Pg253 Keywords, history of life on earth

Pg253 Keywords, history of life on earth - History of Life...

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History of Life on Earth 1. Radimetric dating – using radioactivity to find the age of something 2. Radioisotope - chemicals that we can use to do rad. dating. 3. Half-life – unit of rad. dating. 4. Precursors of the First Cell: Most scientists believe the first cells had RNA genetic material, not DNA. Because: a. You need an RNA primer to replicate DNA. b. To use DNA and turn it into a protein, you first need to turn it into RNA. c. RNA is less stable than DNA. Scientists believe that DNA evolved to be able to better store information since it’s double helix. It’s more stable, so it can hold information longer and we can live longer since RNA would fall apart quickly. RNA is vestigial, and during transcription when we convert the DNA to RNA language (by replacing the uracil nucleotides with thymine), it is actually a waste of time and is a vestigial structure. d. RNA is also an enzyme – more reactive, unstable. DNA on its own will just sit alone and won’t produce life by itself, that’s why we need RNA and DNA. (DNA is more stable and lasts longer, so shouldn’t have produced the first life; evolution gives us what is better and what we need. It has given us DNA to use instead of RNA so that we can live longer.) 8. Cyanobacteria – cyan colored bacteria that were the first organisms on Earth to do photosynthesis, which allowed organisms to evolve and to get used to oxygen. Made the first atmosphere and oxygen. 9. Archaebacteria – The name Archaebacteria means “ancient bacteria,” but archaea are so different from bacteria that many biologists now prefer to use only the name archaea for this group. Also known as extremophiles; live in extreme climate conditions; inside volcanoes, boiling water. 10. Eubacteria – The name Eubacteria means “true bacteria,” distinguishing this group from the archaea, which are no longer | P a g e Gautham – 3/20/2010
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considered to be bacteria. >> There’s a debate about whether Eubacteria or Archaebacteria were the first living
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Pg253 Keywords, history of life on earth - History of Life...

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