BIO 104 5/1/96

Phylogenetic Tree
     SEE FIGURE 29.2

Phylum Arthropoda
     a. marine, fresh water, and terrestrial
     b. segmentation:  segmented bodies
     c. external skeleton:  exoskeleton
     d. ventral nerve cord
     e. open circulatory system
          -gills
          -tracheae (insects)
3 Main Groups
     1. Class Crustacea 
          -2 pair of antennae
          -respire by gills
          -examples:  lobster, crayfish, shrimp, and barnacles
     2. Class Arachnida
          -examples:  spiders, horseshoe crabs, mites, and ticks
          -no antennae
          -reduced segmentation
          -4 pair of legs
          -no jaws
     3. Class Insecta
          -There are more organisms in this class than any other.
          -have a head, thorax, and abdomen
          -1 pair of antennae
          -usually 2 pair of wings
          -3 pair of legs
     Characteristics of Arachnids:
          -Poison gland
               -immobilize their prey
               -digest contents of their prey in the sucking stomach
               -They are scary to some; who might consider 
               themselves arachnophobics.
     Figure 29.21
     Lobster
          -Their claws are modified legs, and they really taste
          good, cooked properly, especially in New Orleans.
     Preying Mantis
          -The female, who is bigger, bites off the head of the
          male, and then copulates with the headless male.  Then
          the female eats the male's body.  Thus, reproducing and 
          finding its food at the same time.
Metamorphosis:
     This is the process where an organism starts as a small larvae
     and develops into an adult.  The larvae collects organic 
     material and then molts into a pupa stage.  After a certain
     time the pupa molts to form the mature larger adult.
     Fleas
     -wingless
     -go through complete metamorphosis
     -can carry disease

NOTE:  SOME MOLLUSKS HAVE OPEN CIRCULATORY SYSTEMS AND OTHERS HAVE
CLOSED CIRCULATORY SYSTEMS.

Deuterostomes:
     A. Echinoderms (spiny skin)
          1. Echinoderms and chordates most likely have a common
               ancestor based on embryonic development
          2. Familiar examples include:  starfish, sea urchins,
               sand dollars, and sea cucumbers
          3. Characterized by:
               a. bilateral symmetrical larvae and radial 
               symmetrical adults
               b. radial 15 part body plan
               c. a vascular water system that is used for loco-
               motion
               d. rings of nervous tissue but no centralized
               brain
          4. Starfish
               -They attach to clams and oysters and avert their 
               stomachs into the shell and suck up the clams or 
               oysters.
               -Regenerates
               -have tube feet
                    -hydraulic pressure: locomotion
     SEE FIGURE 29.25

Chordates:
     1. They are characterized by:
          a. a single, dorsal, hollow nerve cord
          b. a notochord
          c. 5 pharyngeal gill slits
               -Human embryo gill slits become the bones of the
               inner ear, but we have them at early stages of 
               development.
     2. Divided into acraniate {no head (example: tunicates)}
     and craniata {has a head (us, the vertebrates)}
     3. Larval tunicates exhibit chordate features, but adults
     do not.
     4. Vertebrates are characterized by a vertebral column that
     surrounds the dorsal nerve cord.