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Interest Grabber Section 18-1 Order From Chaos When you need a new pair of shoes, what do you do? You probably walk confidently into a shoe store, past the tens or hundreds of pairs of shoes you don’t want and straight to the kind you do want. How do you find them? Shoes are organized in the store in categories. People organize objects by grouping similar objects together. Go to Interest Grabber continued Section 18-1 1. Consider the task facing early biologists who attempted to organize living things. How might they have begun? 2. Suppose that you have been given a green plant, stringy brown seaweed, a rabbit, a mushroom, a worm, and a grasshopper. You’ve been asked to organize these things into categories that make sense. How would you do it? 3. Decide on your categories and write each on a sheet of paper. Next to each category, write the defining characteristics of that category. Then, write in the organisms that fall into each category. Go to Section: Answers Order From Chaos 1. Students may say that early biologists attempted to formulate logical systems for organizing the diversity of life. 2. Students may group the plantlike, sessile organisms (the plant, seaweed, and mushroom) together, grouping the others as animals. 3. Remind students that organizational systems are human-made, and there are no right or wrong ones. Some, however, are more useful than others. Section Outline Section 18-1 18–1 Finding Order in Diversity A. Why Classify? B. Assigning Scientific Names 1. Early Efforts at Naming Organisms 2. Binomial Nomenclature C. Linnaeus’s System of Classification Go to Section: Words to Know Taxonomy – classifying organisms and assigning each organism a universally accepted name Carolus Linnaeus – Swedish botanist who developed a two-word naming system called binomial nomenclature The scientific name: •The first word is the genus and it is capitalized •The second word is the species and it is lowercased •It is always written in italics Examples Felis concolor – mountain lion, puma, cougar, panther Ursus arctos (grizzly bear) and Ursus maritimus (polar bear) belong to the same genus, but not the same species Taxonomic Categories (Taxa) {Singular: taxon} •Kingdom, Phylum, Class, Order, Family, Genus, Species (Larger category to more specific) •Genera that share many characteristics are grouped in a larger category, the family •An order is a broad taxon composed of similar families •A class is composed of similar orders •Several different classes make up a phylum Flowchart Section 18-1 Linnaeus’s System of Classification Kingdom Phylum Class Order Family Genus Species Go to Section: Figure 18-5 Classification of Ursus arctos Section 18-1 Grizzly bear Black bear Giant panda Red fox Coral Sea star Abert squirrel snake KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus SPECIES Ursus arctos Go to Section: Interest Grabber Section 18-2 One Big Family? How can you determine if one organism is closely related to another? It may seem easy, but it isn’t, and looks are often deceiving. For example, roses and orchids are both flowering plants, but roses grow on bushes or vines and have thorns. Many orchids don’t even grow in soil—they can grow in trees! Rose and orchid blossoms look very different, and roses and orchids cannot produce hybrids, or offspring of crosses between parents with different traits. Go to Section: Interest Grabber continued Section 18-2 1. Do you think roses and orchids are closely related? Explain your answer. 2. Now, apply the same logic to dogs. Different breeds of dogs—such as a Labrador retriever and a collie— can breed and produce offspring. So what is the difference between the rose-orchid combination and the Lab-collie combination? 3. What defines a species? Is appearance important? What other factors might be considered? Go to Section: Answers One Big Family? 1. Students may say that their different growth habits and inability to hybridize indicate that they are not closely related. 2. Students may know that all domestic dogs are a single species. 3. Students may suggest that a species is defined by its members’ ability to interbreed, regardless of appearance. Section Outline Section 18-2 18–2 Modern Evolutionary Classification A.Problems With Traditional Classification B.Evolutionary Classification C.Classification Using Cladograms D.Similarities in DNA and RNA E.Molecular Clocks Go to Section: Words to Know Traditional classification – organisms were grouped according to similarities in appearance Evolutionary classification – grouping organisms based on their evolutionary history Cladistic analysis – identifies and considers only those characteristics of organisms that are evolutionary innovations (new characteristics that arise as lineages evolve over time) Derived characters – characteristics that appear in recent parts of a lineage but not in its older members Cladogram – a diagram that shows the evolutionary relationships among a group of organisms (derived characters such as free-swimming larva and segmentation) The genes of many organisms show important similarities at the molecular level. (American vultures are more closely related to storks than to African vultures. A gene that codes for myosin protein indicates that humans and yeast have a common ancestry.) Molecular clock – uses DNA comparisons to estimate the length of time that two species have been evolving independently (Longer=more different) Traditional Classification Versus Cladogram Section 18-2 Appendages Crab Conical Shells Barnacle Limpet Crustaceans Crab Gastropod Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva TRADITIONAL CLASSIFICATION Go to Section: CLADOGRAM Traditional Classification Versus Cladogram Section 18-2 Appendages Crab Conical Shells Barnacle Limpet Crustaceans Crab Gastropod Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva TRADITIONAL CLASSIFICATION Go to Section: CLADOGRAM Interest Grabber Section 18-3 My Way or the Highway Categories that are used to organize an assortment of things should be valid. That is, they should be based on real information. However, categories should be useful, too. Suppose that you are taking a survey of traffic. You sit at the side of a busy intersection and record the vehicles you see in one hour. Go to Section: Interest Grabber continued Section 18-3 1.What categories could you use to organize your count of vehicles? 2. Look at your list of categories. Are all of them equally useful? 3. Is there more than one valid and useful way to organize living things? Go to Section: Interest Grabber My Way or the Highway 1. Students’ answers may include, type of vehicle, color, age, or manufacturer. 2. Students may suggest that the usefulness of the criteria depends on the intent of the study. 3. Students should conclude that the same set of living things could be categorized in several ways, depending upon the criteria used. Section Outline Section 18-3 18–3 Kingdoms and Domains A.The Tree of Life Evolves B.The Three-Domain System C .Domain Bacteria D .Domain Archaea E .Domain Eukarya 1. Protista 2. Fungi 3. Plantae 4. Animalia Go to Section: Two Kingdoms – animals and plants (1700s) Three Kingdoms – animals, plants, and protists (microorganisms) [Late 1800s] Four Kingdoms – animals, plants, protists, fungi (mushrooms, yeasts, molds) Five Kingdoms – monera, protista, fungi, plantae, and animalia (1950s) Six Kingdoms – Eubacteria, Archaebacteria, Protista, Fungi, Plantae, Animalia Three Domains – Bacteria, Archaea (live in extreme environments), Eukarya Concept Map Section 18-3 Living Things are characterized by Eukaryotic cells and differing Important characteristics which place them in Cell wall structures such as Domain Eukarya Prokaryotic cells which is subdivided into which place them in Domain Bacteria Domain Archaea which coincides with which coincides with Kingdom Eubacteria Kingdom Archaebacteria Go to Section: Kingdom Plantae Kingdom Fungi Kingdom Protista Kingdom Animalia Figure 18-12 Key Characteristics of Kingdoms and Domains Section 18-3 Classification of Living Things DOMAIN Bacteria Archaea KINGDOM Eubacteria Archaebacteria CELL TYPE Protista Fungi Plantae Animalia Prokaryote Prokaryote Eukaryote Eukaryote Eukaryote Eukaryote Cell walls with peptidoglycan Cell walls without peptidoglycan Cell walls of cellulose in some; some have chloroplasts Cell walls of chitin Cell walls of cellulose; chloroplasts No cell walls or chloroplasts Unicellular Unicellular Most unicellular; some colonial; some multicellular Most multicellular; some unicellular Multicellular Multicellular MODE OF NUTRITION Autotroph or heterotroph Autotroph or heterotroph Autotroph or heterotroph Heterotroph Autotroph Heterotroph EXAMPLES Streptococcus, Escherichia coli Methanogens, halophiles Amoeba, Paramecium, slime molds, giant kelp Mushrooms, yeasts Mosses, ferns, flowering plants Sponges, worms, insects, fishes, mammals CELL STRUCTURES NUMBER OF CELLS Monera - Eubacteria and Archaebacteria Go to Section: Eukarya Methanogens: produce methane as a byproduct Halophiles: “salt loving” Figure 18-13 Cladogram of Six Kingdoms and Three Domains Section 18-3 DOMAIN ARCHAEA DOMAIN EUKARYA Kingdoms DOMAIN BACTERIA Go to Section: Eubacteria Archaebacteria Protista Plantae Fungi Animalia