Page 15 - CB1.3 Genetic Varation sciPAD

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CB 1.3 GENETIC VARATION
PRINCIPLES OF GENETIC VARIATION
What is Variation?
The term ‘species’ is used by scientists to classify organisms of the same type. Organisms of the
same species are able to reproduce to make more of that species.
All humans belong to the same species - Homo sapiens. Although the people in your class are
all the same species, they are all slightly different. Scientists call these differences variation. The
variation among members of the same species (e.g. your classmates) will always be less than the
variation between two different species (e.g. you and a seagull).
Types of Variation
Variation can be ‘continuous’ or ‘discontinuous’.
In continuous variation, there is a complete range of measurements from one extreme to the
other. For example, human height ranges from the shortest person in the world to the tallest person.
Humans could be any height in between these values.
Discontinuous variation occurs when characteristics fall into a number of distinct classes or
categories. For example, your ear lobes can either be ‘fixed’ to the side of your head, or ‘free’ to
dangle. There is no in-between.
1. Label the photograph below by stating whether the examples show ‘continuous’ or
‘discontinuous’ variation.
Weight
Growth rate
Sex
Colouration
Height
Beak length
Number of toes
Egg size
Eye colour
Blood type
Wingspan
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