Animal Evolution I Animal traits A Heterotrophic B
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. 2. 3. 4. cleavage blastula gastrulation 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. protostomesmolluscs, annelids, and the arthropods • 2. deuterostomesechinoderms and chordates
Early animal development terms • Cleavage
Blastula
Gastrulation
3. Differences between the two • a. cleavage • b. coelom formation • c. fate of blastopore
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