4.6~3.5 Billion Years Ago (BYA)- No Atmosphere:

• surface was molten

• gas from volcanos help Earth cool

• after half a billion years Earth was cool enough for water to form hydroshpere

3.5~2.4 BYA - Cyanobacteria Produce Oxygen:

• No free oxygen

• Oxygen first produced by photosynthetic prokaryotic organisms

• Cynobacteria trapped and bounded sediments, forming wavy structures (stromatolites)

2.4 BYA~600 MYA - Iron Soaks Up Oxygen

• Iron dissolved into oceans

• Settled to ocean floor

• Iron oxide stopped being deposited and oxygen was able to start building up

600~550 MYA - Oxygen Levels Boom:

• Rapid build up of free oxygen

• Little direct effect on life

550~300 MYA - Life Booms with Increased Oxygen:

• Oxygen gave life new possiblities to explore

• Atmospheric oxygen level 2% volume nessecary to make compounds

• Oxygen levels fluctuated between 15-30%

300 MYA to NOW - Oxygen Drops from 35% to 21%

• Oxygen levels reached max of 35%

• May have contributed to large insect size

• Rainforsts and climate evolved

• Dropped to a stable 21%

Recent levels:

• Co2 about 280 ppm

• Co2 levels rise due to fossil fuel increase

• An extinct marine arthropods.

• Earliest known arthropods.

• Highly diverse and extensive fossil record.

• Went extinct during the Permian mass extinction.

Dinosaurs -

• Diverse group of reptiles

• Closest ancestor to modern day birds

• Went extinct during the end of the Cretaceous Period

• During these periods land in North America and Northern Europe were covered by giant ice fields and glaciers.

  
  

  There are periods within ice ages that scientists define as

  • Glacial – A glacial period is a cold period when the glaciers are expanding.

  • Interglacial - An interglacial period is a warm period where the glaciers may be receding.

    
    

The Five Major Ice Ages -

1. Huronian

2. Cryogenian

3. Andean - Saharan

4. Karoo

5. Quateranry

• The last ice age was called “The Great Ice Age”, and it occurred 11,000 years ago.

• Formed 4.5 billion years ago

• Used a dense cloud of interstellar gas and dust

• Collapsed due to a shock-wave of a nearby star

• When dust cloud collapsed it formed solar nebula and a spinning disk

• The gravity in the center caused so much pressure it formed the Sun

• Farther out of the disk it was clumping up and formed the planets due to the clumps having lots of mass and gravity.

• Originated from ape like ancestors

• First humans migrated out of Africa to Asia

• Evolved over a period of 6 million years

• Lived during the Middle Ordovician around 470 million years ago

• Liverworts and mosses were the first plants

• Able to reproduce with spores

First Fungi -

• First appeared one billion years ago

• Extremely ancient group

• Oldest is known as Prototaxites which was common around Devonian Period

• Found around 370 million years ago

• Developed around the Devon Period

• Similar to the modern coelacanth and lungfish

• Used to walk along the sea floor but it's legs helped it go to land and develop lungs

• Known as Archaeopteryx 150 million years ago

• Birds had evolved before then

• A group of primitive birds evolved into the modern day birds during the late Cretaceous

• Overlap period where dinosaurs, primitive birds, and modern birds co-existed

First Mammals -

• Known as Morganucodontids 210 million years ago

• Tiny shrews

• Known as Archaefructus 130 million years ago

• Probably lived in or grew near water

• Ordovician-silurian Extinction: 440 million years ago. Small marine organisms died out.

• Devonian Extinction: 365 million years ago

• Permian-triassic Extinction: 250 million years ago

• Triassic-jurassic Extinction: 210 million years ago

• Cretaceous-tertiary Extinction: 65 million Years ago