BIOEE 1780 Notes 2/13-2/17
BIOEE 1780 Notes 2/13-2/17 BIOEE1780: Evolutionary Biology
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This 2 page Class Notes was uploaded by Carly Siege on Wednesday February 17, 2016. The Class Notes belongs to BIOEE1780: Evolutionary Biology at Cornell University taught by Dr.Sarvary in Spring 2016. Since its upload, it has received 16 views. For similar materials see Biology: Evolution and Biodiversity in Biological Sciences at Cornell University.
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Date Created: 02/17/16
Pre-Lecture Unity of Life Even though we will be focusing throughout the semester on diversity of living organisms, I will start by discussing the unity of all living organisms. These characteristics are ancestral traits, but they comprise so many types and are so fundamental to the nature of all organisms, that there can be little doubt that the life we study had a single shared origin called LUCA – the Last Universal Common Ancestor. Molecular characters All organisms use nucleic acids, RNA or DNA, as hereditary material. All share the same genetic code. ! All use similar molecules (proteins) as enzymes. Shared biochemical pathways are found from E. coli to elephants. Cellular characters All organisms are composed of cells. Viruses have originated many times and represent escaped genomic components or have evolved from degenerated cellular organisms. Thus, they are derived from the Tree of Life (TOL), however, they are so diverse (and degenerated) there is no time to cover them in class. Cells are composed of the same basic elements (cell components). Diversity and the Tree of Life Overall diversity of species on Earth. “The Big Six” model organisms can represent the diversity in the TOL….or not. The ~140 taxa that we will learn. The ranks we won’t learn. Framing diversity in a phylogenetic context. LUCA By working backwards through the TOL and including larger and larger nested sets, we can determine many of the characteristics of the Last Universal Common Ancestor, LUCA, of all living organisms. This does not mean that LUCA was the ﬁrst living organism. Why not? Lecture Neutrally evolving DNA is much more prone to ILS (incomplete lineage sorting) than DNA under selection. Over time selection removed old alleles from species metabolism, reproduction, maintaining homeostasis, cells maybe respiration LUCA Last Universal Common Ancestor Molecular Characteristics used nucleic acids, RNA, DNA and hereditary material used same triplet genetic code for amino acids used similar molecules (proteins) as enzymes used similar biochemical path ways for energy (ATP) Cellular characteristics had a plasma membrane made of glycerol and fatty acids unicellular and lacked organelles the oldest known sedimentary rocks were 3.7 bya - we use old rocks to make the tree of life Tree of Life Archaea Eukarya Bacteria Loki: a staggering, confusing and ambivalent ﬁgure who has been the catalyst of countless unresolved scholarly controversies Viruses - share “life” with nucleic acid, genetic code but don’t metabolize and are dependent on hosts - viruses are mixes of genes pasted together from higher organisms - frequently swap genes between each other (horizontal transfer) Pre-Lectures Prokaryotes consist of archaea and bacteria oldest lineages of life forms on earth in terms of abundance, they’re the most successful organisms on the planet means “before the nucleus" oldest form of life evolved only a billion years after the earth formed makes paraphyletic group unicellular but capable of making large colonial groups called bioﬁlms diﬀerent from eukaryotes organization of genetic material lack of cytoplasmic organelles reproduce with binary ﬁssion (as opposed to eukaryotes who use mitosis) convenient form of asexual reproduction capable of lateral (horizontal) gene transfer the exchange of genetic information without reproduction clouds the phylogeny between the there domains of life because it can pass genes to other species could mean that LUCA was a community… Lecture Prokaryotes Common Shapes describes the shared ancestral attributes of bacteria and archaeans. lack a nucleus and membrane-bound organelles, such as mitochondria and chloroplasts archaeans are more closely related to eukaryotes than to bacteria, thus the grouping “prokaryotes” does not represent a monophyletic group Bacteria and archeans have extremely limited morphological diversity. cocci (spherical) bacilli (rod shaped) spirilla (spiral shapes) Diverse Nutritional Metabolism Photoautotrophs: high levels of atmospheric oxygen is due to cyanobacteria or chloroplasts Chemoautotrophs: most known bacteria are these critically important decomposers Prokaryotes Reproduction reproduce through binary ﬁssion lack of genetic variation is ok for a stable environment conjugation, a genetic exchange between two individual, separate from the process of reproduction individual with F factor DNA in a plasmid enable conjugation with the individual lacking the plasmid one strand of DNA is passed through the plus then both are replicated adaptive genes can spread rapidly through populations Archaea extremophiles: live in the most extreme environments on earth ﬁx C02 anaerobically using methanogens (making methane from C02 and contributing to global warming) Halophiles: a kind of archaea that is very resistant to salty habitats carotenoid pigments which make them pink called Acidophiles they have branched membrane lipids (MAIN SYNAPOMORPHY!) Bacterial Cell Walls Contain Peptidoglycan can either be part of the cell wall (gram positive) or be between layers of the outer and inner membrane (gram negative) is determined with a Gram stain used to diﬀerentiate taxa, although it does not produce completely monophyletic groupings. Spirochetes spiral (helical) shape swim in corkscrew motion syphilis and lyme disease Chlamydias very small all are obligate parasites most commonly sexually transmitted disease elementary and reticulate bodies Cyanobacteria aka blue green bacteria oxygenic photoautotrophs extensive internal membranes that can hold chlorophyll Proteobacteria metabolically diverse E coli, salmonella
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