AND NOW FOR A BRIEF INTRODUCTION TO: THE HISTORY OF LIFE FUNDAMENTAL CHARACTERISTICS OF LIFE Energy acquisition and utilization --- metabolism, growth,
behavior. Information storage --- presence of a genome that specifies a phenotype. Reproduction --- ability to produce progeny of the same type. EVOLUTION BY NATURAL SELECTION ability to change in ways that improve capabilities of energy acquisition, survivorship, and reproduction.
Deciphering the Earliest History of the Earth: Zircon Grains Radiometric dating estimates the age of the earth at 4.56 BY
From: Halliday 2001 Nature 409:144-145 ORIGIN OF THE MOON MOON EARTH
EXTRATERRESTRIAL ORIGIN OF LIFE??? PANSPERMIA Murchison Meteorite
SUGARS FOUND IN THE MURCHISON METEORITE From: Cooper et al. 2001 Nature 414:897-883 EVIDENCE OF LIFE ON MARS? Are these biological microfossils?
From: MacKay et al. 1996 Science SURFACE OF EUROPA SURFACE OF ENCELADUS
Life on the moons of Jupiter or Saturn? Oparin-Haldane Model BIG UNANSWERED QUESTIONS IN ORIGIN-OF-LIFE RESEARCH How did the primordial soup acquire the simple monomeric
building blocks essential for the production of information bearing polymers? What conditions are necessary for the initial(pre-biotic) assembly of such polymers? Can a polymer be produced that is capable of self-replication as well as information storage? How did compartmentalization, necessary for self-recognition during
replication and for the diffusion of gene products, evolve? Which came first---DNA, RNA, protein, or something else, or did complex systems involving all of these emerge simultaneously? Urey Miller Experiment 1952: Demonstrated that many of
the compounds necessary for life could be produced in a pre-biotic atmosphere.
H2CO - Formaldehyde HCN Hydrogen Cyanide Amino Acids Urea REACTIONS IN THE IRON-SULFER WORLD:
DEEP-SEA THERMAL VENTS: Support a diverse fauna completely dependent on hydrogen sulfides. ASSEMBLY OF AN INFORMATION BEARING POLYMER: PROTEINS FIRST?
Strong points: Easy to synthesize amino acids under a variety of conditions and polymers can also be formed. Even small peptides can exhibit catalytic activity. 20 amino acids provides for high information content. Weak points: Globular structure and lack of complementarity
preclude self-replication. Modern proteins can not function without DNA. ASSEMBLY OF AN INFORMATION BEARING POLYMER: AN RNA WORLD? Strong points: RNA has some catalytic properties (self-splicing
introns). RNA is capable of making proteins (Noller 1992). Weak points: RNA lacks the ability to self-replicate. A DNA WORLD? DNA is almost completely lacking in catalytic ability
EVOLUTION OF EARLY LIFE FORMS CURRENT TIME EXTINCT LINEAGES COMMON ANCESTOR OF ALL LIFE ON
EARTH CENANCESTOR ORIGIN OF LIFE ORIGIN OF EARTH
If the theory (of evolution) be true it is indisputable that before the Cambrian stratum was deposited long periods elapsedand that during these vast periods the world swarmed with living creatures (However), to the question why we do not find rich fossiliferous deposits belonging to these earliest periodsI can give no
satisfactory answer. The case at present must remain inexplicable. Charles Darwin 1859 RECONSTRUCTING LUCA Last Universal Common Ancestor
The properties of LUCA have been difficult to reconstruct given the extremely long time periods involved. Whole genome sequences of diverse prokaryotic lineages reveal ~60 universal genes. Far short of the ~600 genes it is estimated are required for a minimal set in a functioning organism. Extensive gene shuffling through horizontal transfer may make it impossible to deduce the properties of LUCA.
Hyperthermophiles seem to at the base of the phylogenetic tree. Number of Predicted Genes from 244 complete bacterial and archaeal genomes
Smallest free living organism Giovannoni et al. 2005 Science 309:1242-1245 More of a network than a tree.
CAPTURE OF ORGANELLE GENOMES Ancient prokaryotes from Western Australia. Filamentous Cyanobacteria
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