Senin, 23 Februari 2009

Asal usul kehidupan: Teori Evolusi

6.1. Evolusi kimiawi
6.2. Evolusi biologis
6.3. Teori evolusi Drwin
6.4. Teori evolusi modern
The origin & Evolutionary History of Life
How did life begin ?
Hipothesis: Chemical evolution
Early earth provide the conditions for chemical
Four conditions for chemical evolution:
The absence of oxygen
Energy to form organic molecules
Chemical building blocks: water, minerals, gases
Sufficient time for moleculesto accumulate

Harold Urey & Stanley Miller
Organic molecules formed on primitive earth
For steps are hypothesized in chemical evolution:
Small organic molecules formed spontaneously and
a. Prebiotic broth hypothesis
b. The iron-sulfur world hypothesis
2. Macromolecules assembleagedbfrom the samll organic molecules
3. Macromolecules assemblages called proptobionts
a. RNA world model
b. Natural selection at the molecular level
c. Directed evolution
4. Cells arouse from macromolecules assemblages

The first cells probably assembled from organic molecules
The first cells were prokaryotic heterotrophs (anaerobes)
Later autotrophs organism that produce their own molecules by photosynthetic arouse.
The evolution of photosynthesis: permited the evolution of aerobes
Eukaryotic cells arouse from prokaryotic cells: endosymbiont theory

The fossil record provide clues to the history of life
Earth history devided into 3 eras, each era devided into period which are devided into epoch
Precambrian time: 4.6 bya to 543 mya
Paleozoic era: microfossils: bacteria, protists, fungi and simple multicellular
Mesozoic era: non-flowering plansts, animals
Cenozoic era: modern order of mammals, birds

Evolutionary Tree of Life

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