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Evolution
• is change in the inherited traits of a
population of organisms from one
generation to the next (over VAST
amounts of time). These changes are
caused by a combination of three main
processes: variation, reproduction, and
selection.
The Record of Life
A. Earth is believed to be about 4.6 billion years old
• This age was determined from meteorites and
moon rocks
• The earliest atmosphere contained H2 (hydrogen)
CH4 (methane), NH3 (ammonia) and H2O (water
vapor)
•
B. Fossils and Ancient Life
• A fossil is any evidence of previous life
Ex: amber, trace fossils, molds & casts,
imprints, tracks
• Fossils are usually found in sedimentary
rocks
– Made from particles of sand, silt, and clay
•
The simplest dating method is called
RELATIVE DATING, where the rocks
closer to the surface are considered
younger and the deeper layers are
older.
C. Radioactive Dating
•Radiometric dating involves using radioactive
isotopes to detect the amount of decay.
Ex: C14 dating
D. Geologic Time
Scale
• A scale which is
a kind of
calendar that
communicates all
the events of the
Earth since its
formation is
known as the
Geologic Time
Scale.
II. Origin of Life
E. Origin of Life
• Spontaneous generation process by which life was
thought to be produced
from non-living matter.
• Fransesco Redi partially
disproved this, but not until
the experiments of Louis
Pasteur was the theory of
spontaneous generation
totally disproved.
• Biogenesis – living organisms come only from other
living organisms.
• The beginning of life is thought to have originated
in the oceans from protocells. All the ingredients
for life were present in the atmosphere and
oceans.
• Primitive life forms are considered to most closely
resemble Archaebacteria (most primitive kind)
• Cyanobacteria – type of photosynthetic
bacteria believed to have been the
earliest group of organisms to evolve.
cyanobacteria
stromatolites
III. First Organic Molecules
• Atoms today do not assemble themselves
– Because atmospheric O2 is reactive and
would destroy any organic molecules
– Bacterial organisms would consume for
source of energy
• Early Earth’s atmosphere is more
conducive to molecular assemblage
– Stanley Miller and Harold Urey questioned
composition of early atmosphere
Miller-Urey
Experiment
(Abiotic
Synthesis)
Made
Amino
Acids
(mostly
GLYCINE)
History of Life Timeline
• Earth formed – 4.6 bya
• Earth cooled, LIQUID water is present – 3.8 bya
• Organic molecules form, including simple carbs,
lipids, proteins, and RNA – 3.7 bya
• Prokaryotic cells arise – 3.5 bya
• Photosynthesis arises, oxygen added to
atmosphere – 2.8 bya
• Eukaryotic cells arise – 2.1 bya
• Sexual reproduction and multicellular organisms
arise – 1.5 bya
• Plants colonize land – 1.2 bya
Important Milestones
1. Photosynthesis releases O2 into the
atmosphere
a. Kills all anaerobic organisms exposed to O2
Leads to aerobic processes being selected
for (precursor to cellular respiration)
Important Milestones
2. Prokaryotic  eukaryotic
a. Provided compartmentalization for the cell,
more diverse functionality
b. Endosymbiotic theory – eukaryotes were
created when one prokaryote engulfed
another but did not digest it
Important Milestones
3. Sexual Reproduction
a. Leads to more genetic diversity in a
population, increases long-term survival of a
species (gene shuffling)
4. Multicellular organisms
a. Bigger organisms
b. Cell differentiation (driven by gene regulation)
c. Not constrained to limits of simple diffusion