C5. Investigating Variation

Question 1

Causes of variation
Variation is the differences that exists between individuals. There’s variation
between species and within species. (3 causes?)

Answer 1

• Variation can be caused by genetic factors. Different species have
  different genes, which causes variation between species. Individuals of the
  same species have the same genes, but different alleles (versions of genes) - this causes variation within a species.
• Variation within a species can also be caused by differences in the environment, e.g. climate, food, lifestyle.
• Most variation within a species is caused by a combination of genetic and environmental factors. E.g. genes determine how tall an organism can grow, but nutrient availability affects how tall the organism actually grows.

Question 2

Random sampling
Because sample data will be used to draw conclusions about the whole population, it’s important that it accurately represents the whole population and that any patterns observed are tested to make sure they’re not due to _______.

To make sure the sample isn’t ________, it should be ________. For example, if you were looking at plant species in a field you could pick random sample sites by …

Answer 2

Random sampling
Because sample data will be used to draw conclusions about the whole population, it’s important that it accurately represents the whole population and that any patterns observed are tested to make sure they’re not due to chance.

To make sure the sample isn’t biased, it should be random. For example, if you were looking at plant species in a field you could pick random sample sites by dividing the field into a grid and using a random number generator to select coordinates