Each element can exist in several different chemical reservoirs. Each element on Earth moves among reservoirs in the solid Earth, oceans, atmosphere, and living things as part of geochemical cycles. Movement of matter between reservoirs is driven by the Earth's internal and external sources of energy. These movements are often accompanied by a change in the physical and chemical properties of matter. Carbon, for example, occurs in rocks as limestone, in the atmosphere as a gas, in water as dissolve carbon dioxide, and in all living things as complex molecules that control the chemistry of life.
Similarities exist within different ecosystems.
NSES Content Topic Population Growth Populations grow or decline through the combined effects of births and deaths, and in countries through emigration and immigration. Populations can reach the limits to growth. Carrying capacity is the maximum number of individuals that can be supported in a given environment. It is not availability of space, but the number of people in relation to resources and the capacity of Earth systems to support human beings. Populations are dynamic with identifiable characteristics and measurable growth patterns.