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Evolution continued!

Evolution continued!. Evolution? What’s that?. Evolution: The gradual development of different species from a common ancestor B ut what does that mean? It means: Where did we all come from? How did the huge number of species on this planet come about?. Notes for your book:.

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Evolution continued!

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  1. Evolution continued!

  2. Evolution? What’s that? Evolution: The gradual development of different species from a common ancestor But what does that mean? It means: Where did we all come from? How did the huge number of species on this planet come about?

  3. Notes for your book: • Variation refers to the differences between individuals of a single species and can result from genetic mutation or environmental factors • Favourable characteristics or adaptations are characteristics that enhance an organisms ability to survive and therefore reproduce.

  4. Notes for your book: Contrasting theories of evolution: • Lamarck: Organisms acquired characteristics during their lives (in response to the environment) and passed them on to their offspring • Darwin: Organisms with characteristics that aid their survival were more likely to produce offspring and therefore pass on these favourable characteristics

  5. Where in the world is Charles Darwin • From 1831 Darwin studied plants, animals, rocks and fossils around the world • While in the Galapagos Islands Darwin identified fourteen species of finches with many similar characteristics but with quite different beak shapes and sizes.......

  6. Where in the world is Charles Darwin • Darwin knew of only species of finch on the mainland of South America, where the finches were all likely to have come from • He came up with the theory of natural selection to explain his observations • Natural selection:the process by which the environment ‘selects’ favourable characteristics and reduces the frequency of unfavourable characteristics

  7. Galapagos island finches....(activity)

  8. In your books answer these: • Was there variation within the original species of finches on the mainland? If yes what was it? • What part of this activity showed natural selection occurring? • In this activity what would be the favourable characteristic /adaptation?

  9. Survival of the fittest • The birds most suited to the island survived to produce offspring which then inherited that beak shape • This is an example of survival of the fittest • What do we mean by fittest in this context?

  10. Survival of the theorist... • While Darwin was travelling around the world developing his Natural selection theory Alfred Russel Wallace was developing a similar theory in the Malayan jungles • Darwin and Wallace both concluded that evolution occurs by natural selection and in 1858 they presented a paper together • In 1859 Darwin published On the Origin of Species • Any thoughts on why Darwin is so well known and Wallace is not?

  11. Natural selection cont. • After many generations of selection for favourable characteristics a species becomes better adapted to its environment • If the environment doesn't change the species becomes highly adapted • If the environment changes natural selection results in an increase in the proportion of individuals with a favourable trait • Natural selection takes several generations to become evident so it is hard to look at in plants or animals • But we can use insects!...

  12. Peppered moth habitat: Light-coloured trees...

  13. Light-coloured moths blend into light trees

  14. Dark-coloured moth more easily seen by predator

  15. More light-coloured moths survive to reproduce, leading to more light-coloured offspring...

  16. However.... ! Environments can change !

  17. Coal-burning factories lead to blackened trees...

  18. Dark-coloured moths blend into blackened trees

  19. Now the light-coloured moth is more easily seen by predator....

  20. More dark-coloured moths survive to reproduce, leading to more dark-coloured offspring...

  21. Peppered moth questions: (a) What characteristic enabled the moths to blend into trees at the beginning? (b) What would you call this characteristic? (a) What happened to the moth population when the coal-burning factories changed the colour of the trees? If the trees eventually returned to their original colour what do you predict would happen to the moth population?

  22. Read through ‘Selection and rabbit control’ on page 97 and ‘Selection and diseases’ on page 98 • What examples of natural selection are given in these sections? Work on textbook questions on Page 92: 4, 9, 11, 13, 15, 16

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