lecture three Flashcards
13.7 billion years ago
big bang
4.6 billion years ago
solar system and the earth
4.5-3.6 billion years ago
Heavy bombardment : gravity pulled debris in its vicinity in, kinetic energy of these things when they hit earth (and became heat) vaporized all surface water. As it ended, rain and earth cooled.
3.7 billion years ago
oldest “suspected” fossils
3.5 billion years ago
some of oldest rocks found in Australia, showing area was underwater - stromatolites with oldest known fossils - possible fossilized microbes - circular deposits
¼ Billion years ago
- first Dinosaurs
6 million y/a
- Hominids appear
reducing conditions of the atmosphere- Why is that significant for the development of life on earth?
Reducing atmosphere/ energy sources allowed formation of simple organic compounds - A reducing atmosphere would have very little oxygen. The organic compounds that were created in this atmosphere would have been oxidized and destroyed by oxygen or other oxidizing agents, so the reducing conditions allowed for the formation of simple organic compounds using light as energy - these organic compounds were sugars and amino acids
Why was there no Oxygen in the atmosphere?
there were no autotrophs breaking down CO2 and water and forming glucose and molecular oxygen, however there was oxygen in other molecules
What was the basic set-up for the Miller-Urey Experiment
Set up: a water cycle where water was heated, and recondensed in what they believed was early earth’s atmosphere - ammonia, methane, H, H2O vapor. Cycle was hit with electric shocks (lightning may have been an energy source).
Miller-Urey Experiment and what sorts of results did they find?
water turned pink over a few weeks: found that the combination had created Adenine and Glycine (amino acids)
These amino acids were old, meaning that they were coded for in the last universal common ancestor.
No macromolecules or nucleotides created - next question to be answered was how this could occur
Important: these molecules were created abiotically
Issues: now do not believe that the atmosphere looked the way Miller -Urey thought - What do we say it is now?
Replication first
genes came first
Leslie Orgel suggested life started out of RNA, not DNA or proteins.
Thomas Cech discovered that RNA could itself cut strands of RNA, suggesting that life might have started as RNA.
metabolism first
proton gradient were an essential part of metabolism. Life must have started where there was a natural proton gradient.
Russel and Martin found that the rocks of alkaline vents were porous and continued pockets of water that also contained essential chemicals. These essential chemicals
integrated with the proton pumps to begin metabolizing and therefore started to make molecules like RNA. The pocket of water would eventually create its own cell and escape the porous rock into the ocean where life will begin.
Compartmentalism first
need a shelter to contain replication/ metabolism
szostak combined clay and magnesium into protocells. Protocells would
began to incorporate other fatty lipids into themselves to expand. Once the protocell began to grow, it would elongate and end up shattering into other fragments called daughter protocells. This daughter cell will contain RNA from the parent cell
