CLASSIFICATION NOTES
I. BIOLOGICAL CLASSIFICATION
Classification is the grouping of objects or organisms based on their
similarities. Scientists classify organisms to organize them; make it easier to
understand and communicate about them. The branch of biology concerned
with the grouping and naming of organisms is called taxonomy. Taxonomy
utilizes evolutionary relationships between organisms to correctly identify and
group them.
A. Binomial Nomenclature
Binomial nomenclature is the universal classification system used today in
which groups are formed according to Physical characteristics and then
each organism is assigned a 2-word scientific name. The scientific name is
the genus and species of the organism. Genus and species names are
always underlined or written in italices. Genus is capitalized, species is
not.
B. Categories of Classification
1. Kingdom – broadest category, groups of closely related phyla
2. Phylum – groups of closely related classes
3. Class – groups of closely related orders
4. Order – groups of closely related families
5. Family – groups of closely related genera
6. Genus – groups of closely related species
7. species – smallest and most similar group; organisms that share specific
characteristics and can interbreed.
C. Scientific Classification of a Human
Kingdom ______Animalia______
Phylum ______Chordata______
Class ______Mammalia______
Order ______Primate______
Family ______Hominidae______
Genus ______Homo______
Species ______sapiens______
II. THE SIX KINGDOMS OF LIFE
A. Kingdom Archaebacteria
1. Cell Type – Prokaryotic
2. Cell Structure - cell wall without peptidoglycan; DNA, cytosol, cell
membrane, & ribosomes present
3. Body Form - All unicellular
4. Nutrition - autotrophic or heterotrophic
5. Other characteristics – considered to be the most ancient of
organisms; live in very harsh conditions like extreme temperatures,
high pH concentration, etc. Another group of Archaebacteria live in the
digestive system of animals and produce methane gas.
6. Examples - methanogens, Thermoacidophiles, Halophiles
Great Salt Lake, UT - The Great Salt Lake, second in salinity only to the Dead Sea, was believed to be as 'dead' until very recently. However, halophilic microorganisms strive in these environments having developed mechanisms to endure high salt concentrations, dessication and constant UV radiation.
B. Kingdom Eubacteria
1. Cell Type - Prokaryotic
2. Cell Structure - Cell wall made up of peptidoglycan; DNA, cell membrane,
cytosol, & ribosomes present
3. Body Form - All Unicellular
4. Nutrition – Mostly heterotrophic; some are autotrophic (photosynthetic
or chemosynthetic)
5. Other characteristics – Most common bacteria. They are ubiquitous
which means they are found everywhere. Very important
decomposers. Some are pathogenic, but most are harmless.
6. Examples - decomposers, E.coli, Streptococcus sp, Staphylococcus sp,
Salmonella sp
C. Kingdom Protista
1. Cell Type - Eukaryotic
2. Cell Structure – May have cell wall; may have chloroplasts; may be
motile and have cilia or flagella.
3. Body Form – Mostly unicellular; may be multicellular
4. Nutrition – autotrophic or heterotrophic
5. Other Characteristics – Nicknamed “ Catch-all” kingdom or “Junk-
Drawer”. Contains organisms that don’t “fit” into other kingdoms. Protists
are sub-grouped according to which Eukaryotic kingdom they’re most like;
for example. Fungi-like, Protist-like, or Animal-like.
6. Examples – slime molds, Euglena, Paramecium, algae, Amoeba
D. Kingdom Fungi
1. Cell Type - Eukaryotic
2. Cell Structure – Have cell wall made of chitin; fungi do NOT have
chloroplasts.
3. Body Form – Mostly multicellular; may be unicellular. Single-celled
fungi are known as yeast.
4. Nutrition – All heterotrophic! Obtain nutrients through a process
called absorption, meaning food is digested outside their bodies by
secretion of cells, then absorbed by fungi.
5. Other Characteristics – Principle decomposers. Also important in
brewing and baking.
6. Examples – mushrooms, molds, yeasts, truffles, morels
E. Kingdom Plantae
1. Cell Type - Eukaryotic
2. Cell Structure – Have cell wall made of cellulose; chloroplasts
present.
3. Body Form – All multicellular
4. Nutrition – All autotrophic
5. Other Characteristics – Most contain organs and organ systems. All
non-motile with specialized reproductive structures.
6. Examples – mosses, ferns, trees, flowering plants
F. Kingdom Animalia
1. Cell Type - Eukaryotic
2. Cell Structure – Never have cell wall
3. Body Form – All multicellular
4. Nutrition – All heterotrophic
5. Other Characteristics – Most complex of all kingdoms. Most
organisms contain organs and organ systems. All members are
capable of movement sometime during their lifetime. Most animals are
invertebrates meaning they lack a backbone. All vertebrates belong to
Phylum Chordata.
5. Examples – sponges, fish, worms, insects, reptiles, amphibians,
mammals
III. THE EVOLUTION OF CLASSIFICATION
Taxonomy, the science of classification, is a work in progress, in large part,
because of evolution, both as a science and a process.
1. The Kingdoms of Life
DNA analysis has had a major impact on the classification system,
changing the long accepted system of 5 kingdoms to 6 kingdoms. The
two prokaryotic kingdoms, Archaebacteria and Eubacteria were
originally classified together as Kingdom Monera.
2. The Three Domains of Life
Recently, further studies have led taxonomists to propose a
classification system which includes three “super-kingdoms” called
Domains.
a. Domain Archaea – Includes the Archaebacteria
b. Domain Bacteria – Includes all remaining prokaryotes or the
Eubacteria
c. Domain Eukarya – Includes the four eukaryotic kingdoms –
Protista, Fungi, Plantae, Animalia