Stated Clearly presents:
What is Chemical Evolution?
Scientists have reason to think that the first living cells on Earth
came about through a natural process called Chemical Evolution.
What is Chemical Evolution,
how does it work, and how is it different from Biological Evolution?
To answer these questions we'll start by first dissecting the terms
and then look at an example of how Ehemical Evolution can take simple
molecules
and organize them into complex structured systems,
similar to those found in living cells. The word "Evolution"
simply means change over time. Biological Evolution deals with changes in things
which were able to reproduce:
living creatures make copies of themselves. The change over time that we
see in Giological Evolution
is not just random change, oftentimes
it is adaptive change. Populations become better able to survive and reproduce
within their environments.
When conditions are right, biological evolution can even drive a species to
develop brand new characteristics
and abilities. For this to happen,
biological evolution typically requires three conditions:
Reproduction, variation, and selection.
Let's see how this works: Many species of Holly have smooth edged leaves.
English Holly, however, is covered in spikes
which protect the plant from deadly predators. How did these weapons first
evolve?
Well, when a holly plant reproduces
its offspring often show a random variation. They are slightly different
from their parents,
and slightly different from each other. In a forest filled with grazing animals,
individual plants which happened to be harder to eat then their siblings
are more likely to grow up and have children or their own.
Nature, simply by being difficult to survive in,
selects who gets to reproduce and pass on their new traits
and who does not. In this case
mutations which simply caused the vanes that these leaves to extend past their
edges,
gave rise to a brand new weapon!
The discovery of biological evolution was an incredible breakthrough in
science.
It explained how new complex traits and abilities
develop naturally in living things. The problem is
Biological Evolution depends on reproduction
in order to work. Reproduction however, is an extremely complex process
in another itself.
This begs the question: How did reproduction first evolve?
To try and solve this mystery, many scientists are looking into Chemical
Evolution.
Chemical Evolution
refers to changes in things that need not be capable or reproduction.
Examples could be individual molecules or entire chemical systems.
A chemical system is a group of molecules that interact with each other.
Molecules, structures,
and chemical systems almost always evolve or change over time,
but they often evolve towards simplicity.
Solid iron corrodes into rust when it comes in contact with the water,
proteins breakdown when exposed to too much heat. If simple chemistry is to
give rise to something advanced enough to reproduce,
there must be situations in which chemical systems can grow in complexity,
form new structures, and gain new functions.
In order for this to happen, reproduction, which
is needed in biological evolution, can be replaced with a much simpler process:
repetitive production.
On planet Earth and all throughout the universe, powerful natural events take
place in regular cycles:
The heating and then the cooling of
day and night. The repetitive eruptions a volcanic
geysers, the rise and then the fall
of ocean tides. These events
repetitively produce, or give birth, to new molecules
and chemical systems. These products increase over time
and often develop new abilities as they interact with their environment.
let's see an example of how this process works!
This here is a special molecule
called a fatty acid. It's a collection of carbon atoms,
hydrogen atoms, and oxygen atoms all stuck together in a specific pattern.
Fatty acids are one of many complex molecules
that living cells use inside their bodies.
They build fatty acids with atoms they get from their environment.
Scientists used to think that living cells were the only things able to
consistently built fatty acids,
but check this out! Lab experiments have shown that when simple common gases:
carbon monoxide and hydrogen, are heated up with minerals like those found in the
Earth's crust,
a variety of complex carbon molecules
including fatty acids began to grow!
Living cells are not needed! This can happen naturally in underground chambers
heated by the Earth's Magma. As pressure builds,
these molecules can belch up into pools of water where a simplified version of
Natural Selection
then takes over. Most particles blasted into water
will either float or they will sink. Nature selects against them staying in the watery
environment.
Fatty Acids however, remain suspended in warm water,
growing in number as the cycle repeats.
When fatty acid concentrations are high enough, they bunched together
automatically self-assembling into a stable ball!
This happens because water molecules are attracted to the oxygen heads of the fatty acids
sorta like a magnet, but water repels their oily carbon tails.
When fatty acids pass near each other, their tails are pushed together by water
eventually forming a ball. As fatty acid collections continue to increase,
they join together to make a large skins! If fluctuations in the skins happened to
make the edges touch,
water forces those edges the fused together
the end result is a stable hollow container
similar to the membrane, or skin, of a living cell!
These containers have a brand new ability. They can trap other molecules
inside,
acting as an entirely new environment for chemical evolution to continue
working within!
It's important to note that these membranes do not qualify as living
creatures.
They can't reproduce on their own the same way living cells do.
That said, the development of these membranes
along with many other molecules and chemical systems that scientists have
observed,
demonstrate an extremely important principle: Chemical Evolution can give
rise
to new characteristics and abilities.
Because of this, scientists hypothesize that under the right circumstances
chemical evolution could give rise to systems that are fully capable of
reproduction!
If they are correct, this would bridge the gap between Chemical Evolution
and Biological Evolution, demonstrating that chemistry can indeed
give rise to life! Scientists at the Center for Chemical Evolution
and other research groups around the globe are working hard to test this
hypothesis.
So to sum things up, the main difference between Chemical Evolution
and Biological Evolution, is that Chemical Evolution can produce new
characteristics and abilities
without depending on reproduction.
Because of this, Chemical Evolution is being investigated
as a possible cause for the origin of life.
I'm Jon Perry
and that's Chemical Evolution
Stated Clearly.
This animation was funded by the Center for Chemical Evolution,
the National Science Foundation, NASA,
and contributions from our viewers. Though we do receive grants from time to time,
Stated Clearly is mainly funded by our viewers.
If you'd like to help out, visit us at statedclearly.com
and click contribute. Special thanks goes out the Tyler Proctor
who volunteered to work on sound for this project and to our team of science
advisors
Christopher Parsons, Dr David Deamer,
Nancy Miorelli, Dr Nicholas Hud.
and Dr Ram krishnamurthy. Until next time,
stay curious!