ENERGY FLOW IN ECOSYSTEMS  Food chains and webs show how eaters, the eaten, and the decomposed are connected to one another in an ecosystem. Figure 3-17

Fig. 3-17, p. 64 Heat Detritivores (decomposers and detritus feeders) First Trophic Level Second Trophic Level Third Trophic Level Fourth Trophic Level Solar energy Producers (plants) Primary consumers (herbivores) Secondary consumers (carnivores) Tertiary consumers (top carnivores)

Food Webs  Trophic levels are interconnected within a more complicated food web. Figure 3-18

Fig. 3-18, p. 65 Humans Blue whaleSperm whale Crabeater seal Elephant seal Killer whale Leopard seal Adelie penguins Emperor penguin PetrelFish Squid Carnivorous plankton KrillHerbivorous plankton Phytoplankton

Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs  In accordance with the 2 nd law of thermodynamics, there is a decrease in the amount of energy available to each succeeding organism in a food chain or web.

Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs  Ecological efficiency: percentage of useable energy transferred as biomass from one trophic level to the next. Figure 3-19

Fig. 3-19, p. 66 Heat Decomposers Tertiary consumers (human) Producers (phytoplankton) Secondary consumers (perch) Primary consumers (zooplankton) ,000 10,000 Usable energy Available at Each tropic level (in kilocalories)