Science: Variation And Inheritance

Variation is the difference between individual animals and plants and others of the same species even when they are offspring of the same parents. Variation can be due to environmental factors, or inherited factors. The following is a basic overview of variation and inheritance:

What is Variation and Inheritance?

Environmental variation can be caused by diet, physical accidents, culture, climate, or lifestyle. Both environmental factors and genetic factors can influence variation as our genes decide what characteristics we inherit and our environment affects how these inherited characteristics develop. For example, an individual might inherit a predisposition to thinness, but a poor diet can result in the individual becoming overweight.

Although identical twins are genetically the same there will be differences in tastes, aptitude or personality according to the differences in their experience or environment. A good example of this would be identical twins adopted into two separate families. The difference in their experience and environment will lead to many variations between the two.

Continuous and Discontinuous Variation

Variation can be either continuous or discontinuous. Continuous variation is gradual or not so clear cut variation. Height is an example of continuous variation - individuals can have a complete range of heights, for example, 1.98, 1.99 or 1.995 metres high. Other examples include weight, hand span, colour of skin, size of feet etc. Genes, environmental variation or both can cause continuous variation.

Discontinuous variation is where individuals have to be within a distinct class or categories. These are cut and dried characteristics. You either have the characteristic or you don't. Genes cause discontinuous variation. For example, you are either one blood group or another - you cannot be in between. Another example is natural hair colour. The environment has little to no effect on this type of variation.

What Causes Genetic Variation?

The mixing of genetic material during sexual reproduction causes genetic variation. Inherited differences are due to genes we get from our parents. Genes control the characteristics we develop. The human body and other plant and animal species contain chromosomes, which carry the genes that control different characteristics. On fertilisation a unique set of chromosomes is created – half from the mother and half from the father. The new individual is genetically unique.

Your Child's Learning

When helping your child to learn about the concept of variation and inheritance you can start by establishing how individuals of the same species differ from each other. Look at pictures of people, animals and plants and discuss differences. Identify any patterns of similarities that may have been inherited. Information about differences could be entered into spreadsheets and graphs created. This could be done on graph paper or on the computer.

Discuss the possible causes of variation. Get your child to think about your own family. Identify characteristics that have been inherited and suggest reasons why differences and similarities exist within families. Discuss ways in which environmental difference may result in variation within a species, e.g. weight, height of a plants etc. explaining what evidence could be used to support their conclusions.

The topic of variation and inheritance is an interesting one, and relating it to your own family, and people, animals and plants in your child’s surroundings will enhance it’s relevance for your child when they are studying it.