Transcript History of the Earth - Green Local Schools

History of the Earth
Chapter 14
Formation of the Earth
Where does life come from?

Spontaneous generation
the belief that living things arise from nonliving
things
 Biogenesis
all living things come from other living things
Redi’s experiments
 Spallanzani’s experiments
 Pasteur’s experiments

Redi’s Experiment (1626-1697)
Italian physician and poet who
demonstrated that the presence of
maggots on rotting meat does not result
from spontaneous generation but from
eggs laid on the meat by flies.
 Pg. 279

Spallanzani’s Experiments (1729-1799)
Italian naturalist whose experiments
disproved that microorganisms
spontaneously generated from meat
broth in open flasks.
 Pg. 280

Pasteur’s Experiment (1822-1895)
A French chemist who proved that
microorganisms are carried by dust and
not air.
 Improved on Spallanzani’s experiment
 Pg. 281

The First Organic Compounds
Alexander Oparin’s Hypothesis, 1920’s):
Thought that primitive atmosphere
contained: NH3, H2, H20, and C-H
compounds
 At high temperatures, these gases might
have formed simple organic compounds like
amino acids

Oparin’s Theory Con’t

When the Earth cooled, the water vapor
condensed into lakes and seas with the
organic compounds within

With the help of lightning and UV
radiation, these organic compounds
reacted with each other forming
macromolecules essential to life.
Can that REALLY happen?

Yes! According to experiments
performed by Miller and Urey

Products of experimental synthesis:
Amino acids
 ATP
 DNA nucleotides

Attempts to Create Life
Miller Experiment
Input
Chamber
Water
Vapor
Forms
Spark
Chamber
Condenser
“It came from outer space!”

Some scientists hypothesize that organic
compounds may have come from
meteoroids from space
Microfossil Lab!
Earth’s Age

More than 4 BILLION years old!
How do scientists “know” this?
 Radiometric dating
Measurement of the decay of commonly
occurring radioactive isotopes
 Ex) Carbon dating

Fossils
The remains of ancient animals and
plants
 Found in every continent on earth
 Formed from sedimentary rock
 Paleontology- the branch of biology that
studies past forms of life (namely fossils!)

Ancient Bat
Saber-Toothed Cat
The Fossil Record

From the 1830s onwards, geologists
noted how fossils became more complex
through time. The oldest rocks contained
no fossils, then came simple sea
creatures, then more complex ones like
fishes, then came life on land, then
reptiles, then mammals, and finally
humans. Clearly, there was some kind of
'progress' going on.
The First Prokaryotes
About 3.5 bya the first prokaryotes,
cells without a true nucleus (like
bacteria), came into existence.
 The first cells were probably anaerobic
and heterotrophic.
 Resemble modern day Archaebacteria,
which live in extreme enviornments

Rise of photosynthesis and
aerobic respiration
Cyanobacteria- group of unicellular,
autotrophic prokaryotes about 3 bya
 Increased the level of atmospheric
oxygen

The First Eukaryotes
Endosymbiosis- about 2.0 bya, a small aerobic
prokaryote began to live inside a larger
anaerobic prokaryote
 aerobic prokaryotes evolved to modern
mitochondria
 Photosynthetic cyanobacteria evolved into
chloroplasts
Endosymbiosis:
Extinction 65 mya

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