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NSCI 1413 (15)
Lecture 9

NSCI 1413 Lecture 9: Classification

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Natural Science
NSCI 1413
Guy Robinson

The Three Domain Classification System ● Originally three kingdoms (Pre-1950s) ● Five kingdoms:​ Monera, Protista, Fungi, Plantae, Animalia, and Archaebacteria (1960s-1990s) ● Three domain system (DNA analysis):​ Bacteria, Archaea, and Eukarya (Today) Bacteria, Archaea, and Eukaryotes Feature Bacteria Arhchaea Eukaryotes Membrane-bound organelles Absent Absent Present Peptidoglycan in cell wall Present Absent Absent RNA Polymerase One type Several kinds Several kinds Introns Absent Present in some genes Present Antibiotic sensitivity to Inhibited Not inhibited Not inhibited streptomycin, chloramphenicol ● Domain Bacteria ○ All are single-celled prokaryote w/ no internal membranes ○ Some are anaerobes; some are anaerobes ○ Bacteria play a vital ecological role as decomposers ○ Many are pathogens ○ Bacteria play a vital role in genetic engineering (insulin-producing E. coli) ○ Some bacteria carry out conjugation ○ Have a thick, rigid cell wall containing peptidoglycan ○ Some carry out photosynthesis ○ No introns (no DNA processing) ● Domain Archaea ○ Unicellular ○ Prokaryotic ○ Includes extremophiles: ■ Methanogens:​ Obtain energy in a unique way by producing methane from hydrogen ■ Halophiles:​ Thrive in environments w/ high salt concentrations (ex: Great Salt Lake) ■ Thermophiles:​ Thrive in very high temperatures (ex: hot springs, deep sea thermal vents) ○ Introns present in some genes ○ No peptidoglycan ● Domain Eukarya ○ Superkindgom; contains four of the original kingdoms (protista, fungi, plants, and animals) ○ All organisms have a nucleus and internal organelles The Four Kingdoms of Eukarya​ ← Must have general knowledge on characteristics and know some organisms from each! Kingdom Characteristics Protista ● Includes widest variety of organisms, but all eukaryotes ● Includes organisms that do not fit into the fungi or plant kingdoms (ex: seaweeds and slime molds) ● Consists of single-celled and primitive multi-celled organisms ● Includes heterotrophs (amoeba and paramecium) and autotrophs ● Euglena are primarily autotrophic w/ red eyespot and chlorophyll ● Protozoans like amoeba and paramecium are classified by how they move ● Mobility by various methods (ex: pseudopods, cilia, flagella) ● Some carry out conjugation (primitive sexual reproduction) ● Some cause serious diseases (ex: amoebic dysentery and malaria) Fungi ● All are heterotrophs ● Secrete hydrolytic enzymes outside the body where extracellular digestion occurs; building blocks of nutrients are absorbed by diffusion ● Play a vital role as decomposers ● Cell walls made of chitin, not cellulose ● Yeast, mold, mushrooms Plantae ● All are autotrophic ● Some have vascular tissue (tracheophytes), some do not (bryophytes) ○ Mosses, ferns, cone-bearing and flower-bearing plants Animalia ● All are heterotrophic and multicellular ● Grouped into 35 phyla, most important being Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Mollusca, Arthropoda, Echinodermata, and Chordata ● Most reproduce sexually w/ a dominant diploid stage ● In most species, a small, flagellated sperm fertilizes a larger, nonmotile egg ● Monophyletic (all lineages can be traced back to a common ancestor) ● Traditionally classified on anatomical features (homologous structures) and embryonic development Evolutionary Trends in Animals ● Organisms began as tiny, primitive, single-celled organisms that lived in oceans ● The first multicellular eukaryotic organisms evolved ~1.5 billion years ago ● The appearance of each phylum represents the evolution of a new and successful body plan ○ ○ Specialization of tissues ○ Germ layers ○ Body symmetry ○ Cephalization ○ Body cavity formation Trends in Animal Development from the Primitive to the Complex From the Primitive To the Complex No ​symmetry or radial symmetry w/ little orBilateral​ symmetry w/ a head end and complex sensory apparatus sensory apparatus No​ cephalization Cephalization Two​ cell layers: Ectoderm and endoderm Three​ cell layers: Ectoderm, mesoderm, and (diploblastic) endoderm (triploblastic) No​ coelom Pseudocoelom to coelom No​ true tissues True​ tissues, organs, and organ systems Life in ​water Life on ​land​ and all modification it requires Sessile Motile Few​ organs, but​ no​ organ systems Many​ organ systems and ​much​ specialization ● Specialized Cells, Tissues, and Organs ○ Cell:​ Basic unit of life (ex: neuron) ○ Tissue:​ A group of similar cells that perform a particular function (ex: sciatic nerve) ○ Organ:​ A group of tissues that work together to perform related functions (ex: brain) ● Germ Layers ○ Main layers that form various tissues and organs; formed early in embryonic development (gastrulation) ○ Complex animals are triploblastic: ■ Ectoderm:​ Outermost layer; becomes skin and nervous system ■ Endoderm:​ The innermost layer; becomes viscera or digestive system ■ Mesoderm:​ Middle layer; becomes the blood and bones ○ Primitive animals are diploblastic​, having an ectoderm, endoderm, and mesoglea (middle glue) that connects the two layers together ● Cephalization—Development of a Head End ○ Along w/ bilateral symmetry comes a front end (anterior) and a back end (posterior) ○ Sensory apparatus and brain clustered at anterior end ○ Digestive, excretory, and reproductive are posterior ○ Enables animals to move faster in order to flee or capture prey more effectively ● The Coelom ○ Fluid-filled body cavity that arises from the mesoderm ○ Provides the space for elaborate body systems (major organs would not have evolved w/o a coelom) ○ Primitive animals (Porifera, Cnidaria, Platyhelminthes) are acoelomates, having three germ layers but only a digestive cavity ○ Nemotodes are pseudocoelomates, having a fluid-filled tube between the endoderm and mesoderm (pseudocoelom acts as a hydrostatic skeleton, ↑ effectiveness of muscle contractions) ● Protostomes and Deuterostomes ○ Coelomates divided into protostomes and deuterostomes ○ Protostomes:​ The first opening (blastopore) becomes the mouth ○ Deuterostomes:​ The second opening becomes the mouth and the blastopore becomes the anus Nine Common Animal Phyla ● Phlya are classified on the basis of embryonic dev← Meaning you must understand that, too! ● Porifera—The Sponges—Invertebrates ○ No symmetry ○ No nerves of muscles; are sessile ○ Filters nutrients from water drawn into the spongocoel ○ Only two cell layers, ectoderm and endoderm, connected by mesoglea ○ No true tissues or organs, but different types of cells ■ Choanocytes:​ Collar cells; line the body cavity and have flagella that circulate water ■ Spicules:​ Support cells (sponges are classified by the material making them up) ■
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