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Chapter 14

VIEWS: 4 PAGES: 7

									                         Chapter 14 – Classification



14:1 The Concept of Classification

- the classification system provides order and logic



The Need for Classifying Organisms

   - Taxa – biological categories

   - taxanomy – the science of classification

   -   New organisms are continually being discovered.

   -   Common names – not enough – can be confusing or sometimes too general

       -   ex – worm – What is it?

       -   ex – cougar, puma, panther, mountain lion – All are common names for

           the same organism

   - the need for scientific names became clear.

   - Scientific names are now in the Latin language



Binomial Nomenclature

   - Aristole’s System – 2 groups: plants and animals

       - Plants – classified by structure and size: 1) herbs 2) shrubs 3) trees

       - Animals – classified by where they live: 1) air 2) land 3) sea
   - *each system should be based on one characteristic – some basis for all

      groupings

- 18th century – Carolus Linnaeus – Came up with a classification system

   based only on structure

   - Linnaeus said each type of organism was a different species.

   - Different features – different species

   - *Linnaeus is also well know because he introduced a two-part system

      called binomial nomenclature for naming and classifying organisms.

   - Each organism is given a two word name

- Binomial Nomenclature –

   - 1st word – a noun – genus to which the organism belongs ex – felis

   - 2nd word – an adjective – the specific name

   - together the genus and specific name tell the species name & scientific

      name of the organism.

   - *A single genus may contain many different species.

   - ex – Genus Felis - Felis sylvestris – wildcat

                         Felis pardalis – ocelot

                         Felis concolor – cougar

                         Felis catus – house cat

   - Also for plants – ex – Quercus alba – white oak Quercus ruba – red oak

      The genus name can be abbreviated – ex – Q. ruba
Determining Relationships

  - Theory of Evolution and theory of natural selection were both helpful to the

      science of taxonomy.

  -   Classification is now based on ancestry of organisms. ex – cats – all same

      genus – have a common ancestor



  Classifying Based on Structure

  - Lines of evidence – 1) Fossil record 2) Homologous structure

  - Linnaeus used homologous structures to group organisms without really

      knowing it.

      - By doing this, he was grouping on the basis of evolutionary relationships

      - ex – Fossil record of horse – shows nearly the complete fossil record of

         the evolution of the horse

  - Sometimes the fossil record is incomplete and causes scientists to be

      mislead.



  Classifying Using Biochemistry & Development

  - Use of microscope and other tools – scientists had new information to use.

  - Comparative Embryology – shows that vertebrates are more closely related

      to Echinoderms (starfish) than other invertebrates – Looking only at adult

      forms this would not appear to be true.
   - Biochemistry – helped identify horseshoe crab closer to spiders than the crab



   Classifying on a Molecular Basis

   - Looking at organisms DNA or genes, or proteins.

   - *Organisms having many proteins or genes in common are closely related.

      -   ex – guinea pigs – were classified with rodents (mice, rat, squirrels) but

          closer study of their proteins showed they were not closely related.

          Instead, they are now classified in a group of its own.

   - Using DNA studies, scientists have determined that chimpanzees and

      humans began to evolve from a common ancestor only 5 million years ago.

   - *Possible study of ancient DNA may tell scientists more about extinct

      animals.

      - ex – dinosaurs – may find DNA in dinosaur blood of a biting insect if the

          insect was trapped in specific conditions.



Phylogeny – “evolutionary history”

   - ex – History of Giant Panda – Western Asia - 1869

   - first classified with the bears – then with the raccoons

   - using DNA studies scientists learned that the giant panda is more closely

      related to the bears
   - A closer look at enzymes & proteins led to the same conclusion. Fig. 14-10

       pg. 375



14:2 A System of Classification



Taxa

   - categories in the biological classification system.

   - there are 7 different taxa (categories)

       1) Kingdom – largest – broadest

       2) Phylum

       3) Class

       4) Order

       5) Family

       6) Genus

       7) Species – smallest – most specific – one type of organism.

          a subspecies – sometimes called breeds, varieties, or race



Some Examples of Classification

   House Cat – Animal Kingdom – can’t make its own food

                   Phylum Chordata – has a backbone – Subphylum – vertebrate

                   Class Mammalia – has mammary glands, hair
                  Order Carnivora – meat eating

                  Family Felidae

                  Genus Felis

                  Species Felis catus

  Comparisons – pg. 377 Cat, Dog, Human, Grasshopper



The Kingdom Problem

  - Most biologists use the 5 kingdom system

  - 1) Monerans 2) Protists 3) Fungi 4) Plants 5) Animals

  - Early classification systems – used only 2 kingdoms – 1) plants 2) animals

  - Microscopic organisms became a problem for biologists to classify – They

     didn’t fit well into either group – ex - Euglena

     - Euglena – mobile – like an animal autotrophic – like a plant

     - Can lose its chlorophyll and become heterotrophic

     - ex 2 – Fungi – can’t move – plant like heterotrophic – animal like

     - Sponges, Sea Anemones and Coral – All animals but they look more like

        plants.

  - The 5 kingdom classification system is not perfect. Biologists still have

     trouble with some organisms.

  - All monerans are prokaryotes.

  - One proposed new system involves 6 kingdoms.
- The 6th kingdom includes ancient bacteria.

- This book will use the 5 kingdom system.

								
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