Transcript Origin of Life Theories

Origin of Life Theories
Where does life come from? 2 ideas:
1. Spontaneous generation (abiogenesis)
– belief held before 1600s
– living things could arise from nonliving things (ex.
maggots from meat)
disproved by the following experiments:
- Francesco Redi (1668) – rotting meat experiment
http://www.sumanasinc.co
m/webcontent/animations/
content/scientificmethod.ht
ml
- Lazzaro Spallanzani (1700s) – broth in closed flask
– Louis Pasteur (mid 1800s) – broth in S-necked flask
http://bcs.whfreeman.com/
thelifewire/content/chp03/
0302003.html
2.Biogenesis
– currently accepted belief
– all living things come from other living things
But, where did life ORIGINALLY come from?
Theories:
1. divine origin/ intelligent design
2. meteorite
3.PRIMORDIAL SOUP THEORY*
– proposed by Alexander Oparin in 1923
• parts of the theory:
a.early Earth was very hot; atmosphere contained
inorganic molecules such as ammonia, hydrogen,
water vapor, methane (very little oxygen)
b.high temperatures, UV light, and lightning
converted inorganic molecules to simple organic
molecules, then to more complex organic
molecules such as amino acids
c. when atmosphere cooled, organic molecules were
washed into the oceans where life began
CRAZY?! – This theory was tested (and
supported) in 1953 by Stanley Miller and
Harold Urey.
http://bcs.whfreeman.com/the
lifewire/content/chp03/03020
01.html
What kinds of organisms were formed first?
– Simple (prokaryotic – bacteria)
– Anaerobic (there was little or no oxygen!)
Where did eukaryotes come from? –
endosymbiosis theory
States that eukaryotic cells formed from a
relationship between two prokaryotic cells.
Mitochondria evolved from aerobic bacteria;
chloroplast evolved from photosynthetic
bacteria
http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation__endosymbiosis.html
Where did oxygen and aerobic organisms come from?
Heterotrophs
were first;
started to run
out of food
Organisms that had
evolved to make
food thrived; did
photosynthesis
Photosynthesis
produced oxygen
Oxygen allowed more ATP to
be made; so organisms that
use oxygen thrived