A week from Wednesday is your first exam. Bring a pencil and an eraser. It is a scantron exam.
You will be given a test booklet. Fill in the correct bubble on the scantron sheet. There‟s a lot of
material in the book that is not covered in the class. I will not be emphasizing that material.
So, where we left off, I had been talking about changes in O16 and O18 ratios in sedimentary
rocks over time, and how we can use that to determine, amongst other things whether or not
there are polar ice caps. Oxygen is so good at measuring temperatures that we can actually get
exact numbers. We can get the average temperature of the oceans at a given point in time. What
we know by looking at sedimentary rock records is that there have been multiple episodes where
there has been no ice, as well long periods where there has been ice. Ice caps come and go. When
we have polar ice, we call it an icehouse climate. When there is no polar ice, it is a greenhouse
climate. Sea levels rise and fall as we go to and from icehouse and greenhouse environments.
The Earth is warming up right now. So, is warming normal? Yeah, warming is normal, but you
just don‟t lose as much polar ice as we have naturally within a few decades. The rate at which
we‟re losing polar ice is hundreds of times faster than the fastest natural process.
At this point, you have a general framework for the planet. There are some things to remember.
It‟s a dynamic, recycling planet. Plate tectonics is driving continental motion, destroying
continents and oceans, and also forming them. Organisms live on the surface of the planet, and
respond to these tectonic changes over time. Essentially, as environments change, organisms
adapt. Organisms can go extinct if they do not adapt. We have the geologic framework.
What about the biologic framework. What is the evidence for evolution and the origin of life?
Today, we‟re going to talk about the origin of life, and give an introduction to evolution. The
best evidence for the origin of life is through one of the best scientific experiments ever
conducted. Remember, science is all about experimentation.
In 1953, Miller and Urey conducted a simple experiment to see what was required to form
organic molecules through purely natural processes. Here‟s the thing: we all know that we‟re
composed of amino acids. DNA is the backbone of the construction of our cells. Where do we
get these amino acids? How do we form them?
Miller and Urey took a big jar and they filled it full of the gasses that would have been present at
the early stages of Earth‟s formation, prior to atmospheric oxygen. In one chamber, they created
an atmosphere of hydrogen, methane, and ammonia. Below it was another chamber which
collected any precipitates which formed. The scientists ran electricity through the atmosphere.
They simulated lightning in an artificial environment. So, they zapped the atmospheric gasses
with lightning. After one week of this experiment, four organic amino acids were spontaneously
formed. In one week, Miller and Urey were able to spontaneously generate four amino acids. The
earth is about 4.8 billion years old. In one week, four necessary amino acids for the origin of
complex life were created. So, we learn that simple natural processes can create organic
molecules from inorganic substance. That in itself is suggesting that natural processes can simply explain the origin of organic life. In one week, they started to build amino acids. The earth is the
one place in the universe where we find organic molecules. However, it is not the only place. We
also find them on meteorites. We also find them on Mars. These building blocks that are
necessary for life are not restricted to Earth. They are simple formations. However, we (humans)
are not just little bits floating around. We have complicated replicated structures. We need to
have those amino acids turned into long repeated chains of amino acids. The amino acids need to
become polymers. These include fats, sugars, proteins, enzymes, and everything else that your
body is made up of. Your entire physical structure is made up polymers, organic polymers.
Sydney Fox, another famous scientist, took a bunch of amino acids, and placed them under
warm, dry conditions. They polymerized (formed complex chains of amino acids) spontaneously.
So, for the two fundamental steps in creating organic material, it took three smart people with
two experiments to generate the necessary amino acids and polymers for the origin of life.
Now, we have nucleic acids that are polymerized, composed of amino acids that can form
spontaneously. What about something as complex as a cell? Cells in living organisms are
basically membranes surrounding an internal environment within which genetic material (either
RNA or DNA) is replicated. Cells need a barrier between the internal and external environment.
Water will dissolve a lot of nucleic acids. You need some form of membrane. This is done by
polymerizing fats into fatty acids. Fatty acids have two different ends. They have a
hydrophobic („water-fear‟) end and a hydrophilic („water-like‟) end. These fatty acids align
themselves so that the two hydrophobic ends face each other, and the two hydrophilic ends face
outwards. Hence, the barrier (the cell membrane) is two fatty acids thick. The hydrophilic ends
face outward (one being exposed to the cell internal environment, and the other being exposed to
the environment outside the cell). The hydrophobic ends face each other.
Now, okay, we can spontaneously form amino acids. We can spontaneously polymerize amino
acids into nuclear acids, and we can form fatty acids which go on to form membranes. What
about something complicated like proteins?
Here comes Sydney fox again. He generated proteinoids in his experiments. They‟re not alive.
However, they do behave like certain living bacteria. They grow, spontaneously bud, and
selectively absorb and emit certain chemicals.
So, talk about life. When you go out in the world, you can see living things around you. There is
a vast diversity of life. Fundamentally, there are three primary divisions.
There is Eubacteria, Archaebacteria, and Eukaryotes. Eukaryotes are us, plants, and slime
moulds. We all share a unique feature: a nuclear membrane, which protects the discrete nucleus
in the cell. The genetic material is locked up in a separate environment in the nucleus.
You will notice in this chart (in the professor’s notes) that there is an arrow linking Eubacteria
with Eukaryotes. It connects mitochondria. We are not truly singular organisms. We‟re actually a
composite organism. You do not have one DNA code for you. You have two. You have regular
DNA and your mitochondrial DNA. In every cell, there are mitochondria. Basically, in the early
evolution of eukaryotes, a symbiotic relationship develops where mitochondria provide energy to power the cells, coming from photosynthesis or respiration. So, every cell in your body has a