BIO153H5 Lecture Notes - Mesozoic, Paleozoic, Cambrian Explosion
Lecture 2
Building blocks of life were made in early atmosphere
• Urey - Miller’s (1953) “primordial soup” experiments recreated “early earth” conditions
able to make monomers:
• Conditions on Early Earth
Life’s timeline:
The Precambrian
• A lot of catastrophic events were happening at this time
• Oxygen wasn’t present in significant amounts, but then it eventually increased, this is
because of evidences like the colour rocks from green to red. (1.5 billion years-Archean
Era)
• Oxygen: single celled organisms with a toxic waste products.
The Paleozoic Era:
• Much less terrestrial exposure: entire planet was essentially a massive ball of water.
• First appeared arthropods
• Rare ancestor found, it was different and has a different structure.
• ‘Fossils Document the Cambrian Explosion eg: jelly fish
• Loss of several special
The Mesozoic Era
• Significant modification and increase in volcanism.
• Triassic: period of recovery (started with 12% oxygen)
o Pangea impact, 1 world
• Jurassic: the earth became more close to what it is today. More of the tropical world,
lush green world, no flowers.
o Pangea begins to break apart, interior of continent arises.
• Cretaceous: Flowers and angiosperms
• These affected the climate: the water ways, no extreme weather but as the continents
separated, it created barriers in the flow of water, this increasing its current. Air flow
was interrupted, extra interferences
o Break continents=diverse temperature
The Cenozoic Era
• Absorption of heat, reason why artic is getting smaller than the northern hemisphere
because of the industrializations.
Mass Extinctions
144 million years ago
365 million years ago
251 million years ago: Mother of all the other extinctions (Permian Triassic extinction event)
• Synapsis most affected ones
End of Jurassic
Third drastic extinction event 65.5 milllion years ago
Climate has an impact on existence, leads to speculation
