What is adaptation? Noun vs. verb (vs. acclimation) Noun: “…[A] feature is an adaptation for some function if it has become prevalent or is maintained in a population… because of natural selection for that function” (Futuyma, p.355) “… the good fit of organisms to their environment” (Gould & Lewontin, 1979) What adaptation is not: Necessary, perfect, progress, harmonious, moral BIOL E-127 – 9/24/07

Origin of life Definition?: Conditions of early earth?:

Origin of life Needed components of first organism?:

First metabolism? Oparin Ocean scenario:

First metabolism? Autocatalytic cycles (Kauffman): (Eigen, 1971)

First genetics? Ultimate chicken & egg… Potential answer?

How get enclosure, metabolism & inheritance together? One scenario: Lipid world (Segrè & Lancet)

Experimental protocells Multiple groups addressing plausibility (Szostak, Rasmussen, Deamer, Luisi) Example: RNA adsorbed to clay & encapsulated into myristoleate vesicles Can replication provide drive for enlargement? (Chen et al., 2004) (Hanczyc et al., 2003)

Early history of life Constrained by ~4.6 Gya age of planet (or not?) Types of evidence?

Chemical evidence of life Isotopic enrichment in organic matter Banded iron formations (BIFs) (Madigan & Martenko, 2006)

New metabolisms with O 2 Global analysis of potential of collective biosphere (Raymond & Segrè, 2006) (Raymond & Segrè, 2006)

Sedimentary textures Stromatolites

Fossil evidence of life Microfossils in stromatolites: (Schopf, 1983)

Fossil evidence of life Microfossils in stromatolites: (Schopf, 1983) Nostoc

Fossil evidence of life Microfossils in stromatolites: (Brasier et al., 2002 )

Fossil evidence of life Microfossils in stromatolites: (Garcia-Ruiz et al., 2003) (Schopf, 2002)

Fossil evidence of life?: ALH84001 (McKay et al., 1996)

Molecular fossil evidence of life Eryops OH FOSSIL SKELETON H carbon skeleton with modified stereochemistry membrane biochemical

Who is it from?

Example molecular fossil: steranes & hopanoids Extract & run on GC-MS Sterols are eukaryotic specific 2-methylhopanoids common in Cyanobacteria (Brocks et al., 1999; Summons et al., 1999)

Extra references Brock Biology of Microorganisms, Ch. 11 Brocks et al., Science 285: Hanczyc et al., Science Huber et al., Science 301: McKay et al., Science 273: Nisbet & Sleep, Nature 409: Raymond & Segrè, Science 311: Segrè et al., PNAS 97: Summons et al., Science 400: Smith & Morowitz, PNAS 101:

When: Wednesday Evening 6:00pm Where: Second floor lounge of Maxwell-Dworkin, 33 Oxford St. On the Harvard Campus Website: Sept 26 Irene Chen, Harvard University: Lipid vesicles during the origin of life