Chapters 16-19: Diversity of Life 1. Taxonomic Classification 2. Viruses and Prokaryotes 3. Protists and Fungi 4. Plants 5. Animals 1. Taxonomic Classification The Classification of Organisms There are ~1.5 million known species on our planet. • total # or species on earth estimated to be anywhere from 7 to 100 million To study so many organisms and their evolutionary relationships requires: • standard nomenclature • same name used worldwide for a given organism • hierarchy, system of classification • allows organization by “relatedness” 1 The Taxonomic Hierarchy Each level of the hierarchy is referred to as a taxa: Humans Domain eukarya Kingdom animal Phylum chordates Class mammals Order primates Family hominids Genus Homo Species sapiens The Major “Taxa” The 3 Domains: Bacteria Archaea Eukarya 4 Kingdoms Protists, Fungi, Plants & Animals of Eukarya: Bacteria: • “common” prokaryotes Archaea (or archaebacteria): • “unusual” prokaryotes or “extremophiles” • thrive in harsh environments (acid, high salt, boiling…) Eukarya: • all organisms made of eukaryotic cells Protists: single-celled eukaryotes Fungi: multicellular; absorb food Plants: multicellular; photosynthesize Animals: multicellular; ingest food 2 2. Viruses and Prokaryotes Viruses are Small, Simple, Non-living Consist of genetic material (DNA or RNA) inside a protein coat (may have a membrane envelope). • no metabolic capabilities • reproduce only within a host • frequently “lyse” or kill host cell bacteria viruses euk. cell Viruses come in Immense Variety Differ in: • size & shape • genetic material • DNA, RNA, double or single strand • mode of infection • host specificity 3 AIDS Virus Infection The AIDS virus is a retrovirus: must convert RNA to DNA Types of Prokaryotes Prokaryotes = single-celled organisms lacking nuclei and other organelles Bacteria • live in every conceivable environment • immense variety of metabolism, physiology • play many essential biological roles • nitrogen fixation (all plants depend on it!) • decomposition (essential for recycling of nutrients) • digestion (gut flora in humans, cattle,…) Archaea • thrive in very extreme environments Prokaryotes come in 3 Basic Shapes spherical rod-shaped (bacillus) (coccus) corkscrew-shaped (spirillum) 4 3. Protists and Fungi Types of Protists Protists = most single-celled eukaryotic organisms • some can form multicellular aggregates • 2 basic types of protist: 1) Protozoa (“first animals”) • heterotrophs (ingest food) • amoebae, paramecia, zooplankton, trypanosomes • many are parasites • e.g., trypanosomes, plasmodium (causes malaria) trypanosomes 2) Algae (“photosynthetic protists”) • phytoplankton (dinoflagellates, diatoms, volvox) • “seaweeds” diatoms seaweed (kelp) volvox 5 The Fungi Types of Fungi include: • molds • yeast • mushrooms Key Characteristics of Fungi Fungi digest organic material externally (they don’t ingest food like animals do): • secrete digestive enzymes, absorb food • some are detritus feeders (consume dead matter) some are parasites (prey on living) • decomposition of dead organic matter is extremely important for ecosystems (recycles nutrients) Fungal cells have cell walls (made of chitin) Can reproduce sexually or asexually 4. Plants 6 What constitutes a Plant? Plants are multicellular, photosynthetic, and share characteristic modes of reproduction Major plant phyla, classes The Bryophytes Liverworts Mosses Key features: • lack true leaves, roots, stems • no internal vasculature • rely mainly on diffusion • limits their size The Tracheophytes Tracheophytes are the vascular plants: • contain vessels to transport material internally There are 3 basic types of vascular plant: • seedless vascular plants (e.g., ferns, horsetails) • gymnosperms (all “cone-bearing” plants) • angiosperms (all flowering plants) 7 Seedless Vascular Plants Horsetails Ferns • most primitive vascular plant Gymnosperms pine All “cone-bearing” plants: • conifers (pines, firs, etc…), cycads, gingko • seeds cycad produced in cones juniper (not flowers) gingko Angiosperms All flowering plants: • produce seeds* in flowers (via fertilization of gametes) • disperse seeds via fruits *seeds are plant embryos + nutrients within a seed coat • most dominant type of plant 8 5. Animals Invertebrates Vertebrates Characteristics of Animals All members of the Animal Kingdom: • are multicellular • consist of eukaryotic cells w/o cell walls • are heterotrophs • consume food derived from other organisms • feed by “ingesting” food • unlike fungi which “absorb” food externally Most members of the Animal Kingdom: • have a symmetrical body plan • radial or bilateral symmetry • have distinct tissues, organs • reproduce sexually Radial vs Bilateral Symmetry Radial Symmetry • symmetrical halves “no matter how you slice it” Bilateral Symmetry • only one plane of symmetry symmetry as viewed from the dorsal (back) or ventral (belly) sides 9 Vertebrate vs Invertebrate Vertebrate animals • have a backbone or “vertebral” column • less than 3% of known animal species Invertebrate animals • NO backbone or “vertebral” column • > 97% of known animal species • any “non-vertebrate” animal The vertebrate/invertebrate distinction is somewhat “old school” They more or less constitute “sub-kingdoms” Major Invertebrate Phyla “Lower” Invertebrates “Higher” Invertebrates Porifera Annelids • all sponges • all “segmented worms” Cnidarians Mollusks • anemones, coral, jellyfish • snails, clams, squids Platyhelminthes Arthropods • all “flatworms” • insects, spiders, crabs Nematodes Echinoderms • all “roundworms” • starfish, sea urchins The Phylum Chordata Main characteristics of the Chordates: • have a notochord • usu. gives rise to the backbone during development • have a hollow nerve cord • becomes brain & spinal cord during development • pharyngeal “gill slits” • may disappear during development • have a tail • may disappear during development ***All vertebrates are chordates but not all chordates are vertebrates*** 10 Major Chordate Classes Agnatha Reptiles • “jawless” fishes • lizards, snakes, turtles… Chondrichthyes Birds (Aves) • cartilagenous fishes • chickens, eagles… Osteoichthyes Mammals • bony fishes • humans, cats, dogs… Amphibians • frogs, salamanders… Key Terms for Chapters 16-19 • taxa, domain, kingdom, phylum… • bacteria, archaea, eukarya, fungi, protists • bacillus, coccus, spirillum • protozoa, algae • bilateral vs radial symmetry, vertebrate vs invertebrate Relevant Review Questions: ch. 16 – 3, 6; ch. 17 – 3, 5, 9 ch. 18 – 1, 3-5, 7-15; ch. 19 – 3 11.