5.5 Classification

Taxonomy

Taxonomy is the scientific discipline that attempts to

identify, classify and name living things.

IB Assessment Statements5.5.1 Outline the binomial system of nomenclature.5.5.2 List seven levels in the hierarchy of taxa: Kingdom, Phylum, Class, Order, Family, Genus, and Species—using an example from two different kingdoms for each level.5.5.3 Distinguish between the following phyla of plants, using simple external recognition features: Bryophyta, Filicinophyta, Coniferophyta, and Angiospermophyta.5.5.4 Distinguish between the following phyla of animals, using simple external recognition features: Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, and Arthropoda.5.5.5 Apply and design a key for a group of up to eight organisms.

Binomial Nomenclature System(“Two Names”)

Swedish naturalist (1735), Carolus Linnaeus, was the first to consolidate and popularize the naming of organisms in his

book Systema Naturae by listing and explaining the binomial nomenclature system.

Why Classify Organisms?1. Show evolutionary links between organisms.2. Predict characteristics shared by members of a group.3. Create a universal system whereby each language,

culture, or region has the same name for one organism.

The pill bug or woodlouse are common names. The scientific name is Armadillidium vulgare. They are the exact same

organism.

Rules for Writing Scientific Names

Homo sapiens1. Notice that the scientific name is italicized.2. Homo is the genus name.3. sapiens is the ‘epithet’.4. Both words indicate the species name. 5. If writing the scientific name for a species, the name must be underlined.

Scientific names/terms are often derived from Latin or Greek words.

The Hierarchy of Classification3 Domains and 5 Kingdoms

The 6 Kingdom System

• Kingdom Bacteria: The bacteria • Kingdom Archaea: The extremophiles• Kingdom Plantae: The plants• Kingdom Animalia: The animals• Kingdom Fungi: The fungi and molds• Kingdom Protista: The protists and algae

An Evolutionary Perspective

The Seven Taxa (Nested) Hierarchy

Species that are similar are grouped into a genus

Genera that are similar are group into a family

Families that are similar are grouped into an order

Orders that are similar are grouped into a class

Classes that are similar are grouped into a phylum

Phyla that are similar are grouped into a kingdom

Kingdoms that are similar are grouped into domains

Two Examples

Plant PhylaWe can classify these phyla according to vegetative

characteristics and reproductive characteristics.

1. Bryophyta: Includes plants of very short stature such as mosses.

2. Filicinophyta: Includes ferns and horsetails. 3. Coniferophyta: Includes cedars, junipers, firs and

pine trees.4. Angiospermophyta: Includes all plants which

make flowers and which have their seeds surrounded by fruit.

Key Features (Plant Phyla)

Phylum Roots, Leaves, Stems Max Height

Reproductive Struct.

Bryophytes (Mosses & Liverworts)

No roots – rhizoids ( root-like hairs). Mosses have simple leaves/stems. Liverworts consists of a flattened thallus.

0.5 meters Spores produced in a capsule. The capsule develops at the end of a stalk.

Filicinophytes (Ferns) Have roots, leaves and short non-woody stems. Leaves usually curled in bud and often pinnate –divided into pairs of leaflet.

15 meters Spores are produced in sporangia, usually on the underside of the leaves.

Coniferophytes (Conifers) Include shrubs or trees with roots, leaves , woody stems. Leaves are often narrow with thick, waxy cuticle.

100 meters Seeds produced. Seeds develop ovules on surface of scales of female cones. Male cones produce pollen.

Angiospermophytes (Flowering Plants/Grasses)

Flowering plants are very variable but usually have roots, leaves, stems. The stems of flowering plants that develop into shrubs and trees are woody.

100 meters Seeds are produced. The seeds develop from ovules inside ovaries. The ovaries are part of flowers. Fruits develop from the ovaries., to disperse the seed.

Self-Assessment

A. Roots, leaves and short non-woody stems. Leaves are usually curled up in bud and pinnate. Spores are produced in sporangia,

usually on the underside of the leaves. (15 meters)

B. Have roots, leaves and stems. Usually narrow leaves (needles). Male cones produce pollen while seeds will develop on the

surface of the scales of female cones. (100 meters)

C. Have roots, leaves, stems and flowers. Seeds develop inside ovaries (part of the flower). Fruits develop from ovaries. (100

meters)

D. No roots but ‘root’ hairs called rhizoids. Simple leaves/stems. Spores produced in capsules. (0.5

meters)

Animal PhylaNone of the animals in these phyla have a backbone.

They are invertebrates.1. Porifera: Consists of sponges.2. Cnidaria: Includes sea jellies (jellyfish) and coral

polyps.3. Platyhelminthes: Includes the flatworms.4. Annelida: Made up of segmented worms.5. Mollusca: Includes snails, clams and octopuses.6. Arthropoda: Includes insects, spiders and

crustaceans.

Key Features

Phylum and Examples Body Symmetry Features

Porifera (Sponges) No clear Symmetry Attached to a surface. Pores throughout body for diffusion. No mouth or anus.

Platyhelminthes-Flatworms (Planaria, Tapeworms, Liverflukes)

Bilaterally Symmetrical Flat bodies. Unsegmented. Mouth but no anus.

Mollusca (Slugs, Snails, Clams, Squids)

Bilaterally Symmetrical Muscular foot and mantle. Shell usually present. Segmentation not visible. Mouth and anus.

Cnidaria (Jellyfish, Corals, Sea Anemones)

Radially Symmetrical Tentacles. Stinging cells called nematocysts. Mouth but no anus.

Annelida (Earthworms, Leeches, Ragworms)

Bilaterally Symmetrical Bristles often present. Segmented. Mouth and anus.

Arthropoda (Insects, Spiders, Crabs, Millipedes)

Bilaterally Symmetrical Hard exoskeleton made of chitin. Segmented. Jointed appendages.

Radial vs. Bilateral Symmetry

Nematocysts

Self-Assessment

E. Bilaterally symmetrical, segmented, exoskeleton, jointed appendages.

F. Bilaterally symmetrical, Flat bodies, Unsegmented, Mouth but no anus.

G. Radially symmetrical, Tentacles, Stinging cells called nematocysts, Mouth but no anus.

H. Bilaterally symmetrical, Bristles often present, Segmented, Mouth and anus.

I. Muscular foot and mantle, Shell usually present, Segmentation not visible, Mouth and anus.

J. No clear symmetry, Attached to its surface, Pores throughout body, No mouth or anus.

Using and Making Dichotomous KeyHow to Use a Dichotomous Key:1. Look at the first section of the key which has a pair of sentences describing

a characteristic. 2. Look at the organism to see if the particular characteristic described in the

first line is present in the organism.3. If the answer is ‘yes,’ go to the end of its line and find the number of the

next pair of statements to look at, follow the number given and continue until the end.

4. If the answer was ‘no,’ go to the second statement just below the first and that one should be true. Go to the end of its line and find the number of the next pair of statements to look at, follow the number given and continue until the end.

5. Keep going until the end of the line has a name instead of a number—if you have answered each question correctly, that will be the name of your organism.

A Simple Dichotomous Key

OR TRY THIS ONE

Designing Your Own Dichotomous Key

LEARN HOW TO MAKE A DICHOTOMOUS KEY HERE