L.5: Sea Urchin Dissection


-Introduction:

The purpose of this lab is to study our friend, the ecosystem's sea urchin. The sea urchin is an echinoderm like the sea star. With the sea star the joints are unfused thus the five separate legs. The sea urchins legs are all connected, fused, together. Our sea urchin had a hard shell like most sea urchins, and was very difficult to view the internal organs, for what we found was green mushy goo.

-Procedure/Materials:

1. Took sea urchin out of preserved liquid filled package.
2. Observed external features of sea urchin.
3. We scraped off all of the spines with a scalpel.
4. We removed the Aristotlešs Lantern to empty out inner goo.
5. Cut endoskeleton in half to receive a better view of internal.
6. Observed internal features and took notes.

1. Dissection kit- scalpel, ruler, pins, probe, tweezers, scissors, and dissection pad.
2. Starfish dissection guide.
3. Marine biology coloring book page #41.
4. Castro/Huber Marine Biology text book, pgs. 132-134.
5. Purple sea urchin.

-Lab Questions/answers:
1. Q: What are ossicles and how are they arranged in sea urchins? How is this different in sea cucumbers?

A: The ossicles are skeletal plates, and in sea urchins they are fused together. Sea cucumbers. unlike the sea urchin have loose ossicles inside of their bodies, and are unfused.

2. Q: Is the oral side of the sea urchin "up" or "down"? That is, which direction is oral side facing?

A: The oral suface is the bottom, where the mouth is facing down.

3. Q: How do sea urchins move?

A: In two different ways, with their long tube feet, or by their long spines.

4. Q: What is Aristotle's Lantern?

A: The stomach like jaw, helping them to clean and eat, located at the mouth.

-Conclusion:

The sea urchin has an outer hard shell called the endoskeleton, the the top part is called the aboral surface, and the bottom is called the oral surface. The spines are used to help the sea urchin to move around and also protection. The Aristotle's Lantern located on the oral surface, near the mouth, is also used to move, but basically for eating. The sea urchin has "fused" legs. A close relative, the sea star, has unfused legs enabling it to move faster. We learned a lot of similar things beteew the sea star and the sea urchin dissections. Some organisms preserve better then others, the Sea Urchin is not one of them.


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