Animal Evolution. I. Animal traits A. Heterotrophic B. Mobile C. Lack cell walls D. Possess nerve...

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Animal Evolution
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Transcript of Animal Evolution. I. Animal traits A. Heterotrophic B. Mobile C. Lack cell walls D. Possess nerve...

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