1. 29/08/2015 Inheritance and variation# Reproduction

2. 29/08/2015Variation Variation is a name given to differences in a species, e.g. dogs: Variation is due to each animal having different GENETIC INFORMATION in their cells.

3. AQA Science © Nelson Thornes Ltd 2006 3Variations There are variations between members of the same species. Because of these variations, some individuals are more successful than others. In harsh conditions, the fittest survive.

4. humans have human genes Genes are the units of inheritance. Organisms differ because they have different genes. What makes organisms different? gerbils have gerbil genes bananas have (yes, you’ve guessed it) banana genes!

5. Sexual reproduction In sexual reproduction, genetic information from two parents is mixed to make a new plan for the offspring. This leads to variation between members of a species.

6. 29/08/2015 Fertilisation in Humans To put it simply, it’s an “egg and sperm race”… Egg Sperm

7. Fertilisation In sexual reproduction, fertilisation happens when a male and a female sex cell join together.

8. 29/08/2015 Eggs and sperm The female egg cell and the male sperm cell are examples of ____________ cells: The egg cell is basically an enlarged cell with massive _____ reserves The ______ cell is specialised in two ways: Words – food, swimming, sperm, specialised, digest Head packed with “enzymes” to ______ its way through the egg Strong tail for ________ Nucleus

9. 29/08/2015 Sexual reproduction Sexual reproduction involves two organisms of the same species. Each organism produces a GAMETE. For example, in animals the gametes are the egg and the sperm: When the sperm penetrates the egg the egg is fertilised and cells start to reproduce to form a new individual:

10. Reproduction 1.After sexual intercourse, one sperm may fertilise an egg. This produces a zygote 2.The zygote forms an embryo and the embryo embeds itself in the uterus lining 3.The embryo grow into a foetus and then a baby 29/08/2015

11. Fertilisation Fertilisation

12. Male reproductive organs

13. Female reproductive organs Femal reproductive organs

14. Fertilisation Fertilisation

15. In all living things, characteristics are passed on in the chromosomes that offspring inherit from their parents. Passing on characteristics What makes this baby human? What determines its gender? This means that all human characteristics must be something to do with chromosomes. Where are chromosomes found?

16. 29/08/2015 Where is this information stored? Section of a chromosome: Genes for eye colour Genes for hair colour Genes for blood group: Different species have different numbers of chromosomes. Humans have 46 (23 pairs) in every cell. Genetic information is stored by genes which are arranged on chromosomes:

17. Chromosomes and their genes are made of a molecule called DNA. DNA molecules carry the code that controls what cells are made of and what they do. DNA stands for deoxyribonucleic acid. Each chromosome is a very long molecule of tightly coiled DNA. Which part of a DNA molecule holds this information? What is DNA?

18. 29/08/2015 Sexual reproduction In plants, the gametes are the egg and pollen: Any type of sexual reproduction helps a species to become more varied because the offspring inherit characteristics from both parents. Fertilisation

19. Reproduction 1.Asexual reproduction can be achieved by plants, bacteria and fungi. It produces clones. 2.Sexual reproduction can be achieved by flowering plants and animals. It produces offspring with varied characteristics. 29/08/2015

20. Asexual & Sexual Reproduction

21. Fertilisation Fertilisation

22. 29/08/2015 Environmental differences Clearly, not all differences are due to just our genes… Variation due to inheritance only Variation due to environment only Variation due to a bit of both