Biology - Evolution

This topic is for an AQA GCSE paper and has four sub-sub topics:

1. Theories of Evolution          2. Accepting Darwin's Ideas          3. Naural Selection          4. Classification and Evolution

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Theories of Evolution

In 1831 Darwin set off on the HMS Beagle to study geology and he collected animals and pants.

In South America, Darwin found a new form of the rhea. As he sailed from island to island he noticed small differences between the animals such a finches and on his long trip home, he had plenty to think about.

When Darwin got back home he spent the next 20 years explaining his findings. Darwin's theory of evolution was that have evolved through natural selection from simpler life forms.

Each organism will have offspring that has over the amount that the environment can survive so the offspring develop features to survive and pass it on to their offspring. This is natural selection.

Noone knew about genes then so he just said that the characterisitics were passed on.

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Accepting Darwin's Theory

It took so long for Darwin to publish his theories as he needed a lot of evidence. He used diifferent types of pigeons and barnacles to prove his theory.

People did not believe him, however, because of three reasons:

  • Evolution challenged their beliefs.
  • Despite Darwin's efforts, scientists felt there was not enough evidence.
  • They could not say how variety and inheritance worked because they did not know about genes.
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Natural Selection

When offspring are born they are born with special features that will help them survive. 

New forms of genes are created through changes, mistakes, in existing genes . These are mutations and they give an organism variety that ables them to survive.

Some mutations are harmful and some have no effect. But there are some that have positive sides that makes the organism more suited to the environment.

With this positive new gene, the organism will be able to survive and reproduce and pass on their genes to their offspring.

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Classification and Evolution

Classification is the sorting of different organisms into groups according to their similarities. The system used is called natural classification system. 

The biggest groups are the kingdoms. There are five kingdoms: Animals, Plants, Bacteria, Fungi and Protoctista. The smallest groups are species.

The models used to classify an organism is an evolutionary tree. Today scientists are using DNA to clasify an organism because it can be tricky just using looks.

Classification can help us see how an animal as evolved, their ecological relationship.

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