Energy and the Ecosystem

Questions for Today: How does energy flow in Ecosystems? What happens to usable Energy as it travels through a food chain or web?

Review Life on Earth Depends on three interconnected factors: 1.The one-way flow of high quality energy. 2.The cycling of matter or nutrients. 3.Gravity

Food Chains and Food Webs Energy in the Ecosystem is transferred through the different trophic (feeding) levels. –Food Chain – a sequence of organisms, each of which serves as a source of food or energy for the next. –Food Webs – a series of interconnected Food Chains. –Chemical energy and nutrients travel through trophic levels primarily through photosynthesis, feeding, and decomposition.

Food Chains and Food Webs As chemical energy travels through trophic levels, some useful energy is lost to the environment as heat. –This would result in the collapse of the ecosystem or biosphere if it weren’t for the Sun.

Food Chains and Food Webs

Energy Efficiency The Chemical Energy in Ecosystems are stored in biomass. –Biomass – the dry weight of all organic matter contained in its organisms. Energy transfer through food chains is not very efficient and a lot of the energy is lost as heat. –The percentage of usable chemical energy transferred as biomass from one trophic level to the next is called Ecological Efficiency. 10% is usually the normal Ecological Efficiency

Energy Efficiency Question Assuming 10% ecological efficiency, if green plants capture 10,000 units of energy, how much chemical energy will be available to support herbivores and carnivores?

Energy Efficiency

Energy pyramids help explain how: –The earth can sustain populations better if they eat at lower trophic levels. –Ecosystems usually only have 4 or 5 Trophic levels.