Environmental Problems, Their Causes, and Sustainability 1

A PPENDIX 4CLASSIFYING AND NAMING SPECIESHow Can Species Be Classified? Biologistsclassify species into different kingdoms,on the basis of similarities and differencesin characteristics such as their (1) modes ofnutrition, (2) cell structure, (3) appearance,and (4) developmental features.In this book, the earth’s organisms areclassified into six kingdoms: eubacteria,archaebacteria, protists, fungi, plants, and animals.Most bacteria, fungi, and protists aremicroorganisms: organisms so small theycannot be seen with the naked eye.Eubacteria consist of all single-celled prokaryotic(Figure 4-3, left, p. 58) bacteria exceptarchaebacteria. Examples are variouscyanobacteria and bacteria such as Staphylococcusand Streptococcus.KingdomPhylumSubphylumClassOrderFamilyGenusSpeciesSpeciesAnimalia Many-celled eukaryoticorganismsChordata Animals with notochord (along rod of stiffened tissue), nervecord, and a pharynx (a muscular tubeused in feeding, respiration, or both)Vertebrata Spinal cord enclosed in abackbone of cartilage or bone;and skull bones that protect the brainMammalia Animals whose youngare nourished by milk produced bymammary glands of females; andthat have hair or fur and warm bloodPrimates Animals that live in treesor are descended fromtree dwellersArchaebacteria are single-celled bacteriathat are evolutionarily closer to eukaryoticcells than to eubacteria. Examples are(1) methanogens that live in anaerobic sedimentsof lakes and swamps and in animalguts, (2) halophiles that live in extremelysalty water, and (3) thermophiles that live inhot springs, hydrothermal vents, and acidicsoil.Protists (Protista) are mostly single-celledeukaryotic organisms such as diatoms,dinoflagellates, amoebas, golden brown andyellow-green algae, and protozoans. Someprotists cause human diseases such asmalaria and sleeping sickness.Fungi are mostly many-celled, sometimesmicroscopic, eukaryotic organismssuch as mushrooms, molds,mildews, and yeasts. Many fungiare decomposers. Other fungikill various plants and causehuge losses of cropsHominidae Upright animals withtwo-legged locomotion andbinocular visionand valuable trees.Plants (Plantae) aremostly many-celledeukaryotic organismssuch as red,brown, and greenalgae and mosses,ferns, andfloweringHomo Upright animals with large brain,language, and extended parentalcare of youngsapiens Animals with sparse body hair,high forehead, and large brainsapiens sapiens Animals capable ofsophisticated cultural evolutionplants (whose flowers produce seeds thatperpetuate the species). Some plants such ascorn and marigolds are annuals, which completetheir life cycles in one growing season;others are perennials, which can live formore than 2 years, such as roses, grapes,elms, and magnolias.Animals (Animalia) are also many-celledeukaryotic organisms. Most, called invertebrates,have no backbones. They includesponges, jellyfish, worms, arthropods (insects,shrimp, and spiders), mollusks (snails,clams, and octopuses), and echinoderms(sea urchins and sea stars). Insects play rolesthat are vital to our existence (p. 64). Vertebrates(animals with backbones and a brainprotected by skull bones) include fishes(sharks and tuna), amphibians (frogs andsalamanders), reptiles (crocodiles andsnakes), birds (eagles and robins), and mammals(bats, elephants, whales, and humans).How Are Species Named? Within eachkingdom, biologists have created subcategoriesbased on anatomical, physiological,and behavioral characteristics. Kingdomsare divided into phyla, which are dividedinto subgroups called classes. Classes aresubdivided into orders, which are furtherdivided into families. Families consist of genera(singular, genus), and each genus containsone or more species. Note that theword species is both singular and plural. Figure1 shows this detailed taxonomic classificationfor the current human species.Most people call a species by its commonname, such as robin or grizzly bear. Biologistsuse scientific names (derived fromLatin) consisting of two parts (printed initalics or underlined) to describe a species.The first word is the capitalized name (orabbreviation) for the genus to which the organismbelongs. This is followed by alowercase name that distinguishes thespecies from other members of thesame genus. For example, the scientificname of the robin is Turdus migratorius(Latin for “migratory thrush”),and the grizzly bear goes by the scientificname Ursus horribilis (Latinfor “horrible bear”).Figure 1 Taxonomic classificationof the latest human species,Homo sapiens sapiens.APPENDIX 4A11