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Trophic Levels Trophic Efficiency Bioaccumulation. Seatwork. Read pages 24-26 and then answer the following questions. LEAVE SPACE after each answer. Define trophic level and give several examples. Define biomass. Define trophic efficiency Define bioaccumulation. Define biomagnification.
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Seatwork Read pages 24-26 and then answer the following questions. LEAVE SPACE after each answer. Define trophic level and give several examples. Define biomass. Define trophic efficiency Define bioaccumulation. Define biomagnification.
Trophic Levels • A trophic level is a category of organisms that is defined by how the organisms gain their energy. Examples: • First trophic level = primary producers • Second trophic level = primary consumers (herbivores) • Third trophic level = secondary consumers
Biomass • Biomass is the total mass of living organisms in a defined group or area. • It includes living cells and tissues that have been assembled by organisms using solar energy. • Plant material is packed with chemical energy that has been converted from solar energy. • Animals indirectly rely on solar energy by eating plants or animals.
Trophic Efficiency • Trophic efficiency is a measure of the amount of energy or biomass transferred from one trophic level to the next higher trophic level. • Trophic efficiencies are quite inefficient – only about 10%. • Organisms use much of the energy from the biomass they consume for life functions and wastes they produce
Reasons for Biomass Decreases Between Trophic Levels • Herbivores don’t eat all of the plant • Not everything that is eaten is digested
Reasons for Energy Decrease between Trophic Levels: • Energy is lost as heat by organisms • Energy is used for life processes
Relative Numbers at Trophic Levels • Because of the inefficiencies of energy transfer among trophic levels, there are usually fewer carnivores than herbivores and fewer herbivores than plants
Water Pollution and Bioaccumulation • Bioaccumulation is a process in which materials, especially toxins, are ingested by an organism at a rate greater than they are eliminated. • Biomagnification is the increase in concentration of a toxin as it moves from one trophic level to the next.
Seatwork • Read pages 25-27 and then answer the following questions: • Explain how the use of DDT and PCB’s are example of bioaccumulation and biomagnification. • Review Questions 5 to 8 on page 27