BIO 124 Lecture Notes - Lecture 8: Dna Replication, Stromatolite, Extremophile
21 Mar 2016
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Document Summary
Diversity and evolution: first cells were almost certainly prokaryotic, oldest microfossils are about 3. 5 billion years old. Carbon isotopic evidence higher levels of c-12 than other surrounding rock. Spectroscopic analysis indicating complex carbon molecules: stromatolites sedimentary deposits trapped by mats of microorganisms. Prokaryote characteristics: unicellularity no multicellular bacteria/archaea. Some form adhesive matrices or biofilm communities: variable cell size greater range than eukaryotes. As small as <1 micrometer, as large as 750 micrometers in diameter. Single circular chromosome only one exception (vibrio cholera) No nucleus just a nucleoid region that is not membrane bound. Plasmids genetic elements that can be transferred between prokaryotic cells (horizontal gene transfer) Simple cell structure no membrane bound organelles. Diverse metabolic systems chemotrophs, aerobic, anaerobic. Vibrios, comma shaped: some exist as single cells, others cluster together, membranes and cell walls. The cell walls of most archaea and certain bacteria are composed of protein or glycoprotein.
