Natural Selection - 3

Question 1

Define allele

Answer 1

variant forms of a gene (ex. Blue or brown allele)

Question 2

Define Locus

Answer 2

position of a specific gene on a chromosome
(ex. eye colour found on specific location of a chromosome)

Question 3

Define allele frequency

Answer 3

Proportion of a specific allele in a population

Question 4

Define genotype frequency

Answer 4

Proportion of individuals with a specific genotype (shows genetic variation) __% homo dominant, ___% homo recessive, __% heterozygous

Question 5

Define natural selection

Answer 5

Process where populations are altered over time as a result of promoting heritable traits that affect the ability of individual organisms to survive and reproduce

Question 6

Darwins 4 claims about the nature of populations and natural selection

Answer 6

1. Population is variable (genetic variation)
2. Variation is heritable
3. Not everyone survives/reproduces (there are more individuals than the environment can sustain)
4. Variation influences differential survival/reproduction

Question 7

What are the 3 types of selection

Answer 7

1. directional
2. diversifying
3. stabilizing

Question 8

Define directional selection

Answer 8

one extreme phenotype is favoured over others, causing a shift over time in one direction of that phenotype
ex. mean weight of salmon because it declines over time to favour smaller fish weight because predators go after the larger fish

Question 9

Define diversifying selection

Answer 9

(or disruptive)
favours extreme phenotypes for a trait over intermediate phenotypes.
ex. black-bellied seedcrackers birds survived with either small or large length beaks because seeds were either large or small, not intermediate.

Question 10

Define stabilizing selection

Answer 10

favours the intermediate phenotypes over either extreme
ex. larvae develop and don’t want to be very small or else parasites can enter and don’t want to be very large because then will experience predation from birds

Question 11

What are the 3 limits of natural selection

Answer 11

1. adaptations are compromises (because single structures often have multiple functions)
2. evolution is not only due to the results of adaptation (some are due to chance -> mutation and genetic drift)
3. acts on already existing variations (doesn’t create new alleles)

Question 12

natural selection acts on ____, but affects _____ (2 sets of answers)

Answer 12

individuals, populations
phenotypes, allele frequencies