6.1.3 Chi squared and Evolution

Question 1

What is the Chi squred test used for

Answer 1

It is used to chekc the results of genetic crosses to see if they significant.

Question 2

What is evolution

Answer 2

It is the change in allele frequency of a populations gene pool over a period of time, usually caused by a mutation and written as a percentage

Question 3

How does evolution occur

Answer 3

It occurs by natural selection
Individuals have different alleles in a population. There will be a struggle for survival through predation disease or competition.
Some individuals are better adapted to survive, and will reproduce and pass on this gene. This means a greater proportion of this gene is present in the next generation

Question 4

How does the environment affect which charecteristics are more common

Answer 4

When the environment isn’t changing much, individuals with charecteristics towards the middle are more likely to survive and reproduce. This is stabilising selection.

When the environmen is changing the individuals with charecteristcis of an extreme type are more likely to survive and reproduce. Directional selection.

Question 5

What is genetic drift

Answer 5

Individuals show variation
The allele of one genotype is passed on to the offspring more often than others. So the number of people with that allele increase. It may become more common in the population.
Genetic drift has a greater effect in small populations where chance has a greater effect.

Question 6

What is a genetic bottleneck and how does it affect genetic drift

Answer 6

It is an event that causes a big reduction in a populations size, leading to a reduction in the gene pool .

Question 7

What is a founder effect and how does it affect the founder effect

Answer 7

It is when a few organisms from a population start a new population and only a small number of different alleles are in the initial gene pool.
Without any gene flow from outside the population will grow with reduced genetic variation.
A small population is more influenced by genetic drift than a large population.

Question 8

What is the hardy weinberg principle

Answer 8

Predicts that frequencies of alleles wont change from one gen to the next
conditions: no immigration, emigration, mutations or natural selection. Random mating

Question 9

2 equations of hardy weinberg and what are they for

Answer 9

P + q = 1
predict allele frequency

p^2 + 2pq + q^2 = 1
predict genotype frequency

Question 10

what is artificial selection

Answer 10

breeding individuals with desirable traits
Modern dairy cattle
Bread Wheat
Artificial selection reduces the gene pool, since similar traits are breed together, this leads to a reduction in the gene pool.
If a disease appears there is less chance the alleles could offer resistance

Question 11

What problems can aritiicial selection cause

Answer 11

They can cause certain traits to be exaggerated which can cause health problems
there will also be more genetic disease.
There are ethical issues

Question 12

What is speciation

Answer 12

It is the development of a new species
It occurs when populations of the same speccies become reproductively isolated and no longer breed to produce fertile offspring

Question 13

Allopatric speciation

Answer 13

It is caused by geographical isolation and natural selection
Physical barriers can divide populations and the condition cna become different on either side. This means different charecteristic will be more common on either side due to natural selection.
Eventually individuals from different populations will have changed so much they wont be able to breed with onea another to produce fertile offspring

Question 14

Causes of reproductive isolation

Answer 14

Seasonal changes - individuals from the same population develop different flowering or mating seasons or become sexually active at different times of year.
Mechanical changes - changes in genitalia prevent successful mating
Behavioural changes - develop courtship rituals that arent attractive to the main population

Question 15

What is sympatric speciation

Answer 15

Random mutations occur which prevent people from breeding with other members of the species.