Taxonomy, or the science of classifying organisms, groups organisms into categories based on various characteristics.
Aristotle’s classification system proposed that if something moves, it is an animal, and if it doesn’t, it is a plant. Of course, sponges were mistakenly taken for plants, and when they threatened the shellfish industry centuries ago, were “killed” by being cut up and tossed back into the sea. To the surprise of the shellfish harvesters, the next year, the number of sponges had increased; the shellfishers were actually helping the sponges reproduce (asexually) by their actions.
Linnaeus proposed naming organisms by a two-name system that we call binomial nomenclature. These were very specific names based on the organism’s characteristics and are the genus and species of today. Note that the genus is always capitalized and the species is not, as in Terrestris americanus, and the entire name is underlined or italicized.
The modern system of classification now contains five major groups called kingdoms. Life on the planet could be seen as analogous to a grocery store. The major consumer item areas, such as produce, dairy, and canned goods, would be analogous to the kingdoms of living things. As with the grocery store, the sub-categories get more and more specific until it is possible to name an item exclusive of all other items in the store. You should know the categories, starting with the largest (the kingdom) and continuing to narrower and narrower groups in the sequence: Kingdom, Phylum, Class, Order, Family, Genus, and Species. In plants, the word “phylum” is replaced with the word “division.” Modern day study has become so detailed that we will now find such categories as sub-genus and super-species. The student is responsible only for the above schema. Most beginning biology students become familiar with the mnemonic—memory device—in a variety of expressions, one being King Phillip Come Out For Goodness Sakes. The first letter of each word, in the order given, is the first letter of each of the major categories in taxonomy.
Absorb, Photsyn., Chemosyn.
Unicellular or colonial
Fungi, yeast, molds
EXAMPLES OF GENUS AND SPECIES
Prokaryotes are single-celled, microscopic prokaryotic cells with no distinct nucleus or other membrane-enclosed organelles.
Bacteria have cell walls composed of peptidoglycan, an amino acid–sugar complex, and circular DNA. Composition of the cell wall provides us with the Gram staining means of identifying certain types
of bacteria. Reproduction of bacteria was outlined in an earlier chapter. Some bacteria possess flagella. While many bacteria are decomposers, some fix nitrogen and other elements in a form usable by organisms, and some are pathogenic.
Bacteria can be found in three shapes: coccus (round-shaped), bacillus (rod-shaped)—the one the SAT II Biology exam commonly refers to when asking a question about bacteria—and spirillus (spiral-shaped).
Aerobic (oxygen-needing) bacteria are the largest group of bacteria. Anaerobic (not needing oxygen) bacteria are found in two groups: those that need an oxygen-free environment (obligate) and those that
do not need a lack of oxygen, but a small amount of oxygen will not kill them (facultative).
Protists belong to the Kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms.
Characteristics of Protists
mostly unicellular, some are multicellular (algae)
can be heterotrophic or autotrophic
most live in water (though some live in moist soil or even the human body)
ALL are eukaryotic (have a nucleus)
A protist is any organism that is not a plant, animal or fungus
Protista = the very first
Classification of Protists
how they obtain nutrition
how they move
Animallike Protists - also called protozoa (means "first animal") - heterotrophs Plantlike Protists - also called algae - autotrophs Funguslike Protists - heterotrophs, decomposers, external digestion
.Animallike Protists: Protozoans
Four Phyla of Animallike Protists Classified by how they move
Zooflagellates - flagella
Sarcodines - extensions of cytoplasm (pseudopodia)
Ciliates - cilia
Sporozoans - do not move
move using one or two flagella absorb food across membrane
moves using pseudopodia ( "false feet" ), which are like extensions of the cytoplasm --ameboid movement ingests food by surrounding and engulfing food (endocytosis), creating a food vacuole reproducing by binary fission (mitosis) contractile vacuole - removes excess water can cause amebic dysentery in humans - diarrhea and stomach upset from drinking contaminated water Other sarcodines: Foraminferans, Heliozoans
move using cilia has two nuclei: macronucleus, micronucleus food is gathered through the :mouth pore, moved into a gullet, forms a food vacuole anal pore is used for removing waste contractile vacuole removes excess water exhibits avoidance behavior reproduces asexually (binary fission) or sexually (conjugation) outer membrane -pellicle- is rigid and paramecia are always the same shape, like a shoe
do not move on their own parasitic Malaria is a sporozoan, infects the liver and blood
Plantlike Protists: Unicellular Algae
contain chlorophyll and carry out photosynthesis
commonly called algae
four phyla: euglenophytes, chrysophytes, diatoms, dinoflagellates
accessory pigments help absorb light, give algae a variety of colors
live in water have 2 flagella for movement use chlorplasts for photosynthesis, but can turn into heterotrophs if they are kept in the dark has an eyespot used for sensing light and dark pellicle - like a cell wall, helps maintain their shapes
Chrysophytes yellow-green algae, "golden plants"
Diatoms produce thin cell walls of silicon, main component of glass
Dinoflagellates Often have two flagella luminescent
Ecology of Unicellular Algae
make up the base of aquatic food chains
phytoplankton makes up half of the photosynthesis that occurs on earth (oxygen)
can cause Red Tides - algal blooms - which are toxic