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The Evolution of Taxonomy: From Aristotle to Modern Classification Systems

This chapter explores the history and development of taxonomy, focusing on early classification systems established by Aristotle and the subsequent contributions by Carolus Linnaeus. It delves into Linnaeus’ binomial nomenclature, the significance of morphology, and the advancements in modern phylogenetic taxonomy, including insights from ribosomal RNA comparisons. The chapter also discusses the six-kingdom system and the three-domain system introduced by Carl Woese, highlighting the complexity of classifying life based on evolutionary relationships and genetic evidence.

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The Evolution of Taxonomy: From Aristotle to Modern Classification Systems

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  1. Chapter 18:Classification

  2. 18-1: History of Taxonomy

  3. Early Systems of Classification • Taxonomy: branch of biology that names and groups organisms according to their characteristics and evolutionary history

  4. Aristotle • 2,000 years ago • Plants: three categories based on their stems • Animals: based on where they live • Land • Water • Air

  5. Problems • Scientific exploration  discover MANY new species • Common name did not describe actual animal • Ex: Jellyfish: NOT a fish • Common names varied by location

  6. Linnaeus’ System • Swedish naturalist, Carolus Linnaeus, (1707-78) • Used organisms morphology to categorize it • Form and structure

  7. Levels of Classification • Kingdom • Phylum • Class • Order • Family • Genus • Species Kings Play Chess On Funny Green Squares

  8. Binomial Nomenclature • Species name has two parts: • Genus • Species identifier: descriptive word • Ex: Homo sapien • Homo is the genus • sapien means “wise”

  9. Further Naming and Classifying • Botanists (plants) further classify • Varieties: subset of species • Subspecies: zoologists refer to species that occur in different geographic locations • Phylogeny: evolutionary history

  10. 18-2: Modern Phylogenetic Taxonomy • Past: • Morphology • Preset: • Morphology • Chromosomal characteristics • Nucleotide and amino acid sequences • Embryonic development

  11. Systematics • Organizes tremendous diversity of living things in the context of evolution • Phylogenetic tree: a family tree that shows the evolutionary relationships thought to exist among groups of organisms • Represents a hypothesis • Based on multiple lines of evidence • Subject to change

  12. The Fossil Record • Often provides clues to evolutionary relationships • HOWEVER: • Some fossil records very complete (ocean-living invertebrates) others are missing large portions

  13. Morphology • Compare morphology of organism to morphology of other living things • Homologous features show descent from common ancestors

  14. Embryonic Patterns of Development • Early on in development most living things look very similar • As they develop it is easier to see how their morphology differs

  15. Chromosomes and Macromolecules • DNA, RNA, and proteins • Number of amino acid differences is a clue to how long ago two species diverged from a shared ancestor • Problem: ASSUMES all changes to sequence occur at random and NOT natural selection

  16. Karyotype • Some similar bands on chromosomes, more related two organisms are

  17. Cladistics • Uses shared derived characters of organisms to establish evolutionary relationships • Derived characters: feature that apparently evolved only within the group under consideration • Cladograms:ancestry diagrams made by means of cladistical analysis

  18. 18-3:Two Modern Systems of Classification

  19. Six-Kingdom System • Archaebacteria • Eubacteria • Protista • Fungi • Plantae • Animalia

  20. Kingdom Archaebacteria • Unicellular prokaryotes • Distinctive cell membrane • Autotrophs: chemiosmosis (use elements/chemicals for energy)

  21. Many live in very harsh environments • Hot spring • VERY salty water • Anaerobic environments (No air) • Archae- in Greek means “ancient” • FIRST organisms on Earth • Reproduce: Binary fission • Nutrition: Autotrophs and heterotrophs

  22. Kingdom Eubacteria • Unicellular prokaryotes • Eu- means “true” • Most bacteria that affect your life • Tooth decay • Milk  yogurt • Food poisoning • Reproduce: Binary fission • Nutrition: Autotrophs and heterotrophs

  23. Kingdom Protista • Eukaryotic and prokaryotic • Difficult to describe • All eukaryotes that are not fungi, plants, or animals • Reproduction: sexual cycles unknown but they do exchange genetic info • Nutrition: Autotrophs AND heterotrophs • Euglena can photosynthesize • Amoeba eats other organisms

  24. Kingdom Fungi • Unicellular and multicellular eukaryotes • Reproduction: sexual cycles unknown but they do exchange genetic info • Nutrition: Heterotrophs; Absorb nutrients • Ex: puffballs, mushrooms, rusts, molds

  25. Kingdom Plantae • Multicellular plants • Reproduction: most have sexual cycle based on meiosis • Nutrition: All but a few are heterotrophic

  26. Kingdom Animalia • Multicellular • Eukaryotic • Reproduction: Sexual by means of meiosis forming gametes • Nutrition: Heterotrophs • Most have body symmetry and move about environment

  27. Three-Domain System • In 1977, molecular biologist, Carl Woese • Classified by comparing ribosomal RNA • Why? All organisms have ribosomes so we can look at every living thing’s rRNA and compare it with others • Three main domains: • Domain Archae • Domain Bacteria • Domain Eukarya

  28. Domain Archae • Same as the kingdom Archaebacteria (in six kingdom system)

  29. Domain Bacteria • Same as kingdom Eubacteria

  30. Domain Eukarya • Protists, fungi, plants, and animals • Have nuclei with linear chromosomes and membrane bound organelles

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