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LAB7answers - LAB 7 THE INVERTEBRATES I Answers to the lab...

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LAB 7 THE INVERTEBRATES I Answers to the lab manual questions: Does the Hydra actively move to capture its prey or does it sit and wait for the prey to bump into its tentacles? (7-2) You are the best judge of your hydra’s behavior. For the most part, they remain attached to their substrate and let their tentacles drift with the water currents. If a prey item (e.g., a zooplankton species) brushes into one of the tentacles, the hydra quickly grabs onto it with the other tentacles subduing it with poisonous threads/filaments from its nematocysts. Watch carefully to see if this description fits the feeding behavior of your hydra. How does the radial symmetry of your hydra (and cnidarians, in general) assist them in this feeding strategy? (7-2) Most cnidarians are opportunistic feeders and capture prey as they bump into their tentacles, rather than stalking or chasing after its prey. Having sensory and feeding structures (tentacles) radiating from their body increases their abilities to sense and capture prey that may be coming at them from any direction. This differs from animals that go after their prey. In this case, being bilaterally symmetrical is more beneficial because the sensory structures are concentrated in one area, which is moving in one direction. How many tentacles does your hydra have? How does this compare to the hydra of the students around you? (7-3) Hydra typically have 6 tentacles. If yours has less, perhaps it is because one was lost. Look to see if it is regenerating. Hydra actually received their name for their ability to regenerate lost tentacles quickly. The mythical 9-headed monster Hydra that was eventually slain by Hercules had the ability to regenerate its heads when they were cut off. What is the probable function of the ciliated cells in the gastrodermis? (7-4) They, along with the muscular contractions of the cells in the gastrodermis, create water currents, which circulate the food throughout the gastrovascular cavity. This increases the distribution of nutrients to all the cells. Gas exchange also occurs in the gastrodermis, so water currents help not only to distribute food but also oxygen and to remove wastes. Identify the cell types and structures involved in the recognition, capture, ingestion, and
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This lab report was uploaded on 04/19/2008 for the course BIOL 111 taught by Professor Brianmcgill during the Winter '07 term at McGill.

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LAB7answers - LAB 7 THE INVERTEBRATES I Answers to the lab...

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