Biology 1002B Lecture Notes - Alanine, Homochirality, Rna World

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18 Apr 2012
Cell Biology & Origin of Life (2.1-2.4)
Seven Characteristics of Life
Display Order
o Arranged in a highly ordered manner
o Cell: fundamental unit of life
Harness & Utilize Energy
o Acquire energy from the environment and use it to maintain state
o Have the ability to make more of their own kind
Respond to Stimuli
o Can make adjustments to their structure, function and behavior in
response to changes to external environment
Exhibit Homeostasis
o Regulate internal environment so that conditions stay relatively constant
Growth & Development
o Increase their size by increasing the size/number of cells
o Populations change over generations to become better adapted to the
The Fundamental Unit of Life
Cell Theory
o All organisms are composed of one or more cells
o The cell is the smallest unit that has the properties of life
o Cells arise only from the growth and division of preexisting cells
(Age of Earth)
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Last Universal Common Ancestor
Evidence (things common to all life):
o Lipid membranes
o Genetic system based on DNA
o Reproduction
o ETC ATP & Glucose
o Linear movement of information from DNA to RNA to Protein
o Common system of protein assembly: ribosomes, mRNA, tRNA
o Cytoplasm
Bacteria and Eukarya used to be grouped together as prokaryotes.
Earliest Life
Life evolved within 600 million years, pretty fast on a geological stage, especially
given that the earth had to cool down.
Stromatolites dated to 3.5 billion years ago represent the earliest fossil evidence
of life
Layered rock that is formed when microorganisms bind articles of sediment
together, forming thin sheets
Formed by cyanobacteria modern posses a sophisticated metabolism
The fact that we have stromatolites from 3.5 billion years ago means that there
must have been life back then.
Panspermia is the hypothesis that very simple forms of life are present in space
and seeded the earth soon after it cooled
Stages of Prebiotic Evolution
So what do you need?
o Abiotic synthesis (in the absence of biology); Ability to produce sugars,
amino acids, etc outside of living cells, in the environment
o Heritable InformationSomething to pass on the information in the cell
o Formation of Cells
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