what does genetic variation come from

A
  • mutation

- gene duplication or other processes that produce new alleles/genes

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12
Q

how are new alleles formed

A

-mutations (change in nucleotide sequence)

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13
Q

what is a point mutation

A

change in one base of a gene

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14
Q

are most mutations harmful

A
  • yes

- natural selection tries to remove harmful mutations but they can pass through generations as recessive allele

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15
Q

what is neutral variation

A

differences in dna sequence without advantage or disadvantage (redundancy of genetic code) ; (mutations only have an effect if the amino acid composition is changed)

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16
Q

what is the key source of variation

A

-duplication of genes due to errors in meiosis, slippage during dna replication, or activities of transposable elements

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17
Q

what does evolution act upon

A

POPULATIONS

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18
Q

what is a mutation

A

changes in organisms genome (random)

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19
Q

what is considered as a way to quickly increase genetic variation

A

mutations

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20
Q

does rna or dna genoma have higher mutation rate

A

rna genome

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21
Q

where is most genetic variation from in sexual reproduction

A

unique combinations of alleles from each parent

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22
Q

what are the 3 mechanisms that contribute to shuffling of alleles in sexual reproduction

A
  1. crossing over
  2. independent assortment of chromosomes
  3. fertilization
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23
Q

what is a population

A

-group of individuals of the same species that live in the same area and interbreed to produce fertile offspring

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24
Q

what is a gene pool

A

-all copies of every allele at every locus in all members of the population

25
Q

what is an allele considered if only one exists at a locus

A

-allele is fixed

26
Q

what is an allele called if there are two or more alleles at a locus

A

-two or more alleles at a locus are homozygous or heterozygous

27
Q

what is considered hardy Weinberg equilibrium

A

a population that is not evolving where allele and genotype frequencies will remain constant from generation to generation where only mendelian segregation and recombination of alleles are at work

28
Q

hardy weinberg equation

A

p2 + 2pq + q2 =1

29
Q

conditions for hardy Weinberg equilibrium

A
  1. no mutations
  2. random mating (no sexual selection)
  3. no natural selection
  4. extremely large population size (genetic drift)
  5. no gene flow
30
Q

what is phenylketonuria (PKU)

A

metabolic disorder that results from homozygosity for a recessive allele

31
Q

natural selection (how it alters allele frequencies)

A
  • selection results from alleles being passed to the next generation in proportion that differs in present generation
  • adaptive evolution
32
Q

what is adaptive evolution

A

process where traits that enhance survival or reproduction tends to increase in frequency over time

33
Q

genetic drift (and how it affects allele frequencies)

A
  • chance events can allele frequencies to fluctuate unpredictability from one generation to the next, especially in small population
  • unpredictable events that affect survival and reproduction
34
Q

the founder effect (genetic drift)

A
  • when a few individuals become isolated from a larger population, the smaller group may establish a new population with a different gene pool
  • could occur due to storm that affects some individuals
  • likely accounts for high frequency of certain inherited disorders among isolated human populations
35
Q

the bottleneck effect (genetic drift)

A
  • severe drop in population size where population is reduced in size
  • certain alleles may be underrepresented, overrepresented, or absent
  • may lead to low levels of genetic variation
36
Q

effects of genetic drift

A
  1. significant in small populations
  2. can cause allele frequencies to change at random
  3. can lead to loss of genetic variation within populations
  4. can cause harmful alleles to become fixed
37
Q

gene flow (how it alters allele frequencies)

A
  • transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes
  • tends to reduce genetic differences
  • alleles that have been transferred can affect how well populations are adapted to environment (can improve or get rid of adaptations)
38
Q

is the outcome of natural selection random? and why

A

-not random but increases frequencies of alleles with advantages

39
Q

what is relative fitness

A
  • contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
  • indirectly acts on genotype
40
Q

what is directional selection

A

conditions favor individuals exhibiting one extreme of a phenotypic change (common with environment change)

41
Q

what is disruptive selection

A

when conditions favor individuals at both extremes of a phenotypic range over intermediate phenotypes

42
Q

what is stabilizing selection

A

acts against both extreme phenotypes and favors intermediate variants

43
Q

key role of adaptive evolution

A

-continuous process that occurs as a species becomes better suited for its environment

44
Q

key role of natural selection

A

-only mechanism that consistently leads to adaptive evolution

45
Q

what is sexual selection

A

-process in which individuals with certain inherited characteristics are more likely than other individuals of the same sex to obtain mates

46
Q

what is sexual dimorphism

A

-difference in secondary sexual characteristics between males and females of the same species (size, behavior)

47
Q

two types of sexual selection

A

-intersexual and intrasexual

48
Q

intersexual selection (mate choice)

A
  • individuals of one sex are choosy in selecting their mate of the other sex
  • females look for males with “good genes” and look showy and well taken care of
49
Q

intrasexual selection

A

selection within the same sex where individuals of one sex compete directly for mates of the opposite sex (common with males looking for females)

50
Q

what does balancing selection do and what are the two types

A
  • preservation of some loci to maintain two or more phenotypic forms in a population
  • frequency dependent selection and heterozygote advantage
51
Q

frequency dependent selection

A
  • fitness of phenotype depends on how common it is in a population
  • selection favors what it least common to keep frequencies of both at about 50%
52
Q

heterozygote advantage

A

-individuals that are heterozygotes at specific locus have greater fitness than homozygotes

53
Q

why can natural selection not produce perfect organisms

A
  1. selection acts on existing variations
  2. evolution is limited by historical constraints
  3. adaptions are often compromise
  4. chance, natural selection, and environment constantly interact
  5. natural selection acts on “better than” basis
54
Q

genotypic frequency

A

-proportion of individuals in a population with a specific genotype

55
Q

allele frequency

A

-proportion of particular allele in a population

56
Q

migration

A

movement of alleles between populations (gene flow)

57
Q

what are the two ways migration can occur

A
  • individuals migrating

- gametes migrating

58
Q

what is fixation

A

every member of the population has the same allele

biology 142 (4 decks)

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