Variation

Variation

1. Sampling

   • Large sample size
     • More reliable data
     • smaller probability of chance occurring and influencing the results
   • Data analysis
     • statistical tests to determine the extent to which chance may affect the data
   • Chance
     • pure chance that the individuals are not representative
   • Sampling bias
     • random sampling is the best way to prevent sampling bias
     • unrepresentative choices either deliberately or unwittingly

2. Genetic factors

   • Mutations
     • sudden changes in the genes may be passed on to offspring
   • Meiosis
     • mixes genetic material before fertilisation so all gametes are different
   • Fusion of gametes
     • offspring inherit some characteristics from each parent, therefore are different
     • which gametes fuse is a random process, further adding to the variety of offspring that two parents produce

3. Environmental influences

   • affect the way that the organism's genes are expressed

4. Classification of characteristics

   • Due to genetic factors
     • a few distinct forms - no intermediate types
   • Due to environmental influences
     • form a continuum. e.g. height and weight
     • can be plotted on a normal distribution curve (bell-shaped)

5. Normal distribution

   • Mean
     • measurement at the maximum height of the curve
   • Standard deviation
     • measure of the width of the curve

6. Types of variation

   • IntERspecific variation
     • the difference between species - a giraffe isn't the same as a sloth
   • IntRAspecific variation
     • the difference within a species - no two humans are the same