Populations and evolution

Question 1

What is a population

Answer 1

A group of organisms of the same species in one area at one time that can interbreed

Question 3

What is a gene pool

Answer 3

All the alleles in a population at any one time

Question 4

What is allele frequency

Answer 4

Proportion of allele of a gene in a gene pool

Question 5

What is the hardy weinberg equation

Answer 5

p squared + 2pq + q squared = 1
and
P + q = 1
P is frequency of dominant allele
q is the frequency of recessive allele
p squared is frequency of homo genotype
2pq - heterozygous genotype
q squared - frequency of homozygous phenotype - recessive

Question 6

Explain why individuals within a population of a species may show a wide range of variation in phenotype

Answer 6

Genetic factors:
Mutations
Crossing over
Independent segregation
Random fertilisation
Environment factors:
Good availability
light intensity

Question 7

What is evolution

Answer 7

Change in allele frequency over time through natural selection

Question 8

What are factors that may drive natural selection

Answer 8

Predation disease and competition

Question 9

Explain the effects of stabilising selection

Answer 9

Organisms with alleles coding for average variations have a selective advantage, so frequency of alleles coding for average variations of a trait increase and those coding for extreme variations decrease
This means standard deviation is reduced

Question 10

Explain the effects of directional selection

Answer 10

Organisms with alleles coding for one extreme variation have a selective advantage
So frequency of alleles coding for this extreme variation of the trait increase and the other extreme variation decreases

Question 11

Explain the effects of disruptive selection

Answer 11

Organisms with alleles coding for either extreme variation of a trait have a selective advantage
So frequency of alleles coding for both extreme variations increase and those coding for average decrease
This can lead to speciation

Question 12

Describe speciation.

Answer 12

Reproductive separation of 2 populations
Difference in gene pools
New species arise due to no interbreeding and producing fertile offspring

Question 13

Describe allopatric speciation

Answer 13

Population is split due to geographical isolation
Leads to reproductive isolation which separates gene pools by preventing interbreeding
Random mutations cause genetic variation
Different selection pressures so different alleles are passed on
so allelic frequency changes
No interbreeding

Question 14

Symmetric speciation

Answer 14

No geographical isolation
Mutations lead to reproductive isolation by preventing interbreeding
Different selection pressures so different alleles are passed on and allelic frequency changes over time
different populations cannot interbreed to produce fertile offspring

Question 15

Explain genetic drift and its important in small populations

Answer 15

Genetic drift- a mechanism of evolution in which allele frequencies in a population change over generations due to chance

It is important in small populations as some alleles are passed onto offspring more/less often by chance
so the strongest effect in small populations as gene pool is small
This can reduce genetic diversity