Understanding Biological Amplification and Trophic Levels in Ecosystems
This chapter explores biological amplification, where higher trophic levels accumulate greater concentrations of toxins, particularly pesticides, from lower levels in the food chain. We will analyze food pyramids, highlighting the energy loss at each trophic level and the reason for fewer organisms at each successive level. The chapter also delves into the impacts of chemicals like DDT on biodiversity, with a focus on how energy transitions from producers to higher consumers. Understanding these concepts is crucial for grasping ecosystem dynamics and the challenges posed by human activities.
Understanding Biological Amplification and Trophic Levels in Ecosystems
E N D
Presentation Transcript
Chapter 6 Ecosystems
Outcomes • 3.2.1 Define the term biological amplification. (k) • 3.2.2 Explain why there are fewer organisms at each trophic level. (Question #11 Farmer question about energy efficiency) P. 97 • 3.2.3 With reference to a food pyramid, explain how pesticides can reach toxic levels for organisms at a higher trophic level. (a) (question # 12. How do food pyramids help explain DDT amplification?) P. 97
Food Pyramid • A Food Pyramid is a diagram showing each trophic level as a horizontal bar (p.96) • Trophic Level:The level of energy resulting after an energy transfer between organisms
Food Pyramid • Producers are located on bottom & higher trophic levels are placed on top of each other; • Each bar is drawn in proportion to the mass of organisms, giving the triangle shape.
Pyramid of Numbers • As we observe a food pyramid, we notice that there are fewer organisms at each increasing trophic level • Why the decrease? • less energy available at each increasing level; • fewer organisms can obtain energy to live; • therefore fewer organisms at increasing levels
Pyramid of Energy • There is a high degree of energy loss at each trophic level. • The producers only store 1% of the sun's energy as food energy. • Each consumer level looses energy for several reasons: • much of the energy is lost as heat; • most of the energy is used to carry out life functions—ie. we burn many calories of energy each day. so do all organisms; • if an organism dies without being eaten the energy goes to the decomposers and not up the trophic levels; • consequently only about 10-15% of the energy is stored as usable food energy at each level
Pyramid of Energy: • If we look at this in terms of units of energy & we start with 1000 units of energy at the producer level then: • the primary consumers would only have 100-150 units of food energy stored for the next level; • the secondary consumers would only have 10-15 units of food energy stored for the next trophic level; • the tertiary consumers would only have 1-1.5 units of food energy stored as food energy—it is easy to see why we do not often see a quaternary trophic level
Energy Flow: Consequences • If toxic chemicals (pesticides, insecticides) are introduced at a low trophic level, they will build up through the food chain & reach amplified proportions by the time the high-order consumers join the chain • High order consumers receive a higher concentration of toxins than did the lower-level organisms
Magnification of Toxin Levels (p.97) • Biological Amplificationis the term used to describe the fact that higher trophic level receive a higher dose of food chain toxins. • This problem has occurred in our environment. • The most common case was that of DDT which was first used to control insect populations in the 1950s • DDT use impacted many of the high-order carnivores throughout the world including the peregrine falcon • In Canada, DDT use was banned in the 1970s when it began showing up in human breast milk
Magnification of Toxin Levels • DDT was a particularly dangerous toxin because it is fat soluble • They collect & remain in the fat tissues of animals & do not get flushed out of the body in waste water (Some poisons are water soluble and can be excreted from the system.) • Lower order organisms ingest some poison which may or may not affect them. • Higher order organisms eat large numbers of lower order organisms. A small amount in a frog becomes large in a hawk that eats 100 frogs.
Section Review • What term is given to a diagram showing each trophic level as a horizontal bar where producers are located on bottom & higher trophic levels are placed on top of each other? • FOOD PYRAMID • Which level of a food Pyramid has the most food energy? • BOTTOM (PRODUCERS)
Section Review • Which level of a food Pyramid has the least food energy? • TOP (THIRD ORDER CONSUMERS) • Which level of a food Pyramid has the largest number of individuals? • BOTTOM (PRODUCERS)
Section Review • Which level of a food Pyramid has the smallest number of individuals? • TOP (THIRD ORDER CONSUMERS) • Which level of a food Pyramid is most in danger because of toxin magnification. • TOP (THIRD ORDER CONSUMERS) • What % of energy in a trophic level is passed onto the next level? • 10-15%
Section Review • What causes the loss of energy between trophic levels? • ENERGY USED TO CARRY OUT LIFE PROCESSES & ORGANISMS NOT EATEN BY THE NEXT TROPHIC LEVEL • What term is given to the fact that higher trophic level receive higher doses of food chain toxins? • BIOLOGICAL AMPLIFICATION
Textbook • Assigned Readings • "Food pyramids" on pages 95-97 of your text book. • Assigned Activities • Complete question #11 on page 97 of your text book.
