Old and New Species

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  • Created by: Amy
  • Created on: 07-05-13 20:11

The Origins of Life on Earth

  • Fossils - important evidence on how life has develpoed
  • imposible to know for sure how life began 
  • No record of the origin of life
  • No one there to see it
  • Fissils give information about organisms that lived long times ago
  • Many beleve that early organisms were soft bodied so fossil records are incomplete
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Fossils

  • Remains of plant and animals
  • Found in rocks
  • Evidence of life years ago
  • GRADUAL REPLACEMENT - things that dont decay easily (bones, teeth etc.) replaced by minerals forming a rock like substance 
  • CASTS/IMPRESSIONS - buried in soft material (clay) clay hardens leaving a cast eg roots, footprints ec. 
  • PRESERVATION 
    • amber - no oxygen so decay microbes cant survive
    • glaciers - to cold for decay microbes to work
    • peat bogs - too acidic
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Extinction

Extinction: 

may be caused by - 

  • new predators
  • new diseases
  • new more sucessful compertition

Mass Extinction:

may be caused by - 

  • a single catastrophic event
  • volcano or asteroid strikes
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Speciation

the development of a new species

speciation takes place when an isolated population becomes so different from the original population that succesful interbreeding can no longer take place. 

specise - a groupe of similar organisms that can reproduce to give fertile offspring.

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Isolation

  • when populations of a species are seperated.
  • can be due to physical barrier
  • geographical isolation - flood or something diving them
  • conditions on either side of the barriers are different (eg different climate)
  • different characteristics with become more common due to natural selection
  • changed so much that they wont be able to breeed = separate species 
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