End Show Slide 1 of 33 Chapter 3 Section 3- Energy Flow in Ecosystems Copyright Pearson Prentice Hall

End Show Slide 2 of 33 THINK ABOUT IT What happens to energy stored in body tissues when one organism eats another?

End Show Slide 3 of 33 Energy moves from the “eaten” to the “eater.” Where it goes from there depends on who eats whom!

End Show Slide 4 of 33 Copyright Pearson Prentice Hall Feeding Relationships Energy flows through an ecosystem in one direction, from the sun or inorganic compounds to autotrophs (producers) and then to various heterotrophs (consumers).

End Show Slide 5 of 33 Copyright Pearson Prentice Hall Feeding Relationships Food Chains A food chain is a series of steps in which organisms transfer energy by eating and being eaten.

End Show Slide 6 of 33 Copyright Pearson Prentice Hall Feeding Relationships Food chains can vary in length. An example of a marine food chain is shown. Phytoplankton

End Show Slide 7 of 33 Copyright Pearson Prentice Hall In some aquatic food chains, such as the example shown, primary producers are a mixture of floating algae called phytoplankton and attached algae. These producers are eaten by small, swimming animals called zooplankton. Note that there are four steps in the food chain shown. The top carnivore is four steps removed from the primary producer.

End Show Slide 8 of 33 Generally, consumers are distinguished from one another by their distance from the producer in the flow of energy. Consumers that eat producers are called first level or primary consumers (i.e. the zooplankton). Consumers that eat primary consumers are called second level or secondary consumers (i.e. the small fish) What do 3 rd level or tertiary consumers (i.e. the squid) eat? What is the quaternary consumer? Copyright Pearson Prentice Hall

End Show Slide 9 of 33 Copyright Pearson Prentice Hall Feeding Relationships Food Webs Ecologists describe a feeding relationship in an ecosystem that forms a network of complex interactions as a food web. Each path through a food web is a food chain. A food web links all the food chains in an ecosystem together.

End Show Slide 10 of 33 Copyright Pearson Prentice Hall This food web shows some of the feeding relationships in a salt-marsh community.

End Show Slide 11 of 33 Copyright Pearson Prentice Hall Decomposers and Detritivores in Food Webs Decomposers and detritivores are as important in food webs as another other consumer is. Unfortunately they are often left out of the “picture.” Most producers die without being eaten. In the detritus pathway, decomposers convert that dead material to detritus, which is eaten by detritivores. At the same time, the decomposition process releases nutrients that can be used by primary producers. They break down dead and decaying matter into forms that can be reused by organisms, similar to the way a recycling center works.

End Show Slide 12 of 33 Copyright Pearson Prentice Hall Without decomposers, nutrients would remain locked in dead organisms.

End Show Slide 13 of 33 Food Webs and Disturbance When disturbances to food webs happen, their effects can be dramatic. For example, all of the animals in this food web depend directly or indirectly on shrimplike animals called krill. Krill are an example of zooplankton.

End Show Slide 14 of 33 Food Webs and Disturbance In recent years, krill populations have dropped substantially. Given the structure of this food web, a drop in the krill population can cause drops in the populations of all other members of the food web shown.

End Show Slide 15 of 33 Copyright Pearson Prentice Hall Trophic Levels Each step in a food chain or food web is called a trophic level. Producers make up the first trophic level. Consumers make up the second, third, and higher trophic levels. Each consumer depends on the trophic level below it for energy.

End Show Slide 16 of 33 Copyright Pearson Prentice Hall Ecological Pyramids The amount of energy or matter in an ecosystem can be represented by an ecological pyramid. An ecological pyramid is a diagram that shows the relative amounts of energy, numbers of organisms, or matter contained within each trophic level in a food chain or food web.

End Show Slide 17 of 33 Copyright Pearson Prentice Hall Ecological Pyramids Ecologists recognize three different types of ecological pyramids: energy pyramids pyramids of numbers biomass pyramids

End Show Slide 18 of 33 Copyright Pearson Prentice Hall Ecological Pyramids 0.1% Third- level consumers 1% Second- level consumers 10% First- level consumers 100% Producers Energy Pyramid: (pg. 77) level.

End Show Slide 19 of 33 Copyright Pearson Prentice Hall Ecological Pyramids There is theoretically no limit to the number of trophic levels in a food web or the number of organisms that live on each level. However, as seen on the energy pyramid in the previous slide, only a small portion of the energy that passes through any given trophic level is ultimately stored in the bodies of organisms at the next level. Organisms expend much of the energy they acquire on life processes, such as respiration, movement, growth, and reproduction. Most of the remaining energy is released into the environment as heat—a byproduct of these activities.

End Show Slide 20 of 33 Copyright Pearson Prentice Hall The more levels that exist between a producer and a top-level consumer in an ecosystem, the less energy that remains from the original amount. Only about 10 percent of the energy available within one trophic level is transferred to organisms at the next trophic level.

End Show Slide 21 of 33 Copyright Pearson Prentice Hall Ecological Pyramids Biomass Pyramid: (pg. 78)

End Show Slide 22 of 33 Copyright Pearson Prentice Hall Ecological Pyramids Biomass Pyramid The total amount of living tissue within a given trophic level is called biomass. Biomass is usually expressed in terms of grams of organic matter per unit area. A biomass pyramid represents the relative amount of potential food available for each trophic level in an ecosystem. Typically, it is greatest at the base.

End Show Slide 23 of 33 Copyright Pearson Prentice Hall Ecological Pyramids Pyramid of Numbers:

End Show Slide 24 of 33 Copyright Pearson Prentice Hall Ecological Pyramids Pyramid of Numbers A pyramid of numbers shows the relative number of individual organisms at each trophic level. Typically, the number of individuals at the base is the greatest.

End Show Slide 25 of 33 Copyright Pearson Prentice Hall In some ecosystems, however, there are fewer producers than there are consumers. Such an example is the forest ecosystem. Here the pyramid of numbers would not resemble a typical pyramid at all (though the biomass pyramid probably would).