27.1 Origin of Life Outline
1. Darwin Connection
a. “trunk” of Darwin’s “tree of life”
b. Common ancestor of all living things was the first cell
c. Oldest prokaryote fossils are 3.5 billion years old (Earth is 4.6 billion years old)
d. The very first living thing had to come from nonliving chemicals
e. Today we say that “life only comes from life”
2. Evolution of Small Organic Molecules
a. Likely took place in the ocean
i. Life seems to have either started on the surface of seas or in seaside pools
ii. Intense UV light was required (no ozone at this time)
b. Miller-Urey experiment (1953)
i. Placed inorganic molecules in a closed system, heated it, circulated it past an
electric spark (simulating lightning) in absence of oxygen
ii. After a week – contained variety of amino acids (protein building blocks)
c. Small organic molecules may also have arisen deep in the sea at mid-oceanic ridges
i. Hydrothermal vents occur here
ii. Vents can be 10-15 m wide and 15-20 m high
iii. Hot water contains mix of iron –nickel sulfides
iv. Many living things exist here today
v. Possible that the right conditions existed here to initiate life
3. Macromolecules
a. Once small organic (carbon and hydrogen containing) molecules existed, they still
needed to form larger molecules (amino acids) and eventually macromolecules
(proteins, RNA, DNA) to create life
b. Macromolecules: Which came first, RNA or proteins???
i. RNA-first hypothesis
i. Just what it sounds like – RNA came first
ii. Formulated after discovery of ribozymes (not ribosomes) – RNA that can
form both genetic substrate and an enzyme
ii. Protein-first hypothesis
i. Again, just what it sounds like – proteins came first
ii. Amino acids can polymerize abiotically (without life) when exposed to
dry heat
iii. Amino acids collected in shallow pools that dried up, heat from sun
caused them to form protenoids (small polypeptides)
iv. When protenoids returned to water, they form microsphere proteins
that may have had enqymatic properties
v. This hypothesis assumes that DNA genes came after protein enzymes
arose
iii. Combonation of the two above hypothesis
i. Grahan Cairns-Smith
ii. Clay was especially helpful in polymerization of proteins and nucleic
acids at the same time.
a. Clay contains iron and zinc (possible inorganic catalysts for
polypeptide formation)
b. Clay tends to collect energy from radioactive decay and
discharge it when temp/humidity changes (possible source of
energy for polymerization)
Complete Check Your Progress p.543 #1-2
27.1 The Origins of Life (cont’d)
1. The Protocell
a. After protocells formed, something like our modern
_______________ _______________ was required to
separate a living thing from its _______________.
b. Structure that had a lipid (fat)- _______________
membrane likely
c. In _______________ environment, phospholipid molecules
automatically form _______________ (droplets that have
their _______________ heads facing out and
_______________ tails facing in)
d. Development of _______________ membrane key to cell
development
e. The Heterotroph Hypothesis
i. Protocell likely a _______________ (was not capable
of making its own food)
ii. Suggests that heterotrophs preceded
_______________ (capable of making own food)
iii. Protocell may have used preformed ___ ___ ___
(energy source), but this source dwindled
iv. Cells that could extract energy from _______________
to make ADP to ATP favoured.
v. _______________ (literally means the splitting of
sugars) pathway common in living things, so it is likely
a pathway that developed very early in the
_______________ of life
vi. No free _______________ at this point meant that
_______________ needed to be used to extract
energy from _______________.
2. The True Cell
a. A true cell is a _______________ -bounded structure that
can carry on protein _______________ to produce the
enzymes that allow DNA to _______________
b. DNA directs protein _______________, and information
flows from DNA to _______________ to proteins
c. How do the three hypotheses of the first macromolecules
connect to the origin of the first true cell?
i. Under the RNA-first hypothesis, RNA would have been
the first _______________ material to evolve, and the
first true cell would have had RNA genes.
ii. The protein-first hypothesis suggests that
_______________, or at least polypeptides, arose
before DNA or RNA.
iii. The combination hypothesis suggest that polypeptides
and RNA evolved _______________.
Complete Check Your Progress p.544 #1-2
1. The Protocell
a. After protocells formed, something like our modern plasma
membrane was required to separate a living thing from its
environment.
b. Structure that had a lipid (fat)-protein membrane likely
c. In aqueous environment, phospholipid molecules
automatically form liposomes (droplets that have their
hydrophilic heads facing out and hydrophobic tails facing in)
d. Development of plasma membrane key to cell development
e. The Heterotroph Hypothesis
i. Protocell likely a heterotroph (was not capable of
making its own food)
ii. Suggests that heterotrophs preceded autotrophs
(capable of making own food)
iii. Protocell may have used preformed ATP (energy
source), but this source dwindled
iv. Cells that could extract energy from carbohydrates to
make ADP to ATP favoured.
v. Glycolysis (literally means the splitting of sugars)
pathway common in living things, so it is likely a
pathway that developed very early in the evolution of
life
vi. No free oxygen at this point meant that fermentation
needed to be used to extract energy from
carbohydrates
2. The True Cell
a. A true cell is a membrane-bounded structure that can carry
on protein synthesis to produce the enzymes that allow DNA
to replicate
b. DNA directs protein synthesis, and information flows from
DNA to RNA to proteins
c. How do the three hypotheses of the first macromolecules
connect to the origin of the first true cell?
i. Under the RNA-first hypothesis, RNA would have been
the first genetic material to evolve, and the first true
cell would have had RNA genes.
ii. The protein-first hypothesis suggests that proteins, or
at least polypeptides, arose before DNA or RNA.
iii. The combination hypotheses suggest that polypeptides
and RNA evolved simultaneously.
Complete Check Your Progress p.544 #1-2
The Origins of Life: The Miller-Urey Experiment Student Hand-out
“Enshrined in high school textbooks, the Miller-Urey experiment raised expectations that scientists
could unravel the origins of life with simple chemistry experiments.”
1. Scavenger Hunt Questions: See if you can find the answers to the following questions in Section 27.1
of your textbook.
a)
b)
c)
d)
e)
Who were Stanley Miller and Harold Urey?
What was the Miller-Urey experiment trying to simulate?
When was the Miller-Urey Experiment performed?
What was discovered by the Miller-Urey Experiment?
Are the results of the Miller-Urey Experiment still considered relevant today? Why or why not?
2. Article
As a class, read and discuss the article “From Old Vials, New Hints on Origin of Life,”
(http://www.nytimes.com/learning/teachers/featured_articles/20081021tuesday.html)focusing on the
following questions:
a) What would a proponent of Dr. Miller say about his experiment today? What would a critic say
about it?
b) Why did the addition of steam to the experiment by Dr. Miller interest Dr. Jeffrey L. Bada?
c) What did Dr. Bada and Adam Johnson discover in the “brown residue at the bottom of an old
vial?” Why was it significant?
d) What other places have been suggested as likely locations for the origin of life and why? Do you
agree or disagree with Dr. Bada’s assessment that “you want to consider everything,” and why
or why not?
3. Modeling Activity
Background: The 10 amino acids that we can produce are alanine, asparagine, aspartic acid, cysteine,
glutamic acid, glutamine, glycine, proline, serine and tyrosine. Tyrosine is produced from phenylalanine,
so if the diet is deficient in phenylalanine, tyrosine will be required as well. The essential amino acids are
arginine (required for the young, but not for adults), histidine, isoleucine, leucine, lysine, methionine,
phenylalanine, threonine, tryptophan, and valine. These amino acids are required in the diet. Plants, of
course, must be able to make all the amino acids. Humans, on the other hand, do not have all the
enzymes required for the biosynthesis of all of the amino acids.
Goal: Using a chemical model set (or other materials to make chemical models such as toothpicks and
colored marshmallows) you will engage in a short, hands-on activity to better understand the
biochemistry behind the content of the article. You will make inferences about the relationship between
the simple compounds used by Dr. Miller and amino acids. You will also explore how amino acids are
similar and different from each other, making it possible for modern techniques to identify additional
amino acids in Dr. Miller’s original samples.
Instructions:
1) Make models of the simple compounds used by Dr. Miller in his experiment: water (H2O), ammonia
(NH3), methane (CH4), and hydrogen (H2).
2) Answer: Do these chemical compounds contain the necessary ingredients to build amino acids?
Could they be these be recombined to form amino acids?
3) Model: Make several of the amino acids from the chart below.
Compare and contrast your amino acid with the other 19. You may wish to use a venn diagram
1) What part of the amino acids is used to distinguish each from the others? (the R groups) What
can you infer about how modern technology works to identify amino acids?
2) How might the compounds in Miller’s experiment: water, ammonia, methane and hydrogen,
have recombined to form amino acids?
3) Are there any amino acids that could not have been formed from these compounds?
4) Amino acids combine to form proteins by creating peptide bonds between the amino group and
the carboxyl group. Why don’t you think this happened in Miller’s experiment? Why is this still
the “missing piece” in our understanding of the origin of life?
Related Times Resources
 ADDITIONAL TIMES ARTICLES AND MULTIMEDIA:
Obituary: Stanley Miller, Who Examined Origins of Life, Dies at 77
Special Section from the Science Times: Evolution
 LEARNING NETWORK RESOURCES:
Lesson Plan: WAKE UP! There’s a Protein for That!
Diagramming Protein Synthesis to Illustrate the Science Behind Narcolepsy
Lesson Plan: You Say You Want an Evolution?
Learning About Biodiversity Since The Beginning of Time
Lesson Plan: Whose ‘Truth’ Is Out There?
Examining the Historical Significance of the ‘Evolution Versus Creationism’ Debate
 ARCHIVAL TIMES MATERIALS:
THE ORIGIN OF LIFE
Historical article from August 18, 1912.
RELIGION AND BIOLOGY; How the Search for the Origin of Life Is Hampered by
Preconceptions
Historical article from March 5, 1905.
Data Backs Idea Life Began in Inferno
Historical article from July 31, 1998
 TIMES TOPICS:
Biology and Biochemistry
Evolution
Earth (Planet)
 OTHER RESOURCES:
http://scrippsnews.ucsd.edu/Releases/?releaseID=930
“Volcanoes May Have Provided Sparks of First Life: Researchers reanalyze classic Miller
experiment to uncover role of volcanoes in early life on Earth”
Article from the SCRIPPS Institution of Oceanography
http://www.chem.duke.edu/~jds/cruise_chem/Exobiology/index.html Introduction to Exobiology
Web site provides an overview of the Miller-Urey experiment and other research on the origin of
life.
http://www.youtube.com/watch?v=jpjaV2zKIfw
On Beyond: Miller/Urey Health Careers Games Math (minutes 1:08 – 13:28) University of
California Television program celebrating the 50 year anniversary of the Miller/Urey Experiment
(October, 2003)
Interdisciplinary Connections:
History – Create a timeline outlining experiments by scientists seeking to discover the origins of
life on earth. Describe the scientists’ experiments, claims, impact at the time and significance
today.
– Write an essay describing how scientists’ search for a chemical basis for the origin of life is
related to the larger theory of evolution. How do their findings support or negate evolutionary
theory?
Technology – Make a “How-It-Works” poster to explain how scientists use modern technology
to identify amino acids.