Chapters 16-19: Diversity of Life
1. Taxonomic Classification 2. Viruses and Prokaryotes 3. Protists and Fungi
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