Biology AS AQA Unit 2 Variation

Made these notes for my year 12 summer exam to revise and read over. There are spelling mistakes in most of my files but due to the busy exam schedule I had no time to correct them (sorry).

Most files have more information than what is needed but I feel it helps you feel more confident walking into the exam if you have a greater knowledge background and may help when having to apply knowledge to questions. Good luck :)

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  • Created by: Chelcie
  • Created on: 02-09-13 12:57
Preview of Biology AS AQA Unit 2 Variation

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INTERSPECIFIC: Differences between organisms/different species
INTRASPECIFIC: Differences between organisms of the same species.
SAMPLING BIAS: The selection process might be biased in that there an unrepresentation.
CHANCE: By pure chance the individuals chosen may not be representative.
RANDOM SAMPLING: Eliminating human choices, hence sampling bias. Can divide area into grid lines,
use random numbers as co-ordinates.
LARGE SAMPLE SIZE: The more individuals selected, the smaller the probability that chance will
influence the result. The greater the sample size, the more reliable the data will be.
ANALYSIS OF THE DATA: Using statistical tests can show how much chance has influenced the data.
Causes of Variation:
MUTATIONS: These sudden changes to genes and chromosomes may or may not be passed onto
the next generation. Increases variety.
MEIOSIS: Nuclear division forming two gametes. Meiosis mixes the genetic material before it is
passed into the gametes.
FUSION OF GAMETES: When gametes fuse at fertilisation, which gamete fusing with which is
Environmental Influences
The environment influences organisms which affect the way an organism's genes are expressed.
The genes set limits, but mostly the environmental factors determine where, within the limits, an
organism lies.
In most cases variation is due to genetic differences and environmental influences.
VARIATION DUE TO GENETIC FACTORS: Represented on bar chart/pie graph.
Discontinuous data- no intermediate types.
Forms a continuum. Controlled by polygenes (many
genes). Environmental factors play a significant role on
where on the continuum an organism actually lies. Plot a normal distribution
MEAN: Average value of data, useful when comparing one sample with
STANDARD DEVIATION: Gives the spread/range of data about/either side of the mean. (Need to
know how to calculate S.D.)


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