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Chapter 18: Classification

Chapter 18: Classification. 18–1 Finding Order in Diversity. Life on Earth has been changing for more than 3.5 billion years 1.5 million species named between 2 and 100 million additional species have yet to be discovered. Why Classify?.

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Chapter 18: Classification

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  1. Chapter 18: Classification

  2. 18–1 Finding Order in Diversity • Life on Earth has been changing for more than 3.5 billion years • 1.5 million species named • between 2 and 100 million additional species have yet to be discovered

  3. Why Classify? • organize living things into groups that have biological meaning • Taxonomy = discipline of classifying organisms and assigning each organism a universally accepted name

  4. Assigning Scientific Names • Common names are confusing and vary among languages or even regions • Ex: cougar, mountain lion, panther, puma • different species sometimes share a single common name • Ex: buzzard: hawk? Vulture? • Scientists have agreed to a single name for each species • Use Latin & Greek

  5. Binomial Nomenclature • Carolus Linnaeus, • a Swedish botanist, 1700s • binomial nomenclature = classification system in which each species is assigned a two-part scientific name • written in italics • first word is capitalized, the second word is lower case

  6. Scientific Names • grizzly bear is called Ursus arctos • Ursus — is the genus • Genus = group of closely related species • arctos – is the species • unique to each species within the genus • Often a Latinized description of some important trait of the organism or an indication of where the organism lives • Ursus maritimus, the polar bear • maritimus, referring to the sea

  7. Linnaeus's System of Classification • Hierarchical - it consists of levels • includes seven levels • from smallest to largest—species, genus, family, order, class, phylum, and kingdom. • Each level is called a taxon or taxonomic category

  8. Ursus arctos (Grizzly Bear) • Kingdom – Animalia • Phylum – Chordata • Class – Mammalia • Order – Carnivora • Family –Ursidae • Genus –Ursus • species - arctos

  9. Humans • Kingdom = Animalia • Phylum (Division for plants) = Chordata • Class = Mammalia • Order = Primates • Family = Hominidae • Genus = Homo • species = sapiens

  10. Taxonomic groups above the level of species are “invented” by researchers who decide how to distinguish between one genus, family, or phylum, and another.

  11. Phylogeny = the study of evolutionary relationships among organisms • Biologists now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities.

  12. evolutionary classification = method of grouping organisms together according to their evolutionary history

  13. The higher the level of the taxon, the farther back in time is the common ancestor of all the organisms in the taxon.

  14. Cladogram = diagram that shows the evolutionary relationships among a group of organisms

  15. The genes of many organisms show important similarities at the molecular level. • Similarities in DNA can be used to help determine classification and evolutionary relationships. • The more similar the DNA sequences of two species, the more recently they shared a common ancestor, and the more closely they are related in evolutionary terms.

  16. Dichotomous Key • A dichotomous key is a tool that allows the user to determine the identity of items in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish. • Keys consist of a series of choices that lead the user to the correct name of a given item. • "Dichotomous" means "divided into two parts". Therefore, dichotomous keys always give two choices in each step.

  17. 18–3 Kingdoms and Domains • There are now 6 Kingdoms – listed below.

  18. Domain = most inclusive taxonomic category; larger than a kingdom

  19. Eubacteria • Unicellular • Prokaryotic • Autotroph or heterotroph • Cell walls with peptidoglycan • Examples: E. coli, Streptococcus, Staph

  20. Archaebacteria • unicellular • prokaryotic • extreme environments • volcanic hot springs, brine pools, and black organic mud totally devoid of oxygen • Auto or heterotroph • cell walls lack peptidoglycan

  21. Protista  • eukaryotic • greatest variety • Most single-celled, some multi • photosynthetic or heterotrophic • Ex: kelp, amebas, slime mold, paramecium, euglena

  22. Fungi  • heterotrophs • feed on dead or decaying organic matter • Eukaryotic • Most multicellular, some uni • Cell walls of chitin • EX: mushroom, yeast

  23. Plantae  • multicellular • photosynthetic autotrophs • Eukaryotic • Cells walls of cellulose

  24. Animalia  • multicellular • heterotrophic • Eukaryotic • No cell walls

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