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: BIOL E-127 – 9/24/0
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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.
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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 O2
• 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
EryopsOH
OH
OH
OH
FOSSIL SKELETON
H
carbon skeleton with modified stereochemistry
membrane biochemical
Who is it from?
Aquifex
Green sulfur bacteria
Cyanobacteria
Nitrospira
Purple sulfur bacteria
Gram positive bacteria
Green non-sulfurbacteria
Methanopyrus
Methanococcus
Methanosarcina
Halobacterium
Archaeoglobus
Thermoplasma
MethanobacteriumPyrococcus
Pyrobaculum
Thermoproteus
Sulfolobus
Desulfurococcus
Pyrodictium
Thermotoga
Microsporidia
Slime moulds
Ciliates
Plants
Animals
Fungi
Flagellates
Diplomonads
Archaea
Eucarya
Bacteria
rRNA tree modified after Woese
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. 11Brocks et al., 1999. Science 285:1033-1036.Hanczyc et al., 2003. Science 618-622.Huber et al., 2003. Science 301:938-940.McKay et al., 1996. Science 273:924-930.Nisbet & Sleep, 2001. Nature 409:1083-1091.Raymond & Segrè, 2006. Science 311:1764-1767.Segrè et al., 2000. PNAS 97:4112-4117.Summons et al., 1999. Science 400:554-557.Smith & Morowitz, 2004. PNAS 101:13168-13173.
When: Wednesday Evening 6:00pmWhere: Second floor lounge of Maxwell-Dworkin, 33 Oxford St. On the Harvard Campus Website: http://www.seas.harvard.edu/projects/weitzlab/squishy.html -------------------------------------------------------------------------------- Sept 26 Irene Chen, Harvard University: Lipid vesicles during the origin of life