Assess students' ability to analyze how adding or removing species in a freshwater pond food web (producers, herbivores, predators, decomposers) changes population sizes, trophic relationships, and energy transfer. Tasks include interpreting or sketching a simple pond food web, predicting direct and cascading population effects, explaining changes in energy flow and biomass across trophic levels, and justifying conclusions using ecological concepts (food chains/webs, carrying capacity, trophic efficiency). Problems may include short explanations, a diagram, and basic quantitative reasoning with simple population numbers or percentages.