6.1.2 (d-f)

Question 1

What are the features and genetic basis of continuous variation?

Answer 1

• No distinct categories and there is a full range between 2 extremes
• Data usually presented in the feature of a line graph
• Data is quantified
• Polygenic: Controlled by several genes
• Cause of variation: Normally genetic and environmental

Question 2

What are the feautres and genetic basis of discontinuous variation?

Answer 2

• Has distinct groups or categories (no in-betweens)
• Data is qualitative
• Presented in a bar graph
• Monogenic: Controlled by 1 or a few genes
• Cause of variation: Genetic

Question 3

Define

Gene Pool

Allele Frequenchy

Selection Pressure

Answer 3

Gene Pool: Sum of all genes in a population at a given time

Allele Frequency: Relative frequency of a particular allele in a population at a given time

Selection Pressure: A factor that gives a selective advantage to one phenotype over another impacting an organism’s chance of survival/reproductive success

They can change the frequency of an allele

Question 4

Name the factors affecting species evolution

Answer 4

Founder Effect

Genetic Drift

Genetic Bottlenecks

Question 5

What is the founder effect?

Answer 5

• When an isolated population grows from a small sample of an entire population
  
  • The small sample will not be representative in terms of alleles from the main population, the new population will lack genetic diversity

Question 6

Explain:

Genetic Drift

Geentic Bottleneck

Answer 6

Genetic Drift

• It is when allele frequencies change by chance
• This can be due to birth and death of individuals or mutations
• Causing changes to the gene pool
  
  • Genetic drift has a greater impact on smaller populations because there are less alleles and individuals

Genetic Bottlenecks

When a significant event occurs (e.g. disease or natural disaster) - many alleles are lost when population drops (reduces gene pool)

• current population exists from few survivors so only their alleles are passed onto future generations
• Gene pool is reduced, genetic and phenotypic diversity is therefore reduced

Question 7

What is stabilising selection?

What is directional selection?

Answer 7

Stabilising Selection

• Natural selection that favours average phenotypes
• The selection pressures are against extreme phenotypes, so as time passes on it is unlikely there will be evolutionary change

Directional Selection

• Evolution occurs when there are selection pressures on species’
• The change in the environment is against normal phenotypes and alleles
  
  • They favour phenotypes at either extreme, the allele frequency shifts to the favoured
• *extreme phenotyp**

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Question 8

What is the Hardy-Weingberg principle?

Answer 8

In a stable population with no disturbing factors, the allele frequencies will remain constant from one generation to another and there will be no evolution

p + q = 1

p is frequency of one allele

q is the frequency of another

Question 9

What are the assumptions of the Hardy Weinberg principle?

Answer 9

• Large population
• Random mating
• No mutation, immigration or emigration
• No selective pressures