9.4: Data Analysis and Discussion

Instructions

Discussion should be typed (double spaced, size 12 font and standard 1” margins). There are no specific length requirements for this discussion but be sure to address all the components in the prompt below. You will submit this discussion along with your sketches and observations for your completed lab report.

Prompt/Questions to Address

Write a discussion for this experiment which explores the characteristics and evolutionary significance of the animals observed during this lab. Be sure to address each of the following in your discussion:

1. Examine the body plan of mollusks. The mussel’s visceral mass houses several organ systems in a compact space. Discuss one advantage and one limitation of having organs concentrated in a visceral mass.
2. Examine the body plan of annelids. Describe how segmentation is evidenced in the earthworm’s external and internal anatomy. What are the advantages of segmentation?
3. Examine the body plan of arthropods. Identify three distinct adaptations of the crayfish that reflect its active, mobile, and often predatory lifestyle. For each adaptation, explain the functional advantage. The crayfish exoskeleton requires periodic molting for growth. Discuss the advantages and disadvantages of having an exoskeleton compared to an internal skeleton/endoskeleton.
4. Examine the body plan of echinoderms. Describe the unique water-vascular system of the sea star (madreporite → stone canal → ring canal → radial canals → ampullae → tube feet). How does this system enable locomotion and feeding?
5. Evaluate the evolutionary relationships between these different animals. Arrange the four phyla examined (Mollusca, Annelida, Arthropoda, Echinodermata) along a short continuum describing increasing organ/system complexity and justify your ordering with two anatomical observations from the lab.