Core Biology - Topic 1 Variation

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  • Created by: Katie
  • Created on: 14-04-13 22:14


Variation - differences in characteristics

  • Some variation within species - much more between different species
  • The variation within species makes classification difficult
  • Ensure a 'new' species isn't just a hybrid or variation of another species
    • find more than one of the organism

Human variation

  • Range in heights caused by inherited and environmental variation
    • example of continuous variation (any number within a certain range)
  • Shoe size is an example of discontinuous variation (fixed set of values)
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Biodiversity Hotspots

Biodiversity - measure of the total number of species in an area

  • To count them you must identify them
    • tricky when many species are very similar to one another
    • more accurate classification system = easier identification
  • Biodiversity is important for medicines and foods
    • the more species = the more choices
    • these areas also recover better from natural disasters
  • Biodiversity hotspots should have the most time and money spent on conserving them
    • greater number of species will be conserved


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Reasons For Variety

  • Adaptation - variation in characteristics that allow organisms to survive in their habitat 
    • all organisms adapt to their surroundings
    • most characteristics show variation between individuals of the same species
  • Organisms from polar areas are adapted for the cold conditions
  • Organisms from deep-sea hydrothermal vents are adapted for extreme heart (350°C+)
    • these organisms cope with extreme temperature changes, complete darkness and huge pressures
  • Discontinuous variation e.g. blood group/gender
    • often caused by instructions in cells - GENETIC VARIATION
  • Continuous variation e.g. height/weight
    • shows a normal distribution curve
    • most individuals measure within the middle part of the range
    • fewer individuals with measuremets at the extremes
    • often controlled by both genetic and envirornmental influences
  • Being short from malnutrition would be an acquired characteristic
    • caused by environment therefore cause environmental variation between organisms
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  • Organisms generally produce more offspring than the environment can support
  • Most die before adulthood because of lack of resources e.g. food/space
    • limited resources cause competition between individuals
    • the ones better adapted will be more likely to survive
    • SURVIVAL OF THE FITTEST - natural selection
  • If these individuals breed they pass their variations onto their offspring
  • Charles Darwin drew facts together about evolution into a new understandable theory
    • realised characteristics were inherited by offspring
  • Evolution - range of variation gradually changing over generations
    • if environment changes, variations appear to suit new conditions
    • individuals with those variations survive and pass on the characterstics to offspring
  • If the environment changes too rapidly species will become extinct
    • no time to adapt to new conditions and die out
  • Darwin published book in 1859
    • theory was discussed and challenge - wasn't liked
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Evolution Continued

  • Warfarin 1940's/1950's
    • most rats died within days
    • after 10 years most rats were resistant
    • because of variations, always some rats were resistant
    • the poison killed the non resistant rats
    • only resistant ones were left to breed
  • Darwin just used oservational characteristics to infer relationships
  • Now new evidence is found for the theory from genetic information in species
  • Darwin's theory helped him explain why neighbouring islands had their own species of mockingbird
  • Guessed that the bird came from South America and inhabited the different islands
    • which had slightly different environmental conditions
    • the different adaptations made life more sucessful on each island
    • each island's population evolved in a different way
    • variations became so different that they cannot interbreed - NEW SPECIES!
  • Process is called speciation
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