A brief history of life

What does the history of the Earth look like if we condense it into a minute?

We start Week 1 by looking at Bugs, by which we mean microbes, single-celled organisms that are only visible down a microscope. Bugs come in three flavours:

1. Archaea: probably the most ancient form of life, these microbes have evolved to be able to live in some of the most extreme environments on the planet including boiling water and concentrated acid.
2. Bacteria: indistinguishable from archaea under the microscope, these bugs have very different biochemical pathways. There are more bacterial cells in and on your body than human ones!
3. Single-celled Eukaryotes: these include organisms such as yeast and amoebae. Biochemically these bugs are almost exactly the same as animals, plants and humans, which are all multi-cellular eukaryotes.

Both bacteria and archaea are classified as prokaryotes. The terms prokaryote and eukaryote refer to how DNA is arranged in cells. Prokaryotic life has been around for BILLIONS of years, during which time the way in which they have grown has literally changed the face of the planet.

In this video, Prof. James Chong discusses some of the challenges that microbial life had to overcome as Bugs conquered the Earth. Here are some questions to consider while you’re watching the video. We’d be happy to hear from you in the comments once you’ve watched the video.

• Apart from energy, what other critical requirements are there for life?
• Most metabolic processes are energy generating. What do you think is the most energy-expensive process in a cell?
• Can you identify three niches where you would find anaerobic microbes now?