Allele frequency change

Question 1

Natural selection

Answer 1

-Individuals exhibit varitions in phenotypes
-Many of these variations are heritable and are passed onto offspring
-Offspring tend to reproduce in an exponential fashion as more offspring are produced than can survive
-This causes struggle for survival as well as the need to avoid external threats
-In the struggle for survival, individuals with particular phenotypes will be more successful than others causing them to survive and reproduce at higher rates

Question 2

Selection

Answer 2

Individuals with particular genotype have survival/reproductive advantage over others
this results in increased genetic contribution of these alleles to future generations

Question 3

Fitness

Answer 3

measure of reproductive success and therefore contribution to future generations

Question 4

types of selection

Answer 4

-Directional
-Stabilisng
Disruptive

Question 5

Directional selection

Answer 5

Trit at one end of the spectrum of phenotypes becomes selected for or against, usually due to environmental changes

Question 6

E.Directional

Answer 6

Drought in 1977 killed 80% of finches in Galapagos
-Bigger beaked birds could consume more seeds and survived more
-Phenotyppe shifted during drought; beack size declined after drought when more plant food sources became availible

Question 7

Stabilising selection

Answer 7

-Selects for intermediate phenotype
-Extremes are selected against
-Phenotypic variance in population is reduced
-Mean phenotype remains stable

Question 8

E.Stabilising

Answer 8

Human birth weight
Babies that were too small or large had a higher mortality rate than babies with intermediate weight

Question 9

Disruptive selection

Answer 9

-Selection against intermediate phenotypes and selection for phenotypes at both extremes
-Opposite of stabilising selection
-Population has bimodal distribution of a trait
-usually artificial

Question 10

E.Disruptive

Answer 10

In drosophila, artificial selection performed where flies with only a high number or only a low number of bristles were allowed to breed

Question 11

G.Directional

Answer 11

Question 12

G.Stablising

Answer 12

Question 13

G.Disruptive

Answer 13

Question 14

New Alleles

Answer 14

-Changes in assortment and recombination produces more genetic variation but not new alleles
-Mutationn alone creates new alleles and in small pop changes allele frequencies
-Mutation rates are difficult to observe in diploid organisms
-In larger populations, there is no significant alteration to allele frequencies due to mutation and only over long periods of time, are these numbers measurable