Scope, Sequence, and Coordination
A Framework for High School Science Education
Based on the National Science Education Standards
Cycles and Ecosystems
Energy Flow Within and Between Living Systems
All matter tends toward more disorganized states. Living systems require a continuous input of energy to maintain their chemical and physical organizations. With death, and the cessation of energy input, living systems rapidly disintegrate.
The complexity and organization of organisms accommodates the need for obtaining, transforming, transporting, releasing, and eliminating the matter and energy used to sustain the organism.
All life, from the simplest cell to the most complex organism, requires a constant supply of energy to maintain itself. Most organisms receive their energy from sugar produced by photosynthesizing organisms.
Ecosystems as well require a continual input of energy from the sun in order to sustain community structure. The energy flow in all ecosystems sets up a food pyramid from producers to consumers. A small amount of sunlight (1% to 3%) is converted by plants (producers). Only 10% of stored energy in plants is available to herbivores (primary consumers), and only 10% of that energy is available to secondary consumers. Much of the energy consumed is dissipated as heat through respiration of organisms. The productivity of any ecosystem is based on the amount of energy stored by the producers that can be passed on to consumers. Measurements of productivity must include rates of photosynthesis in excess of respiration.
All living systems require energy to be maintained. Death of protoplasm results in a "shutdown" of enzyme systems, DNA function, and all activities that require energy, such as growth, reproduction, and metabolism. A constant supply of energy is essential to maintain the activities of living systems. Energy production involves the transfer of electrons from atoms to molecules and from molecules to compounds. Living systems are more complex than what remains after death and the processes that follow death. The degenerated remains are far simpler and reflect an increase in entropy (greater disorder).
Metabolism is based upon the activities of living protoplasm. These activities and associated metabolism account for a continual rearrangement of electrons whereby energy is converted from one form to another. The laws of thermodynamics apply to every living system, from the simplest cell to the most complex organisms on Earth.
Community, respiration, productivity, energy flow, food chain, biomass
Entropy, biomass, productivity, trophic levels, chemical cycles
Pyramids, models, productivity
Exergonic and endergonic reactions, entropy
First and second laws of thermodynamics
Food chains, food webs, trophic pyramids, biomass, energy flow, ten percent law, Hutchinson productivity model