Chapter 18: Classification

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Chapter 18 Classification
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181 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

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Why Classify?

• organize living things into groups that have
  biological meaning
• Taxonomy discipline of classifying organisms
  and assigning each organism a universally
  accepted name

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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

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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

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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

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Linnaeus's System of Classification

• Hierarchical - it consists of levels
• includes seven levels
• from smallest to largestspecies, genus, family,
  order, class, phylum, and kingdom.
• Each level is called a taxon or taxonomic
  category

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Ursus arctos (Grizzly Bear)

• Kingdom Animalia
• Phylum Chordata
• Class Mammalia
• Order Carnivora
• Family Ursidae
• Genus Ursus
• species - arctos

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Humans

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

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

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• 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.

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• evolutionary classification method of grouping
  organisms together according to their
  evolutionary history

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

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• Cladogram diagram that shows the evolutionary
  relationships among a group of organisms

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• 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.

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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.

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183 Kingdoms and Domains

• There are now 6 Kingdoms listed below.

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• Domain most inclusive taxonomic category
  larger than a kingdom

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Eubacteria

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

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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

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Protista 

• eukaryotic
• greatest variety
• Most single-celled, some multi
• photosynthetic or heterotrophic
• Ex kelp, amoebas, slime mold, paramecium, euglena

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Fungi 

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

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Plantae 

• multicellular
• photosynthetic autotrophs
• Eukaryotic
• Cells walls of cellulose

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Animalia 

• multicellular
• heterotrophic
• Eukaryotic
• No cell walls