BIOL 213 - The History of Life

What was in early Earth's atmosphere?

Primarily volcanic with hydrogen sulphide, methane, and carbon dioxide

Earth originally had no oxygen, meaning it was in a _________ state

Reduced

Oxidation, in early earth, was prevented by...

The removal of oxygen, and other oxidizing gases or vapours

How was energy inputted in early earth?

Lightning, transforming organic compounds into 'primordial soup'

What was the Urey-Miller experiment?

A chemical experiment that simulated the conditions thought at the time to be present on the early Earth, and tested the chemical origin of life under those conditions.

First attempt at simulating ancient Earth conditions.

It showed that 2% of carbon was in amino acids, therefore showing that lightning can be used to catalyze complex molecules.

Vent communities and Earth's early atmosphere- how do they relate?

There are still pockets of reducing environments in the deep oceans, where sulphur bacteria/thermophiles may habitat. Vent communities might provide a model for the early evolution of life due to this.

Where were the first prokaryotes found?

Stromatolites, where cyanobacteria form a biofilm that traps layers of sediment. Atmospheric dust eventually weighs it down and sinks.

Why do stromatolites decline in abundance in fossils?

Because of the increase of chemicals eating, therefore biofilaments cannot build up

What started the great oxygenation event?

Cyanobacteria, using an early form of photosynthesis, changing sunlight energy into chemical energy (oxygen)

What did the great oxygenation event do?

It converted the early educing atmosphere into an oxidizing one, allowing for more reactions to happen. This changed the composition of life on Earth, stimulating biodiversiy

What are some pieces of evidence for the great oxygenation event?

Banded iron formations, and major changes in the number of rock types formed (hydrated and oxidized minerals)

Why did it take so long for the great oxygenation event to occur?

There could have been a long period of anaoxygenic photosynthesis, and the oxygen may of reacted with ocean chemistry first. The ocean may have needed to be abundant in oxygen before oxygen could go into hte atmosphere

Where did the first eukaryotes comes from?

Endosymbiosis, where an archaea and bacteria formed together to form a eukaryote?

What are some pieces of evidence for endosymbiosis?

Organelles within the mitochondria and plastids have a similar composition to prokaryotes (bacteria). Similar circular DNA, similar RNA sequence and reproduction via pinching (similar to binary fission)

What are some characteristics of the Cambrian explosion?

The rapid appearance of many groups of organisms, small shell parts forming, and features like heads, mouths, eyes, legs forming

Why did the Cambrian explosion happen?

Due to the increasing levels of oxygen, along with the evolution of grazing, reduction of algal mats, opening new niches. There was also a shift in ocean chemistry favouring the production of calcium carbonate (allowing for shells)

What are some key characteristics of mass extinctions?

They are periodic, and allow for new niches to open. Out of mass extinction, evolving generally outweighs the amount of extinctions