Transcript Chapter 18
Chapter 18 Classification 18 – 1 Finding Order in Diversity • Evolution has lead to a staggering variety or organisms • Biologists have identified and named about 1.5 million species so far • They estimate anywhere between 2 and 100 million additional species have yet to be discovered Taxonomy • The science of classifying and naming organisms Assigning Scientific Names • By the 18th century, European scientists recognized that referring to organisms by common names was confusing • Common names vary among regions within a country Mountain Lion Cougar Puma Panther Early Efforts at Naming Organisms • First attempts at standard scientific names often described physical characteristics • As a result, these names could be 20 words long! • Ex.) The English translation of the scientific name of a particular tree might be “Oak with deeply divided leaves that have no hairs on their undersides and no teeth around their edges.” Binomial Nomenclature • Carolus Linnaeus (18th Century) • Swedish Botanist • Developed a system for naming organisms Binomial Nomenclature • Two word naming system Rules for Binomial Nomenclature • Written in italics • First word is capitalized • Second word is lowercased Ex.) Genus species Genus species G. species • The name often tells you something about the species • Ex.) Tyranosaurus Rex • Tyrant Lizard King Taxon (taxonomic category) • A group or level of organization Linnaeus’s system of classification uses seven taxonomic categories Kingdom Phylum Class Order Family Genus species Largest / Least Specific Smallest / Most Specific Mnemonic Device Kingdom Phylum Class Order Family Genus species • • • • • • • King Phillip Came Over For Good Soup 18 -2 Modern Evolutionary Classification Problems with Traditional Classification • Sometimes, due to convergent Evolution organisms that are quite different from each other evolve similar body structures • Ex.) Crab, limpet, barnacle Evolutionary Classification • Darwin’s theory of evolution changed the entire way that biologists thought about classification • Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similarities Classification Using Cladograms • Many biologists now prefer a method called cladistic analysis • This method of classification identifies and considers only those characteristics that arise as lineages evolve over time Derived characteristics • Characteristics that appear in recent parts of a lineage but not in its older members Cladograms • Diagram that shows the evolutionary relationships among a group of organisms Similarities in DNA and RNA • Suppose you were trying to compare diverse organisms such as yeast and humans • It wouldn’t make sense to try to classify anatomical similarities • The genes of many organisms show important similarities at the molecular level • These similarities can be used as criteria to help determine classification • Ex.) Myosin in humans & yeast Molecular Clocks • Use DNA comparison to estimate the length of time that two species have been evolving independently Molecular Clocks • Mutations happen all the time at about the same rate • A comparison of DNA sequences in two species can reveal how dissimilar the genes are • The degree of dissimilarity is an indication of how long ago the two species shared a common ancestor 18 -3 Kingdoms and Domains • In taxonomy, as in all areas of science, ideas and models change as new information arises, some explanations have been discarded altogether, whereas others such as Darwin’s theory of evolution by natural selection, have been upheld • So it should not be surprising that since the 1800’s, the tree of life has been revised and edited since the discovery of all this new information The Tree of Life Evolves • Before Linnaeus’s time, the only two Kingdoms that existed were Plants and Animals • As scientists discovered new organisms that didn’t fit into the plant or animal category, they made a new category The Old 5 Kingdom System 1. 2. 3. 4. 5. Animals Plants Fungi Protist Bacteria • In recent years, as evidence about microorganisms continued to accumulate, biologists come to recognize that the Monera were composed of two distinct groups The New 6 Kingdom System 1. 2. 3. 4. 5. 6. Animals Plants Fungi Protist Eubacteria Archaebacteria The Three Domain System • Molecular analysis has given rise to a new taxonomic category that is now recognized by many scientists Domain • Larger than a kingdom 3 Domains 1. Bacteria • Eubacteria 2. Archaea • Archaebacteria 3. Eukarya • Protists, fungi, plants, animals (Everything with a nucleus) Domain Bacteria • Unicellular • Prokaryotic - no nucleus, no membrane bound organelles • Thick walls (containing peptigoglycan) • Free living and parasitic • Important decomposers • Some photosynthesize • Some don’t need oxygen – Anerobic • Some need oxygen – Aerobic Agar Bacteria Colonies Petri dish What is this used for? Domain Archaea • Unicellular • Small • Prokaryotic • Live in extreme environments Ex.) volcanic hotsprings, brine pools, black organic mud without oxygen • Acidophiles – live in acidic environments • Thermophiles – can tolerate hot temperatures 50 – 110 degrees • Halophiles – can stand extreme concentrations of NaCl • Methanogens – Produce methane CO2 + H CH4 Acidophiles Thermophile Halophile Domain Eukarya • Consists of all organisms that have a nucleus Protista • Small • Mostly unicellular • Eukaryotic – has a nucleus, and membrane bound organelles • Cannot be classified as animals, plants or fungi, but share many characteristics with plants, animals and fungi Plant like Protists • Algae • Photosynthetic – can make their own food Euglenas Flagella Diatoms Dinoflagellates Dinoflagellates • Red tide Green Algae Red Algae Brown Algae Animal like Protists • Protozoans • Heterotrophic – can’t make their own food Fungus like Protists • Slime molds, water molds • Decompose their food Fungi • Mostly multicellular Ex.) Mushroom, yeast • Cell walls Fungi • Heterotrophs • Feed on decaying organic matter • Secrete digestive enzymes into food source then • Spread and reproduce by spores Spores • Reproductive cells that form new organisms without fertilization Many are used in medicine • Antibiotics • Anti rejection • Anti viral Penicillium Plantae • Multicellular • Photosynthetic autotrophs – make their own food by photosynthesis • Non-motile • Cell walls (cellulose) Animalia • • • • • Multicellular Heterotrophic No cell walls Most move Incredible diversity