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Unformatted text preview: today’s factoid • ‘Komodo dragon venom’ story posted in Biology in the News on BB • it was recently reported that instead of dying from bacterial infec;on as previously thought; prey that are bi>en die from poison, produced in specialized glands in the komodo dragon’s mouth • the poison prevents blood coagula;on – prey suﬀer blood loss and low blood pressure • death takes hours or longer h>p://www.dinosaurtypes.org/images/other_prehistoric‐creatures/ rep;les/komodo/komodo.gif – method enables komodo dragons to hunt and kill large prey Bio Portal and Prep U • these are for your studying purposes • there will be no Bio 201 assignments on these sites Final exam • Wednesday 12/16 from 5:15 – 7:45 PM • Loca;on – to be announced genomes have a lot of genes • where do they come from? • new genes are only very rarely “invented” – could be from puZng together pieces of previously exis;ng genes • many genes arise from duplica;on and diversiﬁca;on of pre‐exis;ng genes – gene families http://www.pnas.org/content/98/19/10763/F1.large.jpg Gene duplica;on 1 specia;on 1 Ancestral copy 2 1 Gene duplica;on SPECIES 1 1a SPECIES 2 2 • Genes 1 and 1a are paralogs of each other (paralogous) • Genes 1 and 2 are orthologs (orthologous) • Genes 1a and 2 are orthologs (orthologous) • All 3 genes are homologous to each other (less speciﬁc term) Evolu;on of gene families (#s are es;mated # of DNA sequence changes) What is a phylogeny? • Also called a phylogene/c tree • Illustrates the hypothesized rela;onships among a set of taxa (singular = taxon) More recent !me ancient Two cri/cal and longstanding pursuits • Taxonomy – systema/c naming and ordering of taxa • Systema/cs – science of classiﬁca/on and reconstruc/on of phylogeny Delimita/on, naming, iden/ﬁca/on Taxonomy La/n binomial Felis catus ‐always italicize Genus name Felis Speciﬁc epithet catus Delimita/on, naming, iden/ﬁca/on, classiﬁca/on Taxonomy Genus Felis Mephi*s Lutra Canis Delimita/on, naming, iden/ﬁca/on, classiﬁca/on Taxonomy Family Felidae Mustelidae Canidae Delimita/on, naming, iden/ﬁca/on, classiﬁca/on Taxonomy Memorize the taxonomic levels in order. All of these levels are taxa. Taxon is deﬁned opera/onally; depending on what level you are interested in. Delimita/on, naming, iden/ﬁca/on, classiﬁca/on Taxonomy animals Species/Species Genus/Genera Family Order Class Phylum / Division Kingdom Domain La*n binomial La*n ‐idae (highly taxon‐speciﬁc) (highly taxon‐speciﬁc) (highly taxon‐speciﬁc) plants ‐aceae ‐ales ‐opsida ‐phyta Phylogene/c Systema/cs Classification according to evolutionary relationships Phylogene/c Systema/cs Phylogene/c Systema/cs Phylogeny construc;on depends on iden;fying homologous characters Bird and bat wings are not homologous. They are homoplaseous (adj.; noun = homoplasy, homoplasies); i.e. they evolved independently BUT, their bones are homologous Two diﬀerent origins of similarity Homology Similarity due to common ancestry – Shared ancestral similarity – Shared derived similarity Homoplasy Similarity due to other reasons (independent evolu/on of similar traits) Similarity can be misleading: Homoplasy Similarity can be misleading: Homoplasy we are now quite certain that this phylogeny is correct therefore the four-chambered hearts of birds and mammals represent a homoplasy Phylogenies are based on shared derived characters • Shared, derived characters = “synapomorphies” salamander snake mouse human Amnio;c egg Mammary glands Assump;ons in building phylogenies • Characters are chosen such that – Derived traits only evolved once in the set of taxa under considera;on – No reversals (loss of a derived character) back to ancestral state • Outgroup is established as branching oﬀ earlier than all the other taxa – From independent data Phylogenies can be constructed from many types of characters/traits • • • • • Morphology Development/embryology Behavior Physiology Molecules – DNA and protein sequences Make sure you understand how this works ‐ - ‐ - ...
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- Fall '08