1. Types of variation

2. Starter The current population of planet Earth is more than
7 billion people!
No two people are exactly the same. How is this possible?

3. Learning Objectives Success criteria
To understand the variation in living organisms
Success criteria
Learners should be able to demonstrate and apply their knowledge and understanding of:
the different types of variation
To include intraspecific and interspecific variation
AND
the differences between continuous and discontinuous variation, using examples of a range of characteristics found in plants, animals and microorganisms
both genetic and environmental causes of variation.

4. Variation Interspecific – between different species
Variation can be described as differences that exist between individuals. There are 2 types
Interspecific – between different species
Intraspecific – within a species

5. Causes of variation
Remember from GCSE what 2 factors affect variation?
Genetic variation
Environmental variation

6. Inherited characteristics
This newborn baby’s characteristics are passed in the genes it has inherited from its parents.
Like all babies, this little boy carries a unique set of genes, half from his mother and half from his father.

7. Genetic causes of variation
What are alleles?
Version of a gene
e.g. Blood groups - 3 different alleles (A, B, O)
giving 4 different blood groups (A, B, AB, O)
What are mutations?
Changes to the DNA sequence, can lead to change in genes and therefore proteins.
Somatic mutation – affects body cells in individual only
Gamete mutation – passed on to offspring

8. Genetic causes of variation
List 3 ways how sexual reproduction produces genetic variation amongst a species

9. Genetic causes of variation
3 ways how sexual reproduction produces variation amongst a species:
Random mating
Random fertilisation of gametes
Independent assortment of chromosomes (and therefore alleles) and crossing over during meiosis

10. Asexual reproduction How does this affect variation?
Organisms that reproduce asexually have less variation
Asexual reproduction results in clones
Only mutation can increase genetic variation

11. Causes of variation
Environment

12. Environmental Variation
Examples in which Environment effects amount of growth
Amount of food available
Amount of water available
Exposure to sunlight
Strong prevailing wind to trees

13. Environmental variation only
In humans – scars on body
In plants – hydrangeas produce blue flowers in acidic soils and pink flowers in alkaline soils

14. Causes of variation Your unique characteristics are caused by:
the unique set of genes you have inherited from your parents
the environment in which you have developed.
Differences in some characteristics are due to a combination of both inherited and environmental factors.
Name three examples of this type of characteristic.

15. A warning!
Be careful when drawing conclusions about the causes of variation.
Eg Overeating
Once thought only to be caused by environmental factors eg increased availability of food in developed countries.
Later discovered that food consumption increases dopamine levels, once enough dopamine was released eating would stop.
Researches discovered that people with one particular allele has 30% fewer dopamine receptors.
Therefore people with this particular allele were more likely to overeat.

16. Studying variation in identical twins
Why are identical twins used in variation studies?
Why do differences between identical twins increase as they age?
Look at this data. What can you determine about the genetic and environmental causes of these characteristics?
Twin
Height (m)
Eye colour
Ear piercing
Body mass (kg) A
1.79
Brown
Yes
100 B
1.81 No 85
Complete the task on p242 of Oxford textbook
Answers p 368 Wh

17. Studying variation in identical twins
Why are identical twins used in variation studies?
Why do differences between identical twins increase as they age?
They have no genetic variation therefore all variation is the result of the environment
Complete the task on p242 of Oxford textbook
Answers p 368 Wh
They have been exposed to a greater amount of environmental influences

18. Studying variation in identical twins
Look at this data. What can you determine about the genetic and environmental causes of these characteristics?
Twin
Height (m)
Eye colour
Ear piercing
Body mass (kg) A
1.79
Brown
Yes
100 B
1.81 No 85
Eye colour – different - solely genetic
Ear piercing – same - solely environmental
Mass and height – varied results controlled by both
Mass shows greater variation, controlled more by environment
Complete the task on p242 of Oxford textbook
Answers p 368 Wh

19. How to classify variation
Characteristics can be classified in different ways.
How would you categorize variation in eye colour?
Could you categorize variation in height in the same way?
Variation in eye colour can be easily categorized in distinct groups. You either have a certain eye colour or you don’t.
Height variation doesn’t fall into separate groups, as it covers a range of values.

20. How to classify variation
Characteristics can be classified into two types:
A feature that can be measured and given a value from a range of values shows continuous variation .
A feature that cannot be measured but is one of a few distinct options shows discontinuous variation.
Which type of variation are eye colour and height?

21. Bar chart to show the frequency of blood groups in a rugby team
What is discontinuous variation?
This type of feature can only be one of a few distinct options. Either you have this type of characteristic or you don’t.
Examples of discontinuous variation include blood group, natural eye colour and inherited diseases.
Bar chart to show the frequency
of blood groups in a rugby team 6 5 4
number of rugby players 3 2 1
Discontinuous variation is controlled by a small number of genes with little environmental influence.
O A B AB
blood group
Discontinuous variation is normally represented using a bar chart but a pie chart may be used.

22. Bar chart to show the range of
What is continuous variation?
This type of feature varies over a continuous range of values.
Examples of continuous variation include mass, height, skin colour, intelligence and leaf area.
Bar chart to show the range of
masses in a rugby team 6 5 4
number of rugby players 3
Continuous variation is due to the combined effects of a large number of genes and the environment. 2 1 1
mass (kg)
Data is collected in a frequency table then plotted into a histogram. Normally a curve is then drawn to show the trend.

23. Learning Objectives Success criteria
To understand the variation in living organisms
Success criteria
Learners should be able to demonstrate and apply their knowledge and understanding of:
the different types of variation
To include intraspecific and interspecific variation
AND
the differences between continuous and discontinuous variation, using examples of a range of characteristics found in plants, animals and microorganisms
both genetic and environmental causes of variation.