Transcript The Origin of Life on Earth - Parma City School District

The Origin of Life on Earth
Chemical Evolution = The study
of how life began
• Heterotroph Theory: the first cells
were heterotrophs, organisms incapable
of making their own food
Steps involved in the
heterotroph theory:
• 1. The Earth and it’s atmosphere
formed.
– The atmosphere originated from outgassing of the
molten interior of the planet (from volcanoes).
Early atmosphere consisted of: CO, CO2, N2, S,
HCl, Water, HCN (hydrogen cyanide), LITTLE OR
NO OXYGEN!
Steps involved in the
heterotroph theory:
• 2. The Primordial Seas formed. As
the Earth cooled gasses condensed to
produce the primordial seas which
consisted of water and minerals.
Steps involved in the
heterotroph theory:
• 3. Complex molecules were synthesized.
Energy catalyzed the formation of organic
molecules from inorganic molecules. An
organic “soup” forms.
 Energy was provided by: UV light, lightning,
radioactivity, and heat
 Complex molecules: acetic acid,
formaldehyde, and amino acids
• Oparin & Haldane independently
theorized that: simple molecules were
able to form only because oxygen was
absent
• Stanley Miller and Harold Urey:
simulation of primordial conditions;
recreated various organic molecules
including amino acids
Steps involved in the
heterotroph theory:
• 4. Polymers and self replicating
molecules were synthesized.
 Monomers combine to form polymers
• Some do this by way of the removal of water
molecules (Dehydration chemical reaction)
 Proteinoids are abiotically produced
polypeptides. They can be experimentally
produced by allowing amino acids to dehydrate
on hot, dry substrates.
Steps involved in the
heterotroph theory:
• 5. Organic molecules were
concentrated and isolated into
Protobionts
 Protobionts = the precursors of cells. They
were able to carry out chemical reactions, but
were unable to reproduce.
• Microspheres and Coacervates are
experimentally produced Protobionts that
have some selectively permeable qualities.
Steps involved in the
heterotroph theory:
• 6. Primitive Heterotrophic
prokaryotes formed.
 Organic soup = food source
• Pathogenic bacteria mainly
Steps involved in the
heterotroph theory:
• 7. Primitive Autotrophic prokaryotes
were formed.
 Probably resulted from a mutation in a
heterotroph
 Cells now able to make their own food
 Cyanobacteria
Steps involved in the
heterotroph theory:
• 8. Oxygen and the ozone layer
formed and abiotic chemical
evolution ended.
 Oxygen was the by product of photosynthesis
 UV light plus oxygen interaction produces
ozone layer
 Ozone layer provides protection from damaging
UV light
Steps involved in the
heterotroph theory:
• 9. Eukaryotes Formed (Endosymbiotic
Theory)
– Eukaryotes originated from a symbiosis between
prokaryotes
– Mitochondria, Chloroplasts, and other organelles took
up residence inside another prokaryote
Evidence for Endosymbiotic
Theory
• 1. Mitochondria & Chloroplasts possess
their own DNA.
• 2. Ribosomes of Mitochondria and
Chloroplasts resemble those of bacteria.
• 3. Mitochondria and Chloroplasts
reproduce independently.
• 4. Thylakoid membranes of Chloroplasts
resemble the phosynthetic membranes of
cyanobacteria.
The History of Life on Earth
• The age of the Earth is estimated to be
around 4.5 Billion Years Old
• The Oldest fossils (of ancient bacteria) date
back to about 3.5 Billion Years Ago
Geologic Time Scale = Earth’s history timetable
Eras = The largest blocks of geologic time
• OLDEST ERA
Cambrian
Paleozoic
• NEWEST ERA
Pre-
Mesozoic
Cenozoic
PRECAMBRIAN ERA
• By far the longest geologic Era
• Lifeforms include:
– Simple Prokaryotes (Bacteria)
– Blue-Green Algae (Cyanobacteria)
PALEOZOIC ERA
• Characterized by the emergence of
Eukaryotes
• Burgess Shale = largest collection of
Cambrian Period fossils
• Lifeforms include:
•
Invertebrates = ocean dwellers (trilobites)
•
jawless fish
•
bony fish
•
amphibians, reptiles
Chambered Nautilus
Trilobites
Jawless
Unlobed Fin
Fish
MESOZOIC ERA
• Characterized by the invasion of lifeforms
onto land
• Cone-bearing plants (Gymnosperms)
• Insects
• reptiles abundant
• dinosaurs dominate the land
• first mammals
• flowering plants (Angiosperms)
Gymnosperm
Flying Insects
First Mammals
Angiosperm
CENOZOIC ERA
• Characterized by the rise and dominance of
mammals
• Primates are the dominant mammal
• Humans first appear
This is the geologic Era that we are currently
in.
Smaller Increments of Geologic
Time
• ERA
– PERIOD
• EPOCH (Only in the Cenozioic Era)
What Marks The End Of Geologic
Eras, Periods, or Epochs?
• Mass Extinction Events = loss of a large
percentage of Earth’s population
• Ordovician, Devonian, Permian (96%),
Triassic, Cretaceous
• Distinct Environmental changes are often
evident as well
What if we compressed the entire
Earth's history down into one 24
hour day?
4.5 Billion Years = 1 day
12:01a.m. = Earth forms
5:00 a.m. = first life; bacteria
4:00 p.m. = first eukaryotes
10:00 p.m. = life on land
11:40 p.m. = end of the dinosaurs
11:59 p.m. = first humans
The Fossil Record
• Fossil = any preserved record of a once
living organism
• The fossil record of life on Earth is
extremely incomplete!
How do fossils form?
• 1. Sedimentary Rock - sediment gets
compressed into rock by intense pressure
over time
• 2. Petrification - dissolved minerals replace
organic tissues
• 3. Casts - imprints filled in with mud, ash,
sand
How do we determine the age of
fossils?
• 1. Relative Dating - based on the fossils
position within a layer of rock
• 2. Half-life Method - the amount of time
that it takes for half of the atoms in a
sample of an element to undergo radioactive
decay and be reduced to half of their
original amount
Half-Life Methods
• Potassium --> Argon = half life of 1.3
Billion Years
• Carbon 14 - half life is 5,600 years
• Uranium --> Lead = 4.5 Billion Years
• 20 g U -----> 10g U -----> 5 g U
• 0g Pb -----> 10g Pb -----> 15g Pb