IB T5 5 Classification

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    5.5: ClassificationTopic 5: Ecology & Evolution

    Miss Friedman

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    5.5.1: Binomial system of nomenclature

    Designed by Carolus Linneaus in 18 th century Based on idea that every species has a Latin

    name, made up of two parts First part is the name of the genus Second part specifies the species

    Name should be printed in italics (underlinedif hand written) and first part capitalizedExample

    Humans are Homo sapiens

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    5.5.2: Hierarchical system of classification

    Organisms that share characteristics are placedinto similar groups

    The more similar their characteristics, the closerthe grouping

    The purpose of classification is to:Clearly identify an organism with a name that is uniqueto the species and avoids confusion with local namingShow evolutionary links

    Allow us to predict anatomical, physiological and geneticcharacteristics it may share with other organisms

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    Need to know:

    -Bryophyta -angiospermophyta

    -Filicinophyta -Coniferophyta

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    Phylum: Bryophyta(Mosses, Liverworts, Hornworts)

    Small terrestrial plants Do not have true roots, stems or leaves but they

    must have structures resembling them Leaf-like structures are often arranged in a spiral Usually have live in clusters which act like sponges

    holding water

    No cuticle Reproductive structures are called sporangium

    which is on long stalks with capsules on end.

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    Phylum: Filicinophyta(ferns)

    Have true leaves New leaves unroll

    Divided leaves Have an underground creeping stem

    (rhizome)

    Height up to 20m Reproduction: sporangia contain

    reproductive spores

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    Phylum: Coniferophytes (conifers & pines)

    All conifers are woody plants, most are treeswith a single wooden trunk with sidebranches

    Leaves are waxy, long thin needles, oftenarranged in spirals, often a dark greencolour

    Produce seeds found in cones Vascular system (tracheids)

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    Phylum: Angiospermophyta (flowering plants and grasses)

    Have flowers, although they may be small inwind-pollinated angiospermophyta

    Seeds are ovaries which become the fruit Leaves usually as leaf blade and leaf stalk,

    with veins visible on the lower surface

    Leaves have waxy cuticle Vascular bundles (veins) are made

    up of xylem & phloem

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    5.5.4: Animal phyla The kingdom of animals is classified

    according to these characteristics: Heterotrophic No cell walls No vacuoles No chlorophyll Store glycogen

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    The syllabus specifies 6 of the 30 or more phylafrom the animal kingdom that you areresponsible for knowing

    The ones selected are what might be calledinvertebrates (lack of a spinal cord)

    The six phyla are classified according to features

    such as:Number of layers in the bodyThe opening for mouth and anusMethod of support

    Phylogenic studies (evolutionary relationship)relies on more genetic studies to support themodern classification of these groups.

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    Phylum: Porifera(sponges)

    No body layer, rather there is an aggregate of different cell types

    Support is from either silica or calcium basedspicules which link together to provide somesupport

    Body plan is built around water canals that

    circulate nutrients through the sponge foringestion by specialized cells There is no mouth or anus

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    Phylum: Cnidaria(Jelly fish, Sea anemones, Corals)

    They have two layers in the body plan There is radial symmetry Jelly fish are mobile organisms. Sea anemones are

    sessile organisms Single entrance that serves the cavity that

    functions as circulation of respiratory gases andnutrients

    These organisms are secondary consumers andposses stinging cells with toxins callednematocysts to disable prey

    Corals secrete a CaCO 3 skeleton

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    Phylum: Platyhelminthes(flatworms)

    3 layers in the body plan One entrance to gut which can have many

    folds to increase surface area. Largely parasitic, includes flukes

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    Phylum: Arthropoda(Insects, Crustaceans, Spiders,

    Scorpions, Millipedes) 3 layer body with bilateral symmetry Hard exoskeleton composed of chitin

    Jointed body segments Jointed appendages to each segment At least 3 pairs of jointed legs

    Some flying organisms in the class Insecta Separate mouth and anus Many free-living but also some parasitic

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    5.5.5: Dichotomous Keys Each questions divides the group of organisms into two

    smaller groups based on a pair of alternativecharacteristics

    Subsequent groups may focus on more minor details In most cases the characteristic will be readily observed or

    measurable It is better to choose characteristics that are uninfluenced

    by environmental variation

    Shape and number are often good characteristics on whichto base alternative pairings A complete key will have each type of organisms being

    classified separated with a final identifying name