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  1. Classification Chapter 18

  2. Characteristics of Living Things Section 1-3 Characteristic Examples Living things are made up of units called cells. Many microorganisms consist of only a single cell. Animals and trees are multicellular. Living things reproduce. Maple trees reproduce sexually. A hydra can reproduce asexually by budding. Living things are based on a universal genetic code. DNA: Flies produce flies. Dogs produce dogs. Seeds from maple trees produce maple trees. Living things grow and develop. Flies begin life as eggs, then become maggots, and then become adult flies. Living things obtain and use materials and energy. Metabolism: Plants obtain their energy from sunlight. Animals obtain their energy from the food they eat. Stimulus: Leaves and stems of plants grow toward light. Living things respond to their environment. Homeostasis: Despite changes in the temperature of the environment, a robin maintains a constant body temperature. Living things maintain a stable internal environment. Taken as a group, living things change over time. Evolution:Plants that live in the desert survive because they have become adapted to the conditions of the desert.

  3. Figure 1-21 Levels of Organization Section 1-3 Biosphere The part of Earth that contains all ecosystems Biosphere Ecosystem Community and its nonliving surroundings Hawk, snake, bison, prairie dog, grass, stream, rocks, air Community Populations that live together in a defined area Hawk, snake, bison, prairie dog, grass Population Group of organisms of one type that live in the same area Bison herd

  4. Figure 1-21 Levels of Organization continued Section 1-3 Organism Individual living thing Bison Tissues, organs, and organ systems Groups of Cells Nervous system Brain Nervous tissue Smallest functional unit of life Cells Nerve cell Groups of atoms; smallest unit of most chemical compounds Molecules DNA Water

  5. Why Do We Classify Organisms? • Biologists group organisms to represent similarities and proposed relationships. • Classification systems change with expanding knowledge about new and well-known organisms. Tacitus bellus

  6. Taxonomy--system of classification • Name organisms • Group organisms in a logical manner • Establishes common set of criterion regardless of language or country

  7. Classification and Phylogeny • Common names are problematic • vary among languages and even among regions within a country • Early naming attempts were up to 20 words • Binomial Nomenclature • Hierarchical Classification • Systematics: Evolutionary Classification

  8. Linnaeus’s System of Classification • Hierarchical system including seven levels or taxons • Species (most specific classification) • Genus (related species) • Family (related genus) • Order (related families) • Class (related orders) • Phylum (related classes) • Kingdom (related phylum--broadest category of classification)

  9. Kingdom Phylum Class Order Family Genus Species Linnaeus’s System of Classification

  10. Hierarchical Classification • Taxonomic categories • Kingdom King • Phylum Philip • Class Came • Order Over • Family For • Genus Good • Species Spaghetti

  11. Coral snake Abert squirrel Sea star Grizzly bear Black bear Giant panda Red fox KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus SPECIES Ursus arctos Figure 18-5 Hierarchical System of Classification

  12. Binomial Nomenclature • Carolus von Linnaeus • Two-word naming system-Latin • Genus • Noun, Capitalized, Underlined or Italicized • Species • Descriptive, Lower Case, Underlined or Italicized Carolus von Linnaeus(1707-1778) Swedish scientist who laid foundation for modern taxonomy

  13. Genus group of closely related species species unique to each species within the genus often Latinized description of some important trait Genus species Homo sapiens man Ursus maritimus polar bear Ursus arctos grizzly bear

  14. Which similarities are most important? • Linnaeus group species into larger taxa according to visible similarities and differences • Modern biologists now group organisms into categories that represent lines of phylogeny or evolutionary relationships (Darwin), not just physical similarities

  15. Phylogenetics • Organism’s classification should reflect phylogeny—the evolutionary history of a species or taxon • Compare visible similarities among currently living species or fossils from extinct organisms • Compare patterns of embryonic development and ways in which different species express similar genes • Compare similar chromosomes, DNA or RNA

  16. Homologous vs. Analogous Structures • Homologous structures share a common structure • Analogous structures have a similar function

  17. Modern Evolutionary Classification • Organisms determine who belongs to their species by determining with whom they will mate! • Species is defined as a group of organisms capable of breeding and producing viable offspring (offspring that are also capable of reproducing) • Taxonomic groups above the level of species are “invented” by researchers are subject to change as our understanding and information improves

  18. Evolutionary Classification • Species within a genus are more closely related to each other than to species in another genus • Members of a genus share a recent common ancestor • Higher the level of the taxon, the farther back in time is the common ancestor of all the organisms in the taxon

  19. Taxonomic Diagrams Mammals Turtles Lizards and Snakes Crocodiles Birds Mammals Turtles Lizards and Snakes Crocodiles Birds PhylogeneticTree Cladogram

  20. Figure 18-13 Cladogram of Six Kingdoms and Three Domains Section 18-3 DOMAIN ARCHAEA DOMAIN EUKARYA Kingdoms Eubacteria Archaebacteria Protista Plantae Fungi Animalia DOMAIN BACTERIA Go to Section:

  21. Dichotomous Keys Identify Organisms • Dichotomous keys versus evolutionary classification • Dichotomous keys contain pairs of contrasting descriptions. • After each description, the key directs the user to another pair of descriptions or identifies the organism.Example: 1. a) Is the leaf simple? Go to 2 b) Is the leaf compound? Go to 3 2.a) Are margins of the leaf jagged? Go to 4 b) Are margins of the leaf smooth? Go to 5

  22. Classification Using Cladograms • Identifies and considers only those characteristics of organisms that are evolutionary innovations • new characteristics that arise as lineages evolve over time • characteristics that appear in recent parts of a linneage but not in its older members are called derived characters • Shared characters are features that all members of a group have in common—hair in mammals or feathers in birds

  23. Cladograms • Help scientists understand how one lineage branched from another in the course of evolution • Represents a type of evolutionary tree showing evolutionary relationships among a group of organisms • Organisms that share one or more derived characters probably inherited those characters from a common ancestor

  24. Appendages Conical Shells Crustaceans Gastropod Crab Crab Limpet Limpet Barnacle Barnacle Molted exoskeleton Segmentation Tiny free-swimming larva CLASSIFICATION BASED ON VISIBLE SIMILARITIES CLADOGRAM Traditional Classification vs Cladogram

  25. Similarities in DNA and RNA • DNA & RNA are so similar across all forms of life, they can be used to compare organisms at their most basic level--their genes • The protein myosin which humans use for muscle contraction is also produced by yeast to help internal cell parts to move • The more similar the DNA sequences of two species--the more recently they shared a common ancestor

  26. Molecular Clocks • Uses DNA comparisons to estimate the length of time that two species have been evolving independently • Relies on a repeating process to mark time--mutation • The degree of dissimilarity is an indication of how long ago the two species shared a common ancestor

  27. Living Things Eukaryotic cells Prokaryotic cells are characterized by Important characteristics which place them in and differing Domain Eukarya Cell wall structures such as which is subdivided into which place them in Kingdom Plantae Kingdom Protista Domain Bacteria Domain Archaea Kingdom Fungi Kingdom Animalia which coincides with which coincides with Kingdom Eubacteria Kingdom Archaebacteria

  28. Kingdoms and Domains • Domains are more inclusive category--larger than a kingdom • Domain Eukarya • Kingdoms Protists, Fungi, Plants, Animals • Domain Bacteria • Kingdom Eubacteria • Domain Archaea • Kingdom Archaebacteria

  29. Kingdoms and Domains The three-domain system Bacteria Archaea Eukarya The six-kingdom system Bacteria Archaea Protista Plantae Fungi Animalia The traditional five-kingdom system Monera Protista Plantae Fungi Animalia

  30. Figure 18-12 Key Characteristics of Kingdoms and Domains Section 18-3 Classification of Living Things DOMAIN KINGDOM CELL TYPE CELL STRUCTURES NUMBER OF CELLS MODE OF NUTRITION EXAMPLES Bacteria Eubacteria Prokaryote Cell walls with peptidoglycan Unicellular Autotroph or heterotroph Streptococcus, Escherichia coli Archaea Archaebacteria Prokaryote Cell walls without peptidoglycan Unicellular Autotroph or heterotroph Methanogens, halophiles Protista Eukaryote Cell walls of cellulose in some; some have chloroplasts Most unicellular; some colonial; some multicellular Autotroph or heterotroph Amoeba, Paramecium, slime molds, giant kelp Fungi Eukaryote Cell walls of chitin Most multicellular; some unicellular Heterotroph Mushrooms, yeasts Eukarya Plantae Eukaryote Cell walls of cellulose; chloroplasts Multicellular Autotroph Mosses, ferns, flowering plants Animalia Eukaryote No cell walls or chloroplasts Multicellular Heterotroph Sponges, worms, insects, fishes, mammals Go to Section:

  31. Domain Bacteria: Kingdom Eubacteria • Unicellular and prokaryotic • Thick, rigid cell walls that contain peptidoglycan • Ecologically diverse • free-living soil organisms • deadly parasites • photosynthetic or heterotrophic • anaerobic and aerobic

  32. Domain Archaea: Kingdom Archaebacteria • Unicellular and prokaryotic • Live in most extreme environments • volcanic hot springs • brine pools • black organic mud devoid of oxygen • Cell walls lack peptidoglycan • Cell membranes contain lipids unique to archaebacteria

  33. Domain Eukarya: Kingdom Protista • Eukaryotic organisms that cannot be classified as animals, plants, or fungi • Display greatest variety • Share characteristics with plants, animals, and fungi • Most are unicellular (except for algae)

  34. Domain Eukarya: Kingdom Fungi • Eukaryotic • Heterotrophs • Feed on dead or decaying organic matter • Secrete digestive enzymes into their food source then absorb smaller food molecules into their bodies • Mushrooms, yeast, mildew

  35. Domain Eukarya: Kingdom Plantae • Eukaryotic, multicellular • Photosynthetic autotrophs • Nonmotile • Cell walls contain cellulose • Include cone-bearing, flowering plants, mosses and ferns

  36. Domain Eukarya:Kingdom Animalia • Multicellular, eukaryotic • Heterotrophic • Lack cell walls • Most are motile