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Early Theories of EvolutionEVOLUTION: change in a population
(DNA) over time
• no scientific explanations of evolution were given until the 18th
Century
1. Lamarck’s Hypothesis of Evolution (Theory of Use and Disuse):
• 1809
• was one of the first to develop a theory of evolution
J.B. Lamarck
Three Main Ideas:i. organisms strive to improve themselves,
to become more advanced
ii. the most used structures develop, while the less used ones waste away. Known as the principle of Use and Disuse
iii. once a modification has occurred it is passed on to the offspring
- disproved by Weisemann• cut off the tails of mice, allowed them to
reproduce and then cut off the offspring’s tails
• he continued this for 20 generations and they continued to produce offspring with tails
2. Charles Darwin’s Theory of Natural Selection(aka: Survival of the Fittest)• 1844(but took him 20 years to publish
his ideas)• 5 main points:
i) there is variation within populationsii) Some variations are favourable. A favourable variation is one that improves the organism’s ability to function and reproduceiii) More young are produced in each generation than can surviveiv) Those with the favourablevariations, survive, reproduce and pass on the favourable trait to their offspring.v) Over enormous spans of time, small changes accumulate and populations change.
Requirements:
2. those with longer necks
get better/more food, have
more babies
(have an advantage in
the struggle for existence)
1. Variation in a trait
within a population.
(some had longer necks
than rest of population)
3. More individuals are born each
generation than can survive
“struggle for existence”
4. those with longer necks are
more likely to survive, and pass
this trait on to their offspring
(variation is heritable)
5. gradually, over many generations, necks
became longer and longer