Transcript Where did life come from? First, where did the earth come from?

Where did life come from?
First, where did the earth come from?
• Everything appears to have started with
the Big Bang – about 14 billion years ago.
• The solar system formed about 5 bya.
• Earth formed from an accumulation of
materials orbiting the sun – about 4.5 bya.
And life???
• Conditions were not suitable for life –
– Hot
– Much radiation
– No organic molecules
• Conditions had to change
• Organic molecules had to be synthesized
• How???
Evolution of Life
Early Earth was hot; atmosphere contained poisonous gases.
Earth cooled and oceans condensed.
Simple organic molecules may have formed in the oceans..
Small sequences of RNA may have formed and replicated.
First prokaryotes may have formed when RNA or DNA was enclosed in microspheres.
Later prokaryotes were photosynthetic and produced oxygen.
An oxygenated atmosphere capped by the ozone layer protected Earth.
First eukaryotes may have been communities of prokaryotes.
Multicellular eukaryotes evolved.
Sexual reproduction increased genetic variability, hastening evolution.
Building Life
• The early earth had no organic
compounds: Where did these come
from?
• 1953 – Miller and Urey hypothesized
that conditions could produce chemical
reactions to synthesize organic
compounds from inorganic.
– The did the experiment and it worked.
Miller and
Urey
Experiment:
• Simulated
early earth
conditions to
model
formation of
organic
molecules.
Mixture of gases
simulating
atmospheres of early
Earth
Spark simulating
lightning storms
Condensation
chamber
Cold
water
cools
chamber,
causing
droplets
to form
Water
vapor
Liquid containing amino
acids and other organic
compounds
Now that we have the building
materials, what makes a cell?
• A membrane - can build this in a dish!
• Nucleic acids: DNA (originally RNA?) –
can assemble these in a dish.
• Protein synthesis machinery – A little
more complicated.
• Enzymes for energy transfer – can make
these work in a dish - sort of - and
definitely work in a proteinoid
microsphere.
Nutrition?
• Simplest organisms just absorb
organic compounds
– Heterotroph hypothesis – Oparin
• Photosynthesis – big advance!
– Byproduct (oxygen) changed everything.
• Availability of free oxygen permitted
more efficient release of energy from
food.
– Aerobic respiration
Endosymbiotic Theory- making a
eukaryote from prokaryotes
Chloroplast
Aerobic
bacteria
Ancient Prokaryotes
Nuclear
envelope
evolving
Plants and
plantlike
protists
Photosynthetic
bacteria
Mitochondrion
Primitive Photosynthetic
Eukaryote
Ancient Anaerobic
Prokaryote
Primitive Aerobic
Eukaryote
Animals, fungi, and
non-plantlike
protists
Classification of Living Things
DOMAIN
Bacteria
Archaea
KINGDOM
Eubacteria
Archaebacteria
CELL TYPE
Eukarya
Protista
Fungi
Plantae
Animalia
Prokaryote
Prokaryote
Eukaryote
Eukaryote
Eukaryote
Eukaryote
Cell walls with
peptidoglycan
Cell walls
without
peptidoglycan
Cell walls of
cellulose in
some; some
have
chloroplasts
Cell walls of
chitin
Cell walls of
cellulose;
chloroplasts
No cell walls
or chloroplasts
Unicellular
Unicellular
Most unicellular;
some colonial;
some
multicellular
Most
multicellular;
some
unicellular
Multicellular
Multicellular
MODE OF
NUTRITION
Autotroph or
heterotroph
Autotroph or
heterotroph
Autotroph or
heterotroph
Heterotroph
Autotroph
Heterotroph
EXAMPLES
Streptococcus,
Escherichia coli
Methanogens,
halophiles
Amoeba,
Paramecium,
slime molds,
giant kelp
Mushrooms,
yeasts
Mosses, ferns,
flowering
plants
Sponges,
worms,
insects, fishes,
mammals
CELL
STRUCTURES
NUMBER OF
CELLS
DOMAIN
ARCHAEA
DOMAIN
EUKARYA
Kingdoms
DOMAIN
BACTERIA
Eubacteria
Archaebacteria
Protista
Plantae
Fungi
Animalia