Animal Evolution

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

E. Common embryology 1. cleavage 2. blastula 3. gastrulation 4. germ layers

F. Homeotic genes 1. genes that control development 2. control placement and location of appendages

Mutations in homeotic genes can cause huge changes in a single generation

II. Monophyletic origin A. Colonial choanocyte B. Flagella with microvilli collar around the flagella C. No division of labor

D. Possible mode of evolution

III. Grades of Evolutionary Tree

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

D. Development of a coelom 1. definition 2. functions

3. Flatworms (platyhelminthes) are acoelomate

4. Roundworms have a pseudocoelom

5. Higher bilateria have a true coelom

E. Protostome vs. deuterostome lineages 1. protostomes- molluscs, annelids, and the arthropods 2. deuterostomes- echinoderms and chordates

Early animal development terms Cleavage

Blastula

Gastrulation

3. Differences between the two a. cleavage b. coelom formation c. fate of blastopore