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Ns and extiction2
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Ns and extiction2


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  • 1. Natural Selection
  • 2. Key termsNatural selectionEvolutionAdaptationMutationTraitVariationHeredityOffspringSpeciesHabitatExtinct
  • 3. Natural Selection• The idea of natural selection was first suggested by Charles Darwin over 150 years ago.• Certain individuals gain an advantage over other individuals they are in competition with.• This animal is therefore more likely to survive and breed – natural selection.
  • 4. Natural SelectionThere is There is There is This results in:variation in differential hereditary: The advantageoustraits: reproduction: trait allows the Not all beetles The brownFor example beetles have beetle to survive reproduce to their and have moresome beetles full potential. Green brown offspring offspring. Over time,are green and beetles are eaten because the trait if this continues thesome brown. so is mainly brown has a genetic whole population beetles that basis. will be brown. reproduce.
  • 5. Survival of the Fittest• Reproduction is a very wasteful process.• Animals and plants always produce way more offspring than the environment can support. Fruit flies produce 200 offspring• Why? every 2 weeks!
  • 6. Survival of the Fittest• Individual species show lots of variation because of the different genes they inherit• Only the offspring with the genes best suited to their habitat will stay alive and breed successfully.• Many animals produce lots and lots of offspring to ensure that at least some will survive and pass on their genes.
  • 7. What about mutation?• New forms of genes result from changes in existing genes.• These changes are mutations.• Mutations happen due to mistakes made when copying DNA when cells divide.• They introduce more variety into the genes of a species.Why is this important for evolution?
  • 8. What about mutation?• If the mutation that occurs results in a characteristic that helps the animal compete and survive then it will be passed on to the next generation.• Over time this mutation may become a common gene in the population.
  • 9. What do these animals have in common? They are all extinct!
  • 10. Extinction• Extinction is the permanent loss of all the members of a species from the face of the EarthIn pairs:• What might cause an animal to become extinct?
  • 11. Extinction• Environmental changes (Dinosaurs) – E.g. If animals suited to hot weather enter an ice age• More competition (Birds species on Guam) – If a mutation happens in one species that helps it survive really well or a new species moves into the area• A new disease (Tasmanian devil) – E.g. If a population of animals gets a disease which none of them are resistant to. This is especially bad if the whole population live close together (e.g. on an island)
  • 12. Questions• What is the link between natural selection and mutation?• Explain how good eye sight in rabbits has come about in terms of natural selection.• Name three causes of extinction.• Explain why the dinosaur became extinct.