Nathan is comparing the cells from a species of amoeba with a species of bacteria. Both species are unicellular, meaning individuals exist as a single cell.

Which characteristic of the cells should Nathan expect to be the same in both species?

Jorge is studying a pond ecosystem in his neighborhood. The pond is home to a variety of plant and animal species, as well as a stop for birds that migrate through the region.

One summer, heavy rains wash an unusual amount of fertilizer into the pond. Jorge observes the algae population growing rapidly, and quickly algae cover the pond's surface. Several weeks later, many fish and other animals die in the pond. However, within two years, the algae population has returned to its previous size, as have the populations of all the ecosystem members.