Theories of Evolution: B1 7.1

Lamark's theory for evolution

Charles Darwin and the origin of species

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Lamark's theory of evolution

  • He believed all organisms were linked by what he called a 'fountain of life'.
  • Suggested that individual animals adapted and evolved to suit their enviroment.
  • His idea was that every type of animal evloved from primitive worms; the change from worms to other organisms was caused by the inheritance of acquired characteristics.
  • His theory was that the way organisms behaved affceted the features of their body- a case of 'use it or loose it'.
  • If animals used something a lot over a lifetime it would grow and develop, and this would then be passed onto the offspring.
  • E.g. If a giraffe used its neck a lot then its offspring would inherit a stronger and longer neck. However if a girraffe did not use its neck then through generations of its offspring, the neck would shrink and be lost.
  • His theory was rejected by people because there was no evidence for his 'fountain of life' and people could clearly see that characteristics (such as big muscles) were not being passed onto their offspring.
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Charles Darwin and the origin of species

  • Darwin travelled to South America and discovered a new form of the common rhea, an osterich-like bird. Two different types of bird living in slightly different area interigued Darwin.
  • On the Galapagos he was amazed by the variety of species.
  • He noticed that each species was different on each island.
  • He found strong similarities between types of finches, iguanas and tortoises on the different islands yet each was adapted differently to suit the local conditions.
  • After 20 years of working on this theory, Darwin came up with a theory of evolution and this was by natural selection.
  • His theory was that all living organisms have evolved from simplier life forms.
  • Reproduction always gives more offspring tha the enviroment can support so only those best adapted to the enviroment will survive.
  • Natural selection- when an organism breeds, genes that are useful characteristics are passed on to their offspring.
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