AQA AS Biology Unit 2: Variation

Here are some notes on Variation for AS Biology Unit 2 AQA

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Variation is the differences that exist between individuals.
There are two types:
Interspecific The variation that exists between different species
Intraspecific the variation that exists within a species
Interspecific Variation
The differences between species are largely due to differences in their DNA.
The structure and sequence of the genes in each organism
The way in which the genes are expressed
A gene can only have an impact on an organism if it is switched on and used to make a
particular protein.
Intraspecific Variation
Intraspecific variation is caused by genetic and environmental factors.
Genetic Factors
All members of a species have the same genes
Individuals within a species have different alleles
The alleles an organism has make up its genotype
Different genotypes result in variation in phenotype
Meiosis: crossover, independent assortment, random fertilisation
You inherit genes from you parents which means genetic variation is inherited
Examples include; eye colour and blood type
Environmental Factors
Plant growth is affected by the amount of minerals available in the soil
Fur colour can be affected by temperature
Weight, hair colour, height etc.

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There are two basic types of intraspecific variation:
Discontinuous Features that fall into one category
Usually controlled by a single allele
Continuous Shows a whole range of values
Controlled by several genes
This involves taking measurements of individual, selected from the population being investigated. If
these individuals are representative then the measurements can be relied upon.
Sampling bias: The selection process may be biased. The investigators may make unrepresentative
choices either deliberately or unwittingly.
Chance: The individuals chosen may be not representative.…read more



Amazing notes, have you get notes for  evidence for relationship between organism, adaptation and selection and biodiversity  

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