what is it?

Identification aids.

Keys are developed by workers for groups of organisms to assist in the identification of organisms, using characters that are distinct.

These keys can be either natural, utilizing characters that are phylogenetically accurate (portraying the true evolutionary linkages) or artificial (use of any character, as long as they don’t overlap between the groups being separated).

Most keys are dichotomous, meaning that at every step along the way, there is a choice to be made between 2 alternatives. In my work, I have had occasion to use trichotomous keys, which are infinitely more difficult.

Thus, most keys are natural dichotomous keys. Two such keys are the ones that you have in this booklet that identifies some of the more common green algae and brown algae in San Diego. The key to some Pacific Coast Subtidal Marine Invertebrates is an artificial, dichotomous/trichotomous one that is fairly easy to use.

Summary of systematics/classification of organisms:

Important discipline to all phases of biology. The naming of a species follows precise procedures and all disputes are mediated by International Commissions on Zoological and Botanical Nomenclatures.

The fully ascribed name of a species consists of the genus and species names, given in that order, with the generic name capitalized and the species name not capitalized and the entire two-part name italicized or underlined.

Often, the author of an article will also be cited (who first legitimately described the species) by citing the last name (not italicized) of that person after the species name, followed by the year of the description. Thus, Ophioderma panamense Lutken, 1872, becomes the full citation for this ophiuroid/brittle star which was described initially by Lutken in 1872.

If the initial describer of the species had made a mistake in the phylogenetic relationships or the groups have been altered since the describer since the description (with the effect that the initial describer placed the species in the wrong genus), then the describer’s name is placed in parentheses. Patiria miniata (Brandt, 1835) is a bat star that was initially described by Brandt in 1835 under the genus Asterina.

The ecologist must know what organisms exist in a community before judging the effects of pollution.

The biochemist must know specifically from what organism a new compound is being isolated.

The fishery biologist cannot manage wild stocks unless it is known which species have been taken.

Thus, this is not just a procedure of name giving but is part of a study of the tremendous diversity of all organisms and an attempt to categorize and bring order to this diversity by looking at the interrelationships between different groups of organisms.