Week 3 - History of Life

This week the topic that I had learned to " Origin of Life". How did life begin? It so caught my attention that how life begin, just like when they ask which come first, the egg or chicken? In this class we learn about how did all the organism came from and where are we from. Below is what  I had learned for this topic

4 billion years ago, earth is not formed. When the planet cooled down, the earth layers is formed. The atoms hydrogen gas (H2), oxygen gas (O2), Methane (CH4), Carbon dioxide(CO2) and Nitrogen (N2) are formed. Chemical evolution happen where the inorganic compound were evolved to organic compound, with the stimulation such as hydrothermal vents, volcanoes and lightning. This chemical evolution is know as prebiotic broth hypothesis which is also proved by the scientist Miller and Urey. How did the organic compound start to form and evolved to more complex organism? First the inorganic compound is stimulates by external forces such as volcanoes or ultraviolet radiation to form organic compound. The oxygen level of the earth is increasing. In the second stage the newly formed organic compound polymerized to produce macromolecules. The larger macromolecules are protein and nucleic acid. In the third stage aggregation of prebiotic molecules form protobiont. Protobionts have the ability to maintain it's chemical properties in the cell. Protobionts also have the ability to replicates and carries out simple metabolism. where this two is the key properties of life. Next the first biological catalyst in RNA, from the theory of origin of life. RNA is the first genetic material and not DNA. Why? This is because RNA have the ability to copy themselves without the presence of enzyme. RNA molecules called ribozymes can involve in many catalytic process, such as make complementary copies of short pieces of RNA. Protobionts contain RNA, with this features it can grow and split, distributing the copies of their heridity macromolecules to their offsping. Besides that, mutation can also occurs in copying RNA which start the biotic diversity. Later on DNA take over as the genetic material as it is more stable and easy packing.

Chemoheterotrophs is the first prokaryotes that can be found in earth, they consume organic molecules for energy and carbon. It takes ATP formed abiotically, as the ATP is losed, natural selection favour those early prokaryotes that can regenarate ATP from ADP to be use as energy. This result the evolution of glycolysis which is fermentation without need of oxygen.

The first autotrophs could be photoautotroph, it used light to derive H2S to fix CO2 into sugar, this process doesn't need the presence of oxygen as well. Cynobacteria is the first photoautotrophs that used light to drive electrons from H20 instead of H2S to fix CO2. O2 is released in this process, hence the releasing of O2 change the atmosphere dramatically. This cause the extinction of many anaerobic organism, natural selection favor those early prokaryotes that able to tolerate O2. This result in aerobic respiration. The change in the atmospheric forced diverse adaptations including cellular respiration which produce energy using O2.

Cyanobacteria - The first of bacteria that release oxygen to earth

The next class we learned the topic of Systematic, Taxonomy & Classification, before this. I had encountered with this topics. The new things that I had learned was Archaebacteria and Eubacteria. Archaebacteria is an ancient bacteria which can live in extreme environment, while eubacteria is a true bacteria. Both of it have diff cell wall components and some other differences. That is all I had learned for Week 3, which is really new for me. I will further look into this topics to make myself more understand and know them.

History of life