Transcript Earth`s History

Earth’s History
4 Eras of Geologic Time
4 Eras of Geologic Time
Precambrian
Paleozoic
Mesozoic
Cenozoic
Precambrian Events
 The
earth’s crust formed
 The atmosphere formed
 The ocean’s formed
 First life forms developed
The earth’s crust
 The
earth was very hot from its
formation (The nebular theory)
 It cooled from the outside
 As it cooled, the earth’s crust
formed and cracked to form plates
An atmosphere developed
 Volcanic
activity was very
common as the crust formed and
cracked
– CO2 and Nitrogen
– H20 vapor
– Methane, ammonia, and sulfur
dioxides
Earth’s atmosphere
Earth has an atmosphere for 3
reasons
1. Volcanic history
2. Mass of the planet
3. Amount of radiation from
the sun
The oceans formed
 As
the earth continued to cool, the
water vapor in the atmosphere
condensed and fell as rain.
 This water formed the oceans,
rivers, lakes, streams, and
underground water ways.
What were the conditions on
the early earth?
 Intense
volcanic activity
 Warm, shallow seas
 Turbulent atmosphere
– Lots of lightning
– Lots of storms
How did life form on this
planet?
 Life
originated on this planet
 Life was seeded here by
– A comet carrying carbon compounds
– An asteroid carrying single-celled
life forms
What did the first organisms
on earth look like?
The
oldest fossils of life on this
planet are
– Bacteria
– Blue Green algae
Bacteria
 Single-celled
life forms
 No true nucleus or organelles
(prokaryotes)
 Very hardy and resistant to extreme
conditions
 Many species do not need oxygen
Blue Green Algae
 Single
celled organisms
 Prokaryotes
 Able to photosynthesize—use CO2
and H2O to produce glucose (food)
and O2
 Put tons of oxygen into atmosphere
Oxygen in the atmosphere
 Toxic
to many forms of bacteria
 Changed our atmospheric makeup
by adding ozone to the earth’s
atmospheric makeup
 O2 is converted to O3 (ozone) by
lightning
What happens to early life
forms?
 In
order to survive they must adapt to
using oxygen
 Single-celled organisms that have welldefined nuclei develop (eukaryotes)
 Multicellular algal forms develop (first
plants)
Paleozoic—Age of Fishes
 “Paleo”—means
early and –”zoic”
means animals
 Life “exploded” on the planet
 Many marine life forms developed
 Plants and animals move onto land
– Small wetlands plants and simple insects
 Amphibians
developed
 Atlantic ocean begins to develop and
continents begin to move apart
Mesozoic—Age of Reptiles
 “Meso”
means middle “-zoic” means
animals
 All continents joined together at the
beginning of this era, but begins to
break apart
 Animals—dinosaurs evolve and
become extinct
 Plants—ferns the predominant plant
form—flowering plants evolve
Cenozoic—Age of Mammals
 “Ceno”
means recent “-zoic”
means animals
 Mammals evolve and flourish
 Humans and human civilizations
develop