Ecosystem Structure Pg 43 48 Food Chains and

Ecosystem Structure Pg 43 -48

Food Chains and Trophic Levels • Food Chain • 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 Wolves Caribou Musk Ox Otters Fish • • • Shrews Bats Insects Small herbivores Roots Rhizomes • • Bulbs Lemmings Arctic fox Snowy Owl

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

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 • A vast number of producers are required to support even a few top level consumers. 5 secondary consumers 5000 primary consumers 500, 000 producers 5, 000

Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms. • Biomass is a measure of the total dry mass of organisms in a given area. • Summary of one given time period tertiary consumers 75 g/m 2 150 g/m 2 secondary consumers primary consumers producers 675 g/m 2 2000 g/m 2

An energy pyramid shows the flow of energy among trophic levels. • 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 energy lost energy transferred

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