2.3.1 Taxonomy and Classification

ClassificationThe science of grouping organisms based

on their similarities.

Why we classify? To help identify organisms To draw parallels and distinctions

between organisms To identify relationships between

organisms To communicate with others (universal

language) To identify evolutionary patterns and

relationships

What’s the basis for classification?

Morphology (structures) Physiology (functions) Biochemistry Genetics

TAXONOMYScientists look for these similarities:

1. Anatomical2. Biochemical3. Embryological development4. Evolutionary relationships

ARISTOTLE (384-322 B.C.)s Greek philosopher.s Came up with the 1st system of

classification.1. Plants:

- stem types2. Animals:

- land, air or water

Carolus Linneaus (1707-1778)

s Swedish botanist.s Came up with

today’s modern system of classification.

6 KINGDOMS

Moner

a

Hierarchy of Classification Kingdom Phylum Class Order Family Genus Species

Phylogenic Tree = each

branch point

represents a common ancestor of the species above that

point.

s Scientists use a 2-word system of naming different organisms called BINOMIAL NOMENCLATURE.

s This 2-word name is called a SCIENTIFIC NAME and it is made up of the genus and species names.

St. John’s Wort: Hypericum perforatum

Dandelion: Taraxacum officianalisDomestic cat: Felix domesticusMosquito: Colex pipensHuman: Homo sapiensMaryland blue crab: Calinectes

sapidus

s A scientific name is either written in italics or it is underlined.

s Genus is capitalized, species isn’t!

Fig. 20.11, p. 320

COMMON NAME:

KINGDOM

GENUS

SPECIES

FAMILY

ORDER

CLASS

PHYLUM

corn

Plantae

Zea

Z. mays

PoaceaeCommelinales

Monocotyledonae (monocots)

Anthophyta (flowering plants)

vanilla orchid

Plantae

VanillaV. planifolia

Orchidaceae

Orchidales

Monocotyledonae

Anthophyta

housefly

Animalia

MuscaM. domestica

MuscidaeDiptera

Insecta

Anthropoda

human

Animalia

Homo

H. sapiens

Hominidae

Primates

Mammalia

Chordata

s In order to identify new organisms and to figure out what species they are, scientists use a DICHOTOMOUS KEY.

s By asking a series of “Yes/No” questions about the organisms anatomy, the organism can be identified.

A simple Dichotomous Key

A Complex Dichotomous Key

1a. Hair present . . . . . . .Class Mammalia1b. Hair absent . . . . . . . Go to 22a. Feathers present . . . . Class Aves2b. Feather absent .. . . . Go to 3

3a. Jaw present . . . . . . .Go to 43b. Jaw absent . . . . . . . Class

Agnatha4a. Paired fins present . . . . Go to 54b. Paired fins absent .. . . . Go to 6

6a. Skin scales present . . .Class Reptilia6b. Skin scales absent . . . Class Amphibia

1a. Body symmetry radial . . . . . . . . . . Go to 21b. Body symmetry not radial . . . . . . . Go to 32a. Tentacles present, body soft . . . . . P. Cnideria2b. Tentacles absent, body hard & rough . . . . . P. Echinodermata

1a. Body symmetry radial . . . . . . . . . . Go to 21b. Body symmetry not radial . . . . . . . Go to 3

3a. Exoskeleton present . . . . . . . . . . . . Go to 43b. Exoskeleton absent . . . . . . . . . . . . . Go to 5

4a. Jointed legs present . . . . . . . . . . P. Arthropoda4b. Jointed legs absent . . . . . . . . . . . P. Mollusca

1a. Body symmetry radial . . . . . . . . . . Go to 21b. Body symmetry not radial . . . . . . . Go to 33a. Exoskeleton present . . . . . . . . . . . . Go to 43b. Exoskeleton absent . . . . . . . . . . . . . Go to 5

4a. Jointed legs present . . . . . . . . . . P. Arthropoda4b. Jointed legs absent . . . . . . . . . . . P. Mollusca