AQA A-level Biology Practice Questions with Expert Solutions

Define variation Differences that exist between individuals In what ways can variation be caused? It can be caused by genetic factors, such as alleles from mutations. It can also be caused by the environment, such as climate. Most variation is caused by a combination of genetic factors and environmental factors Why is it impossible to study a whole population? Because it is too large and would take too long. Instead, scientists use a sample that is representative of the species' population Why should the sample taken be random? So you can make sure that the sample isn't biased in any way. What could you calculate to look at variation between species? The mean (average) What is standard deviation? It tells you how much values in a single sample vary, by measuring the spread of values about the mean