Download Earth history

The history of life on Earth
first _______
200,000 years ago
30 sec before midnight
first __________
organisms
Origin of Earth
_____________
24
22
4.6
0.4
first _______
organisms
18
3
4
4
3.8
1 Billions of
years ago
2
14
first __________
_____________
History of Earth
13.7 b.y.a. ________
Explosion of ______
Explodes out into nothing
Creates _____ – the universe
Cooling energy forms _______ particles
Clouds of Hydrogen and Helium atoms form _____
Within stars, gravity joins particles into _____ atoms
stellar nebula
5 b.y.a.
Large star explodes
A __________
Spews out matter
4.5 b.y.a.
Gravity condenses matter into swirling cloud
Becomes early ______ system
___ condenses and lights up
Matter orbiting the sun gathers into ____________
One becomes Earth
4 b.y.a.
Earth is bombarded by remaining matter
Some meteorites contain _______
Earth becomes molten from pressure & radioactivity
Heavy iron and nickel sink to core
Lighter _______ floats on surface
Earth cools
Water vapor condenses into “primordial” seas
Surface ______ develops
Crust breaks up into _________
Early atmosphere is mostly N, CO2, & H2O
Spewed from _________
Molecular evolution
Complex molecules evolved before life
1: Organic monomers by abiotic synthesis:
Miller & Urey (1950s) “_____________” Experiments
Prove ______ synthesis of molecules was possible
Simulate Precambrian atmosphere in tubes
Early atmosphere was mostly volcanic vapors:
H2O,CO,CO2,N2,CH4(methane), NH3(ammonia)
Many are toxic to modern life
Gaseous oxygen (O2) was _____
Electrode
(__________)
H2O
CH4
__________
NH3
Water vapor
H2
Cooling/condensation
______
H 2O
tap
Flame
(_____________ heat)
-
______________
______________
______________
______________
______________
Process can’t occur in today’s atmosphere
Oxygen ______ compounds, monopolizes them
Many organic monomers also occur in _________
Primordial soup may have been seeded from __
2: : Organic polymers by abiotic synthesis
Fox’s “______________” experiments
Amino acids bond together on ___________
E.g., Ancient ____ flows at sea’s edge
= Dehydration synthesis
3: Information molecules - _________ acids
RNA __________ developed in the primordial soup
May have bonded on _________ surfaces
E.g., charged areas of primordial _____
Occurs in test tubes
Mechanism for nucleic acid ____-replicating developed
Early RNAs could have been _______-like
Catalyzed necessary reactions
Some modern RNA nucleic acids are _______-like
4: Cell-like spheres form around RNA
E.g., Add lipids to water in a test tube
Form bubble-like ____________
Membrane made of ______
5: RNA inside becomes template for _____ synthesis
Simple form of ____________
No ribosomes or tRNA yet
Spheres are “____” at this stage of development
6: Novel proteins allow increasingly ________ cells
Cells that replicate efficiently become more _____
Beginning of Darwinian ______ selection
7: First _______ evolve
Non-living nucleic acid (information) in ______ coat
______ replication mechanism of early cells
First cellular life ~ ____ bya
Had traits attributable to all ‘living’ things:
a) Maintained unique environment inside membrane
b) Controlled the passage of ____________
c) Processed ______ (metabolism)
d) Grew and reproduced
e) Responded to external ________
f) Passed genetic information to daughter cells
Later life-forms occurred in waves
4 major Eras: major changes in fossil biota
Changes resulting from dramatic geological change
GEOLOGICAL TIME SCALE
1) Precambrian: before Cambrian proliferation (1st 4 bill yrs)
Mostly lifeless, ends with ___________________ animals
2) Paleozoic: “ancient” (~250->500 mya)
Begins with _________ diversity & ______ (Cambrian Period)
Ends with first ________ and ________ plants
3) Mesozoic: “middle” (~65->250 mya)
Begins with first _______ and ___________
Ends with first ____________ plants, extinction of ________
4) Cenozoic: “recent” (< 65 mya)
Begins with radiation of mammals, birds, flowering plants
Ends? A new epoch has been proposed, the ____________