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Name________________________________________________Date_________________Period____________________6.2 - Ecological Pyramids Worksheet There are different types of ecological information that can be explained using pyramids. Use the reading below to answer the questions at the end of each section. Ecological Pyramids: A basic pyramid shape often represents a typical food chain or food web because the pyramid shape shows the decrease in the amount of energy, number of organisms and the amount of biomass that occurs from the producers to the higher-level consumers. Different levels represent different groups of organisms that compose a food chain from the bottom up as follows: Producers: Brings energy from the sun into the community; Photosynthetic Plants. Primary Consumers: Eats the producers; Herbivores and Omnivores Secondary Consumers: Eats the Primary consumers: Small Carnivores and OmnivoresTertiary Consumers: Eats the Secondary consumers: Top Carnivores and OmnivoresA Basic Ecological Pyramid: What is the source of energy for all life on the plant? Why does a pyramid shape represent a food chain well? Most food chains only contain 4 trophic levels. What do you think limits the length of a food chain?Energy Pyramids: An energy pyramid is a model of the energy flow through a community. Only PART of the energy that is stored in one trophic level gets passed on to the next. This is because organisms use MOST of the energy they consume for life processes such as respiration, movement, and reproduction. Only 10% of energy available in one level gets passed to the next. This means that 90% of the energy in each trophic level is lost to the environment in the form of waste such as the bones and hair that are not digested, and to the atmosphere as HEAT when energy is “burned” as it is used. For example, if there are 10,000 calories available at the producer level then there is only 10% of 10% or 1%, equaling 100 calories that are transferred to the secondary consumers. Some Examples of Energy Pyramids:What is the 10% rule? Why is energy lost between trophic levels? If there are 30,000 calories of energy available with the produces in an ecosystem, how much energy will be passed on to each of the following trophic levels? ( Hint: 10% Rule)Primary Consumers - Secondary Consumers - Tertiary Consumers –If there are 20,000 calories of energy at the secondary trophic level in an ecosystem, how many calories will not be transferred to the tertiary consumers? (Hint: 90% is lost)Does energy increase or decrease as you move up a food chain? Number Pyramids:Ecological pyramids can also be based on the numbers of individual organisms at each trophic level. The loss of energy at each trophic level often explains why there are usually fewer organisms in each higher trophic level. The total number of plants in a particular area would generally be higher than the number of herbivores so that there is enough to not only feed all of the herbivores but also to be able to survive and reproduce. However, is not always the case, in most forests, for example, there are fewer producers than there are consumers, A single tree has large amount of energy and biomass, but it is only one organism. Many insects, birds, and rodents can live in one of these giant tress but they have less energy and biomass. Thus, a pyramid of numbers for a forest ecosystem would resemble an inverted pyramid or might not even look like a pyramid at all! Some Examples of Number Pyramids: Why are there usually more organisms at the bottom of the food chain than at the top?Describe a desert community where there are fewer producers than consumers. Biomass Pyramids:The total amount of living tissue within a given trophic level is called biomass. A biomass pyramid represents the amount of potential food available for each trophic level in an ecosystem. It is measured as the total dry mass, in grams per unit area. Typically, there is a greater amount of biomass at the base of the pyramid with the producers and each higher trophic level contains less biomass than the previous level.Some Examples of Biomass Pyramids: What is biomass? Why is there more biomass at the producer level than at the consumer levels? How does this relate to the 10% rule? Food Chain Review: Label the trophic level of each organism in the food chain below. Which organism is an herbivore in the diagram above? Which organism is an autotroph in the diagram above? Which organism is a primary consumer in the diagram above? Which organism is a secondary consumer in the diagram above? Which organism is a tertiary consumer in the diagram above? Which trophic level, in the food chain above, has the most available energy? Which trophic level, in the food chain above, has the least available energy? What would happen to the population of frogs, if the population of snakes increased? Why?Extra Credit: On a separate sheet of paper: Describe 2 human activities that interfere with food webs. For each explain how it happens, why we do it, and the short and long term effect. ................
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