5.5: Classification

Pp 142 - 149

Binomial system of nomenclatureSystem of assigning

scientific/binomial names to organisms designed by Carolus Linneaus in 18th 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 (underlined if hand written) and first part capitalized

Example: Binomial name for Humans is Homo sapiens

Hierarchy of TaxaTaxonomy is the study of

classificationOrganisms are placed in groups

based on similarities & differences

Organisms that share characteristics are placed into similar groups

The more similar their characteristics, the closer the grouping

Taxon (plural: taxa)is a group/unit in a classification system

There are seven taxonomic units: Kingdom Phylum Order Family Genus Species

Kingdom Plantae

PhylumBryophyta

PhylumFilicinophyta

PhylumConiferohyta

PhylumAngiospermohyta

Plant Phyla Kingdom: Plantae

Characteristics: Photosynthetic Chlorophyll Cellulose cell wall Permanent

vacuoles Stores starch

Classification 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 them

Leaf-like structures are often arranged in a spiral

Usually have live in clusters which act like sponges holding water

No cuticleReproductive structures are

called sporangium which is on long stalks with capsules on end.

Phylum: Filicinophyta (ferns)

Have true leaves in fronds

New 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 branches

Differentiated into; roots, stem & leaves

Leaves are waxy, long thin needles, often arranged in spirals, often a dark green colour

Stem & roots are woodyProduce naked seeds

found in conesVascular system

(tracheids)

Phylum: Angiospermophyta (flowering plants and grasses)

Differentiated into roots, stem, leaves & flowers

Have flowers, although they may be small in wind-pollinated angiospermophyta

Seeds produced in ovaries which become the fruit

Leaves usually as leaf blade and leaf stalk, with veins visible on the lower surface

Leaves 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 knowing

The 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 support

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

Phylum: Porifera (sponges) no clear symmetry

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

Support 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 cells

There 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 organisms

Single 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 prey

Corals secrete a CaCO3 skeleton

Phylum: Platyhelminthes (flatworms)

3 layers in the body plan

bilateral 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 segments

Mouth is connected via gut to a separate anus

Skin surface is used for gas exchange

Many marine forms but also terrestrial species, usually soil burrowing

Phylum: Mollusca (Snails, Slugs, Octopus)

Bilateral symmetry with significant modification

Have mouth and anusBody plan has three major

featuresFoot, a muscular structure

used for movement and burrowing

Central 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 symmetry

Hard exoskeleton composed of chitin

Jointed 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 characteristics

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 which to base alternative pairings

A 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.