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Powerpoint variation Powerpoint variation Presentation Transcript

  • Variation 1
    Within a species there is usually a great deal of variation between individuals
  • 7
    What variations can you see ?
    There are variations in skin colour, hair colour,
    hair curliness, eye colour and sex
    Human variations
  • 8
    Variations may be inherited or acquired
    • Inherited variations result from the activity of genes
    -They are genetically controlled
    - Genetically controlled variations cannot be altered
    For example, hair colour, skin colour*, blood group,
    finger prints and sex cannot be changednaturally
    Acquired & inherited
  • 9
    Acquired characteristics result from an individual’s activities or nutrition or from environmental conditions during a lifetime
    Examples of acquired conditions in humans are*
    -language -obesity
    -athletic skills -mental skills
    -body building -sun tan
    -Acquired characteristics cannot be inherited
    Acquired characteristics
  • 10
    -The next side shows apples collected from different
    positions on the same tree
    -The differences between the apples are acquired during
    the growing season
    -The differences will not be inherited
  • 11
    North side, upper branches
    South side upper branches
    South side, lower branches
    North side, lower branches
    © Horticultural Research International
    Apples
  • 12
    • What environmental conditions in the different parts of
    the 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 of
    the shade cast by the upper branches. This effect will be
    more pronounced on the North side
    Environmental conditions
  • 13
    • A great many variations are influenced by both genetic
    and 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
  • 14
    Discontinuous variation
    • Discontinuous variations are entirely genetically controlled
    They cannot be altered by external conditions.
    • You are either male or female, there are no intermediates
    • Your ABO blood group is either A, B, AB or O
    • 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 states
    Discontinuous variation
  • 15
    percentage
    in population
    of Britain
    Discontinuous variation in blood group. The figures cannot
    be made to fit a smooth curve because there are no intermediates
    Blood groups
  • 16
    Continuous 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 black
    and blond. People do not belong to one or other of a small number
    of 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
  • 17
    There are as
    many categories
    of hair colour as
    there are children
    Hair colour variation
  • 18
    Continuous variation also occurs when the characteristics
    are 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 recruits
    Continuous variation
  • 19
    thousands
    of men
    height in inches
    There seem to be distinct categories of height but this is because
    measurements are made to the nearest inch
    Graph of heights
  • 20
    If measurements could be made to the nearest millimetre
    there would be a smooth transition in the heights
  • 21
    This is how continuous variation would appear in a graph
  • 22
    Question 1
    Which 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
  • 23
    Question 2
    Variations 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
  • 24
    Question 3
    Which of the following can be changed by conditions other than genetic?
    Blood group
    (b) Weight
    (c) Physique
    (d) Finger prints
  • 25
    Question 4
    Which of the following are acquired characteristics ?
    Lung cancer
    (b) Athleticism
    (c) Curly hair
    (d) Big feet
  • 26
    Question 5
    Discontinuous variations are …
    (a) inherited
    (b) not inherited
    (c) a combination of inherited
    and acquired factors
    (d) acquired during a lifetime
  • Question 6
    27
    Which of the following are examples of continuous
    variation ?
    (a) Height
    (b) Weight
    (c) Sex
    (d) Intelligence