BISC 102 Lecture Notes - Lecture 4: Petrified Wood, Endosymbiont, Cyanobacteria

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No easy definition for “life”
Life: Carbon based membrane-bound structures (cellular) and controlled energy conversion
using ATP
The ability to reproduce with variation (ability to evolve or change)
Approximately 2 million species, thousands more are identified each year
Estimates that actually exist are 10 million to 100 million
99% of species are extinct
Geological Time Scale:
Important events in deep time include evolutionary novelty, adaptive radiation, mass
Evolution of sex
Early Earth: 3.5 billion years ago
First fossils
Very Low O2
Low to High modern diversity
Fossilization: Organic remains (ex. pollen, insects in amber, frozen)
Form in sedimentary rock
Accumulation of sand, silt, can bury dead organisms quickly and if oxygen is
low or absent, preservation is possible
Floodplains, lakes, ocean bottoms are good
Organic material compressed in carbon film (ex. leaf)
● Casts (ex. bark) and molds form from imprints of the original
● Permineralization: Occurs when the organism decomposes slowly and organic
material is replaced by minerals (ex. petrified wood)
Fossil Record:
Remains of organisms (Ex. Bones, teeth, shells, leaves, seed, wood)
Traces (ex. footprints, nests, eggshells)
Preservation: Potential is biased by many factors such as:
Hard vs soft parts
Aquatic vs terrestrial environment
Abundant vs rare species
Long-lived vs short lived species
Wide ranging vs restricted
Recent vs ancient
Prediction from Fossils: What will martians look like?
If life exists on Mars, Stromatolites likely fossils
Misinterpretation of Early fossils
Artifacts planted by devil
Non-Biological origin
Remnants of Noah's flood
Stromatolites (Fossils as evidence of Precambrian life): Sedimentary rocks structures built
by accumulation of sediment on bacterial mats
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