Evolution of Life on Earth

• Konzenvat-Lagerstatten


  Many organisms in one bed
• Konservat-Lagerstatten


  Exceptional preservation
• What Conditions are required for exceptional preservation?

  Rapid burial in fine grained sediment, no scavengers, low energy, anaerobic conditions to stop decay, low pH to slow decay
• What prevented life from Evolving?

  Earth was bombarded in meteorites.
• First Living Things

  In the Sea, evolved shortly after bombardment ended, was simply bacteria, lived in mounds in shallow ocean
• Stromatolites


  Layered rocks produced by certain prokaryotes when they bind thin layers of sediments together
• What was the first living thing on Earth?


  Bacteria
• What cause O2 to occur on Earth?


  Early photosynthesis done by bacteria
• What is a Banded Iron Formation?

  When the oxygen from the bacteria oxidises the iron in shallow water -> creates a red layer, less bacteria and so less O2

  get silicic layers. Stop appearing once O2 became abundant in the ocean 1.8 bill
• When did Eukaryotes appear?

  1.8 Bill yrs ago
• Why did Eukaryotes appear so late?

  They needed O2
• 1.2 Bill yrs ago, Algea evolved sexual reproduction
• What Evolved after Snowball Earth?

  Ediacara
• Where was Ediacara found?

  Charnwood Forest in the Uk
• Why could Ediacara not have been a plant?

  It lived on the sea floor where there was no light - couldnt have photosynthesised
• What was the Cambrian Explosion


  Organisms developed mineralised Skeletons
• Oxygen Availabiltiy


  Allowed the evolution of larger, more complex animals with respiratory and circulatory systems
• Glaciation/Post Snowball Earth

  Lots of species died - allowed for orgamisms to go through adaptive radiations into new habitats
• Developmental Explanations

  The genome became complex enough to create radically new body plans - allowed natural selection to act
• Ecological Explanations

  Emergence of predators stimulated evolution of hard parts or organisms to evolve burrowing as a new habitat