Section 18 Fnding Order in Diversity

18.1 Finding Order in Diversity Assigning Scientific Names Scientific names are used to refer to one species Common names are confusing (figure 18-1; cougar, panther, mtn. lion) Latin or Greek languages are used for scientific names Dichotomous keys can be used to identify organisms Made up of paired statements that describe the presence or absence of physical characteristics. Binomial Nomenclature Two-part scientific naming system created by Carolus Linnaeus Each species has its own scientific name The entire name is written in italic or underlined (when handwritten) The genus (group of similar species) Classifying Species into Larger Groups Systematics is the science of naming organisms Scientists try to organize living things into groups (taxa) that have SIMILAR biological meaning. The Linnaean Classification System Species are organized into 7 taxa species, genus, family, order, class, phylum, and kingdom. Family- group of similar genera Order- group of closely related families Class- group of closely related orders Phylum- group of closely related classes Kingdom- group of closely related phylums Problems with Traditional Classification Scientists all over the world work to classify organisms The characteristics important to one scientist may not be to another. Modern systematics apply Darwin’s idea of descent with modification. 18-1 Review 1. To correctly organize living things in to groups. 2. Because that name could be called something totally different in another part of the world. 3. Acer is Sugar and saccharum is Maple. 4. Species, Genus, Family, Order, Class, Phylum, Kingdom 5. Kingdom 18.2 Modern Evolutionary Classification Phylogeny- a branch of evolutionary systematics that groups species into a larger category that reflect evolutionary descent rather than similarities and differences. Common Ancestors-The larger the taxonomic group the farther back in time all of its members shared a common ancestor. Clades- A group of species that includes a single common ancestor and all descendants of that ancestor. Cladograms Cladograms- Cladograms link organisms by showing how evolutionary lines branch off from a common ancestor. Building Cladograms- Each branching point is called a node and represents a splitting event (ancestral species splits into two new ones). The node is the last point at which species shared a common ancestor The branching pattern indicates relatedness. Derived characters are traits that evolved in one species and then are found in all of its descendants. DNA in Classification Genes as Derived Characters Organisms share genes and genes mutate over time the differences created by mutations can be treated as derived characters. The more derived characters two species share the more recently they shared a common ancestor. New Techniques suggest New Trees Molecular analysis determines genetic similarities. Fig. 18-11 and 18-12 18.3 Building the Tree of Life Changing Ideas About Kingdoms Over time, as scientists learn about the natural world, they have added more kingdoms than Linnaeus’s original two (Animalia and Plantae) Five Kingdoms All microorganisms were once placed into Kingdom Protista Next, scientists grouped yeasts, molds, and mushrooms into Kingdom Fungi Finally, scientists placed all prokaryotes into Kingdom Monera Six Kingdoms Monerans were eventually split into Eubacteria and Archaebacteria Three Domains Domain – taxonomic group more inclusive than kingdom Three domains Bacteria – corresponds to kingdom Eubacteria Archaea – corresponds to kingdom Archaebacteria Eukarya – corresponds to kingdoms Fungi, Plantae, and Animals and Protista The Tree of Life Domain Bacteria Unicellular and prokaryotic Thick, rigid walls that surround their cell membrane Cell walls contain peptidoglycan Diverse group – photosynthetic, parasitic, some need oxygen and some Don’t Domain Archaea Unicellular and prokaryotic Live in extreme environments (volcanic hot springs and black mud) Cell walls lack peptidoglycan Tree Domain Eukarya All have a nucleus “Protists” Most are unicellular Brown algae belong to this group but are multicellular Some are photosynthetic; some are heterotrophic Paraphyletic - do not form a valid clade (figure 18-18) Fungi Heterotrophs with cell walls of chitin Feed on dead or decaying organic matter Secrete digestive enzymes into their food source Yeasts – unicellular fungi Plantae Autotrophs with cell walls containing cellulose Carry out photosynthesis using chlorophyll Plant kingdom is a sister group to red algae but includes green algae, mosses, ferns, cone-bearing plants and flowering plants Animalia Multicellular and heterotrophic Cells do not have cell wall