Taxonomic Systems

Section 9.1

The More Specific The Better

• An eyewitness describing a getaway vehicle could say the following:

• The colour• The model• The year

• The license plate number The best evidence of all!!

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Classifying Organisms

• One purpose of a classification system is to allow the accurate identification of a particular organism.

• The second purpose is to recognize natural groupings of living things.

Taxonomy• The practice of classifying organisms is

known as taxonomy.

• Founded nearly 300 years ago by a Swedish botanist named Carolus Linnaeus.

• He used simple physical characteristics to identify different species and organize them into groups.

Hierarchy of Groups

• As members of the animal kingdom, the bee, shark, horse, dog and oyster have certain things in common.

• On the other hand, these animals are obviously not very much alike.

• There are different degrees of similarity among animals.

• A horse is more like a dog than like a shark.

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Taxa

• To distinguish such different degrees of similarity between organisms, each kingdom is subdivided several times into a series of progressively smaller groups.

• Each group is called a taxon (plural taxa).• Kingdoms are the largest and most

general taxa.• Species are the smallest and most specific

taxa.

Taxon Example Organisms in this taxon

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Kingdom Animalia Bee, frog, shark, horse, oyster, dog, cougar, lynx, bobcat

Phylum Chordata Shark, horse, frog, dog, cougar, lynx, bobcat

Class Mammalia Horse, dog, cougar, lynx, bobcat

Order Carnivora Dog, cougar, lynx, bobcat

Family Felidae Cougar, lynx, bobcat

Genus Lynx Lynx, bobcat

Species Lynx canadensis Lynx

Species Lynx rufus Bobcat

Naming a Species

• Linnaeus’s two word method:

Felis domesticus (the house cat).

• Many of these names are based on Latin or Greek words.

• These names often reflect characteristics of the organisms, or in other cases, the names are given to honour a fellow scientist or historical figure or a location where the animal lives.

Binomial Nomenclature

• The system of using a two-word name for each species is called binomial nomenclature.

• The first word: name of organism’s genus• The second word: identifies the particular

species.• The first letter of the first word is capitalized.• The entire name is in italics.• There may be several species with the same

genus name.

Genus: Canis

• Canis lupus: wolf

• Canis latrans: coyote

• Canis familiaris: domestic dog

• The fact that the above animals have the same first name tells you that they are all in the same genus of dog-like animals and are very similar to one another.

Common Names

• Why not just use common names like cat?• Common names are not precise.• There are many different species of cats:

wild cats and domestic cats.• In addition, people in different regions may

use different common names to refer to the same species. For example: puma, cougar and mountain lion are three different names for the same animal.

Misleading Information

• Common names can give you misleading ideas about the basic characteristics of an organism and the group in which it should be classified.

• Should shellfish, starfish, jellyfish, crayfish and catfish all be in the single group, fish?

• Biologists place each of these members of the animal kingdom in a separate phylum.

Where do we fit in?

Taxon Humans

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Primata

Family Hominidae

Genus Homo

Species Homo sapiens

Chimpanzee

Animalia

Chordata

Mammalia

Primata

Hominidae

Pan

Pan troglodytes

Pan paniscus

Dichotomous Key

• Goal of a taxonomist: identify an organism at the species level.

• Dichotomous key: an identification tool consisting of a series of two-part choices that lead the user to a correct identification.

Example1. a. Organism is microscopic...................................PARAMECIUM.1. b. Organism is macroscopic............................................go to 2

2. a. Organism is a plant.....................................................go to 32. b. Organism is an animal.................................................go to 5

3. a. Plant has a woody stem..............................................go to 43. b. Plant has a herbaceous stem.................................DANDELION.

4. a. Tree has needle like leaves.....................................PINE TREE.4. b. Tree has broad leaves............................................OAK TREE.

5. a. Organism lives on land................................................go to 65. b. Organism lives in water...............................................CLAM.

6. a. Organism has 4 legs or fewer......................................go to 76. b. Organism has more than 4 legs...................................ANT.

7. a. Organism has fur........................................................go to 87. b. Organism has feathers................................................ROBIN.

8. a. Organism has hooves.................................................DEER.8. b. Organism has no hooves............................................MOUSE.

Homework

• Dichotomous key handout

• p. 331 #1-5