Within any species there is room for variation. Not all the organisms will look the same because of different factors. Within species we can see variation in many ways, for example in humans we see variation in hair colour, eye colour and height. This variation is caused by two classes of factors, which are environmental and genetic. Environmental variations are different to genetic variations.
Many features we see in organisms are caused by the environment in which they live. For example, environmental variations in humans could be:
- Hair length - how short or long you decide to have your hair cut
- Scars - caused by accidents personal to you
- Muscle strength - dependant on how much exercise you do
These forms of variation are caused by factors found in the environment. The most important of these factors include lifestyle (diet and exercise), temperature and water level. For plants, light levels could also be included.
Many features we see in organisms are caused by the genes with which they are born. These are passed on from their parent organisms. For example, genetic variations in humans could be:
- Eye colour
- Blood group - either group AB, A, B or O
- Maximum potential height - determined by genetics, but whether this height is reached is due to environmental factors, like diet
These forms of variation are caused by the sequences of genes. When a male sex cell joins with a female sex cell, two opposite sets of genetic material are joined together to create a new, unique individual. This is called sexual reproduction, and creates much variation within a population.