Animal Evolution

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Animal Evolution
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I. Animal traits

• A. Heterotrophic
• B. Mobile
• C. Lack cell walls
• D. Possess nerve and striated muscle

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D. Reproduces sexually

• 1. Diploid generation dominant
• 2. Often has larval form
• 3. Displays metamorphosis

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E. Common embryology

• 1. cleavage
• 2. blastula
• 3. gastrulation
• 4. germ layers

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F. Homeotic genes

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

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Mutations in homeotic genes can cause huge
changes in a single generation
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II. Monophyletic origin

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

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D. Possible mode of evolution
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III. Grades of Evolutionary Tree
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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

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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

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C. Types of symmetry-radial vs. bilateral

• 1. definitions
• 2. body planes
• 3. dorsal vs. ventral
• 4. cephalad vs. caudad
• 5. anterior vs. posterior

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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

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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

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D. Development of a coelom

• 1. definition
• 2. functions

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3. Flatworms (platyhelminthes) are acoelomate
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4. Roundworms have a pseudocoelom
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5. Higher bilateria have a true coelom
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E. Protostome vs. deuterostome lineages

• 1. protostomes-molluscs, annelids, and the
  arthropods
• 2. deuterostomes-echinoderms and chordates

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Early animal development terms

• Cleavage

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Blastula
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Gastrulation
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3. Differences between the two

• a. cleavage
• b. coelom formation
• c. fate of blastopore