Interaction with Light in Social Amoebas

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Interaction with Light in Social Amoebas

Social amoebas (Dictyostelium discoideum) or slime mold are amoebas that exist in leaves that have fallen on the ground where there is moisture and bacteria that they can feed off. Generally, these social amoebas can survive as single cells (myxamoeba), moving around the decaying leaf to feed on bacteria that contain folic acid. If conditions change, either by the leaf becoming dry or having little bacteria to feed on, the myxamoeba may start dying off. The myxamoeba then begins sending out chemical signals that indicate other nearby myxamoebas to gather. The myxamoeba’s membranes stick to each other and begin to pile up until it’s so high that it tips over and forms a slug about 2-4 millimeters long. By doing this, the myxamoeba have become a multi-cellular organism. The slug is capable of moving around, and that’s exactly what it does. The cells in the front of the social amoeba (posterior) secret a slime that helps the slug body move and glide around. The slug will move towards the light and once it is in the correct environment, the posterior end of the slug settles down and forms a stalk. The cells that were once at the end (anterior) begin to climb up the stalk and form the “ball” at the top of the stalk where the cells become spores. This is called a fruiting body, and it quite resembles bread mold. From the fruiting body, the spores will be released into the environment where they will land elsewhere and begin to germinate into myxamoeba again. Our goal in the experiment was to see if having absolutely no light available to one Petri dish of slime mold would make a difference in the behavior of the slime mold in comparison to one that was exposed to a bit of light. We hypothesized that the Petri dish that was exposed to a bit of light (experimental group) would have slugs that moved toward the direction of the light. We predicted that the Petri dish that was deprived of light (control group) would...
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