1. Subtopic (a) Variation
Genetics
Subtopic (a) Variation

2. Inheritance inherited characteristics
e.g. hair colour, tongue rolling, height etc.
determined by genetic information
passed on from generation to generation
each person receives two pieces of genetic information about each characteristic
one from each parent
these may be the same or different

3. Family tree
Red hair
Non red hair

4. Inheritance : Variation
Species
A species is a group of interbreeding organisms whose offspring are fertile
Members of one species
Male horse
Female horse X
Young horses (fertile)

5. The members of two very different species (e. g
The members of two very different species (e.g. horses and cattle) cannot interbreed to form offspring
Sometimes, however, the members of two fairly similar species can interbreed to produce sterile offspring
Fertile offspring?
Sterile offspring?
The young foals are fertile
They will be able to produce offspring on reaching sexual maturity
Sterile offspring will not be able to produce offspring on reaching sexual maturity

6. Sterile offspring
Male horse
Female donkey X
Mule (sterile)
The mule will not be able to produce offspring on reaching sexual maturity

7. Liger

8. Tigon

9. Zorse

10. Inheritance : Variation
Size and shape of cats
Height and diameter of limpets
Size and shape of dandelion leaves
Number of ray florets in daisies

11. Although the members of a species are very similar to one another
e.g. all of these pictures show dogs - they are not identical to one another
This is because variation can occur within a species
Variation is defined as the differences between members of a species

12. Inheritance : Types of variation
Discontinuous
variation

13. Continuous variation
Shoe size
Hand Span
Height

15. Continuous variation CREDIT
In continuous variation
e.g. height in humans / stem length in plants
There is a wide range of individuals ( values)
Between two extremes
Not inherited

16. Discontinuous variation CREDIT
In discontinuous variation
e.g. finger prints in humans / shape of leaves in plants
There are clear cut (discrete) groups
Always inherited

17. CREDIT
discontinuous