Biology 1202B Lecture Notes - Cyanobacteria, Reverse Transcriptase, Photosynthesis
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30 Apr 2012
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Lecture 1
Characteristics of Living Things:
o They are complex and highly organized
o They have the ability to take energy from the environment and change it from one form
to another
o They tend to be homeostatic – can regulate their body and other internal structures
o They respond to stimuli
o They reproduce
o They grow and develop
o They adapt and evolve in step with external changes in their environment
Drake Equation – calculates the probability of other planets having living civilizations in our
galaxy
Universe formed 15 billion years ago (Big Bang)
o Galaxies formed from stars, dust and gas
o Earth formed 4.6 billion years ago
o Oldest fossils formed 3.5 billion years ago
o Eukaryotic fossils formed 2.2 billion years ago
Cell Theory:
o All organisms are composed of one or more cells
o The cell is the smallest unit that has all the properties of life
o Cells arise only from the growth and division of pre-existing cells
Oparin/Haldane – organic molecules could be made in the absence of life
o Early atmosphere was a reducing atmosphere (no free oxygen)
o But, there was free hydrogen and hydrides (Ex: CH4)
o There was lots of energy from electric discharges in storms and solar energy (no ozone)
o Also, the Earth’s surface temperature was probably hotter than today
o These all allow lots of reactions to occur
Miller/Urey Experiment – simulated conditions similar to ones believed to be in the early
atmosphere
o Obtained urea, amino acids, nucleotides and formic/lactic/acetic acids
Panspermia – asteroids and comets could have brought organic matter to Earth
Amino acids changing to polypeptides could have occurred when dry or highly concentrated
monomers are heated
o Condensation reactions (when components of water molecules are removed) create
peptide bonds between amino acids or phosphodiester bonds form between
nucleotides
Polymers
o Polysaccharides (Ex: glucose)
o Proteins (Ex: amino acids)
o Nucleic acids (Ex: nucleotides)
Catalysts – speed up a reaction without affecting itself