Ecosystem Structure Pg 43-48

Food Chains and Trophic Levels Energy flow from one organism to next Shows only one possible sequence Trophic Level Position an organism occupies in a food chain

Food Web Complex network of interrelated food chains

Food Web Kodiak Shrews Bulbs Wolves Bats Lemmings Caribou Insects Arctic fox Musk Ox Small herbivores Snowy Owl Otters Roots Fish Rhizomes

Describe and Explain the relationship between snowy owl nest numbers and lemming abundance

Ecological Pyramids Graphical models of the quantitative differences between amounts of living material at each trophic level Three types of ecological pyramid Pyramid of numbers Pyramid of biomass Pyramid of productivity

A pyramid of numbers shows the numbers of individual organisms at each trophic level in an ecosystem. tertiary consumers secondary primary producers 5 5000 500,000 5,000,000 A vast number of producers are required to support even a few top level consumers.

Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms. tertiary consumers secondary primary producers 75 g/m2 150g/m2 675g/m2 2000g/m2 Biomass is a measure of the total dry mass of organisms in a given area. Summary of one given time period

An energy pyramid shows the flow of energy among trophic levels. energy transferred energy lost Energy pyramids compare energy used by producers and other organisms on trophic levels. Only approx. 10 percent of the energy at each tier is transferred from one trophic level to the next. Show flow over time

Text Book Pg 48 – 55 Advantages and Disadvantages of diff pyramid models Pg 52 TO DO questions 1-4 Test yourself questions 1-3