Fossils

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  • Fossils
    • Fossils are the remains of plants and animals
      • 1) Fossils are the remains of organisms from many years ago, which are found in rocks
      • 2) They provide the evidence that organisms lived ages ago
      • FOSSILS FORM IN ROCKS IN MANY WAYS
        • 1) FROM GRADUAL REPLACEMENT BY MINERALS
          • 1) things like teeth, shells ad bones don't easily decay. This means they can last a long time when burried
            • 2) When they decay, they get replaced by minerals. The minerals form a rock like substance shaped like the original hard part
        • 2) FROM CASTS AND IMPRESSIONS
          • 1) Fossils can be formed when an organism is buried in a soft material like clay. The decay hardens around it and the organism decays
            • 2) The organism leaves a cast itself. An animal's burrow or a plant's roots can also be preserved
            • 3) Things like footprints are passed into soft materials. This leaves an impression when they harden
        • 3) FROM PRESERVATION IN PLACES WHERE NO DECAY HAPPENS
          • 1) Decay microbes only work if there's oxygen, moisture, warmth and the right PH
            • 2) In some substances these conditions aren't all present so decay doesn't happen.
              • e.g. there's no oxygen or moisture in amber so decay organisms can't survive
    • But no one knows how life began
      • 1) Fossils show how many of today's species have evolved over millions of years
      • 2) There are lots of hypotheses suggesting how life first came into being. For example:
        • Maybe the first life forms appeared in a swamp( or under the sea) here on earth.
          • Carbon molecules were brought here on comets and developed into simple life forms
      • 3) These hypotheses can't be supported or dissaproved because there's a lack of valid and reliable evidence
      • 4) There's a lack of evidence because many early organisms were soft-bodied. Soft tissue tends to decay away completely. So the fossil record is incomplete
      • 5) Fossils that did form millions of years ago may have been destroyed by geological activity.
        • e.g the movement of tectonic plates may have crushed fossils already formed in the rock

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