Origins Of Life

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Transcript Origins Of Life

Origins of Life
• Early Idea: Spontaneous
Generation
– The idea that non-living
material can produce life—
Life magically appears!
– Examples
• Meat produces maggots
• Mud produces fish
(mudskippers)
• Grain produces mice
Origins of Life
• Francesco Redi was first to disprove the
theory of spontaneous generation in 1668
– Experiments with rotting meat
Origins of Life
• Also during this time, scientists
were just beginning to use
microscopes…
– They were able to see that
microorganisms were
EVERYWHERE!
– Even though Redi was able to
disprove the theory of
spontaneous generation, many
scientists thought that
microorganisms arose
spontaneously from a “vital
force” in the air
Origins of Life
• Louis Pasteur
– Disproved the spontaneous generation of
microorganisms
– Experiments with broth
Origins of Life
• Pasteur’s experiments showed that
microorganisms do not arise from the
broth alone even in the presence of air
• Biogenesis became the accepted
theory about the origin of life
– Biogenesis is the idea that living
organisms only come from other living
organisms
How Did Life Begin On Earth?
• Early Earth
– Very Hot
– Meteorite Collisions
– Volcanoes
– Very little oxygen
• Atmosphere made of H2O
Vapor, CO2, N gas, CH4 &
NH3
How Did Life Begin On Earth?
• Ingredients for Life: Before life can
occur, you need the molecules of life
– 1st – Formation of simple organic molecules
– 2nd – Organization into complex organic
molecules
• Proteins / Carbohydrates / Nucleic Acids / Lipids
• So… How did this happen in such a
harsh environment?
How Did Life Begin On Earth?
• Miller & Urey (1953)
– Tested theory by simulating
conditions on early Earth in a lab
– Mixture of H20 vapor, NH3, CH4,
and H gasses was zapped with
electrodes
– Cooled gasses condensed in
flask
– After a week, several kinds of
amino acids, sugars, and other
small organic molecules were
present in the flask
How Did Life Begin On Earth?
• The next steps in the origin of life were the
formation of complex organic molecules and
cells
• Heat caused the amino acids to form
proteins and also caused the production of
ATP and nucleic acids
• Doing this formed “protocells” – or large
ordered structures, enclosed by a membrane
that carries out life functions
The First True Cells
• First forms of life were prokaryotes that
likely evolved from protocells
– Anaerobic Heterotrophs
– Later, early prokaryotes evolved to be able
to make their own food
• These were similar to archaebacteria
and used chemosynthesis to produce
their food
The First Photosynthetic
Prokaryotes
• Likely the next kind of organisms
to have evolved
– Were able to use sun to make
glucose
– Produced OXYGEN, which
changed Earth’s atmosphere
– Lightening + Oxygen = Ozone
Layer formation
The Endosymbiont Theory
• Lynn Margulis, in 1960’s
• Eukaryotes evolved from prokaryotes as a
result of symbiotic relationship between
prokaryotic bacteria