Inheritance: Variation
17.1 Variation
Definition
- Variation = differences between individuals of the same species.
- Provides diversity within a population.
Types Of Variation
| Type | Description | Examples | Cause |
|---|---|---|---|
| Continuous | Range of phenotypes between two extremes | Height, body mass, leaf length | Genes + environment |
| Discontinuous | Limited number of distinct categories | ABO blood groups, seed shape | Mainly genes |
Importance Of Variation
- Enables survival in changing environment.
- Provides raw material for natural selection and evolution.
- Populations with more variation adapt better.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course
Examples Of Causes
- Genetic → mutation, meiosis (crossing over, independent assortment), random fertilisation.
- Environmental → diet, climate, exercise.
- Often both play a role (e.g., height influenced by genes + diet).
Investigations
- Continuous variation → measured, plotted on histogram (bell-shaped curve).
- Discontinuous variation → distinct categories, bar chart.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course