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

CH 3 THE BIOSPHERE3.3 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

Biomass 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.