Scientist estimate life began 3 billion years ago and before 18th century, few ideas about how evolution works
Jean-Baptiste Lamarck - 'inheritance of aquired characteristcs' - characteristcs that develop in organisms lifetime are passed onto offspring, people found this hard to believe
Charles Darwin - 'natural selection' - small changes take place in organisms over long period of time, all organisms vary, so some are more likely to survive and they breed and pass on the characteristics - he didn't know about genes, so couldn't prove it
We now say that best adapted organisms survive to breed and then pass on their genes to their offspring
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B1.7.2 - Accepting Darwin's Ideas
Darwins idea was only gradually accepted, because:
Challenged religious views
Many scientists didn't hink there was sufficient evidence
Darwin couldn't explain why there was variety or how inheritence worked - scientists didn't know about genes until around 50 years ago
Darwin had tried to show how environmental conditions could change animals, but he couldn't explain, in terms of genes, why the offspring inherited the useful adaptations
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B1.7.3 - Natural Selection
Most organisms have large numbers of offspring
Individual organisms show wide range of variation beacue of different genes
All organisms compete for food, sheltor (from predators) and mates
Organisms with with best suited characteristics survive - eg. camouflage, eysight, strongest, quickest, best suited to a climate etc. - the 'fittest' will survive and are more likely to successfully breed and pass on genes
Mutations - genes accidentally chane and become a new form of the gene, if the mutated gene controls a characteristic that means it's better adapted it will be passed on
Mutations are important in natural selection - eg. can become immune to a disease and therefore survive to breed and pass on the mutation while others die
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B1.7.4 - Classification and Evolution
Millions of different organisms - classification groups similar organisms
Biologists study similarities and differences between organisms to classify them - natural classification system - large groups that split into smaller ones
Largest: kingdoms - animal, plant and kingdoms containing microorganisms
Smallest: species - organisms in same species can breed together
Evolutionary trees - models drawn to show relationships between different groups of organisms
New evidence can change evolutionary relationship
Ecological relationships show us how species evolved together in an environment
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