Continuous and Discontinuous Variation | A-level Biology | OCR, AQA, Edexcel

Описание: Continuous and Discontinuous Variation in a Snap! Unlock the full A-level Biology course at http://bit.ly/2HAwcXB created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University.

SnapRevise is the UK’s leading A-level and GCSE revision & exam preparation resource offering comprehensive video courses created by A* Oxbridge tutors. Our courses are designed around the OCR, AQA, SNAB, Edexcel B, WJEC, CIE and IAL exam boards, concisely covering all the important concepts required by each specification. In addition to all the content videos, our courses include hundreds of exam question videos, where we show you how to tackle questions and walk you through step by step how to score full marks.

Sign up today and together, let’s make A-level Biology a walk in the park!

The key points covered in this video include:

1. Sources of Variation
2. Variation between Individuals
3. Continuous and Discontinuous Variation

Sources of Variation

In a population there is variation between individuals because all organisms are unique. Even identical twins develop differently and end up having slight differences in appearance and their DNA. There are many ways that organisms can differ from one another because there are many possible sources of variation. Variation between individuals can be due to their genetics or their environment. An individual’s genetics and environment can both influence a particular trait - this is called a combined effect or an interaction.

Variation Between Individuals

Individuals from different species tend to show a large amount of interspecific variation. Interspecific variation is the differences between any two species. Individuals of the same species also differ, and they are said to show intraspecific variation. A population with greater genetic diversity will show greater intraspecific variation.

Continuous and Discontinuous Variation

When looking at a particular characteristic/trait there are two types of variation: Some traits show continuous variation. Continuous variation is when there are two extremes and a full range of values in between. Most individuals are close to the mean value with fewer at the both extremes. Traits that show continuous variation are often regulated by multiple genes and influenced by the environment. Some traits show discontinuous variation. Discontinuous variation is where there are distinct categories with no intermediate values. Individuals tend to be distributed evenly between the different categories.Traits that show discontinuous variation are often regulated by a single gene and aren’t under environmental influence.

Summary

Variation to some degree exists between all organisms
Variation can be caused by a variety of genetic and environmental factors
Variation between individuals of the same species is known as intraspecific variation
Variation between individuals of different species is called insterspecific variation
Variation is continuous if there are a range of possible values for a trait between two extremes
Variation is discontinuous if a trait has discreet categories with no intermediates