Chapter 9.3: Genetic Diversity + 9.4: Types of selection

Biology A- level AQA, Section Four Chapter 9

Population

A group of individuals from the same species that live in the same place at the same time

Genetic diversity

the total number of different alleles in a population.

The greater the number of different alleles in a species, the greater the genetic diversity and the wider the range of characteristics

How do organisms differ

In their alleles

Why is genetic diversity important

The greater the genetic diversity, the more likely that species will be able to adapt to environmental changes

Natural selection

Some alleles are likely to be passed on to the next generation because certain individuals have more reproductive success

Gene pool

all the different alleles in a population

Allele frequency

The portion of a certain allele in the gene pool

What are the steps of natural selection

Random mutations → survival advantage → Reproductive success → advantageous allele is passed on → Frequency of advantageous allele will increase

What are the most common misconceptions

It is not the environmental change that causes the mutation leading to the new allele. Mutations happen at random and frequently.

What is “Advantageous” depends on the environment and it can change as we have seen

What are the types of selection

Direcional selection and stabilising selection

Which type of selection favours average individuals

Stabilising selection

Which type of selection favours those who differ from the mean population

Directional selection

What type of selection is represented by this graph

Directional selection

What type of selection is represented by this graph

Stabilising selection

What is a normal distribution curve

A bell shaped curve produced when a certain distribution is plotted on a graph

What are the steps to calculate SD (Standard Deviation)

Menu

Statistics

Variable

Enter Numbers

OPTN

Option 3

σx = Standard deviation

x= mean

What is an example of stabilising selection

Birth Weight

What is an example of Directional selection

The Use of antibiotics, it puts pressure on directional selection on the bacterial population