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Option D: Origin of Life on Earth

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Arman Lokhandwala

on 2 June 2014

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Transcript of Option D: Origin of Life on Earth

Origin of life on Earth
There are four general proccesses needed in order for the spontaneous origin of life on earth
The non-living synthesis of simple organic molecules
The assembly of these molecules into polymers
The formation of polymers that can self-replicate
The packaging of these molecules into membranes with internal chemistry different from their surroundings
The non-living synthesis of simple organic molecules
The assembly of these molecules into polymers
As mentioned before, the smaller inorganic molecules which ultimately, in theory, made organic molecules then joined to make polymers and make even more complex structures.
Option D1: Origin of Life on Earth
How did Oxygen get to Earth?
It is assumed that before life on earth, all that we had were inorganic and basic elements and compounds. At some point in time, these basic elements combined and overtime became more complex and in a way, evolved.
For all we know, the first source of organic material could have been from outer space.
The formation of polymers that can self-replicate
Replication is of course vital to survival in almost every circumstance. Somewhere along the lines of evolution, replication had to start off very simple. Today, we know that DNA cannot replicate without the use of enzymes and other vital proteins. However, RNA is able to recopy itself.

The theory that the origin of life on earth started with RNA replication is called:
RNA World Hypothesis
The packaging of these molecules into membranes with internal chemistry different from their surroundings
Homeostasis is the maintenance of an stable internal environment. Since there is a term for something like that, it has to be important, right? Well, when polymers evolved to get a membrane, it was a very important step in evolution because this allowed the differentiation of external vs. internal environments which then later allowed greater progress.
Two main properties of RNA that could have allowed it to play a role in the start of life
As mentioned before, RNA can self replicate. RNA can also act as a catalyst.

RNA has four nucleotides, similar to DNA. The short sequences of RNA can accurately replicate other molecules of RNA.
Ribozymes are catalyst used in RNA to remove introns from mRNA and help synthesize RNA molecules. Also, rRNA is found in the catalytic site in ribosomes and often plays a role in the peptide bond formation.
The RNA World Hypothesis
RNA forms from inorganic sources
RNA self-replicates
RNA catalyses protein synthesis
The membrane forms and that changes the internal chemistry
RNA codes both DNA and protein
The DNA then becomes a 'master template'
Below are the hypothesized steps in the RNA World Hypothesis
Miller and Urey
In order to try to figure out if the origin of organic compounds on earth had come from the inorganic materials that were there before, Miller and Urey created an experiment that simulated the environment of ancient earth.

What they did was that they made a series of flasks and tubes in which they places inorganic materials such as the gasses that existed back in the day (not too much oxygen, that was produced later), as well as water vapor. The water vapor was heated in order to simulate volcanic activity and electrical currents were used to stimulate lightning.


Did you know that the world's first organic material could have been delivered by comets? About 20% of a comets' tail is organic material.

An event referred to as 'Heavy Bombardment' happened 4,000 Million years ago and was where comets and other things alike hit and landed on the earth. It is possible that this was when the first organic materials were brought here
What came before living cells?
Before we had living cells, we had something known as protobionts.

Protobionts evolved from coacervate droplets. Coacervate droplets are droplets which have organic molecules.

These too had membranes.
Possible Locations

synthesis of organic molecule?




This video talks about Panspermia. Panspermia is the belief that life on earth originated from materials delivered from comets
Hydrothermal vents
It is possible that the first organic molecules came from vents from the ocean floor. The hydrothremal vents are heated by the Earth's crust and then the hot water is introduced to the ocean floor. In or around these vents is an ideal environment for the formation of polymers.
The gases above hot lava that have come from volcanoes often have a higher level of Nitrogen. Nitrogen fixation is how ammonia is made from the nitrogen gas. The high temperatures and pressure from volcanoes could have provided a good environment for the formation of organic compounds

The idea that life originated on Earth is called
Extraterrestrial Sources
As stated before, the belief that live originally came from outer space is called

Another hypothesis to support the idea of panspermia is that since Mars is smaller than Earth, it most likely cooled faster than Earth did. With Mars being cooler, life could have started there, because the Earth had not yet cooled.
Problems with the theory of life from Mars
The issues with the theory of panspemia which is backed up by the idea that Mars was where life originated and through comets and other ways got to earth, is that there is no evidence or theory of how it started. The idea itself is that it started on Mars, and came to Earth, but no one has a clue of how life could have started on Mars. But nonetheless, it is a good idea.
What is a cell?
How did cells come to be?
Endosymbiotic Theory
A cell is the building block to all living things.
Now, how exactly did living things come to be? Well, a cell can be
. They both, however, consist of more than one organelle.
There are many theories about how cells came to be the way the are today. One of these theories include the endosymbiotic theory.

This theory is when one cell is engulfed by another and instead of destroying it, the cell lets the engulfed cell stay alive so that both cells benefit.

It is thought that eurkaryotic cells developed through this method.

The reason this theory is supported by so many, is because Chloroplast and Mitochondria both have: Their own set of DNA, own ribosomes, own membrane, and because they are both the size of a bacteria.
Endosymbiotic Theory Cont.
This theory works off a similar method to endocytosis. That is when a molecule is engulfed into a cell and the membrane is pinched off. This is how people think cells developed.

Did you know that there was very little oxygen on the Earth back, back in the day?
Oxygen was present it very little quantities before life on Earth. Some how, somewhere, cells evolved and produced oxygen.

http://www.youtube. com/watch?v=51V363V1bkI&Edufilter=Db24N54Eu_vpe4P65Iz5FA&safe=active
(Delete space between '. com' for video to work)
After prokaryotes formed, one of them evolved to have chloroplast.

As we recall, chloroplast uses carbon dioxide and create oxygen as a waste produce
Cells created Chloroplast
Evolution of cells
Increasing the levels of oxygen in the atmosphere lead to:
Eventually, organisms and cells came to be that require oxygen
The added oxygen gas helped build up the ozone layer which helps block out UV radiation from the sun


Citations Cont.
"D1 Origins of Life on Earth." BioNinja Your One-stop Biology Resource. BioNinja, n.d. Web. 2 June 2014. <http://www.ib.bioninja.com.au/options/option-d-evolution-2/d1-origins-of-life-on-earth.html>.

"IB Notes." : Biology Option D Evolution, SL D1-D2. N.p., n.d. Web. 02 June 2014. <http://suviibnotes.blogspot.com/2010/09/biology-option-d-evolution-sl-d1-d2.html>.

"IB Biology Option D.1: Origin of Life." IB Biology Option D.1: Origin of Life. N.p., n.d. Web. 02 June 2014. <http://www.slideshare.net/jasondenys/ib-option-d1-origin-of-life>.
Thank you!

The End!
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