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Published byCarmel Jacobs Modified over 8 years ago
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Darwin’s Theory of Evolution
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What is Darwin’s Theory of Evolution? Introduced the idea that the environment (nature) selects an organisms traits – Natural Selection His theory of Natural Selection has many different parts… – Overproduction – Competition – Variations – Survival of the fittest – Inheritance
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Overproduction Naturally occurring species have a tendency to produce far more offspring than can possibly survive
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Competition Overpopulation results in competition for available resources. – Food – Water – Space – Mates There is a struggle for existence within the species
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Variations Although offspring of a species are similar, there are differences that exist (variations) – Some of these differences have a high adaptive value – Some of these differences have a low adaptive value
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Variations Variations that have a high adaptive value help the organism survive and pass on that trait. Variations that have a low adaptive value can cause an organism to die and not pass on that trait.
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Variations in the species THE DIAGRAM ABOVE ILLUSTRATES THE CHANGE THAT OCCURRED IN THE FREQUENCY OF PHENOTYPES IN AN INSECT POPULATION OVER 10 GENERATIONS. A PROBABLE EXPLANATION FOR THIS CHANGE WOULD BE THAT OVER TIME THERE WAS 1. A DECREASE IN THE ADAPTIVE VALUE OF GENE A 2. AN INCREASE IN THE ADAPTIVE VALUE OF GENE A 3. AN INCREASE IN THE POPULATION OF THIS INSECT 4. A DECREASE IN THE MUTATION RATE OF GENE A
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Survival of the Fittest Organisms with favorable adaptions survive – And pass on their genes Organisms with out these traits become sick and die. – Cannot pass on their genes Note: Fittest does not always mean the strongest!
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Inheritance Individuals that survive (due to their favorable trait) will pass on the traits to their off spring! Survive Reproduce Species Continues
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Example of Natural Selection: - Giraffes had many offspring - Offspring had different length necks (variations) - Offspring competed for limited resources - Long necks = survive Short necks = fewer survive Short necks = fewer survive (survival of the fittest) (survival of the fittest) - Long-necked trait was passed on to the future generations
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