Population genetics, Evolution And Speciation

Question 1

Gene Pool

Answer 1

All the genes and alleles in a population at a particular time

Question 2

Allele Frequency

Answer 2

Proportion of a particular allele in the population

Question 3

Genotype Frequencies

Answer 3

AA p2
aa q2
Aa 2pq

Question 4

Hardy Weinberg Equation

Answer 4

p2 + 2pq + q2 = 1

Question 5

Condition allowing for genotype freq determination

Answer 5

Random Mating

Question 6

Equation for Alleles in population

Answer 6

p + q = 1

Question 7

Hardy Weinberg Principle

Answer 7

No factor operates that would cause the allele frequencies in the offspring population to differ from those in the parental population

Question 8

Conditions for Hardy-Weinberg Equilibrium

Answer 8

•mating is random
•population is large
•no mutations are occurring
•no migration taking place
•no selection taking place

Question 9

How does Mutation make a population genetically variable

Answer 9

Gene mutation introduces new alleles into the population

Chromosome mutation occurs when chromosomes fail to separate during meiosis - extra occur

Question 10

How does Meiosis make a population genetically variable

Answer 10

Produces variety of haploid cells through independent assortment and recombination

Question 11

How does Sexual Reproduction make a population genetically variable

Answer 11

when cross-fertilisation is ensured
most important factor promoting genetic variability

Involves mixing of genetic material from haploid cells of 2 diff individuals

In life cycles meiosis and sex act to shuffle the allelic combinations

Question 12

How does Diploidy make a population genetically variable

Answer 12

Variability is preserved by diploidy - shelters rate, recessive alleles

Heterozygotes act as important reservoirs of genetic variation in populationss

Question 13

Natural Selection

Answer 13

The unequal transmission of alleles to subsequent generations by different genotypes

Question 14

Fitness

Answer 14

Ability of an org to pass on alleles to subsequent generations

Question 15

Polymorphic Populations

Answer 15

Used to study natural selection

Polymorphism is presence in pop of 2 or more distinct forms e.g. snail shell colour and bands

Thrush predation - powerful agent of selection - camouflage- result is balanced polymorphism

Question 16

Apostatic Selection

Answer 16

Predator hunts most common form (easier to see) until it becomes the less common form

Question 17

Heterozygous Advantage

Answer 17

means of maintaining different forms in a population

Question 18

Stabilising Selection

Answer 18

Occurs where environmental conditions are largely unchanging

Favours the modal or intermediate forms and acts against the extremes

Does not lead to evolution - maintains adaptive norm

Question 19

Example of Stabilising Selection

Answer 19

Birth records London 1935 and 1946

Shows optimum birth weight for babies - babies heavier or lighter were at a selective disadvantage

Question 20

Directional Selection

Answer 20

Associated with changing environmental conditions

Majority of an existing form may no longer be best suited to the environment - some may have selective advantage in changed conditions - contribute more offspring and alleles to next generation

Question 21

Evolution

Answer 21

Change in genetic composition of the population

Change in allele frequency in pop

Question 22

Speciation

Answer 22

Evolution of new species from ancestral species

Question 23

Species

Answer 23

Group of organisms with similar morphological, physiological, biochemical and behavioural features that can interbreed to produce fertile offspring, and which is reproductively isolated from other species

Question 24

Allopatric Speciation

Answer 24

evolution of new species as a result of geographical isolation

Question 25

Process of Allopatric Speciation

Answer 25

•ancestral species expands into new locations - regular gene flow in gene pool •in One locality some physical barrier isolates a population geographically - gene flow prevented •isolated population and ancestral are subjected to diff selection pressures - if small genetic drift and founder effect •isolated and ancestral pop diverge genetically - e.g. diff morphological appearance- still capable of interbreeding (not diff species) •two pops may diverge genetically to the extent that interbreeding is prevented - new species evolved

Question 26

Genetic Drift

Answer 26

Random fluctuations in allele frequencies

Question 27

Founder Effect

Answer 27

Individuals that become isolated were not genetically representative of ancestral population

Question 28

2 possible outcomes if allotropic species come back into interaction

Answer 28

•one species will eliminate the other •both species evolve further and there will be niche divergence - most intense competition occur between members of species in area of niche overlap - selected against

Question 29

Graph of Niche divergence

Answer 29