PYRAMIDS

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Ecological Pyramids Instead of representing trophic levels in a food web, an ecological pyramid can be used.

Ecological Pyramids Does this pyramid represent a food chain or web? How could this pyramid be changed to represent a food web? A chain as there is only one eating path. Different species of organisms could be added at each level to show more eating “opportunities for the organisms above it. Broaden the discussion by asking “What organisms could you add at each trophic level for a web??

Ecological Pyramids What do the big numbers represent? What does the kcal mean? The trophic levels. Have them identify the type of organism at each level. It stands for kilocalories, a measurement of energy.

Pyramid of Energy What happens to the energy as you go up? How much energy is available for the next level? What type of pyramid is this? It gets less and less; lost in heat energy or used in metabolism. The rule of thumb is 10% (although it is an average across levels and chains.) No trophic level can contain more energy than the level below. Energy Pyramid, sometimes also called a pyramid of productivity. It represents the energy content of organisms. The kcal is calculated by measuring the calories produced at each level.

Ecological Pyramids How is this pyramid different from the previous ones? What could the multiple pictures of the species at each level represent? It shows multiple pictures of each species at the different trophic levels. They could represent the total number of organisms of each species or their total biomass.

Pyramid of Biomass What information would this pyramid include if it were a pyramid of biomass? How do they get a number total for the biomass of a population? It would have the total biomass at each level or it would have a key for how much biomass was represented by each picture. The total mass of the organisms is determined by drying and weighing a sample number of organisms at each level and then calculating the total mass for the species at each level.

Pyramid of Numbers What information would this pyramid include if it were a pyramid of numbers? How do they get a number total for a population of organisms? It would have the total population at each level or it would have a key for how organisms were represented by each picture. The population is determined by counting the organisms of a species in a sample portion at each level and then calculating an average for the total area.

Ecological Pyramids Why is a pyramid used to represent these feeding relationships? How is this also a pyramid? Explain what happens to the mass, numbers,and energy from trophic level to trophic level. Normally there is more energy, biomass and number of organisms at the lower level, decreasing as you move upward. It has the same general pyramid shape decreasing toward the top and shows trophic levels. In general they decrease as you go up.

Ecological Pyramids What is different about this pyramid? How can the producer level be so small and support the trophic levels above it? It has a very small trophic level 1 (producers) How can the producer level be so small and support the trophic levels above it? (Rhetorical question - lead in for the next two slides.)

Pyramids of Aquatic Ecosystems Numbers Biomass Energy Pyramids of Aquatic Ecosystems Numbers - Follows the normal pattern of having many more phytoplankton at TL1 Biomass - The phytoplankton reproduce a a rate only just slightly higher than the rate at which they are eaten. Since they are so small and weigh so little there is a very small biomass. Energy - Follows the normal pattern of having much more energy available at TL1 Pyramid of biomass in aquatic ecosystems (ocean & fresh) and some terrestrial ecosystems such as the pyramid of numbers for the temperate forest. Because the trees are so large their numbers are small compared to the number of organisms at the higher trophic levels.

Pyramids of Temperate Forests Numbers Biomass Energy Pyramids of Aquatic Ecosystems Numbers - In the temperate forest, the trees are huge but smaller in number compared to the grasses in a prairie and so are fewer compared to the number of organisms at the higher trophic levels. Biomass - Follows the normal pattern of having much more mass at TL1 from the huge trees. Energy - Follows the normal pattern of having much more energy available at TL1

Ecological Pyramids How is this an ecological pyramid? It shows the feeding organisms in successive levels like a pyramid. Note the small number of producers to reflect the aquatic pyramid of numbers with a very small trophic level 1.

Ultimate Predator? Why is man sometimes called the “Ultimate Predator”? Ultimate Predator? Why is man sometimes called the “Ultimate Predator”?