Learning Targets
15. Recognize that evolution has occurred in all organisms and
continues to occur.
17. Identify dates of big events in earth’s 4.6 billion year history.
18. Describe the basic models for the origin of life and the evidence
that supports them.
19. Understand the evidence that RNA was the earliest genetic
material.
27. Describe the evidence for the endosymbiotic theory.
History of Earth


4.6 Billion years earth formed

Hot

Constantly hit with chunks of
ice and rock

No atmosphere
4 billion years  bombardment
ended earth cools oceans

Atmosphere forms!

Little to no oxygen

Lots of H2O, Nitrogen, CO2,
Methane, Ammonia &
Hydrogen
History of Earth

Direct fossil evidence of early life
on earth  microorganisms 3.5
billion years ago

How did THEY get there?
1.
Abiotic (nonliving) synthesis of
amino acids & nitrogen bases
2.
Macromolecules such as protein &
nucleic acids
3.
Protocells (droplets of nucleic
acids & proteins with a membrane
to maintain internal environment)
4.
Origin of self-replicating
molecules
History of Earth

Is it possible?

1953 Stanley Miller

Heated water  vapor mixed
with early atmosphere 
“lightning”  cold water
condensed the atmosphere
(made it “rain”)  collected
sample water returns to
“sea”

Voila! Organic
molecules!!...so yes, it is
possible!

http://viewpure.com/mF9U5x6Nxnw
History of Life

How do we get from amino acids to life?

2009 study abiotic synthesis of RNA in test tubes

First genetic material likely was RNA

Supported by important role RNA plays in making proteins (mRNA,
tRNA, rRNA)

RNA can also act as an enzyme (ribozyme) --> replication

RNA much more versatile  shape & function
Big Events

First single-celled organisms

Earliest evidence 3.5 billion
years ago Stromatolites

Layered rocks form when
prokaryotes bind sediment
together
Big Events


2.7-2.4 billion years ago oxygen-releasing
Prokaryotes gradually change
atmosphere! (oxidation of rocks)
1.8 billion years ago fossils of first
eukaryotes

Endosymbiosis Theory
 Aerobic
cells (ex: mitochondria &
chloroplasts) began living inside larger
cells (either as prey or parasites)
 Evidences:
inner membrane, own DNA
(you inherit mother’s mitochondrial
DNA), replication similar to prokaryotes

http://viewpure.com/3ESXvLHceDc
Big Events

1.2 Billion years ago


Multicellular eukaryotes red algae
535-525 million years ago

Cambrian EXPLOSION!!!!

Present day phyla began to appear

Predators (claws & other prey-capturing features appear)

Prey (defensive mechanisms appear sharp spines, heavy body
armor)
Big Events

500 Million years ago


Plant and animal begin to colonize land

Plants colonized land with company of
fungi…even now, a lot of plants rely on
fungi to help absorb nutrients

Animals  arthopods among the first
(450 mya), tetrapods (365mya)
195,000 years ago humans arrived
(lineage diverged from other primates
6-7 mya)
Learning Check

Evolution is

Oldest fossils are
A) only a theory and still needs to be
proven
A) 3.5 billion years old and are
prokaryotes
B) an explanation for how life came
to be, but no longer happening
B) 1.4 billion years old and are
prokaryotes
C) observed currently, but cannot
explain the evidence we see in the
history of life
C) 3.5 billion years old and are
eukaryotes
D) observed currently and best
explains the evidence we see in the
history of life.
D) 1.4 billion years old and are
eukaryotes