ps1_sol - Systems Microbiology 1.084J/20.106J PROBLEM SET#1...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Systems Microbiology 1.084J/20.106J PROBLEM SET #1 – Solutions Problem 1 a. Describe the different sorts of evidence for life’s appearance on the early Earth ~ 3.5 bya. The evidence for this phenomenon is isotopic record, rocks and microfossils, organic geochemical records, and molecular evolution.Microfossils exist that look as though they could be from cyanobacteria. Stromatolites have been formed from cyanobacteria and other algae binding sediment together forming ‘bio-layers’. Carbon isotope signatures from 3.4 billion year old mat-like structures suggest carbon dioxide fixation. The presence of stable carbon and oxygen isotopes also suggest bacteria were producing large quantities well before other oxygen-consuming organism were present. Molecular signatures, such as steranes and 2-methyl hopanes, only known to be produced by eukaryotes and cyanobacteria, respectively, have been isolated from extremely old rock. The presence of iron beds is another clue to the presence of bacteria changing the atmosphere over from mainly carbon dioxide to more nitrogen and oxygen. b. Which evidence seems most compelling to you, and why? Answers will vary. c. What dramatic change ~ 2.5 billion years ago has influenced biology on Earth ever since, and how did it happen? Great Oxidation event. Bacteria evolved that were capable of producing oxygen via photosynthesis, cyanobacteria. They pumped (and continue to pump) large amounts of oxygen into the atmosphere. Problem 2
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/11/2011 for the course BIO 20.010j taught by Professor Lindagriffith during the Spring '06 term at MIT.

Page1 / 2

ps1_sol - Systems Microbiology 1.084J/20.106J PROBLEM SET#1...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online