Powerpoint variation


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Powerpoint variation

  1. 1. Variation 1<br />Within a species there is usually a great deal of variation between individuals<br />
  2. 2. 7<br />What variations can you see ?<br />There are variations in skin colour, hair colour, <br />hair curliness, eye colour and sex<br />Human variations<br />
  3. 3. 8<br />Variations may be inherited or acquired<br /><ul><li>Inherited variations result from the activity of genes</li></ul>-They are genetically controlled<br />- Genetically controlled variations cannot be altered<br />For example, hair colour, skin colour*, blood group,<br />finger prints and sex cannot be changednaturally<br />Acquired & inherited<br />
  4. 4. 9<br />Acquired characteristics result from an individual’s activities or nutrition or from environmental conditions during a lifetime<br />Examples of acquired conditions in humans are* <br /> -language -obesity<br /> -athletic skills -mental skills<br /> -body building -sun tan<br />-Acquired characteristics cannot be inherited<br />Acquired characteristics<br />
  5. 5. 10<br />-The next side shows apples collected from different<br />positions on the same tree<br />-The differences between the apples are acquired during <br />the growing season<br />-The differences will not be inherited<br />
  6. 6. 11<br />North side, upper branches<br />South side upper branches<br />South side, lower branches<br />North side, lower branches<br />© Horticultural Research International<br />Apples<br />
  7. 7. 12<br /><ul><li>What environmental conditions in the different parts of</li></ul>the tree might have caused the differences in size of the <br />apples ?<br />-The upper branches will receive more sunlight than the <br />lower branches, but on the North side the sunlight would <br />have been less intense<br />-The lower branches will receive less sunlight because of<br />the shade cast by the upper branches. This effect will be <br />more pronounced on the North side<br />Environmental conditions<br />
  8. 8. 13<br /><ul><li>A great many variations are influenced by both genetic</li></ul>and environmental effects.<br />-For example your height will depend on what genes <br />you inherit and the amount of food you get during your <br />growing period<br />-You may inherit a good physique but unless you take <br />exercise you will not develop to your full potential<br />-You may inherit the genes to make the pigment, melanin,<br /> in your skin but you will need to expose your skin to<br /> sunlight to acquire a tan <br />Heredity & environment<br />
  9. 9. 14<br />Discontinuous variation<br /><ul><li>Discontinuous variations are entirely genetically controlled</li></ul>They cannot be altered by external conditions.<br /><ul><li>You are either male or female, there are no intermediates
  10. 10. Your ABO blood group is either A, B, AB or O
  11. 11. Genetic defects such as colour blindness, albinism,</li></ul>achondroplastic dwarfism, sickle cell anaemia are all <br />Genetically controlled and expressed in a discontinuous way.<br /><ul><li>You either have these conditions or you do not. There are no </li></ul>intermediate states<br />Discontinuous variation<br />
  12. 12. 15<br />percentage<br />in population<br />of Britain<br />Discontinuous variation in blood group. The figures cannot<br />be made to fit a smooth curve because there are no intermediates<br />Blood groups<br />
  13. 13. 16<br />Continuous variation<br />-Continuous variation is influenced by genes and environment, <br />resulting in a range of phenotypes between two extremes,<br />e.g. height in humans.<br />-For example, there is every shade of hair colour between black<br />and blond. People do not belong to one or other of a small number<br />of distinct categories.<br />-Variations such as these are under genetic control but there are <br />several pairs of genes involved.<br />-The genome AA BB CC DD might give black hair while the <br />genome aa bb cc dd might give blond hair.*<br />-Genomes AaBbCcDd or AABbCCdd or aaBBccDd and all the <br />other possible combinations would give intermediate colours<br />
  14. 14. 17<br />There are as <br />many categories<br />of hair colour as<br />there are children<br />Hair colour variation<br />
  15. 15. 18<br />Continuous variation also occurs when the characteristics<br />are controlled by the genesand the environment<br />-Your height will depend on the genes you inherit and on <br />the amount of food you eat during your growing period <br />The next slide shows the range of heights of army recruits<br />Continuous variation<br />
  16. 16. 19<br />thousands<br />of men<br />height in inches<br />There seem to be distinct categories of height but this is because<br />measurements are made to the nearest inch<br />Graph of heights<br />
  17. 17. 20<br />If measurements could be made to the nearest millimetre<br />there would be a smooth transition in the heights<br />
  18. 18. 21<br />This is how continuous variation would appear in a graph<br />
  19. 19. 22<br />Question 1<br />Which of these statements are correct?<br />(a) Wild plants of the same species do not vary<br />(b) There is always variation between individuals <br /> of the same species<br />(c) Individuals in the same species may show variations<br />(d) Daschunds and greyhounds are varieties of the same<br /> species<br />
  20. 20. 23<br />Question 2<br />Variations in an individual’s weight…<br />(a) are entirely genetically controlled<br />(b) result exclusively from the amount of food <br /> taken in<br />(c) are the result of food intake and genes<br />(d) are the result of chance<br />
  21. 21. 24<br />Question 3<br />Which of the following can be changed by conditions other than genetic?<br />Blood group<br />(b) Weight<br />(c) Physique<br />(d) Finger prints<br />
  22. 22. 25<br />Question 4<br />Which of the following are acquired characteristics ?<br />Lung cancer<br />(b) Athleticism<br />(c) Curly hair<br />(d) Big feet<br />
  23. 23. 26<br />Question 5<br />Discontinuous variations are …<br />(a) inherited<br />(b) not inherited<br /> (c) a combination of inherited <br /> and acquired factors<br />(d) acquired during a lifetime<br />
  24. 24. Question 6<br />27<br />Which of the following are examples of continuous <br />variation ?<br />(a) Height<br />(b) Weight<br />(c) Sex<br />(d) Intelligence<br />