ENERGY PYRAMIDS & Freshmen Biology FOOD CHAINS/FOOD WEBS May 4 – May 8 Lecture ENERGY FLOW

•Energy → powers life’s processes •Energy = ATP! •Flow of energy determines the system’s ability to sustain life FEEDING RELATIONSHIPS

• Energy flows through an ecosystem in one direction • Sun → autotrophs (producers) → heterotrophs (consumers) FOOD CHAIN VS. FOOD WEB FOOD CHAINS • Energy stored by producers → passed through an ecosystem by a food chain • Food chain = series of steps in which organisms transfer energy by eating and being eaten FOOD WEBS

•Feeding relationships are more complex than can be shown in a food chain

•Food Web = network of complex interactions •Food webs link all the food chains in an ecosystem together

ECOLOGICAL PYRAMIDS

• Used to show the relationships in Ecosystems • There are different types: • Energy Pyramid • Biomass Pyramid • Pyramid of numbers ENERGY PYRAMID • Only part of the energy that is stored in one trophic level can be passed on to the next level • Much of the energy that is consumed is used for the basic functions of life (breathing, moving, reproducing) • Only 10% is used to produce more biomass (10 % moves on) • This is what can be obtained from the next trophic level • All of the other energy is lost 10% RULE

• Only 10% of energy (from organisms) at one trophic level → the next level • EX: only 10% of energy/calories from grasses is available to cows • WHY? • Energy used for bodily processes (growth/development and repair) • Energy given off as heat • Energy used for daily functioning/movement • Only 10% of energy you take in should be going to your actual biomass/weight which another organism could eat

BIOMASS PYRAMID

• Total amount of living tissue within a given trophic level = biomass • Represents the amount of potential food available for each trophic level in an ecosystem PYRAMID OF NUMBERS

•Based on the number of individuals at each trophic level