1. Review- Energy is said to flow in a “one-way stream” through an ecosystem. In your own words, describe what that means Form a Hypothesis- Explain what you think might happen to the food chain on pg 65 if there were a sudden decrease in the number of crayfish 2. Review- On average, what proportion of the energy in an ecosystem is transferred from on trophic level to the next, where does that energy go Calculate- Draw an energy pyramid for a five step food chain. If 100% of the energy is available at the first trophic level, what percent is available at the highest trophic level

3.3 Energy Flow in Ecosystems Ch 3 The Biosphere 3.3 Energy Flow in Ecosystems

What happens to energy stored in body tissues when one organism eats another Energy moves from the “eaten” to the “eater.” Where it goes from there depends on who eats whom.

Food Chain Diagrams that shows what eats what Arrows point from food source to what eats it Arrow shows flow of energy Series of steps in which organisms transfer energy by eating and being eaten.

Food Web Combination of all the food chains in the community Arrows point from food source to who eats it.

Decomposers and Detritivores Most producers die without being eaten Decomposers convert that dead material to detritus, which is eaten by detritivores Decomposition process releases nutrients.

Food Webs and Disturbance All of the animals in this food web depend directly or indirectly on krill- zooplankton In recent years, krill populations have dropped substantially.

Trophic Levels and Ecological Pyramids Energy Pyramids Show the relative amount of energy available at each trophic level Biomass Pyramids Illustrates the relative amount of living organic matter at each trophic level Numbers Pyramids Shows the relative number of individual organisms at each trophic level in an ecosystem.

Trophic Levels Each step in a food chain or food web Primary producers always make up the first trophic level Various consumers occupy every other level.

Pyramids of Energy Each level passes on roughly only 10% of the energy Organisms expend much of the energy they acquire on life processes, such as respiration, movement, growth, and reproduction 10 Percent Rule Only 10% of the energy at any given level is available for use by organisms in the next higher level What do you like to eat What would be the best for humans to eat.

Pyramids of Energy

Pyramids of Biomass and Numbers Total amount of living tissue within a given trophic level Usually greatest biomass and numbers are at the base of the pyramid Size of pyramid depends on amount of energy available.