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Summary Origin of an Idea about Origins
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Summarised notes on Matric Origin of an Idea about Origins from the Mind Action series Life Science textbook.
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ORIGIN OF AN IDEA ABOUT ORIGINSDevelopment of the theory of evolution
Development of the theory of evolution
What is evolution
- The gradual change or development of something
- BIOLOGICAL EVOLUTION: A change in the gene pool of a population during the course of time by such
processes as mutation, natural selection and genetic drift
- Aka: descent with modification
- Covers microevolution (within species) & macroevolution (different species w common ancestor)
Biological evolution importance:
- Unifying concept & acts as a foundation for biology
- Supports & explains life aspects
- Challenges people to think
Origin of life
- Current opinion: there was a single origin of life
- All life shares the same genetic code and similar basic enzymes
Origin of species diversity
Before 1700 it was believed that:
- Species were unrelated and remained unchanged
- Earth was young
1700-1800:
- Erasmus Darwin and Jean-Baptiste Lamarck challenged the concepts and were convinced that:
- Species had changed gradually over time
- The earth was v old
Erasmus Darwin
- Doctor, scientist, philosopher, inventor, poet and author
- Put forward the idea that life on earth descended from a common ancestor in his book, Zoonomia
- Had no mechanism for what he termed ‘transformation’ (evolution)
, Jean-Baptiste Lamarck
- French naturalist
- His book Philosophie Zoologique made the following observations:
- Living species are different to fossils so life must have changed
- Domestication & selective breeding resulted in animals & plants changing
- Cross-breeding of plants led to new characters appearing
How he suggested that species changed
- Believed it occurred naturally and not by intervention
- Organisms changed during their lifetime so they could survive in new environments and that their
acquired changes were passed onto offspring
HIs hypothesis on how change took place:
- Use and disuse of body parts
- When the environment changed the organism would respond by changing to adapt
- Ie the more organs were used they would increase in size or efficiency and the opposite for if
they were not used
- Inheritance of acquired characteristics
- The phenotypic changes or characteristics acquired by parents were passed onto offspring
- Aka: soft inheritance or Lamarckism
- Eg: giraffe theory that long necks/legs were as a result of short ones stretching over time to
feed on high leaves and these characteristics were passed on
- His hypothesis about phenotypic changes due to an environment was correct but he was
incorrect about thinking it caused evolutionary change
Eg: bodybuilding alters the phenotype but the acquired characteristic does not change the genotype of offspring
Therefore acquired characteristics during life are not heritable
Summary:
They both believed that:
- Species have common ancestors
- Evolution occurred as species adapted to their environment
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