theories of evolution

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Theories of Evolution. Students know the theory of evolution That there is evidence that evolution has taken place. Some of the other theories of how life began on Earth HSW – interpret evidence relating to evolutionary theory - PowerPoint PPT Presentation

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  • Theories of EvolutionStudents know the theory of evolutionThat there is evidence that evolution has taken place.Some of the other theories of how life began on EarthHSW interpret evidence relating to evolutionary theoryHSW learn that the credibility of the evidence may increase if it is consistent with existing ideas or scientific consensus

  • Learning OutcomesAll students know that the theory of evolution is the one accepted by most scientists

    Most students can state the theory of evolution and describe some of the evidence that evolution has taken place. They have some understanding of why Darwins theory of natural selection was only gradually accepted.

    Some students can identify the differences between evolution and other theories. They can suggest reasons for the different theories explaining life on Earth

  • Dates of theories: Lamarck (1809), Cuvier (1825) & Darwin (1844, but not published until 1859).Theories for changeCuvier (1769-1832)Darwin (1809-1882)

  • Theories for change

    Dates of theories: Lamarck (1809), Cuvier (1825) & Darwin (1844, but not published until 1859)

    In the early 19th century:

    1 The generally accepted date of the creation was 4004 BC.2 The Church taught that the Bible was the literal truth.3 More was known about variation and adaptation of animals and plants than ever before.4 Many accepted that fossils were the remains of organisms from the past.5 Scientists saw that different layers of rocks contained different sets of fossils.6 Some taught that fossils showed that some living things died out and were then replaced by others.7 The Earths crust is constantly changing . why not living things?8 Small changes in living things had been observed.

  • Lamarcks theory of evolutionThe short-necked ancestors of modern giraffes needed to reach the leaves on tall trees when food was scarce. How would this theory explain a giraffes long neck?Over their lifetimes these giraffes stretched their necks; a trait which was then passed on to their offspring. Jean-Baptiste Lamarck (1744-1829) was a French botanist who believed that species evolved because they inherited traits acquired through the over or under-use of body parts.

  • Lemarcks theory of acquired characteristicsEvery type of animal evolved from primitive worms.He believed that the change from worms was causes by the inheritance of acquired characteristics.Useful changes in the parents are passed on to the offspring ( so body builders all have children with huge muscles?)

  • Who was Charles Darwin?

  • Darwins theory of evolutionThe British naturalist Charles Darwin (18091882) later suggested a more persuasive argument for evolution. Darwin proposed that evolution took place through natural and sexual selection.Darwin developed his theory of evolution after noticing close similarities between certain fossils and the adaptations of modern day animals he saw during his round-the-world voyage on the HMS Beagle.

  • Darwins theory of evolutionThat all living organisms have evolved from simpler life forms. This evolution comes about by a process of natural selection.Only those most suited to their environment survive the survival of the fittest

  • Natural selection

  • How the giraffe got its neckDue to natural variation, the ancestors of modern giraffes would have had necks of different length. How does Darwins theory explain a giraffes long neck?As a result, the long-necked giraffes were more likely to be healthy and live to produce more high-quality offspring.This, in turn, would increase the chances of their long-necked characteristic (an adaptive trait) being passed on to future generations.Giraffes with longer necks would have been able to reach more food than those with shorter necks.

  • Galpagos finchesDarwin thought all the finches could have evolved from one type of finch that came from the mainland.Some finches had strong and claw-like beaks, suitable for crushing seeds.Other finches had thin and delicate beaks, suitable for picking insects from holes in the ground.In the Galpagos, Darwin noticed that different islands had different types of finches, with different types of beak.

  • What happens when habitats change?Adaptive evolution ensures that individuals within a species have traits allowing them to survive and reproduce in their habitat.If the habitat changes, however, successful traits can become a disadvantage.Individuals that fail to reproduce, compete effectively for food or survive against new predators will eventually die out. If the last individual of a species dies, the species is extinct.For example, if global warming caused Arctic snow to melt, brown rabbits may be better camouflaged and so more likely to survive than white rabbits.

  • New theories are new, creative ideasTo get a theory accepted, you must explain how it could happen (a mechanism) A good theory may not always be accepted, even when the evidence is.

  • CreationismThis is where people believe that God made the world in seven days.

  • Intelligent designWhat is the theory of intelligent design?The theory of intelligent design holds that certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection.

  • Is intelligent design incompatible with evolution?It depends on what one means by the word "evolution." If one simply means "change over time," or even that living things are related by common ancestry, then there is no inherent conflict between evolutionary theory and intelligent design theory. However, the dominant theory of evolution today is neo-Darwinism, which contends that evolution is driven by natural selection acting on random mutations, an unpredictable and purposeless process that "has no discernable direction or goal, including survival of a species." It is this specific claim made by neo-Darwinism that intelligent design theory directly challenges.

    Teacher notesThis five-stage sequence examines natural selection among a population of different coloured rabbits. Suitable prompts could include:

    These rabbits look different. Could natural selection happen if every member of the rabbit population was identical?What's the key thing the rabbits have to be able to do to make sure their genes are passed on to the next generation?What might prevent a rabbit living long enough to reproduce?Which of these rabbits looks best adapted to their icy environment?How is the number of white and brown rabbits likely to change in the future?

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