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Evolutionary Biology > Inheritance of phenotypes > Flashcards

Inheritance of phenotypes Flashcards

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1
Q

Homology

A

possession by two or more species of a trait derived from their common ancestor

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2
Q

Vestigal organs

A

features that serve no current function

-cave organisms eyes(stages of degeneration)

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3
Q

Biogeography

A

-many similar species found clustered within the same archipelagom

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4
Q

Fossil evidence

A

-fossils organised in specific sequence in rock strata

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5
Q

artificial selection

A

-pigeon breeding

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6
Q

What is evolutionary modification?

A
  • change in characteristics of individuals within a population from generation to generation
  • replacement of one kind of individual with another
  • relies on the existence of variation that is heritable (=genetic variation)
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7
Q

phenotypic variation

A

-variation in natural populations
eg.
peppered moths
spotted ladybird

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8
Q

Natural selection

A

-trait variation within a population is due in part to differences amoung individuals in their genetic constitution (HERITABILITY)

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9
Q

Natural selection

A

Trait variation within a population is associated with the variation in survival or reproduction in the current environment (SELECTION)

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10
Q

Natural selection

A

-over generational time, there will be a rise in the frequency of individuals having those trait values that confer a relative increase in reproductive success (EVOLUTION)

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11
Q

How much of the variability in a trait can be accounted for by the contribution of genetic variation?

A

Breeder’s equation

-estimates heritability

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12
Q

If heritability is > 0

A

genetic factors have some influence

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13
Q

Maximum heritability is 1

A

-indicates only genetic effects acting

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14
Q

Twin studies:

Concordant

A

-both of a pair of twins share a trait

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15
Q

Twin studies:

Discordant

A

-one has trait other does not

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16
Q

Strong heritability

A

-no effect of environment

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17
Q

Weak heritability

A

environment modulates

18
Q

Breeders equation:

Heritability INCREASES if…

A

environment is made less variable

because total variance decreases- denominator less in equation

19
Q

Penetrance

A

is the degree of expression of the trait/phenotype in the particular environment

20
Q

R = h2S Breeder’s Equation

A

R=h2S
h2 = S/R
S = h2/R

21
Q

h2 =

A

heritability

-proportion of trait variation that can respond to natural selection

22
Q

S =

A

selection differential

-mean trait value in population before selection (within a generation)

23
Q

R =

A

evolutionary response
-mean trait value in population in current generation (offspring) - mean trait value in population in previous generation (parents)

24
Q

Directional selection

A

-changes the mean trait value

25
Q

Stabilising selection

A
  • removes the trait extremes

- reduces variance but leaves the mean unaltered

26
Q

Disruptive selection

A

-splits the population into two groups with different means

27
Q

Truncation selection

A
  • changes mean and reduces variance

- natural selection that favours individuals above a fixed value for phenotypic trait

28
Q

how is fitness assessed

A

complete lifetime reproductive output

29
Q

Differential shell strength of Cepea nemoralis - snails

A
  • pink stronger than yellow
  • labium- where mice do damage
  • apex - where birds crush
30
Q

Evolution

A

change in allele frequencies through time

31
Q

gene pool

A

sum of all the alleles present in a populatio

32
Q

Polymorphisms

A
  • source of genetic variation between individual
  • each variant is an allele
  • genotype = combination of two alleles (for diploids)
33
Q

Relative fitness =

A

(N offspring per parent of one genotype)/(N offspring per parent of different genotype)

34
Q

Complete dominance

A

-fitness of homozygote for favoured allele A and heterozygotes have equal fitness, but fitness of alternate allele is lower

35
Q

Heterosis (hybrid vigour)

A

-fitness of heterozygotes is higher than either of the alleles when found as homozygotes

36
Q

Codominance

A

-heterozygotes have intermediate fitness

37
Q

The lactase gene

A
  • encodes enzyme lactase (lactose–>sugars)
  • mammal infants need lactase to digest maternal milk (lactase expressed in infancy)
  • a mutation occured in one copy of the lactase gene in the gametes of one person
38
Q

Result of mutation in lactase gene

A
  • change in function
  • genotype (regulatory part) C->T
  • mutation caused lactase gene to remain turned on after weaning
  • phenotype = lactase persistence into adulthood
39
Q

C/T variant

A 
polymorphism
genotypes:
CC intolerant
CT tolerant
TT tolerant
40
Q

Hypothesis of T allele frequency

A

-lactase persistence selected on basis that those able to drink milk as adults survive drought better?

Evolutionary Biology (11 decks)

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