THE ORIGIN AND HISTORY OF LIFE

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THE ORIGIN AND HISTORY OF LIFE

• Chapter 18

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• A. The Origin of Life
• Clues from geology paleontology provide us with
  information of Early Earth.

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• Prebiotic simulations demonstrate how life might
  have arisen.

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A Theory of Lifes Beginnings
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• How might metabolic pathways have arisen?

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• B. Major Events of Lifes History

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• Precambrian Era
• Origin of life (3.8-3.7 bya) Earliest
  prokaryotic fossils are 3.5 billion years old.
• Origin of photosynthesis (3.5-2.8 bya)
• Fossils from Rhodesia contain breakdown products
  of chlorophyll.
• Origin of eukaryotic cells (1.9 bya)
• Earliest eukaryote fossils (unicellular algae)
  are 1.7 billion years old.

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• Endosymbiont theory - eukaryotic cells arose from
  ancient cells (perhaps archaea) that engulfed
  aerobic photosynthetic bacteria.

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• Origin of multicellular organisms (1.2 bya)
  Fossils of multicellular algae found in Canada
  Siberia.
• Paleozoic Era
• First vertebrates (jawless fishes) appeared
  during Ordovician period (505-435 mya).
• First land plants animals appeared during
  Silurian period (435-410 mya).
• First amphibians appeared in early Carboniferous
  period (360-290 mya).

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• First reptiles appeared in late Carboniferous
  period (300 mya).
• Mesozoic Era
• First dinosaurs appeared during Triasic period
  (240-205 mya).
• First flowering plants birds appeared during
  Jurassic period (205-138 mya).
• First mammals appeared during Cretaceous period
  (138-65 mya).

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• C. The Age of Mammals
• Extinction of the dinosaurs 65 mya opened many
  niches that mammals filled via extensive adaptive
  radiation.
• All mammals possess hair have mammary glands
  that produce milk.
• Egg-laying mammals (monotremes) were probably
  first to evolve, followed by pouched mammals
  (marsupials) finally placental mammals.

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Placental Mammal Migration
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• The Road to Humanity
• Primates first appeared 60 mya
• Aegyptopithecus, a monkey like animal, appeared
  40-30 mya believed to be ancestors of gibbons,
  apes humans.
• First hominoids (primates ancestral to apes
  humans) believed to have appeared 32-22 mya.
• First hominids (primates ancestral to humans)
  believed to have appeared 19-4 mya.

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• Australopithecus appeared 4 mya exhibited
  bipedalism (walked upright) several species have
  been identified in Africa coexisted with Homo
  habilis.
• Homo habilis (handy man) appeared 2 mya lived
  in caves, cared for young exhibited tool use
  coexisted with Homo erectus.
• Homo erectus (upright man) appeared 1.6 mya
  left fossil evidence of social organization,
  cooperation use of fire.

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• H. erectus coexisted with Homo sapiens.
• Homo sapiens appeared 200,000 years ago had well
  developed frontal brain regions.
• Neanderthals appeared in Europe 150,000 years ago
  coexisted with H. sapiens from 40,000-30,000
  years ago unlikely that Neanderthals H.
  sapiens interbred probably represent an
  evolutionary dead end.