Tag: origin of life

Asteroids: The Origin of Life?

The … organic materials in [some] meteorites probably originally formed in the interstellar medium and/or the solar protoplanetary disk, but was subsequently modified in the meteorites’ asteroidal parent bodies. … At least some molecules of prebiotic importance formed during the alteration.

Herd et al., 2011: Origin and Evolution of Prebiotic Organic Matter As Inferred from the Tagish Lake Meteorite

Amino acids are the building blocks of life as we know it. They can be formed from abiotic (non-biological) chemical reactions (in a jar with electricity for example). It’s been known for a while that amino acids can be found on comets and asteroids, but now this fascinating article suggests that a lot of the chemical reactions that created these precursors to life happened on the asteroids themselves. Then when the asteroids bombarded the Earth, the seeds of life were delivered. More details here.

Leonid meteor shower seen from orbit. Image credit: BMDO/APL via NASA JPL.

This, of course, is just one of several hypotheses about the origin of life on Earth: livescience.com outlines seven.

Life in Four Domains

The four domains of life, according to Boyer et al. (2010).

This wonderful, impressionistic image shows representatives of the three domains of life and large viruses, the proposed fourth.

This figure represents the living species in the four small pictures according to the current classification of organisms: eukaryotes (represented by yellow cell), bacteria (represented by green cell), Archaea (represented by blue cell) and viruses (represented by magenta colored Mimivirus).

— Boyer et al. (2010): Boyer M, Madoui M-A, Gimenez G, La Scola B, Raoult D (2010) Phylogenetic and Phyletic Studies of Informational Genes in Genomes Highlight Existence of a 4th Domain of Life Including Giant Viruses. PLoS ONE 5(12): e15530. doi:10.1371/journal.pone.0015530

Carl Zimmer has an excellent piece in Discover Magazine that summarizes the research, and sets out the new tree of life. Particularly important, is the fact that viruses can transfer genes with each other. The other domains tend to mix their genes during reproduction.

Toilet Paper Timeline of Earth History

Image from Wikimedia Commons.

Jennifer Wenner has posted a beautiful demonstration of geologic time using toilet paper for the timeline at SERC. You’ll need a 1000 sheet roll and by the time you’re done there will be toilet paper everywhere.

This is a great demonstration because as you unroll the toilet paper you get a great feel for the long spans of time in the preCambrian when nothing much happens, and then, as you approach the present, events occur faster and faster. There’s 300 million years between the formation of the Moon and the formation of the Earth’s atmosphere. That’s 60 sheets! while modern man only turns up about 10,000 years ago, which is 0.002 sheets; about the width of the line drawn by a pen. Even the dinosaurs went extinct only 14 sheets from the end.

The SERC webpage has a spreadsheet with most of the important dates marked and translated into toilet paper units. The Worsley school in Canada has some nice pictures of the toilet paper being rolled out all the way down the hall.

History of life on Earth timeline (from NASA).

Origin of life lab

ENSI has a set of great labs that can be used all the way from the middle school to the university level. They deal with the nature of science, the origin of life, evolution and genetics/DNA. (Thanks again Anna Clarke for the link.)

Amoeba (image from Wikipedia). This image is part of a neat video of amoeba movement.

I’m thinking that the Creating Coacervates lab, the only one on the origin of life section, might fit into my orientation cycle plans. Coacervates are small, microscopic blobs of fat (lipids) that look like, and have many of the same properties as cells, amoebas in particular. They can be produced with simple chemicals. One of the key things I’d like to start the year with, is the idea that:

complex life-like cell-like structures can be produced naturally from simple materials with simple changes. Flammer, 1999.

These abiotic blobs can be compared to the protozoans in a water droplet sample while we learn how to use the microscopes. It also ties into the Miller–Urey experiments that produced amino acids using electricity and simple compounds: water, methane, ammonia and hydrogen gas. The Miller-Urey experiments will pop up later when we read Frankenstein.

Timeline of life

Timeline of Life on Earth.

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.

From the Exploring Earth's Origins website.

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.

The Earth's magnetic field protects us from the solar wind. Image from NASA.

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.