This KS3 Science quiz takes a look at variation and classification. It is quite easy to recognise your different friends at school. They look different, they sound different and they behave differently. Even 'identical' twins are not perfectly identical. These differences are called variation and occur in all animal or plant species. Some of these variations are caused by genetics and others are environmental. Variations that are caused by the genetics of an individual can be passed on during reproduction.
Variation can also be described as being continuous or discontinuous. An example of a variation that is continuous would be height. The height of an adult can be any value within the normal height range of our species. Someone could be 167.1 cm tall, someone else 163.25 cm tall and so on. Discontinuous variables are those with only certain definite values, for example tongue rolling. Some people can curl their tongue edges upwards but others can't. No one can partly roll their tongue, it is either one thing or the other.