Flow vs. Cycle Energy enters an ecosystem by photosynthesis and exits as heat Producers capture sun’s energy and convert it to carbohydrates (sugars) Consumers use carbohydrates for life functions Matter is cycled between living things, the Earth and chemicals

Food Chains & Webs Food chains and webs show the “direction” of energy transfer in an ecosystem Begins with producers/autotrophs Photosynthesis makes energy available to consumers Herbivores are primary consumers Eat plants Secondary (and up) consumers eat animals Carnivores and omnivores

Food Chains & Webs Arrows show the direction of energy transfer Examples: grass  cow gazelle  cheetah salmon  bear Energy transfer is unidirectional... ONE WAY ONLY!

Food Chains & Webs

Pyramids Pyramids show the distribution of energy in an ecosystem Lower levels are larger and contain more biomass Fewer organisms higher up in the pyramid

Pyramids When a consumer eats another organism, the energy is used to … Keep the organism alive Allow the organism to grow (adds to biomass) Lost as heat due to inefficiency Only about 10% of energy at one level is available to the next level

The “10% Rule” Starting energy (for example) = 1000 Calories -50%due to non-predatory deaths (not being eaten) _____________ 500 Calories -50%due to digestive system inefficiency (solid waste … poo) _____________ 250 Calories AT LEAST -50%due to heat loss to the environment _____________ AT MOST 125 Calories remaining … AROUND 10% of the starting energy

Matter Cycles Elements like carbon, nitrogen, and phosphorous are important to all living things Biogeochemical cycling Elements are part of organism’s molecules … minerals in the Earth’s rocks … and, chemicals in the ecosystem.

Matter Cycles - Carbon Carbon is in all organic molecules Carbohydrates, proteins, lipids, nucleic acids The Carbon Cycle Important terms: carbon dioxide, respiration, photosynthesis, combustion, fossil fuels, decomposers, decomposition

Matter Cycles - Nitrogen Nitrogen is found in all proteins The Nitrogen Cycle Important terms: nitrogen gas (in atmosphere), nitrogen-fixing bacteria, ammonium, nitrifying bacteria, nitrites, nitrifying bacteria, nitrates, decomposers, decomposition, ammonification, denitrifying bacteria