Notes 16

Where did life on Earth come from?

- Life emerged as a result of natural selection choosing for complex organic molecules (such as sugars and amino acids)

- If amino acids were stuck to clay, then they could have bonded to form chains of amino acids called proteins

- Organisms would also need a way to store information for making proteins. It is thought that RNA was able to store information and then build proteins.
- Another necessary component of life was a membrane that would surround and protect the molecules inside

What were the first forms of life on Earth?

- The first organisms on Earth were prokaryotic that used photosynthesis to produce food to be used for energy

- These primitive bacteria (known as cyanobacteria) have been found in rocks as old as 3.5 billion years

What is the endosymbiont theory? Why do many scientists accept it?

- The mitochondria and chloroplasts found inside of eukaryotic plant and animal cells were originally prokaryotic organisms that shared a mutually beneficial relationship with the ancestors of eukaryotic cells.

- The “mitochondria” and “chloroplasts” got protection in exchange for giving up some of the energy/food that was produced

- The evidence for the endosymbiont theory is that chloroplasts and mitochondria contain unique DNA of their own that is arranged in the same way as that in a prokaryotic cell. Also, chloroplasts and mitochondria are smaller like prokaryotes and divide in the same way as prokaryotes.

How do we know what we know about the origins of life on Earth? Describe the evidence that supports the theories that scientists currently accept.

- Miller and Urey did an experiment that recreated the conditions of early Earth and were able to produce many organic compounds including amino acids.

- The video clip from class today showed how scientists were able to recreate the conditions of early Earth and produce RNA nucleotides.