![]() Reuse: This item is in the public domain and maybe reused freely without restriction. Provenance: Image from US Geological Survey In either case, the overall productivity of an ecosystem is controlled by the total energy available. There are a few exceptions to this, such as ecosystems living around hydrothermal vents on the ocean floor, which derive their energy from chemical compounds such as methane and hydrogen sulfide. This process is the fundamental source of organic material in the biosphere. Sunlight allows plants, algae, and cyanobacteria to use photosynthesis to convert carbon dioxide and water into organic compounds like carbohydrates. The continual input of energy, mostly from sunlight, sustains the process of life. ![]() The changes happen, for example, as a result of changes in agricultural and food processing technology, consumer habits, and human population size. ![]() Humans are modifying the energy balance of Earth's ecosystems at an increasing rate. The amount and kind of energy and matter available constrain the distribution and abundance of organisms in an ecosystem and the ability of the ecosystem to recycle materials.ģ.6 Humans are part of Earth's ecosystems and influence energy flow through these systems. Eating producers is the lowest and thus most energy-efficient level at which an animal can eat.ģ.5 Ecosystems are affected by changes in the availability of energy and matter. An organism that eats lower on a food chain is more energy-efficient than one eating higher on a food chain. Continual input of energy, mostly from sunlight, keeps the process going.ģ.4 Energy flows through food webs in one direction, from producers to consumers and decomposers. At each level in a food chain, some energy is stored in newly made chemical structures, but most are dissipated into the environment. The chemical elements that make up the molecules of living things are passed through food chains and are combined and recombined in different ways. The breakdown of food molecules enables cells to store energy in new molecules that are used to carry out the many functions of the cell and thus the organism.ģ.3 Energy available to do useful work decreases as it is transferred from organism to organism. Food is composed of molecules that serve as fuel and building material for all organisms as energy stored in the molecules is released and used. 3.2 Food is a biofuel used by organisms to acquire energy for internal living processes.
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