Variation

Variation

What Is Variation?

Variation means differences between individuals of the same species. It can be caused by genetic factors, environmental factors, or both.

💡 Key Concept: Variation is important for natural selection and evolution.

Types of Variation

Type

Caused by

Examples

Genetic variation

Inherited from parents (DNA)

Eye colour, blood group, genetic disorders

Environmental variation

Caused by surroundings

Scars, language, dyed hair

Both

A mix of genes and environment

Height, weight, skin colour

Causes of Genetic Variation

✔ Mutation – random changes in DNA that can introduce new traits.
✔ Meiosis – shuffling of genes during gamete formation.
✔ Fertilisation – random combination of gametes gives each offspring a unique mix of alleles.

💡 Most mutations have little or no effect, but some are beneficial and can lead to evolution.

Mutations

Definition

A random change in the DNA sequence.

Effect

Most are neutral, some harmful, rarely beneficial.

Example

A mutation in a gene may produce a faulty protein or change a trait.

Discontinuous vs Continuous Variation

Discontinuous

Continuous

Clear categories

Range with gradual changes

Bar charts

Histograms/line graphs

E.g. blood group, eye colour

E.g. height, mass, hand span

Why Does Variation Matter?

✔ Allows natural selection to happen – individuals better suited to the environment survive and reproduce.
✔ Drives evolution.
✔ Helps species adapt to changing environments.

Questions 

  1. What is variation?
  2. Name one cause of genetic variation.
  3. Is height genetic, environmental or both?
  4. What is a mutation?
  5. Give one example of discontinuous variation.

Summary 

  • Variation is caused by genetics, the environment, or both.
  • Mutations can lead to new traits and sometimes affect survival.
  • Continuous variation shows a range of values; discontinuous variation fits into categories.
  • Variation is essential for natural selection and evolution.