History of Life on Earth

• Where did life begins?

  1. Land - very unlikely; not enough oxygen, and UV rays are too strong.
  2. A SHALLOW POND - bit likely; since it's full of organic material and when evaporated, experiments cannot prove it.
  3. DEEP SEA VENTS - highly likely; DNA evidence survive on high temperature like in deep sea vents.
• Who conducted the Deep-sea vents experiment?

  Miller and Urey
• Miller and Urey prove that life begins on deep-sea vents using water cycle.
• sea + atmosphere = life "young" Earth
• Amino acids are complex organic compounds that are predecessors of life on Earth.
• Stromatolites: are "living" rock samples that scientists have discovered and dated up to 3.5 bya.
• Microfossils: fossils were thought to be minerals that live 3.5 bya but it is microbes found in Western Australia.
• The Earth is the only known planet with the existence of life, meaning it can provide the necessary ingredients and conditions for life to exist
• Life exists on Earth because of the favorable conditions it has
• Life is complex and not as simple as favorable conditions equaling existence of life
• Scientists narrow down into 3 probable places where life FIRST appeared on Earth: land, shallow pond, deep-sea vents
• Land is unlikely as a place where life first appeared due to lack of oxygen and strong UV rays
• A shallow pond is a bit likely as a place where life first appeared due to higher concentration of organic materials when evaporated
• Deep-sea vents are highly likely as the exact place of origin of life on Earth due to DNA evidence suggesting early life forms can survive in high-temperature conditions
• The experiment conducted involved Flask A representing the earth's primitive ocean, Flask B with methane and ammonia representing the primitive atmosphere, and connecting tubes representing water cycle processes
• Certain conditions such as heating/boiling of the primitive ocean and providing electricity from the power supply to create a spark were found to be important in the success of the experiment
• The experiment yielded amino acids and complex organic materials, showing that high chemical energy and heat are needed for such a process to take place
• Organic Compounds are molecules linked with life and developed through reactions between atmospheric processes and the watery area of Earth
• RNA is the resulting molecule when organic compounds self-assembled into a self-replicating molecule
• Development of the most likely earliest life form on Earth

  1. Organic Compounds developed through reactions between atmospheric processes and the watery area of Earth

  2. RNA resulted from self-assembly of organic compounds into a self-replicating molecule

  3. Pre-cells resulted when self-replicating RNA enclosed itself in a membrane

  4. Primitive Cells are pre-cells with improved function through evolution

  5. Modern Cell developed into a structure familiar today, a cell with a DNA genome
• The first classification of life form on Earth is bacteria or prokaryotes
• As oxygen levels on Earth increased, the next archetype of cells developed: The Eukaryotes
• Prokaryotes and eukaryotes

  Prokaryotes are simpler, eukaryotes are more complex and have more cell organelles
• Life adapts to existing conditions and changes and evolves through the process from the simplest to the most complex
• Life on Earth began most probably 3.5 billion years ago
• Stromatolites are rock formations dated up to 3.5 billion years old, showing layers of microbes and sediments
• Microfossils found in western Australia are fossils of microbes who lived 3.5 billion years ago
• Panspermia theory suggests life came from outside Earth and evolved in suitable environments like deep-sea vents
• Organic molecules are found on rocks from other celestial bodies like Mars
• Some bacteria can withstand radiation and stay dormant under low atmospheric conditions, suggesting they may exist anywhere in the universe
• Continental drift has influenced the distribution of organisms and greatly affected the history of life
• Continental mergers triggered extinctions and the separation of continents caused the isolation and diversification of organisms
• Plate tectonics, the movements of Earth’s crustal plates, are associated with volcanoes
• Separation of continents

  Caused the isolation and diversification of organisms
• Plate tectonics, the movements of Earth’s crustal plates, are associated with volcanoes and earthquakes
• Volcanoes can create opportunities for organisms, but volcanic activity can also destroy life
• Mass extinctions were followed by diversification of life-forms
• At the end of the Cretaceous period, many life-forms disappeared, including the dinosaurs
• Mass extinctions may have been a result of an asteroid impact or volcanic activity
• Every mass extinction reduced the diversity of life, but each was followed by a rebound in diversity