9A Inheritance and Selection_2017-04-05 10-22-5766.PPTX

Inheritance and Selection

1. Biology Inheritance and Selection

2. Inheritance and Selection Contents Types of variation Causes of variation Variation investigation Selective breeding Chromosomes and gender

3. What characteristics have been passed on in this family? Family characteristics

4. The members of this family tree are related and so they share certain similar characteristics. Inherited characteristics Shared family characteristics are inherited from parents. So why don’t all family members look exactly alike?

5. Variation can come about for two reasons. What are they? 1. People inherit characteristics from both of their parents and each person gets a different combination of features. This is called inherited variation . 2. Other characteristics are affected a person’ surroundings. This called environmental variation . Which features are environmental and which are inherited ? Different types of variation People are similar, but not identical, to their parents or each other. The differences in a species are called variation .

6. Variation – environmental or inherited?

7. Inheritance and Selection Contents Types of variation Causes of variation Variation investigation Selective breeding Chromosomes and gender

8. Deciding whether a characteristic is inherited or environmental can cause a lot of discussion. Scientists have now decided that only four features are truly inherited and not affected by the environment at all. What are the four truly inherited characteristics? natural eye colour Inherited characteristics only? natural hair colour blood group some inherited diseases

9. From a cell to DNA

10. Fertilization and cell division – animation

11. Identical twins – animation

12. Non-identical twins – animation

13. Variation in humans can be due to inherited factors, environmental factors or a combination of both factors: Inherited variation When humans reproduce via sexual reproduction , the nuclei of the male sex cell and the female sex cell fuse. This cannot happen the same way twice, which makes each individual unique. Variation summary Environmental variation Some features are due to the conditions in a person’s surroundings . For example, accent is just affected by environment but skin colour is due to both inherited and environmental factors.

14. Inheritance and Selection Contents Types of variation Causes of variation Variation investigation Selective breeding Chromosomes and gender

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

16. What are chromosomes?

17. What are chromosomes? Chromosomes are long strands of genetic information located in the nuclei of cells. Chromosomes are most visible during cell division when they replicate and look like this… You will see chromosomes represented both ways.

18. Homologous chromosomes In most cells chromosomes are matched in pairs based on their size and shape . Matching pairs of chromosomes are called homologous chromosomes. Where do homologous chromosomes come from? Each pair of homologous chromosomes contains one chromosome that has been inherited from each parent . chromosome from female parent chromosome from male parent homologous chromosomes

19. Homologous chromosomes

20. Human chromosomes You inherit half your chromosomes from your mother and half from your father. How many chromosomes do you inherit from each parent? In human body cells there are a total of 46 chromosomes . How many pairs of homologous chromosomes are there in human body cells? 23 pairs of chromosomes 23 unpaired chromosomes

21. Human chromosomes

22. There are two types of sex chromosome with names that are very easy to remember! X and Y chromosomes Females have two X chromosomes, one from each parent. X chromosome Y chromosome XY XX Males have one X chromosome and one Y chromosome. Which parent does a baby boy inherit its Y chromosome from?

23. Does this set of chromosomes come from a male or female? X and Y chromosomes What kind of sex chromosomes are there in this person’s sex cells? XY 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

24. Chromosomes and sex cells Why is there an equal chance of a baby being a boy or a girl? What happens to the sex chromosomes when sex cells are formed? All ova have one X chromosome. Sperm have an X or Y chromosome. female body cell (XX) meiosis X X X X male body cell (XY) meiosis X X Y Y

25. Chromosomes, genes and gender quiz

26. Inheritance and Selection Contents Types of variation Causes of variation Variation investigation Selective breeding Chromosomes and gender

27. Eric bought 50 beefsteak tomatoes for his restaurant. The mass of each tomato was measured (in grams) and the results are given in the following table. Variation investigation – beefsteak tomatoes

28. The masses of the beefsteak tomatoes can be made into a frequency graph by counting how many tomatoes weigh between 78 g and 82 g, 82 g and 96 g and so on. Variation investigation – beefsteak tomatoes What does this graph show? Distribution of Mass of Beefsteak Tomatoes mass (g) frequency

29. Eric also bought 50 plum tomatoes from the local farm, which were also weighed. The masses (in grams) of this second type of tomatoes are listed in the table below: Variation investigation – plum tomatoes

30. The masses of the plum tomatoes can be displayed in a frequency graph by counting how many tomatoes weigh between 40 g and 44 g, 44 g and 48 g and so on. Variation investigation – plum tomatoes Distribution of Mass of Plum Tomatoes mass (g) frequency What does this graph show?

31. Variation investigation – comparing results Compare the frequency graphs for the masses of the beefsteak and plum tomatoes. mass (g) frequency Distribution of Mass of Beefsteak Tomatoes Distribution of Mass of Plum Tomatoes frequency mass (g) Are there any differences between the two sets of results?

32. Are there any other measurements of the tomatoes that can be easily recorded and would show a similar set of results to the measurements of mass? Some quantities cannot be measured immediately but are important to those who grow and those who buy a crop of tomatoes, e.g. disease resistance and time taken to ripen. Can you think of any more quantities like this? Variation investigation – analyzing results Other questions to consider when comparing the frequency graphs for the masses of the beefsteak and plum tomatoes. What can you say about the variation of mass within each species of tomato and the variation between the two sets of results?

33. Inheritance and Selection Contents Types of variation Causes of variation Summary activities Variation investigation Selective breeding

34. Selective breeding is a process used to produce different breeds of animals or varieties of plants that have useful characteristics . Farmers can choose individual cows to mate in order to produce a generation of cows that will yield more milk . Apple growers want to produce a type of apple that is tasty and resistant to disease. This can be done by crossing a variety of apple known for taste with another variety that shows strong resistance to disease. What is selective breeding?

35. Selective breeding – true or false?