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Ch. 27 - Diversification of Eukaryotes
All textbooksFreeman 8th EditionCh. 27 - Diversification of EukaryotesProblem 16
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Chapter 26, Problem 16

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Researchers have proposed that slime molds could be used to help to plan the paths of future roadways and railways. Justify this statement.

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Hello everyone and welcome to today's video. So today we have given the following descriptions. We need to identify the option that is incorrect regarding slime molds. So before we jump into the problem, let me quickly remind you of a few facts about slime molds that we need to know in order to solve this. First of all, they're decomposing organisms. And second of all, they formed the structure called the plasmodium. And the plasmodium is a mass of cytoplasm that they use in order to decompose things. So now that we know this, let's just start going over the options that were given so that we can identify the one that is incorrect. Beginning by P. So there's land modes cause the decay and decomposition of the organic matter in the soil. We already said that there D composers. So this is the correct answer choice. And we're going to cancel it out because we're looking for the incorrect one. Then we have our slime molds leave a slimy material along the pathway of their locomotion. All these slimy material is going to be what they used to decompose is going to be these these enzymes that are going to be living behind as they move. So we're going to cancel this out as well because this is correct is why they're called slime molds. So then we have s the plasmodium, which is what we saw here of lime modes are an excellent material for the study of the structure and physiology of protoplasm. While this protoplasm just includes many things, but one of them is cytoplasm and cytoplasm already saw here that the plasmodium is a mass of cytoplasm. So because of this, this is going to be a correct answer choice. The plasmodium can be used to study the protoplasm. So now this all lifts us with Q. They play an important role as primary producers in the foot wave. So we already established that they're decompose ear's as we saw here. So this is going to be incorrect as if an organism is a D. Composer, it is very likely that it's not going to be also a producer. So we're going to highlight this as the final answer to our question. I really hope this helped you and I hope to see you on the next one.
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Textbook Question

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Does an organism without a brain have the ability to use an externalized 'memory'—a spatial 'slime map' that the organism uses to avoid moving to regions where it has been before? Researchers addressed this question by placing a U-shaped trap between Physarum and its food (see diagram that follows). Twenty-three out of 24 slime molds reached the food when plain agar was used as the growth substrate. However, when the agar was coated with extracellular slime, only 8 of 24 found the food. The mean time in hours that it took the successful slime molds to reach the food when placed on plain agar or agar pre-coated with extracellular slime was compared (P=0.012). Use the P value provided to determine if the difference is significant or not. What conclusion can be drawn from the graph shown here?

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Textbook Question

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Propose an experiment that would test whether the coating of extracellular slime changed the speed at which the slime mold moved across the substrate.

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Textbook Question

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Develop simple experiments to test whether Physarum prefers (1) brightly lit or dark environments; (2) dry or moist conditions; (3) oats or sugar as a food source.

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