The Fossil Record
How good is it?
Types of Fossils
Body Fossils - Remains of the whole body or parts of the body
Hard parts of the body are fossilized more readily than are soft however under the right kind of conditions soft tissues or their impressions can be preserved. In some cases (e.g. clam shells) the hard parts are preserved in their original condition. However more often the original fossil is altered. There are three basic modes of fossilization
Trace Fossils - Indirect Evidence of Past Life
Burrows, tracks and trails,
Bias in the Fossil Record
Since water is required for most types of fossilization organisms that live in the oceans or rivers tend to be preserved preferentially.
Mineralized body parts
Bones and shells preserve much better than do soft body parts. Hence we have excellent records for shelled marine invertebrates but poor ones for terrestrial invertebrates like insects (Insects make up 75% of all living animal species but less than 1% of fossil species)
When fossilization occurred - The pull of the Present
Relative Age - Based upon Stratographic position
Absolute Age Based on Radiometric Dating
Geological Time Scale
See Table 6.1
Yes you are expected to know them
The continents are not fixed they are moved by currents in the molten mantle
We can see the phenomenon of sea floor building in the mid-Atlantic and the effect of plates moving against each other in the action of the San Andreas Fault
The position of the continents has a major effect on the planetary climate. Central Pangaea was a very dry place.
The Present distribution of animals is in part a function of past continental drift
See Fig 7.22
See Fig 7.22
The Origin of Life
A quick review
Chemical Evolution 4550-3800? Mya
Abiotic synthesis of Monomers
Miller-Urey Experiment 1953
Polymerization of Organic Monomers
The RNA hypothesis
RNA nucleotides are concentrated in a saline solution they will self-assemble into an RNA polymer
3600- 2500 MYA
Tree of Life
The Earliest Living Things
What type of metabolism did the earliest forms of life have?
The oldest living things were simple prokaryotic cells which were heterotrophic and were anaerobic.
Types of Metabolism
Isua, Greenland 3800 mya
12C to 13C ration in graphite suggests that it originated via photosynthesis
Warrawoona, Australia 3550 mya
Stromatolites - indicative of a shallow tidal environment or highly saline environment
Fig Tree Chert, South Africa 3400mya
Surprisingly the cyanobacteria in Stromatolites used photosynthesis based on H2O evolved about billion years ago. The "Calvin Cycle" using NADPH and ATP from the non-cyclical photophosphorylation is much more efficient than the more ancient anaerobic pathway.
Ancient Bacterial Blooms
Banded Iron Formations - These were initially thought to be indicative of atmospheric O2 the discovery of a group of ancient purple, non-sulfur bacteria in 1993 has changed the interpretation.
These bacteria use dissolved iron carbonate as a carbon source.
Sewage Treatment Plants
Great Salt Lake, Dead Sea
Alkaline Lakes (pH 9.0)
Hot Springs (<80°C pH < 2.0)
Smoldering Gob Piles
Purple Bacteria - mainly anaerobes use H2S as an electron donor
Chemoautotrophic Proteobacteria - mainly nitrogen fixers e.g. Rhizobium
Chemoheterotrophic Proteobacteria - enteric bacteria e.g. E. coli and Salmonella
Spirochetes- chemoheterotrophs, include free-living species, pathogens and symbioints.
Spirosymplokos forms microbial mats
Treponema pallidum the cause of syphilis
Pillotonia found in the hind-gut of of wood eating cockroaches and termite
Cyanobacteria - have plant like photosynthesis although some are also capable of utilizing H2S in high sulfur conditions.
Entophysalis colonial form that still produce stromatolites.
Nostoc obligate symbioints with fungi to form lichen.
Synechococcus nitrogen fixers
Saprospirae - fermenting gliders
Bacteroides inhabit the human intestinal tract in large numbers anaerobes
Spirospira oxygen-respiring aerobes live in organic rich environments where they decay vegetation.
Chloroflexa - Green nonsulfur phototrophs
Chloroflexus thin filamentous photosynthetic bacteria - heat tolerant found in hot springs 40-70 C
Chlorobia - Anoxiygenic green sulfur bacteria
Chlorobium tolerant of very high and low temperatures or salinities, very intolerant of oxygen (use H2S as an electron donor)
Aphragmabacteria - mycoplasmas wall less eubacteria
Mycoplasma pnumoniae causes a type of pneumonia
Endospora - Endospore forming gram-positive bacteria
Bacillus anthracis - anthrax
Lactobacillus - lactic acid producing bacteria (found in milk)
Pirellulae - Protinaceous walled bacteria obligate intracellular parasites
Chlamydia - species responsible for a parrot transmitted disease in humans and with a trachoma type of blindness
Actinobacteria - gram positive bacteria
Streptomyces - anti-biotic producing species .
Deinococci -Radiation or heat resistant bacteria
Thermus aquaticus discover in hot springs in Yellowstone is the source of Taq polymerase. This DNA polymerase is the basis for PCR (Polymerase chain reaction) which is used to amplify DNA
Deinococcus can withstand a doses of up to 3,000,000 rads (500 is enough to kill a human most bacteria can be killed with 100 rads)
Thermotogae - thermophilic fermenters
A newly discover group of eubacteria in their own phylum. They are found to inhabit the hot vents at the see bottom they live at temperatures between 50 and 100°C and grow optimally at 80 C