Archaean Era

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Archaean Era

• By Corinne Attwood
• 3rd hour

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Introduction

• 3,850- 2,500 mya
• Earth was nothing like it is now.
• Atmosphere consisted of methane, ammonia and
  other toxic gases and very little oxygen.
• The Earths crust had begun to cool so rocks and
  continental plates began to form.
• One billion years of this era was inhabited by
  bacteria.

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Time Line3,800 mya

• Bacteria began to become more diverse.
• Bacteria copy in process called fission.
• Mutations on bacteria allow them to pass genes,
  between cells of the same type and different
  types of bacteria.
• Known as lateral transfer.

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3,700 mya

• Early microbes thrived in oxygen free
  environments of the Archaean era
• They fed on organic molecules like glucose and
  produced energy through fermentation.
• Bacteria began to generate their own food and
  energy evolved.

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3,500- 3,400 mya

• Stromatolites appear
• Stromatolites are colonies of photosynthetic
  bacteria.
• Oldest bacterial life found.
• Stromatolites create first reef systems.
• Several chunks of smaller land blocks combine and
  continents form.

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3,400- 2,500 mya

• Lithosphere- rocky outer shell that covers the
  Earth, is broken into slabs known as tectonic
  plates.
• Plates are moved by currents caused by the
  Earths heat.
• Moving between the plates causes mountains to be
  formed and can cause earthquakes and produce
  volcanoes.
• By 2,600 mya, about 85 of the Earths total
  landmass is created.
• Around 2,500 mya, the continents joined together
  to create the super continent.
• When the continents collide which scientists
  believe had only happened 4 or 5 times, the
  terrain changes drastically. Mountains and island
  seas appear and the climate and species migration
  patterns spread out.

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2,700 mya

• The first eukaryotes are traced to be have been
  during this time.
• Traces of oil in rocks found contain sterols
  which are fatty acids that hold cell membranes
  together.

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2,700- 2,600 mya

• Scientists believe that the first eukaryotes
  evolved from endosymbiosis, a process where 2
  different kinds of single celled organisms join
  together in a way that benefits both parties.
• Early eukaryotes multiply.
• Oxygen becomes more abundant and cellular
  respiration is more productive.
• Eukaryotes get bigger and bigger.

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2,600 mya

• The presences of large groups of photosynthetic
  bacteria suggests that a primitive ozone layer
  had begun to form.

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Climate Changes

• Changes of climate because of the atmosphere
  cooling caused rock to flake off and moving water
  would move to other parts of the area.
• Some rock became sandstones such as quartz.
• Some minerals disintegrated to form limestone.

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Origin of Life

• No one really knows when life first appeared on
  the Earth.
• Oldest fossils show us that life has been around
  as long has conditions have been able to handle
  it.
• Microorganisms of this period probably used the
  methane in the air rather than oxygen in their
  metabolism.
• First organisms may have been chemoautotrophs
  which get their carbon from inorganic compounds.
• The first autotrophs/ plants of the Archaean
  ecosystem were similar to the modern blue-green
  algae.

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