You will be evaluating 3 media about the origins of life (i.e., abiogenesis, “life from nonlife”).
How life originated is a fundamental question in science, but also theology. Science estimates the
Earth to be 4.54±0.05 billion years old, with life on Earth appearing at least 3.5 billion years ago.
You will be analyzing three types of media for their presentation of data and theory about the
origins of life and then thinking about how/why data and theory are utilized as they are.
a) Analysis of media: (1) An article from about.com, a commonly referenced website for basic information (2) An excerpt from a science textbook focusing on evolution (3) A video from Coldwater Media, a Christian educational films company
For each of the media, box theories, theoretical models, & predictions based on theories
and underline data and data models. Alternatively, you can use two different color
highlighters! Make sure to provide a key linking the colors to data versus theory.
For the video, you will need to write down key statements of data and theory; you are
advised to re-watch the video several times to capture as many statements as possible.
b) You will also be interpreting your results to answer several questions.
Preliminary questions (do these before you analyze the media)
1. Make a hypothesis about the proportion of data vs theory in these media. (Do you think
they will be the same for all media? Different? How? Why? Explain your rationale.)
2. This kind of analysis doesn’t lend itself to a 50% data:50% theory null hypothesis. What
do you think a reasonable ratio of data to theory would be? Why?
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Media #1: Website article
Understanding Chemical Evolution (Heather Scoville, Evolution Expert on About Education);
The term “chemical evolution” can be used in many different ways
depending on the context of the words. If you are speaking to an
astronomer, then it could be a discussion about how new elements are
formed during supernovas. Chemists may believe chemical evolution
pertains to how oxygen or hydrogen gases “evolve” out of some types
of chemical reactions. In evolutionary biology, on the other hand, the
term “chemical evolution” most often is used to describe the hypothesis
that organic building blocks of life were created when inorganic
molecules came together. Sometimes called abiogenesis, chemical
evolution could be how life started on Earth.
The Earth’s environment when it was first formed was very different
than it is now. The Earth was somewhat hostile to life and so the
creation of life on Earth did not come for billions of years after the Earth
was first formed. Because of its ideal distance from the sun, the Earth is
the only planet in our solar system that is capable of having liquid water in the orbits the planets are in now. This
was the first step in chemical evolution to create life on Earth.
The early Earth also did not have an atmosphere surrounding it to block ultraviolet rays which can be deadly to the
cells that make up all life. Eventually, scientists believe a primitive atmosphere full of greenhouse gases like carbon
dioxide and perhaps some methane and ammonia, but no oxygen. This became important later in the evolution of
life on Earth as photosynthetic and chemosynthetic organisms used these substances to create energy.
So just how did abiogenesis or chemical evolution happen? No one is completely certain, but there are many
hypotheses. It is true that the only way new atoms of non-synthetic elements can be made are through the
supernovas of extremely large stars. All other atoms of elements are recycled through various biogeochemical
cycles. So either the elements were already on Earth when it was formed (presumably from the collection of space
dust around an iron core), or they came to Earth via the continuous meteor strikes that were common before the
protective atmosphere was formed.
Once the inorganic elements were on Earth, most hypotheses agree that the chemical evolution of the organic
building blocks of life began in the oceans. The majority of Earth is covered by the oceans. It is not a stretch to think
that the inorganic molecules that would undergo chemical evolution would be floating around in the oceans. The
question remains just how these chemicals evolved to become organic building blocks of life.
This is where the different hypotheses branch off from each other. One of the more popular hypotheses says that the
organic molecules were created by chance as the inorganic elements collided and bonded in the oceans. However,
this is always met with resistance because statistically the chance of this happening is very small. Others have tried
to recreate the conditions of early Earth and make organic molecules. One such experiment, commonly called the
Primordial Soup experiment, was successful in creating the organic molecules out of inorganic elements in a lab
setting. However, as we learn more about the ancient Earth, we have found out that not all of the molecules they
used were actually around during that time.
The search continues to learn more about chemical evolution and how it could have begun life on Earth. New
discoveries are made on a regular basis that help scientists understand what was available and how things may have
happened in this process. Hopefully one day scientists will be able to pinpoint how chemical evolution happened
and a clearer picture of how life began on Earth will emerge.