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. Which of the following best describes movement in Physarum?
a. Cilia propel the slime mold.
b. Flagella propel the slime mold.
c. The slime mold moves by amoeboid motion.
d. The slime mold moves by gliding motility.

Early estimates suggested that the oxidation of glucose via aerobic respiration would produce 38 ATP. Based on what you know of the theoretical yields of ATP from cellular respiration, show how this total was determined. Why do biologists now think this amount of ATP per molecule of glucose is not achieved in cells?

Chlamydomonas is a unicellular green alga. How does it differ from a photosynthetic bacterium, which is also single-celled? How does it differ from a protozoan, such as an amoeba? How does it differ from larger green algae, such as sea lettuce (Ulva)?

Suppose a friend says that we don't need to worry about the rising temperatures associated with global climate change. She claims that increased temperatures will make planktonic algae grow faster and that carbon dioxide (CO₂) will be removed from the atmosphere faster. According to her, this carbon will be buried at the bottom of the ocean in calcium carbonate shells. As a result, the amount of carbon dioxide in the atmosphere will decrease and global warming will decline. Comment.

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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.

Physarum is a plasmodial slime mold, whereas Dictyostelum is a cellular slime mold. Compare and contrast movement by the migrating slug stage of Dictyostelium to the plasmodial stage of Physarum.

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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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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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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.