Evolution 4.4 4.5 5.17-5.19

Question 1

Describe how adaptations become more common due to evolution and natural selection

Answer 1

1. Mutations introduce new alleles into a population to show a variation of the phenotype
2. Some characteristics have a survival advantage so individuals with the advantageous alleles survive selection pressure
3. Individuals survive and reproduced to pass on their advantageous alleles to their offspring
4. Number of individuals with advantageous allele increases
5. Over time change in allele frequency = EVOLUTION

Question 2

Define ‘species’

Answer 2

A group of similar organisms that can reproduce to give fertile offspring

Question 3

What is speciation

Answer 3

The development of new species that occurs when populations become reproductively isolated due to changes in allele and phenotype preventing them breeding together

Question 4

Describe the 3 changes that prevent different species successfully breeding together

Answer 4

1. Seasonal changes - individuals become sexually active at different times of the year
2. Mechanical changes - genitalia
3. Behavioural changes - courtship rituals become unattractive

Question 5

What is sympatric speciation

Answer 5

Speciation without geographical isolation

Question 6

What is evolution

Answer 6

A change in allele frequency over time

Question 7

What is alopatric speciation

Answer 7

Geographical isolation that forms new species

Question 8

Describe geographical isolation leading to speciation

Answer 8

1. Physical barrier divides a population of a species
2. Conditions on either side are slightly different
3. Different characteristics become more common due to natural selection
4. Different characteristics will become advantageous on each side, allele frequencies will change in each pop.
5. Mutations will also take place further altering allele frequency
6. Phenotypes will differ
7. Populations can no longer mate to produce fertile offspring so new species

Question 9

What does the Hardy-Weinberg principle tell you? What conditions does this require?

Answer 9

The allele frequencies in a population won’t change from one generation to the next

Large population with no mutation, natural selection, immigration, emigration and has to allow random mating

Question 10

Give the equation that predicts allele frequency

Answer 10

p+q=1

p = frequency of dominant allele
q = frequency of recessive allele

Question 11

Give the equation that predicts genotype and phenotype frequency

Answer 11

p ² + 2pq + q ² = 1

p ² = frequency of homozygous dominant genotype
2pq = heterozygous genotype
q ² = frequency of homozygous recessive genotype