Overview of natural history

Breakdown of time

• Different periods of Earth’s history are broken into sets of time

– just like a year is broken into months, weeks, days and hours

• Earth history is broken into eons, eras, periods, epochs

Eons – Millions and Billions of years • Haden: Earth before life evolved

4.6 to 3.5 Billion years ago (13% of Earth’s history) • Achaean: Earth with only bacteria like cells

3.5 to 2.5 Billion years ago (28% of Earth’s history) • Proterozoic: Multicellular life forms

2.5 BYA to 540 MYA (48% of Earth’s history)

• Phanerozoic: Dinosaurs to now• 540 MYA – present day

(11% of Earth’s history)

How time periods are distinguished

• Major geological events: The movement of tectonic plates to form continents & super-continents

• Changes in climate: a change from an ice ace to a warming period

• Mass extinctions or explosions: Changes in the types of life forms on earth

Haden Eon 4.6-3.5 BYA• So hot that the rock was molten &

Water was vapor

• Lifeless, little O2 in the atmosphere

• Relative to a calendar year:

• Jan 1st – Feb. 25th

Achaean Eon 3.5-2.5 BYA

• Earth cooled enough to have a crust & ocean

• Life forms in the sea• Bacteria & photosynthetic blue-green algae

Feb. 25th - April 17th

Proterozoic Eon: Precambrian Era2.5 BYA – 540 MYA

• Super continent Rodinia

• 21% O2 in Atmosphere

• First complex cell -July 13th

• First multicellular organism (seaweed/algae)– Aug 31st

Haden

lifeless Earth

Achaean Achaean

Prokaryotic lifeProkaryotic life

Little OLittle O22

Review of Earth’s first 3.9 Billion years

Proterozoic

Eukaryotic life, multicellular plants, First plants & soft bodied animals in oceans later vascular

plants fish, arthropods in ocean

Insects, amphibians & reptiles on land

Paleozoic Era From the Cambrian explosion to the

dawn of the dinosaurs

Cambrian - Permian period:540 MYA – 248 MYA

• Cambrian: Starts with a burst of new life forms & all life in ocean

• Plants & animals evolved from simple seaweed & sponges

• to fish in the oceans & insects, amphibians, and early reptiles on land

• 1 Mass extinction in the ocean • Nov. 17 – Dec 6

Triassic period to Holocene Epoch 248 MYA – present

• From the early dinosaurs to extinction 65 MYA

• 1st mammals, birds, and flowering plants

• The ice age to modern civilization

• Dec 7th - Midnight Dec 31st

Review of last 248 Million years

First Dinosaurs

Last Dinosaurs

Flowering Plants

First Mammals

First bird

First monkeyFirst human

Review

1. What was the surface of the earth like during the Haden Era?

2. During which era did multicellular life evolve?3. Which is a shorter period of time and eon or an era? 4. Which came first birds or mammals?