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I. Animal traits
• A. Heterotrophic• B. Mobile• C. Lack cell walls• D. Possess nerve and
striated muscle
D. Reproduces sexually
• 1. Diploid generation dominant
• 2. Often has larval form
• 3. Displays metamorphosis
F. Homeotic genes
• 1. genes that control development
• 2. control placement and location of appendages
II. Monophyletic origin
• A. Colonial choanocyte
• B. Flagella with microvilli collar around the flagella
• C. No division of labor
A. Major branches of the phylogenetic tree are called grades• 1. The grade is like a fork in the road that represents
a major anatomical change that opens up new possibilties
• 2. Once a lineage begins down a grade, it once was thought of as an irreversible path-male passing down a road
• 3. Now with new tools of discovery-DNA sequencing some of older pathways are now being reconsidered
• 4. We will stay with the older story for the time being
B. First bifurcation-cellular vs. tissue specialization• 1. sponges possess cellular specialization but not
true tissues• 2. sponges are referred to as parametazoans-kind of
animal-like• 3. second branch represents eumetazoans-true
animals• 4. the eumetazoans possess two qualities that are
more animal-like than the sponges– a. true tissue level specializations– b. symmetry
C. Types of symmetry-radial vs. bilateral
• 1. definitions• 2. body planes• 3. dorsal vs.
ventral• 4. cephalad vs.
caudad• 5. anterior vs.
posterior
6. Radial symmetry
• a. no cephalization• b. adapted for
sessile existence• c. either drifts or
stays attached to a surface
• d. nothing sneaks up on it
• e. these organisms are diploblastic
7. Bilateral symmetry• a. in addition to a top and a
bottom-dorsal and ventral surface
• b. there is an anterior and a posterior end of the animal
• c. cephalization• d. there is also a
longitudinal nerve cord that runs toward the posterior end of the animal
• e. these animals concentrate their sense organs at the end of the animal that meets the world
• f. tend to be active and highly mobil
• g. triploblastic
E. Protostome vs. deuterostome lineages
• 1. protostomes-molluscs, annelids, and the arthropods
• 2. deuterostomes-echinoderms and chordates