Biology 013

Topics: Gene, DNA, Evolution Pages: 75 (20091 words) Published: April 22, 2013
Chapter 25
Process of fossilization
·      Moving water can suspend sediment – inorganic particles ·      Moving water fills into still body of water
o   Sediment flats to the bottom
o   Forms a layer
o   More layers form with different compositions on the bottom of the lake or ocean ·      Living things in the ocean die and get buried in the sediments in the ocean ·      A lot of weight and pressure pushing down

·      The organic material is replaced by rocks – mineralization resulting in fossils ·      Fossils: representations of living things that used to exist ·      Ocean is not the only possibility for fossils to form o   Wind can move a lot of sediments as well

o   Water is ideal but not only possibility
·      Places that are dry land now may have been under water at some time ·      Water dries, erosion occurs etc. exposing the different layers of rock and uncover fossils ·      Mountains forming can uncover fossils as well

·      Gives a relative picture of time (this is older than something above it) 25.1 Conditions on early Earth made the origin of life possible ·      Origin of life
o   Oparin – Haldene Model
§  Steps
·      Assemble simple molecules into building blocks for complex molecules – need to make DNA ·      Assemble polymers that can store information and catalyze reactions ·      Add membrane and an energy source to make a living organism o   Miller-Urey experiment

§  Hypothesize what early earth would’ve been like
§  Put inorganic material in what you think early atmosphere is like and run electricity through it – to see spontaneous formation of life §  Evidence that inorganic materials to amino acids is possible o   Bacteria living in hostile environments

§  Extremophobes
§  Things living there were using a different environment that would normally be toxic o   People have found amino acids inside meteorites
§  First amino acids could have come from outer space
o   In a water environment, the bonds of amino acids and nucleotides break as fast as they’re assembled §  When in a clay and water environment, amino acids adhere to the clay and so the clay catalyzes their formation §  Evidence for spontaneous assemble into macromolecules

o   Life?
§  Store info (genotype)
§  Express info (phenotype)
·      The ribozyme
o   DNA needs protein, but protein needs DNA     ??? §  Chicken and the egg
o   Ribozyme – piece of RNA that catalyzes a reaction – functions like a protein, can make another one of itself §  May have been the first living things
§  RNA world hypothesis
o   Have not found a ribozyme that makes another copy of itself §  Big piece of the puzzle
o   Life is cellular – ribozymes to cells
o   Lipids in a water environment form a sphere spontaneously o   First kind of cellular life form – protobiont
o   A lot of evolutionary events had to happen before the first prokaryotic fossil 3.5 billion years ago o   All prokaryotic fossils before 2 billion years ago
o   Prokaryotes
§  Bacteria
§  Archaea
·      Heterotrophs
·      Autotrophs → cyano bacteria →Oxygen
§  Oxygen levels increase 2.2 billion years ago
o   Eukaryotes
§  Mitochondria have their own DNA (and chloroplasts)
§  Endosymbiosis – living together
§  Figure 25.9
§  Heterotrophs, instead of one eating the others lived together §  Compare DNA in mitochondria to bacteria and host nucleus, DNA in mitochondria looks closer to bacteria than host DNA ·      Support endosymbiosis

o   Single cell to multicellular
§  Opens the door for cellular specialization
§  600-700 million years ago
·      Could be back as far as 1 billion
§  Large multi-cellular (3 billion years)?
o   “Cambrian Explosion”
§  Boom in diversity
·      Chemical and physical processes on early earth, aided by the emerging force of natural selection, could have produced very simple cells through a sequence of four major stages: o   The abiotic synthesis of small organic molecules such as amino acids and nucleotides o   The joining...
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