population genetics

Question 1

define population genetics

Answer 1

the study of how allele frequencies within populations of a species change over time leading to evolution

Question 2

define population

Answer 2

a group of organisms of the same species living in the same place at the same time

Question 3

define allele frequency

Answer 3

the proportion of an allele within the gene pool compared to the total number of alleles for that gene

Question 4

define gene pool

Answer 4

the total set of all the alleles for all of the genes in a population

Question 5

what does the hardy weinberg principle state?

Answer 5

frequency of alleles in a population remains constant from generation to generation

Question 6

under what 5 conditions does the hardy weinberg principle work?

Answer 6

• no natural selection
• no sexual selection
• no mutations
• no gene flow
• large population

Question 7

define ‘species’

Answer 7

a group of organisms with similar physical characteristics that can interbreed to produce fertile offspring

Question 8

define ‘speciation’

Answer 8

the evolution of a new species

Question 9

define ‘isolating mechanism’

Answer 9

ways in which organisms become isolated from each other with no gene flow, in order to form new species

Question 10

define ‘isolation’

Answer 10

separation of members of a species so there is no gene flow

Question 11

define ‘geographical isolation’

Answer 11

• an isolating mechanism
• a physical barrier between members of a species, causing them to become reproductively isolated

Question 12

give an example of geographical isolation

Answer 12

members of a population colonising a new island

Question 13

define ‘allopatric speciation’

Answer 13

• type of speciation
• different lands

Question 14

what does geographical isolation lead to?

Answer 14

allopatric speciation

Question 15

why can an isolated species no longer produce fertile offspring?

Answer 15

• as phenotypes have been changing, DNA has been changing
• new alleles/genes/chromosomes
• cannot produce viable gametes through meiosis

Question 16

define ‘total reproductive isolation’

Answer 16

reproducing isolated species together, but they will not produce fertile offspring

Question 17

summarise the steps in allopatric speciation

Answer 17

1. geographical isolation results in no gene flow between population
2. random mutations occur in both populations
3. different selection pressures and evolutionary forces act on each population
4. accumulation of mutations and allele frequency leads to the populations becoming pheno/genotypically different
5. population members are now so different they can no longer interbeed to produce fertile offspring - they are totally reproductively isolated
6. allopatric speciation has occurred

Question 18

define ‘sympatric speciation’

Answer 18

type of speciation
- same land

Question 19

describe sympatric speciation

Answer 19

• members of a species stop breeding with each other despite still living together

Question 20

summarise the steps in sympatric speciation

Answer 20

1. random mutation leads to reproductive isolation of some of that population
   - changes behaviour/ecology etc of some members
2. this results in no/reduced gene flow between populations
3. more random mutations occur in both populations
4. different selection pressures and evolutionary forces act on each population
5. accumulation of mutations and change in allele frequency over many generations lead to large changes in phenotype
6. members of population are so different they can no longer interbreed to produce fertile offspring (total reproductive isolation)

Question 21

define ‘pre zygotic isolation’

Answer 21

mechanisms that prevent a zygote being created

Question 22

define ‘post zygotic isolation’

Answer 22

mechanisms that prevent the zygote developing to full term

Question 23

state the 4 pre zygotic isolation mechanisms

Answer 23

• temporal
• ecological
• behavioural
• mechanical

Question 24

state the 3 post zygotic isolation mechanisms

Answer 24

• hybrid inviability
• hybrid infertility
• hybrid breakdown

Question 25

define ‘temporal’ isolating mechanism

Answer 25

2 species mate at different times of year

Question 26

define ‘ecological’ isolating mechanism

Answer 26

2 species occupy different habitats

Question 27

define ‘behavioural’ isolating mechanism

Answer 27

2 species have different courtship behaviours
- eg bird song

Question 28

define ‘mechanical’ isolating mechanism

Answer 28

physical differences prevent copulation/pollination
- eg dog breeds size

Question 29

define ‘hybrid inviability’

Answer 29

hybrids produced but fail to develop to reproductive maturity

Question 30

define ‘hybrid infertility’

Answer 30

hybrids fail to produce functional gametes

Question 31

define ‘hybrid breakdown’

Answer 31

F1 hybrids are fertile but F2 generation fails to develop properly