Students learn what a population is, how different populations form communities, and how changes in population size affect an environment.
Students learn how people can change and sometimes pollute habitats.
Students also learn about ways that people can protect living things and their habitats. Students learn how habitats differ and how organisms can change their environments. National Science Standard 4.7 Science in Personal and Social Perspective. By the end of fourth grade, students will develop an understanding of environmental changes. Students observe polluted water at the beginning of the activity and after five minutes, then compare it with tap water.