Transcript Modern Ideas on the Origin of Life

Modern Ideas on the Origin
of Life
copyright cmassengale
1
Formation of the Earth
• 4.5 billion years
ago
• Cosmic debris
attracted to one
another
• Collisions = heat
= melting
• Atmosphere =
hydrogen
cyanide, CO2,
CO, N2, H2S, H2O
Formation of the Earth
• 3.8 billion years ago
• Cooling = oceans
• Brown oceans due
to dissolved iron
• Life Begins
– Prokaryotic,
anaerobic,
heterotrophs
First Organic Molecules
• 1920s – Oparin and
Haldane
• Earth’s early
atmosphere had all
elements necessary
to cause reactions
producing organic
molecules (amino
acids)
• Gases, UV light,
lightning
PRIMORDIAL SOUP HYPOTHESIS
First Organic Molecules
• 1950s – Miller and
Urey
• Suggests how
mixtures of organic
compounds
necessary for life
could have come from
simpler compounds
present on primitive
Earth
First Organic Molecules
Animation of Miller and Urey’s Experiment
• http://ircamera.as.arizona.edu/NatSci102/
movies/anim_miller_urey_exp.gif
• Proved amino acids could be produced in
primitive Earth’s conditions
Early Life
- the first cells were
probably heterotrophs that
simply absorbed nutrients
and ATP from the
environment.
- as these substances
became rare, there was
strong selection for cells
that could manufacture
their own energy storage
molecules.
Early Life
- the second type of
cells were probably
like green-sulphur
bacteria which in the
presence of sunlight,
are able to
photosynthesize.
Early Life
- the evolution of oxygenic photosynthesis was
MAJOR. It allowed life to exploit more habitats.
These stromatolites, which date to > 3 bya are
microbial communities.
Early Life
- about 2.3-1.8 bya, the concentration of oxygen
began to increase in the ocean. Oxidized iron shows
rust bands in sediment.
Endosymbiont Theory
• 1966- Lynn Margulis
• Explains origins of
mitochondria and
chloroplasts
• Mitochondria and
chloroplasts were
once free-living
bacteria which had a
mutualistic
relationship with
another bacterium
Endosymbiont Theory
• Mitochondria and
chloroplasts are
same size as
bacteria and
contain similar
structures (DNA,
ribosomes) and
reproduce by
binary fission
infolding of membrane
Endosymbiosis - mitochondria and
chloroplasts (Margulis - 1970's)
Evolutionary Tree – shows evolutionary
pathways of living organisms
So, reconstructing
the patterns of
relatedness among
these ancient life
forms is difficult.
Different genes give
different patterns of
relatedness among
domains