Origin of life

Miller-Urey Experiment

         The origin of life, probably the most spoken subject ever since the beginning of human wisdom. Since the beginning of human existence we have always wondered about the origin of life. Some have tried to explain the origin of life through illogical reasoning such as biblical theories. However, if you are simply a logical person you will not be able to accept this because it has no factual evidence. A number of experimental investigations have provided evidence of how life began on planet Earth. For example the Miller-Urey experiment, this experiment showed that organic compounds could be synthesized from inorganic precursors. This also follows the hypothesis of the "organic soup" model which hypothesized that the primitive atmosphere contained inorganic precursor from which organic molecules could have been synthesized through natural chemical reaction catalyzed by the input of energy.
        

The Murchison meteorite may be a fragment of a comet. It contains ancient grains that formed in stars long before the solar system was formed. Also present are organic molecules such as amino acids — the building blocks of life — that may provide clues to the origins of life.  

          There are also many other hypotheses about the natural origin of life on earth, which mostly have scientific factual evidence. For instance, a meteor seeding earth with organic molecules from space.This hypothesis came about because a meteorite hit Australia in 1969 and is very rich in organic compounds, including 70 amino acids and nucleotide bases. Which are extremely vital for life, especially when our physiological proteins consist of 20 different amino acids. So this lead to scientist hypothesize that a meteor hit earth 4.6 billion years ago and from these simple molecules came about more complex molecules.The monomers produced polymers with the ability to replicate, store and transfer information. 
    
        Many scientist believe that earth formed 4.6 billion years ago but the environment was way to harsh for life because of the lack of oxygen, numerous amounts of volcanoes, and etc. Only until 3.9 bya do scientist believe that life actually formed on earth. The earliest fossil record evidence can be dated back to 3.5 bya. With this evidence  is gives a reasonable range of when the origin of life could have occurred. Molecular and genetic evidence from extant and extinct organisms also tell scientist that all organisms share a common ancestral origin of life. A lot of evidences that scientist have found include a common genetic code.
  
        Sources: "Meteorite Sites in Victoria." : Melbourne Museum. N.p., n.d. Web. 14 Oct. 2014.

"The Miller/Urey Experiment." The Miller/Urey Experiment. N.p., n.d. Web. 12 Oct. 2014.

Speciation

Example of Speciation

Example of an extinct animal

    In my last blog I spoke about phylogenetic trees and how organisms are placed upon the diagram. This blog I will be speaking a bit more in depth as to why the organism earned their spot on the cladogram or phylogenetic tree. The reason to why they earned a spot on both diagrams is due to speciation. Speciation is the evolutionary process by which new biological species arise. Hence, being able to place them on a phylogenetic tree according to when they arose. When speaking about speciation is vital to not forget extinction because it also plays an important role in the evolutionary process. Extinction occurs when a species is dying out or is completely terminated. So a good way to distinguish the two is to remember that speciation is when 1 species goes to 2 species and extinction is when 1 species goes to 0 species. Speciation and extinction have been happening throughout the entire history of Earth. Although, the rates of speciation and extinction can be very random at times. Speciation has tendencies to be slow or as described in punctuated equilibrium, can happen at any given moment followed by certain periods of nothing. Moments of ecological stress, extinction rates are extremely rapid and can be seen before your eyes, and mass extinctions are followed by adaptive radiation. Adaptive radiation is simply the rapid evolution of species when they're exposed to new environments.

       Species are groups of individuals capable of interbreeding or exchanging genetic information to produce fertile offspring. Speciation occurs when two populations diverge from a common ancestors and become reproductively isolated. Reproductive isolation is when two populations that live in the same environment are unable to reproduce because their genes are no longer able to interbreed. Although speciation can happen by different processes, reproductive isolation must be maintained so species can remain distinct. Speciation creates a diversity in life formations. Species are spread throughout the earth which causes a geographical barrier, for example species on land and species who live in the ocean. Also pre- and post-zygotic mechanisms can maintain this reproductive isolation and also prevents gene flow. So the main thing to grasp is that new species arise from reproductive isolation over time.

Darwin's Finches

       Something interesting to know is that even today population are continuing to evolve. Everyday is a new day of possibility for species to speciate or become extinct. There is scientific evidence to back this up. Scientific evidence has also proved that evolution has occurred in all species. Take Grants' observation of darwin's finches for example in the Galapagos for example. The "Grants'" are a married couple who have recently studied and observed the continuation of evolution happening on the Galapagos Island. They saw how the finches of the birds are still evolving from when darwin studied them. This is a directional phenotypic change in population.     




SOURCES

"Darwin's Finches." Wikipedia. Wikimedia Foundation, 10 Nov. 2014. Web. 11 Oct. 2014.

"Speciation." Evolution 101:. N.p., n.d. Web. 09 Oct. 2014.

"007 - Speciation and Extinction." Bozemanscience. N.p., n.d. Web. 11 Oct. 2014.

Phylogenetic Trees

   

Figure 1 - Tree of life

     Its time, to speak on the unspeakable, the truth about phylogenetic trees. You may have been told things which are totally false of phylogenetic trees and unlike christmas trees, this is the tree of life. Phylogenetic trees represent traits that are either derived or lost due to evolution. For a better understanding, think of the absence of legs in some sea mammals.  Originally whales were four footed land animals but due to evolutionary changes these legs began to disappear and become a vestigial structure. The Phylogenetic tree can explain this process by illustrating the speciation that has occurred, in that relatedness of any two populations on the tree is illustrated by how recently two groups came from a common descendant.

     

 Figure 2 - Cladogram.

     Cladograms also play a major part when dealing with phylogenetic trees. A cladogram is a diagram used in cladistics which also shows relations among organisms. Basically these two diagrams are identical when explaining how organisms lost or gained certain traits. Click the link to have a more broad understanding of cladogram.  Video on Cladograms 

    Now that I have explained the significance and the use of Phylogenetic trees and cladograms. Stay tuned so I can explain how phylogenetic trees and cladograms can be constructed from morphological similarities of living fossil species, and from DNA and protein sequence similarities. Usually phylogenetic trees are constructed from morphological similarities. Such as if you begin to look at the vertebrae of one animal this can lead to the conclusion of how other animals may have, "so to speak", came from this this organism. If you take a glance at the image in figure 2  you can see that sharks were the first ones to have a vertebrae and from this came the Ray-finned fish and so on. Now when looking at DNA sequences you get the exact similarities in an organisms so this will be much easier to place organism along a phylogenetic tree or cladogram.

Newly founded skull.

     It is also important to remember that phylogenetic trees and cladograms are dynamic, meaning that they are constantly being revised. These changes happen because of the progression of technology and are based on the biological date used, new mathematical and computational ideas, and current and emerging knowledge. For example theres been a new skull that has been found recently and reports are saying that is will spark evolution controversy. If this skull is accepted by scientist it will have the possibility to change the current phylogenetic tree. 


Sources

"Reading Trees: A Quick Review." Reading Trees: A Quick Review. N.p., n.d. Web. 05 Oct. 2014.

"How to Read a Phylogenetic Tree." Emergence, Evolution and Epidemiology. N.p., n.d. Web. 06 Oct. 2014.

"UNM Biology Undergraduate Labs." Untitled 1. N.p., n.d. Web. 06 Oct. 2014.