for prof the great

Biology 103 Laboratory Exercise – Classification You will be given a group of organisms from the mythical phylum, Nawga, to classify based on structural similarities and differences. Modern taxonomists have many aids to sorting and classifying organisms. You have only your eyes and a dichotomous key. This a “two choice” key to the identification of organisms with either/or and yes/no decisions. Begin by taking each Nawga and following the options presented in the Nawga Key. Proceed down the key to the numbers indicated and continue making choices until all choices end. You may see natural relationships that will offer short cuts. If not, proceed one step at a time. Phylum: Nawga Living Nawgas were recently discovered on an island in the South Pacific. Nawgas are characterized by:

1. A flexible one-piece carapace made of chitin and polymers of esters that extend over the head.

2. Two external noses (nostrils, nares) penetrating the carapace. 3. Three pairs of jointed legs.

These characteristics differentiate Nawgas from all other organisms and place them in their own mythical phylum, Nawga. The phylum name was chosen because these strange creatures molt twice a year producing pelts of nawgahyde. Because the pelts become available by molts instead of by killing the organism, they are extremely valuable to humans. They range in length from 1 to 1.5 meters. The measurements for this lab will all be done in millimeters (mm.). Terms Used in Dichotomous Key Carapace A shell-like plate covering the body of an organism.

Rudimentary Small structures that are present but not well-developed

Antennae Long, slender, paired appendage extending from the head of an organism.

Setae Hair or needle-like projections extending from the body of an organism.

Bifurcate Forked; divided into two branches.

Distal Located away from the body or point of attachment.

Proboscis Long, more or less flexible snout.

Striations Fine lines located on or throughout an area or structure.

Key to the Genera and Species of Nawgas of the South Pacific 1. a. The organism has well-developed eyes, no tail; the second pair of legs is rudimentary . . . . go to 2.

b. The organism is without eyes, usually a tail that may be segmented and has flattened leg segments, most often the first two pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .go to 5.

2. a. The antennae are at least 30 millimeters long; the setae are restricted to the head and tail regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..go to 3.

b. The antennae are reduced to no more than 20 millimeters; the third pair of legs has 4 segments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .go to 4.

3. a. The antennae are slightly bifurcated at distal ends; perforations near margins of carapace . . . . . . . . Genus, Fatopteris; one species, noholensis

b. The antennae are deeply bifurcated at distal ends . . . . . Genus, Forbantensis two species:

curved antennae, curla straight antennae, straighta

4. a. Antennae have proboscis-like projections . . . . . . . . . . . . . . . . . . . Genus, Elephantiasis

one species, grasshopperi

b. Eyes lack striations, setae continuous along margins . . . . . . . . . . .Genus, Blanki two species: larger nawga, brushes smaller nawga, petiti 5. a. Antennae with distal setae tufts; tail longer than 30 millimeters, or if shorter, segmented . .go to 6.

b. Antennae tapering to points; setae restricted to tail region . . . . . . . . . . . . . . . . . . . . . . . . . . go to 7. 6. a. Tail long and unsegmented; black coloration solid and in bands . . Genus, Bandus

two species: straight tail and antennae, pacifica curved tail and antennae, fattus

b. Elongated snout, reduced segments in legs; segmented tail . . . Genus, Sluggi two species:

tail in 2 segments; carapace margin unnotched, sluggi tail in 3 segments; carapace margin notched, segmenti

7. a. Tail absent, nares very reduced . . . . . . . . . . . . . . . . . . . Genus, Nonosi; one species, smithi

b. Tail thickened and prominent . . . . . . . . . . . . . . . . . . . . Genus, Thickus; one species, slickus

*Genus names are capitalized and underlined or italicized. Species names are not capitalized but are also underlined or italicized. *All measurements for this lab will be done in millimeters.

Biology 103 Laboratory Exercise – Classification

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