1. Name: Date: Thurs 11/16/15 Topic – Ch3L2 – Ancient Earth (Pages 96-104)
Query: (SC.7.E.6.4)
How did early earth changes affect the evolution of life?
Student Objective I can describe how early earth changes affected the evolution of life.
I Do/We Do – Guided notes and Class discussion
You/Do – Lesson 2 Review

2. The Ancient Earth

3. Early History In the beginning… there was DARKNESS!
The solar system is believed to have been formed from a nebula
Nebula: a cloud of gas, ice, and dust floating in space.
a precursor to our solar system
Over time, gravity pulls all this matter together.
The majority of this matter gets more densely packed, forming the sun
The remaining matter formed the planets

4. The formation of the Earth
Matter kept colliding, producing excessive amounts of thermal energy
This warmed the planet
The Hadean Eon: the first 640 million years of Earth history
4.6 – 4 billion years ago
Named for the Greek god Hades (due to the excessive heat during this period)
Two sources: thermal energy from radioactive decay and from asteroidal collisions.
All this heat melted metal, making the denser metal move towards the center (due to gravity)
This is why we have a core of iron and nickel

5. The formation of the Earth
The Earth started to cool
Fewer asteroid collisions
Radioactive elements decayed, making more stable elements
Because of all the heat, the Earth must have been covered in molten rock
As the earth cooled, small islands would be formed, only to be destroyed by the motion of the lava/asteroid impact
The constant eruption of lava also produced gases
Earth’s first atmosphere, which would have killed modern organisms
Contained water vapor, carbon dioxide, poisonous gases, but NO OXYGEN

6. The Archean Eon
The Archean Eon: the period that occurred billion years ago
Still twice as hot as it is today
This is when the first solid surface formed
Protocontinents: the small early continents formed during the Archean Eon
Convection currents of the magma caused collisions between protocontinents
Sometimes, they came together and became larger landmasses

7. The Archean Eon
Lowering temperatures meant more water vapor condensing, bringing rain
Gases made precipitation acidic.
Dissolved mineral salts from land, flowing into the water
Cyanobacteria: blue-green algae that were some of the first life-forms
Formed stromatolites (sedimentary structures that held microbial mats of cyanobacteria)

8. The Proterozoic Eon
Proterozoic Eon: the time from 2.5 to billion years ago
Cooling still continued, with landmasses continuing to collide
Changes in the atmosphere resulted in two big occurrences
Increase in oxygen
The Earth froze over

9. The Proterozoic Eon Increase in oxygen Two ways:
Sun split water molecules into hydrogen and oxygen
Cyanobacteria broke down carbon dioxide into oxygen through photosynthesis
Oxygen on the planet jumped up to 20% of atmospheric makeup
Called “The Great Oxygenation Event”
This was bad for the early organisms. WHY?

10. The Proterozoic Eon Snowballing Earth 800 to 600 million years ago
The entire planet was believed to have been covered in ice

11. The First Supercontinent
You heard of Pangaea?
Rodinia was the first supercontinent
The waters near there were shallow and warm, which favored life
The first multicellular life came about around the end of this period

12. DO NOW
Lesson 2 Review on pg 104

13. Extra Resources https://www.youtube.com/watch?v=bxHhhZJqnoE

14. Ending reflections – Min. 40 words