Powerpoint variation
- 1. Variation 1Within a species there is usually a great deal of variation between individuals
- 2. 7What variations can you see ?There are variations in skin colour, hair colour, hair curliness, eye colour and sexHuman variations
- 3. 8Variations may be inherited or acquiredInherited variations result from the activity of genes-They are genetically controlled- Genetically controlled variations cannot be alteredFor example, hair colour, skin colour*, blood group,finger prints and sex cannot be changednaturallyAcquired & inherited
- 4. 9Acquired characteristics result from an individual’s activities or nutrition or from environmental conditions during a lifetimeExamples of acquired conditions in humans are* -language -obesity -athletic skills -mental skills -body building -sun tan-Acquired characteristics cannot be inheritedAcquired characteristics
- 5. 10-The next side shows apples collected from differentpositions on the same tree-The differences between the apples are acquired during the growing season-The differences will not be inherited
- 6. 11North side, upper branchesSouth side upper branchesSouth side, lower branchesNorth side, lower branches© Horticultural Research InternationalApples
- 7. 12What environmental conditions in the different parts ofthe tree might have caused the differences in size of the apples ?-The upper branches will receive more sunlight than the lower branches, but on the North side the sunlight would have been less intense-The lower branches will receive less sunlight because ofthe shade cast by the upper branches. This effect will be more pronounced on the North sideEnvironmental conditions
- 8. 13A great many variations are influenced by both geneticand environmental effects.-For example your height will depend on what genes you inherit and the amount of food you get during your growing period-You may inherit a good physique but unless you take exercise you will not develop to your full potential-You may inherit the genes to make the pigment, melanin, in your skin but you will need to expose your skin to sunlight to acquire a tan Heredity & environment
- 9. 14Discontinuous variationDiscontinuous variations are entirely genetically controlledThey cannot be altered by external conditions.You are either male or female, there are no intermediates
- 10. Your ABO blood group is either A, B, AB or O
- 11. Genetic defects such as colour blindness, albinism,achondroplastic dwarfism, sickle cell anaemia are all Genetically controlled and expressed in a discontinuous way.You either have these conditions or you do not. There are no intermediate statesDiscontinuous variation
- 12. 15percentagein populationof BritainDiscontinuous variation in blood group. The figures cannotbe made to fit a smooth curve because there are no intermediatesBlood groups
- 13. 16Continuous variation-Continuous variation is influenced by genes and environment, resulting in a range of phenotypes between two extremes,e.g. height in humans.-For example, there is every shade of hair colour between blackand blond. People do not belong to one or other of a small numberof distinct categories.-Variations such as these are under genetic control but there are several pairs of genes involved.-The genome AA BB CC DD might give black hair while the genome aa bb cc dd might give blond hair.*-Genomes AaBbCcDd or AABbCCdd or aaBBccDd and all the other possible combinations would give intermediate colours
- 14. 17There are as many categoriesof hair colour asthere are childrenHair colour variation
- 15. 18Continuous variation also occurs when the characteristicsare controlled by the genesand the environment-Your height will depend on the genes you inherit and on the amount of food you eat during your growing period The next slide shows the range of heights of army recruitsContinuous variation
- 16. 19thousandsof menheight in inchesThere seem to be distinct categories of height but this is becausemeasurements are made to the nearest inchGraph of heights
- 17. 20If measurements could be made to the nearest millimetrethere would be a smooth transition in the heights
- 18. 21This is how continuous variation would appear in a graph
- 19. 22Question 1Which of these statements are correct?(a) Wild plants of the same species do not vary(b) There is always variation between individuals of the same species(c) Individuals in the same species may show variations(d) Daschunds and greyhounds are varieties of the same species
- 20. 23Question 2Variations in an individual’s weight…(a) are entirely genetically controlled(b) result exclusively from the amount of food taken in(c) are the result of food intake and genes(d) are the result of chance
- 21. 24Question 3Which of the following can be changed by conditions other than genetic?Blood group(b) Weight(c) Physique(d) Finger prints
- 22. 25Question 4Which of the following are acquired characteristics ?Lung cancer(b) Athleticism(c) Curly hair(d) Big feet
- 23. 26Question 5Discontinuous variations are …(a) inherited(b) not inherited (c) a combination of inherited and acquired factors(d) acquired during a lifetime
- 24. Question 627Which of the following are examples of continuous variation ?(a) Height(b) Weight(c) Sex(d) Intelligence