wFZCY

Pop Quiz How old is the universe? How old is the earth? When did life start on earth?

This dude has just been told that 4.5 billion years ago the earth was just a giant rock and then 1 billion years later life had begun. He just doesn’t believe it. Can you design an experiment that could show him that it is at least theoretically possible?

Your Experiment You will need some information in order to begin designing your experiment. What might you need to know?

How will we define something as living?

What you need to know Four Processes Needed for Life on Earth 1.Non-living synthesis of simple organic molecules 2.The assembly of such molecules into polymers 3.The origin of self-replicating molecules – what molecules might this be? 4.The packaging of these molecules into membranes. – Why is this important? – What molecules would form membranes?

So WHERE on earth might this have occurred? Four Processes Needed for Life on Earth 1.Non-living synthesis of simple organic molecules 2.The assembly of such molecules into polymers 3.The origin of self-replicating molecules 4.The packaging of these molecules into membranes.

Volcanoes They spew water vapour, gases and various minerals. Maybe the hot conditions could favor the formation of organic compounds?

Deep-Sea Hydrothermal Vents Hot water escapes from the vents and they are nutrient rich. This may catalyse the formation of organic compounds. We know bacteria can survive in these environments so it shows life is possible

Comets may have delivered water and organic compounds to the Earth. We know that the Earth was bombared with comets around 4 billion years ago. We also know comets today have been found to contain organic compounds. It is possible that ife on Earth originated in Space – this theory is known as panspermia Extra-Terrestrial Locations

Four Processes Needed for Life on Earth 1.Non-living synthesis of simple organic molecules 2.The assembly of such molecules into polymers 3.The origin of self-replicating molecules 4.The packaging of these molecules into membranes. RNA RNA is the best candidate for the first self- replicating molecule. Why is DNA not a suitable candidate?

Four Processes Needed for Life on Earth 1.Non-living synthesis of simple organic molecules 2.The assembly of such molecules into polymers 3.The origin of self-replicating molecules 4.The packaging of these molecules into membranes. Experiments have shown that when clay dries out and is heated, as many as 200 amino acids can join together to form a polypeptide. In the right conditions, these polypeptides (proteins) can form little microspheres. If these microspheres surround another polymer than you have a significant step towards life.

Do you know anything that resembles the structure we’ve described? (Genetic material surrounded by a protein coat)

Lipids can do a similar thing as the amino acids – i.e. come together to form a kind of membrane capsule surrounding the RNA. This protects the genetic material from the destructive external environment. We call the precursors of life: PROTOBIONTS Over time true cell membranes could have evolved and then other characteristics of life may have evolved too.

0.7 billion years later… Prokaryotes evolved!