B3 Revision Cards

Revision Cards to help with OCR's Science for the 21st Century B3.

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  • Created by: kanojyoxx
  • Created on: 17-06-10 09:07

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:
    • God
    • Outer Space
    • Chemical that could replicate itself.
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Natural Selection

  • 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:
    • Radiation
    • Chemicals
    • 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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Human Evolution

  • 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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Nervous System

  • 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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Hormonal System

  • 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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