theories of evolution

Biology 1b Evolution and EnvironmentBiology 1b Evolution and EnvironmentGCSGCSEE

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Key words: acquired, natural Key words: acquired, natural selectionselection


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Lets get a grip of Evolution and Natural Selection through the following interactive video;

http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/environment/evolutionact.shtml




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Objective

What are the theories of evolution?What are the theories of evolution?

Success CriteriaBy the end of the lesson I:

• can explain the two theories of evolutionand who has created them• can explain evidence that supports one of the theories• can identify the evidence for evolution


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Who was Charles Darwin?


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Natural selection of Finches

This is just one of the examples that got Darwin thinking about

natural selection.


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Summary Darwin's finches

• He noticed that the finches (songbirds) on He noticed that the finches (songbirds) on the different islands there were fundamentallythe different islands there were fundamentallysimilar to each other, but showed wide variations insimilar to each other, but showed wide variations intheir size, beaks and claws from island to islandtheir size, beaks and claws from island to island.. • For example, their beaks were different dependingFor example, their beaks were different dependingon the local food source.on the local food source. • Darwin concluded that, because the islands are soDarwin concluded that, because the islands are sodistant from the mainland, the finches that haddistant from the mainland, the finches that hadarrived there in the past had changed over time.arrived there in the past had changed over time.


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Darwin’s theory of evolutionThe British naturalist Charles Darwin (1809–1882) 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.


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Darwin knew that in religious Victorian society his findings would be controversial and blasphemous. He was unwilling to publish and risk his reputation.

However, when Darwin learned that another British naturalist, Alfred Russel Wallace, had proposed an almost identical theory of natural selection, he published his findings.

Controversial research

Luckily, a handful of influential scientists were convinced by Darwin's work and spoke out in public to promote his ideas.


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Darwin made extensive use ofspecimens and fossil evidence toexplain his theory of evolution,but because DNA andgenes had not yet beendiscovered, he was unableto explain why traits varied within individuals or how they were inherited.

Could Darwin explain everything?

Victorian scientists found it difficult to test Darwin’stheory. For his theory to work, the Earth needed to be millions of years old, but its age was not known at that time.

In addition, little was known about the process of fossilization or how to explain gaps in the fossil record.


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The short-necked ancestors of modern giraffes needed to reach the leaves on tall trees when food was scarce.

Lamarck’s theory of evolution

How would this theory explain a giraffe’s 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.


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What evidence for evolution?


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Theory of EvolutionThe theory of evolution states that all present day The theory of evolution states that all present day

organisms (and many more that are now organisms (and many more that are now extinct) have evolved from simpler organisms extinct) have evolved from simpler organisms over long periods of time (billions of years)over long periods of time (billions of years)

DARWINs theory is that evolution takes place DARWINs theory is that evolution takes place through through natural selectionnatural selection

LAMARCKs theory is that all organisms originated LAMARCKs theory is that all organisms originated from worms and that this was caused by the from worms and that this was caused by the inheritance of acquired characteristicsinheritance of acquired characteristics


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Science vs religion

Read page 116 and answerRead page 116 and answer

Why is it important for students to know Why is it important for students to know about evolution?about evolution?

Include – evidence of evolution- the current scientific theories- final comment stating your opinion


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Objective

What are the theories of evolution?What are the theories of evolution?

Success CriteriaBy the end of the lesson I:

• can explain the two theories of evolutionand who has created them• can explain evidence that supports one of the theories• can identify the evidence for evolution

theories of evolution

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