Transcript HISTORY OF LIFE

Chapter 26: Origin of life
Figure 26.2 Clock analogy for some key events in evolutionary history
Unnumbered Figure (page 512) Evolutionary clock: Origin of life
Unnumbered Figure (page 512) Evolutionary clock: Prokaryotes
HISTORY OF LIFE
• Earth is 4.5 billion years old
• Oldest rock
– 3.8 billion years old
– Contains isotopes of carbon
• Oldest fossils
– 3.5 billion years old
– Stromatolites
• Banded domes of sedimentary rock
• Resemble layered mats of cyanobacteria today
– Probably photosynthetic but not the first life form
Figure 26.0x Volcanic activity and lightning associated with the birth of the
island of Surtsey near Iceland; terrestrial life began colonizing Surtsey soon
after its birth
Figure 26.1 Some major episodes in the history of life
Figure 26.3 Early (left) and modern (right) prokaryotes
Figure 26.4 Bacterial mats and stromatolites
Figure 26.3x1 Spheroidal Gunflint Microfossils
Figure 26.3x2 Filamentous cyanobacteria from the Bitter Springs Chert
ONE HYPOTHESIS
• CONDITIONS ON
EARTH
• Atmosphere had little
O2
• Intense
• Lightning
• Volcanic activity
• Meteorite bombardment
• UV radiation
• SCENARIO
• Abiotic synthesis of
organic monomers
• Abiotic synthesis of
polymers
• Formation of
protobionts
• Origin of hereditary
material
OPARIN & HALDANE 1920s
• Worked independently
• Postulated
• Conditions on primitive Earth favored
abiotic synthesis of organic material
• Atmosphere
– Contained less O2
– Less oxidizing than today’s
– More reducing than today’s
MILLER & UREY 1953
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Tested Oparin & Haldane hypothesis
Created early Earth conditions in lab
Atmosphere: H2O, H2, CH4, NH3
Added spark
Created organic material
Other labs have created
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All 20 AA
Some sugars & lipids
Purine & pyrimidine bases
ATP
Figure 26.10 The Miller-Urey experiment
ABIOTIC SYNTHESIS OF
POLYMERS
• Example: connecting amino acids (AA)
together to form proteins
• Occurred without enzymes
• Evidence
– Synthesis of protenoids
– Drip of sol’n of AA on hot sand or clay
– AA bonded together to form protein
– Zn and Fe ions act as catalysts
FORMATION OF
PROTOBIONTS
• Aggregates of abiotically produced molecules
with an internal environment different from
external
• First primitive “cells”
• Evidence
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Coacervates
Proteinoids
Microspheres
Liposomes
ORIGIN OF HEREDITY
• Genetic information made it possible to pass
along information for making new molecules
• Today: DNA  RNAProtein
• Originally: RNA  protein
• Support
– RNA acts as enzyme (ribozymes)
– Synthesized short segments of RNA in lab;
replicate short segments of RNA without enzymes
Figure 26.11 Abiotic replication of RNA
Figure 26.13 Hypothesis for the beginnings of molecular cooperation
MAJOR LINEAGES OF LIFE
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5 Kingdoms
Monera
Protista
Plantae
Fungi
Animalia
• Domains
– Bacteria
– Archaea
– Eukarya
• 5 proposed protist
kingdoms!!!
• Kingdom Plantae
• Kingdom Fungi
• Kingdom Animalia
Figure 26.15 Whittaker’s five-kingdom system
Figure 26.16 Our changing view of biological diversity