Populations and evolution

Question 1

Gene pool definition

Answer 1

Total information from all the genes and alleles of the breeding individuals in a population at a particular time

Question 2

Allele frequency definition

Answer 2

The number of that allele divided by the total number of alleles for that gene in a population

Question 3

Hardy Weinberg principle

Answer 3

The proportion of dominant and recessive alleles in a population remains constant from one generation to the next.

Question 4

What are the 5 conditions needed for the hardy Weinberg principle to be met

Answer 4

• no mutations
• isolated population
• no selection
• large population
• random mating in the population

Question 5

Is p the frequency of the dominant or recessive allele

Answer 5

Dominant

Question 6

Is q the frequency of the dominant or recessive allele

Answer 6

Recessive

Question 7

What is the first equation for hardy Weinberg

Answer 7

P + Q = 1

Question 8

What is the hardy Weinberg formula

Answer 8

P2 + 2pq + Q2 =1

Psquared is the frequency of homdom
2pq is frequency of hetero
Q2 is frequency if homrec

Question 9

Strategy for working out hardy Weinberg

Answer 9

1) work out the hardy Weinberg frequency
2) turn this into a probability
3) usually need to calculate p and q
4) work out hardy Weinberg frequency you need to work out
5) calculate it (probability)
6) check by adding up to 1
7) multiply to make units needed in the answer I.e %

Question 10

What are the ways to get variation

Answer 10

Environment
Mutation-new alleles
Meiosis -crossing over(new combinations)
Meiosis-independent segregation
Meiosis-random assortment of sister chromatids
Any sperm can fuse with any egg - random fertilisation

Question 11

Discontinuous variation

Answer 11

• bar charts
• limited number of traits, no intermediate forms
• controlled by few genes(usually multiple alleles)
• environment has little effect on these characteristics
• eg blood group

Question 12

Continuous variation

Answer 12

• histograms
• range of gradation of characteristics
• controlled by many genes (polygenic)
• environment has significant effect
• eg height

Question 13

Selection pressures definition

Answer 13

Environmental factors that limit the population of a species e.g. predation, disease and competition

Question 14

Species definition

Answer 14

Group of organisms that can interbreed successfully to produce fertile offspring

Question 15

Limitations of the species concept

Answer 15

Doesn’t apply to all

Can’t tell if extinct animals can/can’t breed

Question 16

Natural selection process

Answer 16

Apply to Q

1) variation occurs in a species
2) due to mutation
3) selection pressure causes some organisms to be disadvantaged
4) some organisms are better adapted(phenotype)-anitomical, physiological or behaviours
5) these survive and reproduce(differential reproductive success
6) increasing the frequency of their successful alleles in the next generation

Question 17

Evolution means natural selection depends on

Answer 17

Over production - produce more than can support with supply of food light space etc
Genetic variety in populations of all species
Variety of phenotypes that selection operates against

Question 18

Role of overproduction

Answer 18

Ensure enough organisms survive to reproduce in next generation

Alternative is lower rate but good parenting to ensure young survive

Question 19

What is the selection pressure for over producing species

Answer 19

Intra specific competition

Question 20

Role of variation in natural selection

Answer 20

Is essential when there are changing selection pressures so natural selection can occur

Question 21

Stabilising selection

Answer 21

• mean stays the same
• standard deviation occurs
• reduces variation
• occurs in an unchanging environment

Graph gets thinner >

Question 22

Directional selection

Answer 22

• mean changes
• standard deviation not altered much
• phenotype at end of a range is selected for
• environment changing

Graph moves to either side but is same shape
> or

Question 23

Disruptive selection

Answer 23

• opposite of stabilising
• selection pressure toward extremes, creates 2 moral values
• over time when species evolve 2 means and 2 standard deviation form —— 2 different species

Graph has two bumps <>

Question 24

What is evolution

Answer 24

A change in allele frequencies in a population

Question 25

What is speciation

Answer 25

Evolution of a new species from existing ones

Question 26

What is reproductive isolation

Answer 26

Members are reproductively separated from others (can’t breed)

Is the most important way new species are formed. Followed by genetic change

Question 27

What is adaptive radiation

Answer 27

Changes in different populations to local selection pressures

Question 28

Genetic drift

Answer 28

Occurs most in small isolated populations
Genetic diversity is less because there is a smaller gene pool
Any favourable mutation will spread more quickly through this population
Population will change more quickly and is more likely to develop into a new species

Question 29

What is allopatric speciation

Answer 29

The formation of a new species when there has been geographical isolation

A geographical barrier for one organism might not be for another

Question 30

What are the 7 steps in allopatric speciation

Answer 30

1) organisms of Same prices are separated into 2 groups b physical barrier so can’t interbreed
2) prevents gene flow between the 2 groups’ gene pools
3) variation exists in each population due to mutations occurring in each population
4) if there are different selection pressures on the 2 groups it will cause different phenotypes to be selected in natural selection
5) 2 groups evolve differently (as have different alleles)
6) in time differences between 2 gene pools are so great that they are now separate species
7) the 2 species groups will not be able to interbreed to produce fertile offspring as they are now different species

Question 31

What is sympatric speciation

Answer 31

Speciation where the organisms are living in the same area( not geographically isolated) but reproductive isolation occurs

Question 32

What are the methods of sympatric speciation

Answer 32

• geographical > isolated by physical barriers
• ecological > different habitats in same area
• temporal > different breeding seasons
• behavioural > different courtship
• mechanical > anatomical differences
• gametic > gametes can’t meet due to genetic/biochemical incompatibility