Chapter 20.txt

  1. autotrophs
    [Gk. auto, self, and trophos, feeder] An organism that synthesizes its own food from simple inorganic compounds in its environment with energy captured from the sun or from oxidizing inorganic substances; e.g., a photoautotroph or chemoautotroph.
  2. chemoautotrophs
    Any prokaryotic cell that makes its own food by oxidizing inorganic substances.
  3. cyanobacteria
    A type of single-celled photoautotroph; the first to use a noncyclic pathway of photosynthesis, which slowly enriched the early atmosphere with oxygen.
  4. endosymbiosis
    [Endo�, within + symbiosis, living together] An intimate, permanent ecological interaction in which one species lives and reproduces in the other�s body to the benefit of one or both.
  5. eukaryotic cells
    Type of cell that starts life with a nucleus and other membranebound organelles.
  6. heterotrophs
    [Gk. heteros, other, + trophos, feeder] Organism that cannot make its own food; feeds on other organisms, their wastes, or their remains.
  7. prokaryotic cells
    [L. pro, before, + Gk. karyon, kernel] A single-celled organism, often walled, that does not have the organelles characteristic of eukaryotic cells. Only bacteria and archaeans are prokaryotic.
  8. Proterozoic
    Era between 2.5 million to 544 million years ago. An oxygen-rich early atmosphere formed, sparking the Cambrian explosion of biodiversity.
  9. proto-cells
    Presumed stage of chemical evolution that preceded living cells.
  10. RNA world
    Model for a time prior to the evolution of DNA; a self-replicating system chemically evolved in which RNA strands were templates for protein synthesis.
  11. stromatolites
    Fossilized remains of domeshaped mats of shallow-water communities, cyanobacterial species especially, that were infiltrated with dissolved minerals and fine sediments. Some are 3 billion years old.
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Chapter 20.txt
Chapter 20