BISC 100 Lecture Notes - Lecture 12: Phosphorus Cycle, Ecological Pyramid, Cellular Respiration
8 Mar 2020
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Bisc 100 ecosystem part 3: all organisms require energy for growth, maintenance, reproduction, and, in many species, locomotion. Each day, earth receives about 1019 kcal of solar energy, the energy equivalent of about 100 million atomic bombs. Most of this energy is absorbed, scattered, or reflected by the atmosphere or by earth"s surface. Of the visible light that reaches plants, algae, and cyanobacteria, only about 1% is converted to chemical energy by photosynthesis: the amount of energy available to top-level consumers is small compared with that available to lower-level consumers. Only a tiny fraction of the energy stored by photosynthesis flows through a food chain to a tertiary consumer, such as a snake feeding on a mouse. This explains why top-level consumers such as lions and hawks require so much geographic territory. While an organism is alive, much of its chemical stock changes continuously, as nutrients are acquired and waste products are released.
