Classifying Organisms Notes

Current Taxonomic System:

Domain—Kingdom—Phylum—Class—Order—Family—Genus—Species

--->  ( more specific)  --->

                                    Scientific name = Genus species

Three factors determine how an organism is classified:

  • Observation (what Aristotle used)
  • Physical Structure and characteristics
  • DNA

*not all differences are easily identified without careful observations, may need DNA testing to show relationships

 

Domains – highest taxonomic level, made up of kingdoms

  • divided by the type of cell(s) an organism has

1) Bacteria—unicellular with no nucleus

  • Kingdom = Eubacteria

2) Archaea—unicellular, no nucleus, but a different cell wall

  • Kingdom=Archaebacteria

3) Eukarya—organisms with cells that have a nucleus, keep DNA in the nucleus

  • (Kingdoms = Animalia, Plantae, Fungi, and Protista)

 

Kingdoms – group of Phyla

  • Eubacteria (Bacteria Domain) and Archaebacteria (Archaea Domain)
    • Both: together, make up most life on Earth (millions of species)
    • only about 200 are harmful to humans
    • organisms are microscopic; were not discovered until 1800s
    • unicellular, no nucleus
    • 3 shapes of bacteria: spiral, rod, spherical
      1. Spiral—“spirilla”; twisted like a corkscrew
        • move with a whip-like tail called a flagella
      2. Rod—“bacilli”; shaped like rods or capsule pills, includes Botulism
      3. Spherical—“cocci”; can grow single, in pairs, or in groups/chains

 

    • bacteria reproduce through binary fission (“splitting in half”)
      • DNA is copied , split into two rings, and the two rings split apart

 

    • bacteria is critical to life because bacteria convert Nitrogen in air to ammonia for plants to use
        • “Nitrogen fixation”

 

1) Archaebacteria: survive in extreme environments (high heat, pressure, salt, etc)

    • ancient species, probably oldest life on Earth
    • more closely related to Eukarya than to Bacteria

2) Eubacteria: survive in “normal” environments

    • some are decomposers, some use photosynthesis
    • photosynthesis by Cyanobacteria out Oxygen into atmosphere

 

3) Plantae (plants)—sessile (stay in one place), use photosynthesis

    • autotrophs—make own food
    • multicellular, have a cell wall
    • more than 260,000 species, divided into four groups:
    • Nonvascular Plants—no vascular tissue to transport nutrients, water, food
        • evolved first, most basic
        • similar to algae
    2. Seedless Vascular Plants—have tissues for transport, but no seeds
    3. Gymnosperms—have transport tissues and seeds, but no flowers (ie: pines)
    4. Angiosperms (Flowering Plants)—have transport system, seeds, and flowers

4) Fungi (mushrooms, molds, etc)—sessile, get energy from other organism, remains

  • heterotrophs (eat other organisms) or decomposers (energy from dead/dying)
  • typically multicellular
  • over 100,000 species

  • Penicillin: discovered by Alexander Fleming, kills bacteria, first antibiotic

 

5) Animalia (animals)—usually motile (moving), multicellular, heterotrophs

  • no cell walls
  • include mammals, birds, reptiles, amphibians, fish, insects
  • largest singular kingdom (800,000 species)

            Herbivores—eat plants

            Carnivores—eat other animals (meat)

            Omnivores—eat plants and animals

  • some may be sessile: coral and sponges stay put and filter nutrients from the water

 

6) Protista—Eukaryotic organisms that do not fit into other Eukarya kingdoms

  • include microscopic unicellular organisms (algae and plankton) and multicellular organisms (seaweed)
  • can be plant-like or animal-like

  • get food in 1 of 3 ways:
    • producers/autotrophs (use photosynthesis)
    • consumers/heterotrophs (eat other things)
    • Parasites—live off, and harm, other organisms

 

Phylum

Chordata—part of Animalia kingdom

  • organisms with a stiff dorsal (back) supporting rod (like a spine)
  • includes all vertebrates (have a backbone)

 

Classes

In Chordata: Mammalia, Amphibia, Reptilia, Aves (birds), 3 classes of fish

Mammalia—feed offspring milk and have hair somewhere

  • most are placental (live birth, nourish infant with specialized organ inside mother)
    • others: marsupial (have pouch) or monotremes (lay eggs)

 

  • characterized by anatomy, habitat, or feeding habits

            Examples:

            Lagomorphs—hares/rabbits                          Carnivores—meat eaters

            Rodents—small, gnawing mammals              Primates—apes and monkeys

            Insectivores—eat insects (moles, shrews, etc)

            Ungulates—hoofed animals and marine mammals