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3. 1 1 KS3 SCIENCE - BIOLOGY KS3 SCIENCE - BIOLOGY Genetic Variation Genetic Variation

4. VARIATION 2 2

5. 3 3 Different species look very different, but members of the same species also vary Different species look very different, but members of the same species also vary

6. VARIATION 4 4 Different species look very different, but members of the same species also vary Different species look very different, but members of the same species also vary Characteristics like height, weight and the colour of eyes or hair differ from one person to another Characteristics like height, weight and the colour of eyes or hair differ from one person to another

7. VARIATION 5 5 Some characteristics have Continuous Variation - you can see gradual differences, e.g. in people’s height Some characteristics have Continuous Variation - you can see gradual differences, e.g. in people’s height Men’s Height (cms) Number of Men

8. VARIATION 6 6 But some characteristics are Discontinuous - they are one thing or another, e.g. eye colour But some characteristics are Discontinuous - they are one thing or another, e.g. eye colour

9. INHERITED VARIATION 7 7

10. 8 8 Inherited Variation is due to differences in the Genetic make-up of individuals Inherited Variation is due to differences in the Genetic make-up of individuals The Nucleus contains Chromosomes - humans have 23 pairs, or 46 of them The Nucleus contains Chromosomes - humans have 23 pairs, or 46 of them

11. INHERITED VARIATION 9 9 Genes are information for making the animal - the information is in chemicals on the chromosomes Genes are information for making the animal - the information is in chemicals on the chromosomes

12. Baby has 46 Chromosomes INHERITED VARIATION 10 Egg and Sperm cells have half the usual number of chromosomes, so that when they join together the baby has the right number Egg and Sperm cells have half the usual number of chromosomes, so that when they join together the baby has the right number 23 of Mum’s Chromosomes 23 of Dad’s Chromosomes

13. INHERITED VARIATION 11 So the child has some of mum’s characteristics and some of dad’s So the child has some of mum’s characteristics and some of dad’s 23 of Mum’s Chromosomes 23 of Dad’s Chromosomes

14. ENVIRONMENTAL VARIATION 12

15. ENVIRONMENTAL VARIATION 13 Many characteristics are affected by an individual’s environment Many characteristics are affected by an individual’s environment For example, some people won’t eat much and become very thin For example, some people won’t eat much and become very thin

16. ENVIRONMENTAL VARIATION 14 A lot of characteristics depend on both genetic and environmental factors, but these four are NOT affected by the environment: A lot of characteristics depend on both genetic and environmental factors, but these four are NOT affected by the environment:  Blood Group  Eye Colour  Inherited Disease  Albinism  Blood Group  Eye Colour  Inherited Disease  Albinism

17. VARIATION IN PLANTS 15

18. VARIATION IN PLANTS 16 Plants also inherit characteristics through their genes, e.g. some specimens are taller than others Plants also inherit characteristics through their genes, e.g. some specimens are taller than others

19. VARIATION IN PLANTS 17 And the environment also affects them, e.g. sunshine, temperature, soil conditions and moisture And the environment also affects them, e.g. sunshine, temperature, soil conditions and moisture This is why skilled gardeners can grow bigger, stronger plants This is why skilled gardeners can grow bigger, stronger plants

20. SELECTIVE BREEDING 18

21. SELECTIVE BREEDING 19 By breeding from specimens who have the best characteristics it is possible to get high yield crops, fast race horses or cute dogs By breeding from specimens who have the best characteristics it is possible to get high yield crops, fast race horses or cute dogs