Unformatted text preview: today’s factoid • • • • • 163 new species found in a recent expedi6on in the Mekong river of southeast Asia the river goes through 16 global ecoregions h?p://www.cnn.com/2009/TECH/ science/09/26/mekong.species/ Story posted in Biology in the News folder on Blackboard one species found was the khorat big‐ mouthed frog, Limnonectes megastomias, which preys on small birds and insects h?p://i2.cdn.turner.com/ cnn/2009/TECH/science/ 09/26/mekong.species/ art.mekong.03.wwf.jpg h?p://chinaview.ﬁles.wordpress.com/ 2007/01/mekong‐river‐map‐320x.jpg note • the original (s6ll posted as of Friday’s lecture) version of this lecture had two slides about the ﬁrst mid term last fall embedded in it – please ignore these • updated version will be posted soon more on extra credit assignment • TA John Waldron is in charge of this assignment – see e‐mail and oﬃce hours on BB Staﬀ info • see next slides for Blackboard pages • How to refer to papers – in bibliography (“Literature Cited”): • Helfenstein, F., Losdat, S., Pape Møller , A., Blount, J.D., Richner, H. 2010 Sperm of colourful males are be?er protected against oxida6ve stress. Ecology Le?ers 13: 213–222 – in text (Helfenstein et al. 2010) • You will need to provide the correct bibliographic reference in order to get full points • No revisions will be allowed student version of this page should look different -follow links to submit assignment do not submit .docx files use .doc, .pdf, .rtf, or .txt formats Earliest fossils Eukarya Bacteria Stromatolites ‐ structures formed by cyanobacteria‐like organisms h?p://www.usc.edu/dept/mda/180evolu6on/IMAGES/ Evolu6on of Earth’s ancient ecosystem • • • Marine photosynthe6c bacteria dominated the earth for 1‐2 billion years Before this 6me ‐ no oxygen in atmosphere Massive produc6on of oxygen for a very long 6me – Oxygenated the oceans – Oxidized (Fe2+‐>Fe3+) most of the iron on Earth (now mined as iron ore) – Then, increased percentage of oxygen in atmosphere Enabled the evolu6on of organisms with respiratory metabolism Current composi:on of Earth’s atmosphere • h?p://en.wikipedia.org/wiki/Earth's_atmosphere#Composi6on Eukaryotes appear in the fossil record 2.3 billion years [email protected] prokaryotes Earliest eukaryote Fossil ~1.2 bya Earliest prokaryote fossil ~3.5 bya The 3 domains of life • • • • Bacteria Prokaryotes Archaea Eukarya (Eukaryotes) All three have in common: – Glycolysis h?p://en.wikipedia.org/wiki/Glycolysis – – – – DNA replica6on mechanism Transcrip6on, transla6on, gene6c code Plasma membranes Ribosomes Diﬀerences between Prokaryotes and Eukaryotes • Prokaryotes do not have cytoskeleton • Prokaryotes do not divide by mitosis – They use binary ﬁssion • Prokaryotes do not have a nucleus • DNA is usually circular • Prokaryotes do not have membrane‐enclosed organelles (mitochondria, chloroplasts, Golgi apparatus) – But they can have infoldings of the plasma membrane for various func6ons • For diﬀerences between two domains of Prokaryotes, see table 26.1 – Don’t have to memorize these When did Prokaryotes originate? • First fossils • First fossil evidence of cellular life • Billions of years to adapt and diversify before Eukaryotes appeared – But there was already signiﬁcant diversity – 3.5 billion years ago (bya) >3 bya >2 bya Prokaryote success • Es6mated 3x1028 bacteria and archaea cells in the ocean • “The bacteria living in a single human intes6nal tract outnumber all the humans who have ever lived” (Life 8e, p. 563) • Found in just about all imaginable environments – Many extreme environments • Most are unicellular (but some mul6cellular forms known) • Large diversity, but three most common forms are: cocci, bacilli (rods), and helices Cell wall diversity in Prokaryotes • Chemically very diﬀerent from plant, algae, and fungal cell walls • A major method of classifying bacteria: Gram staining ‐ [purple dye followed by iodine, then alcohol wash and a red counterstain] An6bio6cs like penicillin and ampicillin interfere with pep6oglycan synthesis Bacterial cell well components are good targets for an6bio6cs. (why?) Some other Prokaryote features: movement Salmonella • Some species use ﬂagella (structurally diﬀerent from Eukaryote ﬂagella) • Other species – Axial ﬁlaments • Spiral movement a spirochaete – Gas vesicles • Up and down in water column a cyanobacterium Some other Prokaryote features: sex • Reproduc6on is asexual • But many species can – Binary ﬁssion undergo gene6c recombina6on – e.g. E. coli bacteria use a conjuga6on system – Bacteria can also take up DNA from the environment and some6mes use the sequences as func6onal genes h?p://www.textbookosacteriology.net/growth.html ...
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- Spring '08
- Biology, Office Open XML, circular • Prokaryotes, • • Marine, Bacteria Prokaryotes Archaea