1. Variation and Inheritance
National 5 Biology
Key Area 5:
Variation and Inheritance
National 4 Biology
Key Area 4
Genetic Information

2. By the end of the lesson you will be able to …..
Name the two types of variation that exist amongst members of a species.
Give examples of traits that demonstrate the two types of variation.

3. How the pupils below different from each other?
Differences between members of the same species is called ‘variation’.
Combining genes from two parents contributes to variation within a species ~ sexual reproduction!
Spot the difference!
How the pupils below different from each other?
Gender
Eye colour
Hair colour
Eye shape
Hair type/ texture
Nose shape
Skin colour
Face shape
‘Brainstorm ideas then show them what I came up with. Emphasis that the list is endless because we are all genetically unique individuals.
Skin type
Ear shape
Height
Leg length

4. It’s not just humans….
Any organism (animals and plants) produced by sexual reproduction will display variation….

5. Variation within a species
Our genes determine our features, e.g. our height.
Combining genes (during sexual reproduction) from two parents contributes to variation within a species.
N4 and N5 note. Lifted from N4 and N5 support notes.

6. Why is variation important?
Variation is important because it allows organisms to adapt and survive.
Try to link this back to the start of Natural selection and adaptations studied in Life on Earth.

7. Discrete Variation
E.g. 4 Blood groups: A, B, AB and O

8. Discrete Variation
E.g. Fingerprint Type

9. Discrete Variation
E.g. earlobe attachment

10. Discrete Variation
A characteristic shows discrete variation if it can be used to divide the species into two or more distinct groups
These traits are controlled by single gene inheritance
E.g. Tongue rolling
N5 only note.

11. Discrete Variation
Statistics on discontinuous variation are presented using BAR GRAPH
Bars DO NOT touch each other or the Y-axis
Labels on both X and Y-axis

13. Continuous Variation
E.g. Weight

14. Rumaisa Rahman weighed 8.6 oz – same as a can of coke
Continuous Variation
E.g. Birth weight
In 2005, 17lb Ademilton dos Santos
was born.
Rumaisa Rahman weighed 8.6 oz – same as a can of coke
In 1879, Anna Bates in Canada gave birth to a 23.12lb baby (died 11 hours after birth)

15. Continuous Variation
E.g. Skin colour

16. Continuous Variation
A characteristic shows continuous variation if members of the species vary in a smooth continuous manner over a range of values – there are NO DISTINCT GROUPS
These traits are controlled by many genes - polygenic inheritance
E.g. height
N5 only note.

17. Continuous Variation
Statistics on continuous variation are shown on a HISTOGRAM
The range of values are divided into small groups
Bars should touch each other

18. Can you now ….
Name the two types of variation that exist amongst members of a species.
Give examples of traits that demonstrate the two types of variation.