BEHAVIOR OF Hydra All animals respond to their environment with either instinctive or learned behavior. Even forms, which lack a well-defined brain or nervous system, such as man possesses, do nevertheless have distinctive behavior patterns. In many simple animals, there is behavior of an instinctive or fixed pattern, which we speak of as being taxis. A taxis is either a direct movement in response to some stimulus in the environment or it is a series of random movements that ultimately lead the animal into appropriate conditions or favorable environments. In higher animals and especially in man, behavior is modified by insight, the ability to learn, to remember, and similar processes whereby we possess not a fixed but a modifiable, intelligent type of behavior. * The purpose of this exercise is to observe the responses to the environment made by Hydra and to determine what type of behavior it shows. MATERIALS Hydra culture Methylene blue White vinegar Depression slide or small dish Probe or dissecting needle Beaker (50 ml) Watchglass Flashlight PROCEDURE Part A 1. With a medicine dropper, obtain a hydra from the culture jar. You may have to gently scrape the hydra loose from the glass. 2. Place the hydra and some of the water from the jar in the depression of a concave microscope slide. Cover the depression with a coverslip. 3. Carefully remove the coverslip from the slide. While looking at the Hydra through the dissectiong microscope, touch a tentalcle with the tip of a probe or dissecting needle. Part B 1. Place several live hydra in a watch glass, be sure to add enough water to the cover the hydras. 2. Tap on the watch glass and watch how the hydras react. 3. Shine a flashlight (white light) on one side of the watch glass notice whether the hydras move away or towards the light. 4. Repeat using different color acetates. Defense Mechanisms 1. With a medicine dropper, obtain a hydra from the culture jar. Place it on a clean, flat, glass slide. Gently lower a coverslip over the hydra. Do not press down on the coverslip. 2. Stain the hydra by placing a drop of methylene blude at the edge of the coverslip. Place a small piece of paper towel on the opposite edge to draw the stain under the coverslip. 3. Using a light microscope, focus on the tnetacles of the hydra under low power. 4. Obtain a small amount of vinegar in a 50 ml beaker. While observing the tentacles, use a medicine dropper to place one drop of vinegar at the edge of the coverslip. Observe how the hydra's tentacles react to the vinegar. Record your observations. Biology 10