Energy is all around us and flows through our lives in many ways. It flows through both nonliving and living systems, including human societies.
Energy flow through nonliving systems creates the weather patterns and shapes the Earth's surface. For example:
- The solar energy that is absorbed and distributed on Earth's surface gives rise to weather systems and ocean currents.
- The thermal energy that is in Earth's interior shapes and moves Earth's crust as in earthquakes, mountain building, and volcanic activity.
Energy flow in living systems enables humans and other organisms to survive. Living systems use energy to grow, change, maintain health, move, and reproduce. Examples include:
- Plants and other autotrophs convert solar energy to chemical energy via photosynthesis.
- Animals and other heterotrophs convert chemical energy in plants or in other animals to chemical energy in their own structures that they can use via cellular respiration.
Energy is also needed for maintaining the health, including nutrition and the quality and quantity of food, of all organisms, including humans.
Living systems differ in how fast they use energy. Some living systems, such as birds, use energy quickly for growth and metabolism, and therefore must replace it quickly. Others, such as turtles, use energy more slowly and, therefore, need to replace it less frequently.
Energy Flow Characterizes Systems
Energy not only flows through systems, it characterizes it. Ecosystems use energy to maintain biogeochemical cycles - such as the sedimentary, gaseous, and hydrologic cycles - between living and nonliving systems.
Ecosystems are characterized by:
- Types and quantities of available energy sources, such as the chemical energy in plants.
- Types and characteristics of energy flows, such as food chains and food webs.
- Energy budgets, which are the amount of energy available with respect to the amount of energy used by an ecosystem. The total energy budget of an ecosystem determines its carrying capacity.
- An ability to use energy to maintain a balanced or steady state.
Wisconsin has five main biological communities: northern forests, southern forests, prairies, oak savanna, and aquatic regions, which vary in these characteristics.
Human societies, like natural ecosystems, need energy to organize and maintain themselves. The human use of energy follows the natural laws that govern energy flow in all systems. Human societies range from hunter-gatherer to industrial societies, and like living systems, use energy at different rates and can be classified by that rate of use. For example:
- Hunter-gatherer societies are adapted to their natural environments. They depend on energy and materials available directly from nature, and their rates of consumption of the energy and materials they use are often in balance with nature.
- Non-industrial agricultural societies modify their natural environments primarily to domesticate food sources. They depend on modest technologies to provide energy and materials.
- Industrial societies, like the United States, attempt to remake and control their natural environment. They have high rates of energy consumption.
This unit will look at energy use in systems, including human societies. It will address energy use in ecosystems, measuring and calculating wattage, and community energy use.