Life 103 Biology of Organisms Week 2
Life 103 Biology of Organisms Week 2 life 103
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This 5 page Class Notes was uploaded by Devrrae Russell on Friday September 2, 2016. The Class Notes belongs to life 103 at Colorado State University taught by Heather Baker Blackburn in Fall 2016. Since its upload, it has received 10 views.
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Date Created: 09/02/16
August 29, 2016 Life 103 Week 2 Phylogeny (continued) Practice maximum parsimony Some assumptions of cladistics approach: ● Characteristics of lineages change through time\ ● Any combination of groups shares a common ancestor ● Bifurcation pattern of descent ○ 2 lineages branch off at once Phylogenetic tree are hypotheses, not established facts ● Often revised ● Can use to make predictions about characteristics of related groups Molecular clocks allow us to estimate time since common ancestor ● Calibrate molecular clock use fossil record or samples to estimate average rate of mutation accumulation ● Estimates time since divergence when was there no difference ● HIV history has been studied through molecular clocks ○ Early common strain of HIV probably spread to humans between 1910 to 1950 Prokaryotes domains Archaea and bacteria ( concepts 2.6, 27.2) ● Based on rRNA sequences ● If this hypothesis is correct then Eukarya and archaea Different types of genes can yield different results ● Horizontal gene transfer non parental ○ Genes transferred between genomes without sexual reproduction ○ Most genes in prokaryotic genomes seem to have moved between species ○ Doesn't fit assumptions of phylogenetic tree ○ Eukaryotes can also experience hgt ■ Crown gall caused by agrobacterium tumefaciens ■ ⅓ chance of carrying genes from something like this (controversial) August 31, 2016 Phylogeny cont. How does HGT work? 1. Transformation uptake of foreign DNA a. SPontaneous or genetically engineered 2. Transduction phages (bacteriophages) carry prokaryotic genes between cells a. Inject genes from donor into recipient 3. Conjugation DNA transferred between 2 cells that are temporarily joined How do prokaryotic lineages evolve so quickly? Where does genetic diversity come from? ● In prokaryotes ○ Genetic recombination ○ Rapid reproduction and mutation Protists Eukarya ● Membrane bound organelles ● Well developed cytoskeleton ○ Often able to change shape ○ Often asymmetric or complex ● Animals plant and fungi ● Everything else? Protistits ○ Protists are polyphyletic Protists ● Mostly unicellular, but some colonial or multicellular ● Diverse life cycles, nutrition, morphologies, reproduction ● Sometimes informally ○ Plantlike protists ■ Photosynthetic ○ Animal like protists ■ Heteosynthetic ○ Fungi like protists September 2, 2016 Protists cont. Protists in clades: Excavata ● Cytoskeleton similarities ● Many have feeding groove ● Ex: Giardia i ntestinalis SAR Clades ● Common DNA sequences ● Ex: paramecium Unikonta ● Diverse related to fungi and animals ● Ex: Slime molds Invertebrates Kingdom animalia: ● Multicellular eukaryotes ● Heterotrophic ● No cell walls ● Most closely related to choanoflagellates ○ Morphological and molecular evidence ● Reproduction and development ○ Sexual reproduction, dominant diploid stage ○ Sperm fertilizes egg Reproduction 1. Zygote undergoes cleavage 2. Multicellular blastula forms 3. Blastula undergoes gastrulation, forming a gastrula 4. 2 layers are created, ectoderm and endoderm Invertebrates: Phylum Porifera ● Lack true tissues ● Water is drawn through pores into spongocoel; out through the osculum Phylum Cnidaria ● Include hydras, corals, and jellyfish ● Has true tissues ● Two tissue layers diploblastic ○ Gastrodermis derived from the endoderm ○ Epidermis derived from the ectoderm ● Two forms ○ Polyp hydra and coral ○ Medusa jellies ● Cnidocyte are specialized cells that bear nematocysts which are venomous barbs ● Two groups
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