First 321 words of the document:
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
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
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.
VARIATION DUE TO ENVIRONMENTAL INFLUENCES:
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.)