This year the theme is life. My central organizing structure is the timeline of life on Earth. I plan to link all of the discussions of taxonomy, phylogeny and genetics to this timeline over the course of the year.

The timeline above will be the first lesson. As with these things the trick is deciding how much detail to keep in and how much to keep out.

What I like is that it gives the general overview of when important things happen while leaving a lot of space for students to investigate. Most of what we’ll be seeing this year happened in the Cambrian and this timeline conveys that this is a very small part of the whole history of life. In fact, it’s only when we cover the biochemistry of genetics that we will be talking about the origins of life.

The website Exploring Life’s Origins has a great timeline. It also has some really neat sections, with very useful videos, on the formation of protocells and the origin of RNA on the early Earth that lead to life as we know it.

The Magnetic Field?

The one thing I left out that I’m still conflicted about is the Earth’s magnetic field. Recent research indicates it has been around since 3.2 billion years ago and its presence or absence may have had profound effects on life.

Having a magnetic field protects the Earth from the charged particles spewing out of the Sun, the solar wind. This makes life on land a lot easier since the solar wind’s particles are quite damaging to DNA. However, prior to the magnetic field forming all this damage to DNA may have also accelerated mutation and thus evolution.