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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