Chapter 33 Lecture Enrichment Ideas


  • Provide either specimens or slides to compare size, structure, habitats, and relative complexity of the different invertebrates.
  • Discuss possible reasons why there appeared to be a sudden explosion of development of animal phyla during the early Cambrian period.
  • Contrast the inverted structures of the medusa and polyp forms of cnidaria, and examine how the body structure is different from that of a sponge.
  • Compare the body structure of the flatworm and the roundworm, with emphasis on body layers, digestive tract, and reproduction.
  • Most of these parasitic diseases are tropical; utilize slides or other audiovisuals to illustrate the ravages of elephantiasis, fluke infestations, etc. Many cultural habits have evolved to circumvent ingestion of these parasites; describe the benefits of hygiene, plumbing, etc. noting that some depend upon a minimal affluence that is not available in poor regions of the world. Many students do not realize the extent they avoid suffering due to U.S. customs and engineering, etc.


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