27/9/15

This week the lesson was about History of Life. It was really an interesting topic because I didn’t learn it before and I like cell topic the most. I did wonder before how the first cell was formed and here’s the answer. There were inorganic compounds on Earth a few million years ago. They undergone chemical evolution to form organic compounds. After that, the organic compounds polymerized to form polymer and eventually formed RNA, protein and nucleic acid. RNA then evolved to form DNA. The first cell, protobiont is formed when a plasma membrane formed to separate the internal and external environment. Protobiont then metabolised to become prokaryote. Evolution occurred and eukaryote is formed. 

The evolvement of organic compound from inorganic compound is proven by Prebiotic Broth Hypothesis. Milley and Urey proved that when the ocean is heated by the Earth high temperature, the ocean vapourised to form water vapour. When they meet an external energy like lighting, organic compound in gases form are produced. When the Earth cooled down, the gases condensed and reacted with water to form amino acid. Moreover there were different types of organic gases that condensed and reacted with water to form different organic compounds. 

I learnt that there were 4 criteria for chemical evolution to occur which were little or no free oxygen, availability of energy source, availability of chemical building blocks and sufficient time. I was surprised that the Earth was once without oxygen as it is a crucial element for us to stay alive. However it did make sense that no organisms were present around 4 million years ago.

There was a SCL activity about arranging the words given to form the process of the formation of eukaryotes . Although I made a few mistakes when answering the question, I have learnt from my mistakes. I understood what I didn’t and I’m glad with the knowledge I gained. I like this topic so much!