What natural process can students understand better by observing mounds of sand and their erosion when watered?

The natural process that students can better understand by observing mounds of sand and their erosion when watered is erosion. Erosion refers to the process by which soil and rock are removed from one location on the Earth's crust and transported to another location, often influenced by the action of water. When students observe how water interacts with sand mounds, they see firsthand how water can change the shape and structure of the mound, washing away particles and altering the landscape. This observation helps them grasp the concept of erosion and its implications in nature, including how it can lead to changes in environments over time and affect plant growth, habitats, and even human structures.

The other processes listed, such as photosynthesis, pollination, and fertilization, do not directly relate to the effects of water on sand mounds. Photosynthesis involves the conversion of light energy into chemical energy by plants, while pollination is the transfer of pollen from one flower to another, and fertilization involves the union of male and female gametes. Each of these processes occurs in different contexts and does not correspond to the physical changes observed in sand due to water erosion. Thus, erosion stands out as the relevant natural process in this scenario.