Population and Evolution

Question 1

Define species

Answer 1

Group of similar organisms that reproduce to give fertile offspring

Question 2

Define population

Answer 2

Same species living in particular area at same time

Species can exist as 1/more populations

Question 3

Define gene pool

Answer 3

Complete range of alleles in population

Question 4

Define allele freq

Answer 4

How often allele occurs in population

Question 5

What does the Hardy Weinberg principle predict?

Answer 5

Freq of alleles in population won’t change from one generation to next

Question 6

The Hardy Weinberg prediction only occurs w/in certain conditions.

State the conditions

Answer 6

• Large population
• No : immigration, emigration, mutations, natural selection
• Random mating

Question 7

What is the Hardy Weinberg equation used for?

Answer 7

• Calculate freq :
• Alleles
• Genotype
• Phenotype
• Test whether principle applies to specific alleles in particular pop - if change then other factor involved

Question 8

Predicting allele freq. equation

Answer 8

p + q = 1

• p = freq. dominant
• q = feq. recessive

Question 9

Predicitng genotype and phenotype freq. equation

Answer 9

p² + 2pq + q² = 1

• p² = freq. homo dominant
• q^{<strong>2</strong>} = freq. homo recessive
• 2pq = freq. hetro

Question 10

What are the causes of genetic variation?

Answer 10

• Mutation
• Meiosis - crossing over + independent segregation
• Random fertilisation

Question 11

What are most variation w/in species caused by?

Answer 11

Combination of genetic + env factors

Question 12

Define evolution

Answer 12

Change in allele freq. over time

Question 13

Give examples of selection pressures

Answer 13

• Predation
• Disease
• Competition

Question 14

What are the diff. types of natural selection?

Answer 14

• Stabilising selection
• Directional selection
• Disruptive selection

Question 15

Define stabilising selection

Answer 15

• Env favours individuals w/in the middle range
• Occurs when env isn’t changing
• Reduces range of phenotype
• Mean stays the same

Question 16

Define directional selection

Answer 16

• Env favours individuals at one extreme
• Response to env change
• Mean changes

Question 17

Define disruptive selection

Answer 17

• Env favours individuals at either end of extreme - more than 1 phenotype
• Opposite of stabilising bc characteristics towards middle are lost

Question 18

Define speciation

Answer 18

Development of a new species from existing species

Question 19

Why does speciation occur?

Answer 19

• Population of same species become reproductively isolated
• No interbreeding
• Genetic variation occurs w/in population due to mutations
• Diff. selective pressures
• Best adapted survive + reproduce, passing it onto offspring
• Change in allele freq.
• Can no longer interbreed to produce fertile offspring

Question 20

What are the types of speciation

Answer 20

• Allopatric speciation
• Sympatric speciation

Question 21

Outline what happens during allopatric speciation

Answer 21

• Geographical isolation - experience diff. conditions
• Physical barriers prevent interbreeding

Question 22

Outline sympatric speciation

Answer 22

• Occurs in same env - doesn’t require geographical isolation
• Mutation prevents interbreeding
• Become reproductively isolated

Question 23

Outline ways reproductive isolation occurs

Answer 23

• Seasonal - develop diff. flowering/mating seasons, or become sexually active at diff. times of year
• Mechanical - changes in genitalia prevent successful mating
• Behavioural - develop courtship ritual that aren’t attractive to main population

Question 24

Define genetic drift

Answer 24

When chance, rather than env factors, dictates which individuals survive, breed + pass on their alleles

Question 25

When does evolution by genetic drift usually have a greater effect?

Answer 25

Small population - chance has greater influence

Question 26

What might cause changes in allele freq?

Answer 26

• Natural selection
• Mutations
• Genetic drift

Question 27

Which factors are involved in evolution?

Answer 27

• Natural selection
• Genetic drift
• BUT one can drive evolution more than other depending on population size