Inheritance of phenotypes

Question 1

Homology

Answer 1

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

Question 2

Vestigal organs

Answer 2

features that serve no current function

-cave organisms eyes(stages of degeneration)

Question 3

Biogeography

Answer 3

-many similar species found clustered within the same archipelagom

Question 4

Fossil evidence

Answer 4

-fossils organised in specific sequence in rock strata

Question 5

artificial selection

Answer 5

-pigeon breeding

Question 6

What is evolutionary modification?

Answer 6

• 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)

Question 7

phenotypic variation

Answer 7

-variation in natural populations
eg.
peppered moths
spotted ladybird

Question 8

Natural selection

Answer 8

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

Question 9

Natural selection

Answer 9

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

Question 10

Natural selection

Answer 10

-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)

Question 11

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

Answer 11

Breeder’s equation

-estimates heritability

Question 12

If heritability is > 0

Answer 12

genetic factors have some influence

Question 13

Maximum heritability is 1

Answer 13

-indicates only genetic effects acting

Question 14

Twin studies:

Concordant

Answer 14

-both of a pair of twins share a trait

Question 15

Twin studies:

Discordant

Answer 15

-one has trait other does not

Question 16

Strong heritability

Answer 16

-no effect of environment

Question 17

Weak heritability

Answer 17

environment modulates

Question 18

Breeders equation:

Heritability INCREASES if…

Answer 18

environment is made less variable

because total variance decreases- denominator less in equation

Question 19

Penetrance

Answer 19

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

Question 20

R = h2S Breeder’s Equation

Answer 20

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

Question 21

h2 =

Answer 21

heritability

-proportion of trait variation that can respond to natural selection

Question 22

S =

Answer 22

selection differential

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

Question 23

R =

Answer 23

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

Question 24

Directional selection

Answer 24

-changes the mean trait value

Question 25

Stabilising selection

Answer 25

- removes the trait extremes | - reduces variance but leaves the mean unaltered

Question 26

Disruptive selection

Answer 26

-splits the population into two groups with different means

Question 27

Truncation selection

Answer 27

- changes mean and reduces variance | - natural selection that favours individuals above a fixed value for phenotypic trait

Question 28

how is fitness assessed

Answer 28

complete lifetime reproductive output

Question 29

Differential shell strength of Cepea nemoralis - snails

Answer 29

- pink stronger than yellow - labium- where mice do damage - apex - where birds crush

Question 30

Evolution

Answer 30

change in allele frequencies through time

Question 31

gene pool

Answer 31

sum of all the alleles present in a populatio

Question 32

Polymorphisms

Answer 32

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

Question 33

Relative fitness =

Answer 33

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

Question 34

Complete dominance

Answer 34

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

Question 35

Heterosis (hybrid vigour)

Answer 35

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

Question 36

Codominance

Answer 36

-heterozygotes have intermediate fitness

Question 37

The lactase gene

Answer 37

- 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

Question 38

Result of mutation in lactase gene

Answer 38

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

Question 39

C/T variant

Answer 39

``` polymorphism genotypes: CC intolerant CT tolerant TT tolerant ```

Question 40

Hypothesis of T allele frequency

Answer 40

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