5.5: Classification

5.5: Classification

Pp 142 - 149Binomial system of nomenclatureSystem of assigning scientific/binomial names to organisms designed by Carolus Linneaus in 18th centuryBased on idea that every species has a Latin name, made up of two partsFirst part is the name of the genusSecond part specifies the speciesName should be printed in italics (underlined if hand written) and first part capitalizedExample: Binomial name for Humans is Homo sapiens

Hierarchy of TaxaTaxonomy is the study of classificationOrganisms are placed in groups based on similarities & differencesOrganisms that share characteristics are placed into similar groupsThe more similar their characteristics, the closer the groupingTaxon (plural: taxa)is a group/unit in a classification systemThere are seven taxonomic units:KingdomPhylumOrderFamilyGenusSpecies

Kingdom PlantaePhylumBryophyta

PhylumFilicinophytaPhylumConiferohytaPhylumAngiospermohytaPlant PhylaKingdom: PlantaeCharacteristics:PhotosyntheticChlorophyllCellulose cell wallPermanent vacuolesStores starchClassification of the major plant phyla is based on external observables structures

Using external recognition features only, distinguish between the following phyla of kingdom plantae: bryophyta, fillicinophyata, coniferophyta & angiospermophyta

Need to know:

-Bryophyta -angiospermophyta

-Filicinophyta -Coniferophyta

Phylum: Bryophyta (Mosses, Liverworts, Hornworts)Small terrestrial plantsDo not have true roots, stems or leaves but they must have structures resembling themLeaf-like structures are often arranged in a spiralUsually have live in clusters which act like sponges holding waterNo cuticleReproductive structures are called sporangium which is on long stalks with capsules on end.

Phylum: Filicinophyta (ferns)Have true leaves in frondsNew leaves unrollDivided leavesThere is cuticle on leavesHave an underground creeping stem (rhizome)Height up to 20m but not woodyReproduction: sporangia (sori) contain reproductive spores

Phylum: Coniferophytes (conifers & pines)All conifers are woody plants, most are trees with a single wooden trunk with side branchesDifferentiated into; roots, stem & leavesLeaves are waxy, long thin needles, often arranged in spirals, often a dark green colourStem & roots are woodyProduce naked seeds found in conesVascular system (tracheids)

Phylum: Angiospermophyta (flowering plants and grasses)

Differentiated into roots, stem, leaves & flowersHave flowers, although they may be small in wind-pollinated angiospermophytaSeeds produced in ovaries which become the fruitLeaves usually as leaf blade and leaf stalk, with veins visible on the lower surfaceLeaves have waxy cuticleVascular bundles (veins) are made up of xylem & phloem

Animal phylaThe kingdom of animals is classified according to these characteristics:HeterotrophicNo cell wallsNo vacuolesNo chlorophyllStore glycogen

Distinguish between the following phyla of animals, using simple external recognition features: porifera, cnidaria, platyhelminthes, annelida, mollusca and arthropoda.

The syllabus specifies 6 of the 30 or more phyla from the animal kingdom that you are responsible for knowingThe ones selected are what might be called invertebrates (lack of a spinal cord)The six phyla are classified according to features such as:Number of layers in the body partsThe opening for mouth and anusMethod of supportPhylogenic studies (evolutionary relationship) relies on more genetic studies to support the modern classification of these groups.

Phylum: Porifera (sponges)no clear symmetryNo body layer, rather there is an aggregate of different cell typesSupport is from either silica or calcium based spicules which link together to provide some support i.e. they are attached to a surface Body plan is built around water canals that circulate nutrients through the sponge for ingestion by specialized cellsThere is no mouth or anus

Phylum: Cnidaria (Jelly fish, Sea anemones, Corals)Body has radial symmetry They have two layers in the body planJelly fish are mobile organisms. Sea anemones are sessile organismsSingle entrance that serves the cavity & functions as circulation of respiratory gases and nutrients i.e. they have mouth but no anus Have tentacles & stinging cells These organisms are secondary consumers and posses stinging cells with toxins called nematocysts to disable preyCorals secrete a CaCO3 skeleton

Phylum: Platyhelminthes (flatworms)3 layers in the body planbilateral symmetry unsegmented, flat body One entrance to gut which can have many folds to increase surface area i.e. have mouth, but no anus Largely parasitic, includes flukes

Phylum: Annelida (segment worms)3 layers to the body planBilateral symmetryBody is divided into ringed segments with some specialization of segmentsMouth is connected via gut to a separate anusSkin surface is used for gas exchangeMany marine forms but also terrestrial species, usually soil burrowing

Phylum: Mollusca (Snails, Slugs, Octopus)Bilateral symmetry with significant modificationHave mouth and anusBody plan has three major featuresFoot, a muscular structure used for movement and burrowingCentral visceral mass, contains all the organ structures (separate mouth & anus)Mantle, a folded membrane structure that can surround other tissues and create a cavity containing gill. The mantle frequently secretes a calcareous shell.

Phylum: Arthropoda(Insects, Crustaceans, Spiders, Scorpions, Millipedes)3 layer body plant with bilateral symmetryHard exoskeleton composed of chitinJointed body segmentsJointed appendages to each segmentAt least 3 pairs of jointed legsSome flying organisms in the class InsectaSeparate mouth and anusMany free-living but also some parasitic

Dichotomous KeysEach questions divides the group of organisms into two smaller groups based on a pair of alternative characteristicsSubsequent groups may focus on more minor detailsIn most cases the characteristic will be readily observed or measurableIt is better to choose characteristics that are uninfluenced by environmental variationShape and number are often good characteristics on which to base alternative pairingsA complete key will have each type of organisms being classified separated with a final identifying name

Revision QuestionsOutline the binomial system of nomenclature.List down the seven levels in the hierarchy of taxa. Using simple external recognition features, distinguish between the following phyla of kingdom plantae: bryophyta, filicinophyta, coniferophyta and angiospermophyta.Using simple external recognition features, distinguish between the following phyla of kingdom animalia: porifera, cnidaria, platyhelminthes, annelida, mollusca and arthropoda.

Using observable characteristics only, design a dichotomous key for identifying the following arthropods.