THE ORIGIN OF HEREDITY
DNARNAPROTEIN
SOME RNA MIIGHT BEHAVE LIKE PROTEINS AND CATALYZE
CHEMICAL REACTIONS
ROLES OF RNA
1) RIBOZYME—THOMAS CECH (1947) RNA THAT CAN ACT AS AN
ENZYME AND REPLICATE ITSELF
2) REPLICATIONHEREDITYNATURAL SELECTION (EVOLUTION
REQUIRES SUCCESSFUL ABBILITIES, SUCH AS MORE SUCCESSFUL RNA
GETTING THE NUCLEOTIDES, GIVING IT AN ADVANTAGE
3) RIBOSOMES FROM RIBOSOMES??
4) RIBOSOMES/RNACELLULAR LIFE??
5) MICROSPHERES/COACERVATES—MAYBE SELF-REPLICATING RNA
EVOLVED INSIDE COACERVATES—WOULD PROVIDE THE HEREDITARY
INFO THE SPHERES LACKED
I.
THE FIRST PROKARYOTES
1) NO FREE OXYGEN GAS IN EXISTENCE—THEY WERE ANAEROBIC,
PROKARYOTIC AND HETEROTROPHIC
2) THIS PROBABLY REMOVED MOST ORGANIC MOLECULES FROM THE
ENVIRONMENT; PUT A STRONG ENVIRONMENTAL PRESSURE ON THE
EVOLUTION OF AUTOTROPHS
3) CHEMOSYNTHESIS (ARCHAEBACTERIA)—CO2 SERVES AS A CARBON
SOURCE FOR ASSEMBLY OF ORGANIC MOLECULES; ENERGY FROM
OXIDATION OF SULFUR INSTEAD OF THE SUN
4) PHOTOSYNTHESIS AND AEROBIC RESPIRATION
A. OXYGEN FROM PHOTOSYNTHESIS WAS DAMAGING TO
EARLY UNICELLULAR ORGANISMS AND MOLECULES
B.
WAS REMOVED BY AEROBIC RESPIRATION
C. PHOTOSYNTHETIC ORGANISMS AROSE ABOUT 3 BILLION
YEARS AGO (3.8 mya IN GREENLAND/3.5 mya IN AUSTRALIA); WERE
SIMILAR TO MODERN CYANOBACTERIA
D. IT TOOK 1 BILLION YEARS TO REACH TODAY’S LEVELS OF
OXYGEN, AND LIFE COULD EXIST ON LAND ONLY BECAUSE OF OZONE.
II.
FIRST EUKARYOTES
A. ENDOSYMBIOSIS—LYNN MARGULIS—2.0 TO 1.5 BILLION YEARS
AGO, AEROBIC PROKARYOTES INVADED CELLS AND BECAME FIRST
MITOCHONDRIA AND CHLOROPLASTS IS BELIEVED TO BE EVIDENCE
III.
DARWIN’S THEORY OF NATURAL SELECTION
1.
ORGANISMS HAVE MORE OFFSPRING THAN CAN SURVIVE
2. SOME OF THOSE ORGANISMS WILL HAVE VARIATIONS IN TRAITS
(MUTATIONS)
3. SOME OF THESE VARIATIONS WILL GIVE INDIVIDUALS
ADVANTAGES/DISADVANTAGES OVER OTHERS
4. THE MORE “FIT” INDIVIDUALS WILL SURVIVE AND PASS THESE
ADVANTAGES ON TO OFFSPRING (SURVIVAL OF THE FITTEST)
5. GIVEN TIME, LIFE WILL CONTINUE TO CHANGE IN THIS WAY TO GIVE
ALL OF THE DIFFERENT FORMS OF LIFE WE SEE TODAY