Population And Evolution

Question 1

Population

Answer 1

A group of organisms of the same species that live in the same area, at a particular time and can interbreed

Question 2

Gene pool

Answer 2

All the alleles of all the genes of all the individuals in a population at a given time

Question 3

Allelic frequency

Answer 3

The number of times an allele occurs within the gene pool

Question 4

Hardy - Weinberg principle

Answer 4

Calculates the frequency of alleles of a particular gene in a population

Assumes- proportion of dominant and recessive alleles of any gene in a population remains the same from one generation to the next

Question 5

Why Hardy Weinberg might not apply

Answer 5

Mutations 
Population is not isolated 
There maybe selection - only some alleles passed
Population is small 
Mating within population is not random

Question 6

Hard Weinberg equation

Answer 6

P (dominant)
q (recessive)

P+q = 1

P2 + 2pq + q2 = 1

Question 7

Causes of genetic variation

Answer 7

Mutations

Meiosis - different alleles passes

Random fertilisation of gametes- new combination of alleles for offspring

Question 8

What kind of variation is genetic variation

Answer 8

Discontinuous variation
Controlled by a single gene

Organisms fit into a few distinct forms

ABO blood group - variation controlled by single gene

bar chart can be produced

Question 9

Environmental factors that influence the way organisms genes are expressed - variation

Answer 9

Climatic change (e.g. Temperature, rainfall, sunlight)

Soil conditions

PH

Food availability

Question 10

What kind of data is continuum

Answer 10

Continuous data
A continuum - e.g mass and height

Controlled by poly genes

Bell shaped curve called normal distribution curve can be drawn

Question 11

Selection pressures

Answer 11

Environment that limit the population of a species

Determine the frequency of alleles

Question 12

Types of selection pressures

Answer 12

Predation
Disease
Competition

Question 13

How does evolution occur

Answer 13

By natural selection

Question 14

For natural selection to occur what factors are needed

Answer 14

Organisms to produce more offspring than can be supported

Genetic variety within the population of all species

A variety of phenotypes that selection operates against

Question 15

Why is Over production of offspring in natural selection needed

Answer 15

So that a large population survives to breed and produce next generation

Compensates for high death rates (from disease, natural disasters, extreme temp, competition for food)

Question 16

Natural selection

Answer 16

Some organisms are better adapted for survival in their given habitat

Individuals best suited to environment more likely to survive

Individuals are more likely to breed and pass on favourable allele to next generation

Frequency of this allele in the gene pool will increase

Question 17

Why is there variation in natural selection

Answer 17

Conditions change overtime and having a range of genetically different in the population - some will have the genes needed to survive in any circumstance

Populations showing little variation - more vulnerable to disease etc

Question 18

Stabilising selection

Answer 18

Preserves the average phenotype of a population

Selection against the the extreme phenotypes

Question 19

Directional selection

Answer 19

Changes the phenotypes of a population by favouring phenotypes that vary in one direction from the mean of the population

Selection for one extreme phenotype

Question 20

Disruptive selection

Answer 20

Favours individuals with extreme phenotypes rather than those with phenotypes around the mean of the population

Question 21

Speciation

Answer 21

The evolution of new species from existing ones

Question 22

How new species are formed

Answer 22

Reproductive separation

Question 23

Speciation lead to different species to evolve

Answer 23

1. Geographical isolation
2. Variation due to mutation
3. Different environmental conditions - causes selection pressure
4. Selection for different favourable allele
5. Organism survive and reproduce
6. Leads to change in allele frequency
7. Each population unable to interbreed/ each population becomes different species/ each with own gene pool

Question 24

Genetic drift in small populations

Answer 24

1. Genetic diversity is less
2. Allele passes or mutations - quickly Affects the population because frequency is high
3. Population will change rapidly + more likely to develop into separate species

Question 25

Genetic drift in large populations

Answer 25

1. Affect of mutant allele is diluted
2. Frequency is less in a larger gene pool
3. Affect is less, and slower development into new species

Question 26

2 forms of speciation

Answer 26

Allopatric speciation

Sympatric speciation

Question 27

Allopatric speciation

Answer 27

Geographical separation due to psychical barrier

Different environment on either of the barrier

Many generations time lead to seperate species

Question 28

Sympatric speciation

Answer 28

Population in Same area leads to species becoming reproductively separated

Mutations in each population lead to evolution of genetic differences

Over time - unable to interbreed, become separate species