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Chapter 18: Classification

Chapter 18: Classification. 18-1 History of Taxonomy. 18-2 Modern Phylogenetic Taxonomy. 18-3 Two Modern Systems of Classification. 18-1 History of Taxonomy. I. Early Systems of Classification (Aristotle, Greece ~2,100 years ago).

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Chapter 18: Classification

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  1. Chapter 18: Classification 18-1 History of Taxonomy 18-2 Modern Phylogenetic Taxonomy 18-3 Two Modern Systems of Classification

  2. 18-1 History of Taxonomy I. Early Systems of Classification (Aristotle, Greece ~2,100 years ago) • Classified organisms as plants or animals BASED on HABITAT  LAND, WATER, and AIR dwellers, used COMMON names. • 17th Century DRAWBACKS: Common names began to VARY from one locale to next; Common names did NOT describe accurately AND stated nothing about INTERRELATEDNESS between organisms.

  3. (1) Taxonomy • NAMES and GROUPS organisms according to MORPHOLOGY and EVOLUTIONARY history.

  4. II. Carolus Linnaeus’s System (Swedish botanist—1700s) • Grouped organisms INTO hierarchical categories, based on MORPHOLOGY. [Father of “Binomial-Nomenclature”]

  5. Critical Thinking (1) Linnaeus’s work was done many years before Darwin and Mendel. Explain why many of Linnaeus’s categories are still relevant in light of genetic and evolutionary relationships among organisms.

  6. (A) Levels of Classification • A nested hierarchy of 7 levels, allowing species to be GROUPED with increasingly RELATED organisms.

  7. (1) Kingdom: Animalia (2) Phylum: Arthropoda (3) Class: Insecta (4) Order: Mantodea (5) Family: Mantidae (6) Genus: Mantus (7) Species: religiosa

  8. (B) Binomial Nomenclature (written in Latin and italicized) • Species name (scientific name) of an organism consists of 2 parts: (1) Genus (gets capitalized) (2) Species Identifier (usually a descriptive word, lowercase) Exs: Homo sapiens, Pisum sativum, Drosophila melanogaster

  9. (1) Varieties • Plants belong to SAME species BUT with slightly different MORPHOLOGY. • Ex: Peaches and nectarines are FRUITS of TWO slightly different varieties of the peach tree, Prunus persica.

  10. (2) Subspecies • Variations of a species that occur in DIFFERENT geographic areas. Ex: Terrapene carolina triungui is a SUBSPECIES of the common eastern box turtle, Terrapene carolina, and gets its NAME from having THREE (rather than four) toes on its HIND feet.

  11. (3) Phylogeny • Evolutionary HISTORY of a species. NOTE: By using morphology, Linnaeus focused on PHENOTYPES that were largely influenced by GENES and are STILL clues of common ANCESTRY.

  12. 18-2 Modern Phylogenetic Taxonomy I. Systematics (Systematic Taxonomy) • Organizes the DIVERSITY of species in context of EVOLUTION (i.e., uses PHYLOGENETIC approach to construct an evolutionary TREE)

  13. Critical Thinking (2) Biologists believe that there are probably millions of undescribed and unclassified species on Earth. Why might so many species still be undescribed or unclassified today?

  14. (1) Phylogenetic Tree • Shows the relationships (or phylogeny) among groups of organisms. • NOTE: Although ONLY a hypothesis, a phylogenetic tree is BASED on several lines of EVIDENCE: (a) Fossil Record (b) Morphology (c) Embryology (d) Biochemical Comparison (amino acid, DNA, and chromosomes)

  15. (A) The Fossil Record • MAY provide evidence, BUT a SYSTEMATIC TAXONOMIST would require OTHER sources of evidence.

  16. (B) Morphology • The GREATER the number of HOMOLOGOUS structures between 2 species, the MORE closely-related phylogeny.

  17. (C) Embryological Patterns of Development • EARLY development  EVIDENCE of phylogeny BETWEEN species. (from ZYGOTE to BIRTH)

  18. (1) Blastula (in Kingdom Animalia) • A ball of dividing cells arising from ZYGOTE; only HOURS after fertilization (conception) a blastula is formed.

  19. (2) Blastopore (in the blastula) • Small indentation becomes POSTERIOR end of digestive system in vertebrates AND echinoderms. (BUT…in invertebrates—it becomes the ANTERIOR end of the system)

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