Please help this is a 7th grade science problem

Why is excretion necessary to maintain homeostasis?

What are two ways that harvesting algae from the ocean may benefit human society? how might the harvest of algae negatively impact the ocean communities where that algae grows? how could this be prevented?

Did the vinegar diffuse all the way to the center of any of the cubes? if so, which ones? what does this tell you about surface area-to-volume ratio and the diffusion rate?