Chapter 4
The Origin and Early History of Life
Review info – has already been read as summer
reading.
Objectives:
1. Evolution Activity – Hopefully it will work with just 7 kids 
2. Visual Book Page on Types of Selection.
3. Complete notes on Origin and Early History of Life.
Due Tmo:
3 pages of review book using evolution notes.
Quiz on first 20 vocabulary words.
How Did Life
Originate On
Earth?
• ?
• What do we know?
– Earth formed 4.6
billion years ago.
– 3.5 bya is the oldest
clear evidence of
life (microfossils).
• Needed the correct
combination of
physical events and
chemical processes.
After Earth Formed
• Water vapor in atm condensed into
liquid water.
• Accumulated in chemical rich O
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–
–
–
–
–
–
Ammonia
Formaldahyde
Formic acid
Cyanide
Methane
Hydrogen sulfide
Organic hydrocarbons
Where did life form?
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Did life begin in the Ocean?
On the edge?
At hydrothermal vents?
Elsewhere?
• Complex molecules  Life?
– movement, sensitivity, death, complexity?
– Necessary vs. sufficient
Necessary vs. Sufficient
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Cellular organization?
Sensitivity?
Growth?
Development?
Reproduction?
Regulation?
Homeostasis?
Heredity?
Change for the sake of change?
Change passed to next generation?
No Eyewitnesses to Origin of Life
• Special Creation: Life forms put on E by
supernatural or divine forces. Core of most
religions – most widely accepted. Biblical
account word for word is unscientific.
No Eyewitnesses to Origin of Life
• “Panspermia”
Extraterrestrial Origin:
Began on another
planet and infected E.
Meteors and cosmic
dust brought complex
molecules. Some
evidence that early
meteorites may have
carried organic matter.
No Eyewitnesses to Origin of Life
• Spontaneous Origin: Life evolved from inanimate matter as
associations between molecules became more complex.
• Most scientists tentatively accept.
• As molecule change occurred is allowed to be more stable, persist
longer, associate in complex ways, and may have led to the
evolution of cells.
So How Do We Decide?
• Which do scientists go with and why?
No Eyewitnesses for Where
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Ocean Edge Origin with Reducing Atmosphere: E history reveals origin probably
occurred at high T.
Molten hot 4.6 bya – 3.8 bya.
As solar system stopped slamming E the T dropped.
3.8 bya temperature dropped to 120-190 degrees F.
3.8-3.5 bya life appeared.
Ea atm content… No agreement
– CO2, N2, H2O. Also H2, H2S, NH3, CH4 (methane, ammonia, hydrogen sulfide)
•
High Hydrogen = reducing atmosphere – allows for Carbon macromolecules. Low
O2 though so photosynthesis HAD to come first. Our O2 atm content now is 21%.
BUT
• No carbonates found in early E rock.
• Also, no O2 = no ozone = organic compounds
broken down by UV rays.
No Eyewitnesses for Where
• Under Frozen Ocean?
• Like Europa but evidence suggests that Earth
was warm.
BUT
• Probably E not frozen.
No Eyewitnesses for Where
• Deep In Earth’s Crust?
• Volcanic activity with Iron and Nickel sulfide =
chemical catalysts to recombine gasses into
blocks of life.
• Recreated and made precursors to amino
acids with peptide bonds.
BUT
• Chemical concentration used to prove this
reaction was higher than was available in ea.
E.
No Eyewitnesses for Where
• Within Clay?
• Silicate surface chemically attracts clay
surface.
• The positive charge attracts organic molecules
and repels water.
BUT
• There’s little evidence that this is even
possible.
No Eyewitnesses for Where
• Deep Sea Vents?
• Metal sulfides in vents react
to create prebiotic
molecules.
• + sulfides attract –
molecules
• Genomics says prokaryotes
today most related to
bacteria on deep sea vents.
Ice Article
Experiments to Determine How and
Where
• Miller/Urey 1953
• Attempted to reproduce conditions at O edge under reducing atm.
1. Assembled reducing atm w H but no gasseous O.
2. Placed over liquid H2O (O edge)
3. Kept T below 100 degree C.
4. Simulated Lightning (sparks)
• Within One week 15% of C present as methane gas CH4.
Converted to compounds CH20 (formaldahyde) and HCN
(hydrogen cyanide).

•
Formic acid (HCOOH) Urea (NH2CONH2) carbon bonds and forms aa
glycine and alanine.
Similar experiments made 30 carbon compounds and 6aa.
Which came first?
• RNA Theory:
• Without hereditary molecules no consisten
molecules could have formed.
• Ribozymes – are RNA molecules that act like
enzymes to help own assembly… so were
proteins needed?
• rRNA acts like Ribozymes.
Which came first?
• Protein Theory:
• Simple protein synthesis easier than
nucleotide synthesis.
• Nucleic acids (RNA) are too complex to form
spontaneously repeatedly.
• Can make synthetic replicating nucleic acids
and some can even mutate.
Which came first?
• Some Kind of Combo?
• Peptide-Nucleic Combo Theory
• PreRNA (peptide nucleic acid PNA)
– Basis for life
– Stable and simple enough to form spontaneously
and self replicates.
Spontaneous molecules… ok.
Spontaneous compounds… ummm ok.
Cells from these…HOW???
• Cells = little bags of
fluid with contents
different from the
environment.
• Bubble Theories =
Hydrophobic
region on
molecules will
form bubbles in
water
spontaneously.
Oparin’s Bubbles 1930
• Life causing conditions different from
todays environment.
• Primary Abiogenesis – for cells to
evolve they must dev’l chemical
complexity, separating contents from
env. With cell membrane and
concentrating their contents.
• Protobionts – Ea. Chemical
concentrating bubble like structures.
Published 1938.
– Inspired Miller/Urey to create life.
– This allowed Oparin be become more
accepted.
Bubble Theories
• Microspheres, protocells, protobionts, micelles, liposomes,
coacervates are all hollow spheres and exhibit cell like properties.
• Differences depend on the structure (protein vs. lipid) and how they
form.
• Coacervates – are lipid bubbles with two layers. They resembel
biological membranes.
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Can form projections and divide by pinching.
Grow by accumulating more lipids.
Contains aa and used for acid/base reactions in decomposition of glucose.
NOT ALIVE!!!
Bubble Scenario
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Bubbles in Ocean
Some have aa.
They persist then disperse.
If aa have side groups for growth
promoting rxn surviving longer.
Protenoid microspheres and lipid
coacervates.
Persistence increases with
metabolic rate.
Bubbles better able to incoporate
molecule and energy would persist
longer and grow.
Edge of O frothy with bubbles. UV
and ionizing radiation, methane and
organic molecules.
Bubbles
• Successful bubbles could make daughter
bubbles.
• As soon as they could dev’l heredity life could
begin.
Lipid Bubbles
Protein Bubbles
Coacervates form readily in
water
Heritable mechanism
imaginable
How do they get heredity?
Don’t form readily in water –
forms usually in dry conditions.
Bubbles
• RNA acts like an enzyme to make new RNA so
maybe they were first.
– Became complex and stable
– More so when surrounded by bubbles.
• DNA came later as replacement because
replicates and stores more stably since double
helix.
Skipping A Step
• Fossil evidence shows progression from
simple to complex organisms begins 3.5
bya.
• Ea. Evidence of life in microfossils (1-2
micrometers). Single celled with no
external appendage on internal
structures.
• Resembles bacteria
• Prokaryotes (“before” “kernel”
[nucleus]).
• Eukaryotes appeared 1.5 bya so 2bya
bacteria only orgs on E.
Archaea
• NOT BACTERIA!!!!!!!!!!!
– In Black Sea where there is no O2.
– Boiling Hot Springs
– Deep Sea vents
• Similar environments to ea E.
– Methanogens – methane producing simple anaerobic
CO2 + H2  CH4
– Have DNA, membrane, wall, and metabolism with ATP
Archaea vs. Bacteria
Archaea
Bacteria
No cross link. Carbohydrte peptodiglycan
in walls
Peptodiglycan – very strong cell waslls
and simple gene architecture
Different Lipid Structures
Phospholipids
Major differences in biochemcial process
of metabolism
“Regular” biochemical activity. “normal”
metabolism.
Methanogens: Methanococcus from deep
sea vents survived at 185 degrees F with
pressure 245x sealevel.
2/3 genes unlike any ever seen.
Sequence compared to bacteria indicates
split 3bya.
Photosynthetic Cyanobacteria – have
chlorophyll pigment and produce O2.
Appeared ~3bya and increased E O2 from
4-21%  increased ozone to keep
proteins/nucleic acids safe.
Responsible for limestone deposits.
Extreme Theremophiles: bery hot =
hydrothermal volcanic vents and boiling
water. 230 degrees F ok.
May be relics of first orgs on hot E.
Extreme Halophiles: Very salty living env
= Dead Sea.
The Three Domains
Archaea
Bacteria (Eubacteria)
Eukaryotes
Microfossils appear 1.5 bya
Different from previous.
Larger
Internal Membrane
Thicker Walls
“true” “nucleus”
Basic TimeLine
See page 70 in your text.
600 mya Eukaryotes are
Multicellular organisms
1.4 bya Eukaryotes are larger than 10
micrometer and have small membrane
bound structures.
1.5 bya 6micrometer
Eukaryote largest found
2.5 bya Chemoautotrophs and
Cyanobacteria
3.5 bya Prokaryotes and
Archaea
4.6 bya E forms
From Bacteria to Us
• Bacteria have infolding membranes for
internal passages.
– The Eukaryotic ER may have evolved from this.
– The nuclear envelope may have been an extension
o f the ER to protect the nucleus.
• http://www.youtube.com/watch?v=i6efxaviopI evolution is
impossible
• http://www.youtube.com/watch?v=dMH0bHeiRNg
evolution of dance
• http://www.youtube.com/watch?v=_ksdV9HPwBY evo in 2
minutes
• http://www.khanacademy.org/video/introduction-toevolution-and-natural-selection?playlist=Biology Evolution
explained again.
• http://www.youtube.com/watch?v=mmDAse1DusA&featur
e=related Awesome endosymbiosis – quick
• http://www.youtube.com/watch?v=SY3MZ_wNFW8 eras
AP Objectives
1.
2.
3.
4.
5.
Quiz on first 20 vocabulary words.
Article on origin of life.
Review endosymbiosis.
Complete chapter 4 notes on origin of life.
Evolution in a nutshell.
Homework: complete article. Next 20 vocab.
words quiz pushed off until Friday.
Lynn Margulis 1970
• Endosymbiotic Theory
• Critical stage of evolution of Eukaryotes when
evolutionary relationships with prokaryotes
occurred.
• Energy producing bacteria reside in larger
bacteria  became mitochondria
• Photosynthetic bacteria also  became
chloroplasts.
Far Out?
Not Really
• Evidence:
1. Many symbiotic relationships do occur in nature.
2. Mitochondria and chloroplasts have their own
DNA which is similar to bacteria in size and
characteristics.
3. Double membrane.
Advantages to being Eukaryotic
• Euk can sexually reproduce – produce offspring with a copy
of each chromosome. +genetic recombination +evolution
+diversity. Meiosis and sexual reproduction led to diversity.
• MultiCellularity – single Euk cells began living in colonies.
Eventually members took on different duties to take on
characteristic of one individual. +fosters specialization!
Organize the information on page 72
into one cohesive and easily
understandable chart
Diversity
Domains:
Archaea
Eubacteria
Eukaryotes
Kingdoms:
Archaea
Eubacteria
Protista
Fungi
Plantae
Animalia
Cell Type:
Prokaryote
Prokaryote
Eukaryote
Eukaryote
Eukaryote
Eukaryote
Cell Number
Uni
Uni
Uni / Multi
Multi / Uni
Multi – Non
Motile
Multi - Motile
Feeding
Methanogens
Cyanobacteria
Photosynthetic
/ heterotrophic
Hetero
Photosyn
Hetero
Examples/ addl
info
Halophiles,
Thermophiles
Nitrogen
Fixing… could
be pathogenic
Amoeba,
paramecium
Outer wall of
chitin
Mushrooms
Trees, grasses,
moss
Sponge, spider,
newt, penguin,
human
Answer Questions about phylogenic
tree. Pg. 72
Extraterrestrials?
• E = C molecules and water to form life.
• Under different conditions maybe Si could act
like C and Ammonia like water.
Extraterrestrials?
• Universe has 10^20 stars like our sun.
– At least 10% of those have planetary systems.
– If ONLY 1/10,000 is the right shape and distance…
Extraterrestrials?
• =10^15 possible E conditions!
Extraterrestrials?
• Life on Mars?
• 4.5 byo rock found with microfosslils 20-100
nanometers in length.
• Not compelling enough though so not
scientifically accepted.
Europa?
• Seems possible.
• There is liquid water under the ice which is
warmed by the push and pull of gravitational
attraction.
• Satellite missions were scheduled to keep
checking and exploring.
More to Think About
• Archaea found here are most ancient.
Sheltered environment.
• Maybe life originated here?
Virus Article
Chapter 4 Assignments that need to be
finished:
1.
2.
3.
4.
Interior assignments
40 question quiz/team creator
Create-a-book pages (5)
Pictures to go with important concepts – Assignment
given by instructor
5. 2 articles (Ice and Viruses)
6. Time Line
7. AP Free Response Q.
8. Lab on Termites #1
9. Lab on Termites #2
10. Vocabulary Flashcards
11. AP Test Flashcards - begun