Life on Earth
- Life started around 3500 million years ago.
- Organisms were orginally simple, but have evolved to be complex and varied.
- Evolution happens because of Natural Selection.
- Evidence for Evolution is the fossil record and DNA.
- There are three different theories on how life started:
- Outer Space
- Chemical that could replicate itself.
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- Variation within a species.
- Limited resources.
- Some varieties have an advantage to win the resources.
- More likely to survive and reproduce.
- Over a period of time, the entire species will be well adapted.
- Artifical selection is where humans decide what characteristics animals should have.
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- Caused by:
- Mistakes in cell division.
- Mutations can have no effect.
- They could be of a benefit.
- They can only be passed onto the next generation if they occur in sex cells.
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Darwin and Lamarck
- Darwin came up with the idea of evolution by natural selection.
- Lamarck came up with the laws of use and disuse and the law of inheritance (using a characteristic more meant that it would get more developed and that would pass onto the next generation.
- People didn't believe Darwin because:
- Most people were religious and thought God created life.
- Darwin's ideas were only one interpretation of the observations.
- The data challenged what people had believed in for a long time so its hard to change their opinions.
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- We devloped a bigger brain to make tools and to communicate with each other.
- We developed the ability to walk upright - to spot prey and predators.
- All other hominids have died out.
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- Stimulus -> Receptors -> Sensory Neurones -> Relay Neurones -> Motor Neurones -> Effectors
- Electrical impulses
- Quick but-short lived.
- Responsible for eyes, moving your hand, etc.
- Controlled by the CNS - Central Nervous System made of the Brain and Spinal Cord.
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- Chemicals that travel in the blood.
- Made in glands.
- Slow moving but long-lived.
- Responsible for blood sugar, adrenaline, and ovaries/testes hormones.
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- Change in environment.
- New competitor.
- New predator.
- New disease.
- Another organism on the food web becomes extinct.
- Humans kill them.
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