Classification of Living Things

Taxonomy

Taxonomy

• Definition:– The branch of biology that deals with the

classification and naming of living things

Early Attempts at Classification• Aristotle

– animals– based groupings on habitats

• air-dwellers, land-dwellers, water-dwellers

• Theophrastus– plants– groupings on stem structure

• herbs (soft stems), shrubs (several woody stems), trees (one woody stem)

• Exploration & Microscopes made these two methods obsolete!

Early Attempts at Classification

• John Ray– advanced classification via plant studies– first to use term species

• Carolus Linnaeus– father of modern taxonomy– developed hierarchy of classification based

upon structural similarities– methods are still in use today

Classification Categories• Animal Taxonomy

– Kings Play Chess On Fine Green Silk• Kingdom• Phylum• Class• Order• Family • Genus • Species

• Plant Taxonomy– Division replaces Phylum

Binomial Nomenclature• Definition: a system for naming organisms based

upon two words• Naming of organisms used to be extremely confusing

– many organisms had multiple, multiple names

• Linnaeus “streamlines” by giving each organism a Genus and species name– i.e., Homo sapiens

• Eliminates the confusion of so-called “common naming”

Modern Taxonomy• Theory of Evolution serves as the basis for

modern taxonomic methods– Species: group of like individuals who can breed with

each other and produce fertile offspring• species separated for periods of time become different

species base upon mutations

• Phylogeny– evolutionary history of a species or a group of

organisms

– similar to a family tree

Human Phylogenic

Tree

Another Human

Phylogenic Tree

What Things Do We Use to Classify?• Structural Information

– skeletal, leaves, etc.

• Biochemical Information– DNA, RNA, protein structure, etc.

• Cytological Information– cell structure, chromosome number, etc.

• Embryological Information– structure in early stages of develpment

• Behavior Information– mating calls in crickets, etc.

What are the Kingdoms?

• “Old School” (Kingdoms)

– Monera

– Protista

– Fungi

– Plantae

– Animalia

• “New School” (Domains)– Archaebacteria– Eubacteria– Eukaryote

• Protista• Fungi• Plantae• Animalia

Archaebacteria

• Live in hostile environments

• Most in oxygen-free environments

• Unicellular & prokaryotic

• Examples– Methanogens– Halophiles– Thermoacidophiles

Eubacteria

• Make up the majority of modern bacteria• Most are unicellular

– chains or colonies

• Prokaryotic• Most heterotrophic• Disease-causing • Cyanobacteria

Protista

• Most are unicellular– some colonial and

multicellular

• Eukaryotic

• Heterotrophic are protozoa

• Phototrophic are algae

Fungi• Includes molds, yeasts, mushrooms, etc.• Function as either parasites or decomposers of

dead matter• Most multicellular, some unicellular• Eukaryotic• Have cell walls but of different chemical

structure than plants (chitin v. cellulose)• Cannot photosynthesize• Eat like flies!

Various Fungi

Plantae• Include mosses, ferns, liverworts, and seed

plants

• All have cell walls as part of cell structure

• Most all are photosynthetic

Animalia

• More species in this kingdom than all others

• All are multicellular with a higher level of organization

Animal Phyla• Porifera• Cnidaria• Platyhelminthes• Nematoda• Annelida• Mollusca• Arthropoda• Echinodermata• Chordata

Porifera

• Includes the sponges

Cnidaria

• Includes two body forms,:– polyp – medussa

Platyhelminthes

• Flatworms

Nematoda

• The Roundworms

Annelida

• Segmented worms

Mollusca• Mollusks

– clams, snails slugs

Arthropoda

• Segmented bodies, exoskeletons– crustaceans– centipedes– millipedes– spiders– insects

Echinodermata

• Starfish

• Sea urchins and cucumbers

• Sand dollars

Chordata

• Spinal cord