Transcript Primordial Soup Theory

Early Earth Conditions
Origin of Life Beliefs
• 1. Spontaneous Generation- idea that
nonliving material can produce life
ex. People believed decaying meat
produced maggots
ex. Mice suddenly appearing in sacks of
grain
• 1668- Francesco Redi (Italian physician)
disproved spon. gen.
Redi’s Spontaneous Generation Experiment
Disproving spontaneous generation
• Redi disproving spon. Gen. allowed people to
believe in biogenesis (idea that living
organisms come from other living organisms)
The Modern Ideas
1. Meteorites
a. Life started when a meteorite containing organic matter
collided with the Earth
b. Could explain how organic molecules that are necessary for
cell formation arrived on Earth and entered the oceans
2. Divine Origins (Intelligent Design)
a. Many major religions teach that life was created by supreme
being
1. Explain it as life could not have been created without the
intervention of a divine force
The Modern Ideas (continued)
3. Primordial Soup
a. Idea that Earth’s ancient atmosphere probably
contained nitrogen, methane, ammonia, and carbon
dioxide
1.
Energy from sun, volcanoes, and lightning fueled chemical
reactions among these gases, which combined into small
organic molecules like amino acids
2.
Rain washed these molecules into the oceans
making…primordial soup!
b. Harold Urey and Stanley Miller provided evidence to
support this.
Early Earth Conditions
• According to the geologic time scale it’s believed
that the Earth formed approximately 4.6 billion
years ago
• SO HOT!!! Due to radiation (left over from big
bang), volcanoes, friction from colliding meteorites
• All eruptions of volcanoes made all gases present
(CO2, N2, H2, CO, methane, and ammonia)
• H2O is present as water vapor b/c it’s so hot!!
Early Earth Conditions
• About 3.5 byo (billion years ago) earth started to
cool and H2O condensed to form liquid H2O
*Rock evidence shows 1st signs of life (from
fossils) was around 3.5 byo
• Led to millions of years of rainstorms to form the
oceans
• Helps support Miller/Urey experiment
How do scientists believe life began?
• SO HOW DID LIFE BEGIN ON EARTH??
• TO GET LIFE YOU NEED TO FORM ORGANIC
MOLECULES (CONTAIN CARBON)!!!
Formation of Organic Molecules
• 1. Believed early atmosphere contained
little to none free O2
• 2. Most atmosphere was made of (water
vapor, carbon dioxide gas, nitrogen gas,
methane gas, ammonia, hydrogen gas,
and carbon monoxide)
Key point- No Free Oxygen Yet!!
• *1938 Alexander Oparin proposed Primordial
Soup Theory (says life began in the oceans)
Primordial Soup Theory
• Oparin said energy from sun, lightning, &
Earth’s heat triggered chem rxns. to produce
small organic molecules from substances
present in Earth’s atmosphere
• Then rain washed these molecules into oceans
making this primordial soup
• 1953 Stanley Miller/Harold Urey (American
Scientists) wanted to test Oparin’s theory by
simulating Earth’s early conditions in the lab
Miller/Urey Experiment
• 1. Mix water vapor (steam) w/ ammonia,
methane gas, and hydrogen gas
• 2. Send electric current (simulates lighting)
through it
• 3. Cool gases- which produces a liquid
that simulates rain
• 4. Collect liquid in flask
• 5. Results- found several kinds of amino
acids, sugars, nucleotides & other organic
molecules that supported Oparin’s
hypothesis
So, how do organic molecules lead to
cells??
• Evolution of Cells
• 1st cells- protocells- large structure w/ a
membrane that contains the primordial soup &
carries out cell division
• Believed that prokaryotes (bacteria) evolved
from protocells
*Remember there is no free O2 present yet
Evolution of Cells Timeline
4.5 byo
3.5 byo
2.5 byo
1.5 byo
0.5 byo
3.5 byo- So, 1st prokaryotes were
non-photosynthetic bacteria
(heterotrophic anaerobes) that ate
primordial soup or others did
chemosynthesis & made own glucose
Evolution of Cells Timeline
4.5 byo
3.5 byo
2.5 byo
1.5 byo
0.5 byo
• 3.2 byo- 1st photosynthesizing prokaryotes
•
•
(autotrophic bacteria) evolved
which released O2 in the atmosphere
Evolution of Cells Timeline
4.5 byo
3.5 byo
2.5 byo
1.5 byo
• 2.0 byo-2 major events occurred: Due to
•
the accumulation of oxygen the 1st
•
eukaryotic cells evolved…lightning
•
striking the O2 would have formed O3
•
(ozone) and allowed more complex
•
organisms (eukaryotes) to thrive
•
0.5 byo
Endosymbiont Theory
• *Believed that eukaryotes evolved from
prokaryotes
• 1960s- Lynn Margulis proposed this theory
• She said eukaryotes evolved by symbiotic
relationships w/ prokaryotes
Evidence to support Margulis’ beliefs
• Cyanobacteria & chloroplasts (contain DNA &
ribosomes) look similar & can both do
photosynthesis
• Some bacteria & mitochondria (contain DNA
& ribosomes) look similar