Theories of Evolution Key words: acquired, natural selection

Starter 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

What are the theories of evolution? Objective What are the theories of evolution? Success Criteria By the end of the lesson I: can explain the two theories of evolution and who has created them can explain evidence that supports one of the theories can identify the evidence for evolution

Who was Charles Darwin?

Natural selection of Finches This is just one of the examples that got Darwin thinking about natural selection.

Summary Darwin's finches He noticed that the finches (songbirds) on the different islands there were fundamentally similar to each other, but showed wide variations in their size, beaks and claws from island to island. For example, their beaks were different depending on the local food source. Darwin concluded that, because the islands are so distant from the mainland, the finches that had arrived there in the past had changed over time.

Darwin’s theory of evolution The 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.

Controversial research 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. Photo credit: Darek Krzeminski Luckily, a handful of influential scientists were convinced by Darwin's work and spoke out in public to promote his ideas.

Could Darwin explain everything? Darwin made extensive use of specimens and fossil evidence to explain his theory of evolution, but because DNA and genes had not yet been discovered, he was unable to explain why traits varied within individuals or how they were inherited. Victorian scientists found it difficult to test Darwin’s theory. 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.

Lamarck’s theory of evolution 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. How would this theory explain a giraffe’s long neck? The short-necked ancestors of modern giraffes needed to reach the leaves on tall trees when food was scarce. Over their lifetimes these giraffes stretched their necks; a trait which was then passed on to their offspring.

What evidence for evolution? Observing how changes in genes can be passed from one generation to another Fossil record Studying similarities and differences between living species

Theory of Evolution Plenary The theory of evolution states that all present day organisms (and many more that are now extinct) have evolved from simpler organisms over long periods of time (billions of years) DARWINs theory is that evolution takes place through natural selection LAMARCKs theory is that all organisms originated from worms and that this was caused by the inheritance of acquired characteristics

Why is it important for students to know about evolution? Science vs religion Read page 116 and answer Why is it important for students to know about evolution? Include – evidence of evolution - the current scientific theories - final comment stating your opinion

What are the theories of evolution? Objective What are the theories of evolution? Success Criteria By the end of the lesson I: can explain the two theories of evolution and who has created them can explain evidence that supports one of the theories can identify the evidence for evolution