Why do we start the discussion of biology with a discussion of geology? Here are some reasons why one would do this:

• All life on earth is linked to geology; likewise, many surface geologic features and processes have been influenced by life on earth. The origin and early evolution of the earth are especially important when looking at the origin and early evolution of life on earth.
• Life chemistry had its origin with the elements available to it during the formation of the earth. These provided the basic raw materials available for life.
• The evolution of life is in response to changes in environment. Many of these changes are linked to changes in climate and/or geology.
• All life is (so far) limited to placement upon the earth, so it is crucial that we understand the processes of the earth.

Other theories have been postulated (i.e. the oscillating universe theory which states that the universe expands and contracts in a cycle every 100 billion years) and these are hotly debated

A. The earth formed approximately 4.6 BYA (billion years ago.) Initially, there was a cloud of gasses and dust particles, possibly originating from the ejected particles of a nearby supernova.  B. The cloud gradually contracted and flattened, concentrating about 99% of its mass in the center with the rest rotating counterclockwise in a flattened disk.  C. As the disk rotated, turbulence was created, causing condensation of the disk into small, turbular eddies. These gradually accreted together to form protoplanets. D. These protoplanets further accreted, creating the mature planets of the solar system.  The sun also accreted, pulling in most of the mass. As these accumulated, the pressure and temperature caused the initiation of thermonuclear fusion. This thermonuclear fusion is what provides the ultimate source of energy for all life on earth. In the hot accretions of planetesimals, iron-rich elements condensed first, creating the cores (the inner and outer cores). Next, the lower-density silicates began to condense and aggregate, forming the mantle and the crust. Further differentiation of the crust was fueled by the energy output from radioactive decay deep within the earth

There are three clearly defined regions of the earth: Cores (inner (1250 km) and outer (2100 km)) - composed primarily of iron (85%) and nickel. Other heavy elements (such as radioactive elements) are also found here Mantle (2900 km) - a "fluid" region primarily composed of oxygen and silica - derived minerals Crust (5-70 km) - thin film of "crud" which has floated to the surface. We are simply passengers, living on this geologic flotsam.

• These plates move relative to each other at speeds measured in centimeters per year
• This is the approximately the rate at which our fingernails grow
• The plates move very slowly on top of the layer of hotter, softer mantle
• Mantle is a liquid - but not in the sense that you think of a liquid
• It is similar to glass
• Where the plates grind against each other, stress builds up and is relieved intermittently through earthquakes
• The areas where plates move are called faults
• Near plate boundaries, molten magma can rise to the surface and erupt to form volcanoes

Plate Interactions - Divergent Plate Boundaries The process of adjacent plates moving away from each other is best seen at the oceanic spreading ridges New crust spews out from extensive oceanic ridge systems, like the one seen in the middle of the Atlantic Ocean Smaller scale systems can be seen in rift valleys, such as the African Rift Valley Divergent plate boundaries are the only source of new oceanic floor Plate Interactions - Convergent Plate Boundaries When two plates meet, a convergent plate boundary forms Usually one plate will slide underneath the other - this will cause some mountain building and lots of volcanic activity The Andes mountains in Chile are a classic example of this Sometimes plates will collide but one will not "smoothly" flow under another - extensive and rapid mountain building will occur The Himalayans are an example of this

The effects of these movements on life on earth cannot be underestimated.

• Climate is tied to the position of the plates
• Ocean currents, heat flow, salinity, and oxygen leves are dependent upon plate positions
• Glaciation is tied to plate position
• Migration is possible if the plates are close together and isolation is possible if the plates are far apart

Note that there is no O2 present in the early atmosphere. Any O2 outgassed would have reacted with the metals of the crust, causing oxidation. This lack of O2 is crucial for the formation of organic molecules!

• Order Living organisms partition resources and nutrients within their systems. This is an energy-requiring process which must be maintained for life to continue.
• Reproduction Organisms reproduce their own kind. Life only comes from life.
• Growth and Development Heritable characters direct the pattern of growth and development, producing an organism that is characteristic of its species.
• Energy Utilization Organisms take in energy and transform it to do work. Almost all of life's functions require energy.
• Homeostasis Regulatory mechanisms maintain an organism's internal environment within tolerable limits, even though the external environment may fluctuate. This process is known as homeostasis.
• Evolutionary Adaptation Live evolves as a result of the interaction between organisms and their environment. As the environment is rarely stable, life must adapt to survive in these new living conditions.

Experiments concerning the origin of life must answer the following questions:

• How were small organic molecules (amino acids, nucleic acids, lipids) formed in the primitive earth environment?
• How were these small organic molecules joined together to form polymers (long chains of organic molecules)?
• How were abiotically produced molecules segregated into droplets called protobionts that have chemical compositions different from their surroundings
• What was the origin of heredity?

As materials circulated through the apparatus, the solution in the flask changed from clear to murky brown. After one week, Miller and Urey analyzed the contents of the solution and found a variety of organic compounds, including amino acids, nucleic acids, and ATP, providing one scenario in which the first criterion could have been met.

The primitive atmosphere was reducing (electron adding) which facilitated the joining of monomers into polymers. The addition of sand and clays into apparatus similar to the Miller-Urey can generate longer polymers. The clays and sand act as catalysts which facilitate the formation of polymers.

Experiments show protobionts form spontaneously from abiotically formed organic molecules. These protobionts have membranes which are selectively permeable, store energy (voltage difference), etc.

Lastly, simple, self-replicating systems have been created in the lab. These consist of RNA systems. RNA systems can be self-catalyzing and are relatively unstable. This would lead to a rapid evolution.

Much in not known about the origins of life, nor will it probably ever be known. It is a very passionately debated subject. However, this is what makes it interesting and will assure the study of this science for many years to come.

Links to cool related sites

For a more complete look at plate tectonics, check out The Dynamic Earth, the Story of Plate Tectonics

Extraterrestrial life? Check out the SETI (Search for Extra Terrestrial Intelligence) project or CNN's mars life page

If you have any questions or comments, please feel free to e-mail me.