2All organisms require energy to live Recall Photosynthesis:Energy from the sun is “captured”. The energy becomes chemical energy stored in organic compounds (PE).Producers: use energy from the sun to make their own food (organic compounds)Usually plantsCan also be bacteria, plankton, and algaeConsumers: obtain energy by consuming organic compounds (eating other living things).Can be herbivores or carnivores.
3Trophic Level PyramidTrophic level pyramid: a way to organize organisms based on the level at which they feed.Producers form the base of the pyramid. All energy for an ecosystem originates in the organic compounds made by the producers.
4Energy flow: the trophic level pyramid Producers form the base of the pyramid.Primary consumers are the next level, followed by secondary consumers, then tertiary consumers.Energy flows through an ecosystem as consumers feed on other organisms (i.e.: as they consume the organic molecules contained within them).
5Energy Flow: Food chains All energy in an ecosystem begins with the producers that make their own food. Energy is stored within these compounds, so an organism acquires energy if it consumes these compounds.A food chain shows that energy flows from a producer to a primary consumer and beyond.
6An arrow is drawn indicating the movement of food molecules and, therefore, energy.
7Energy Flow: The Food Web Food chains in an ecosystem often overlap as a result of an organism being eaten by more than one type of consumerFood Web: A diagram that shows how energy flows between all of the organisms in an ecosystem (a series of interconnected food chains)
9All organisms require energy continued… Many organisms get their energy from other organismsConsumersHerbivores– get their energy from eating plants or other producers (1o consumer)Carnivores– get their energy from eating other animals (2o or 3o consumer)Omnivores– eat plants and animalsDetritivores– eat only “dead” organismsDecomposers– bacteria and fungi that break down large molecules found in waste into smaller molecules
10Why is the bottom of the pyramid so much bigger than the top? The size of each level represents the amount of energy that is available at that levelOnly about 10% of the available energy makes its from one level to the next level (not all of an organism is eaten, some energy is lost as heat during metabolism, etc.)Since producers create their own food/energy from the sun or molecules, they have 100% energyUsing the 10% assumption, the primary producers would only have 10% of the producers’ original energySecondary consumers would have 1%, tertiary consumers 0.10%, etc.
11Energy at the 2nd trophic level Amount of energy contained within plant material eaten by the caterpillarAmount of energy that is stored in the body of the caterpillar that can potentially be passed on to the third level.
12Pyramid shape continued… The result is that many producers are required at the bottom of a pyramid to support only a few higher-level consumers at the very topThis low level of energy transfer keeps food chains fairly short
13Pyramid Shape, cont’dThe pyramid shape of a trophic level diagram also shows that producers are more numerous than herbivores, herbivores are more numerous than secondary consumers, etc.
14Why aren’t detritivores part of the trophic level pyramid? Detritivores rarely pass energy onto the next level in the pyramid. Rather, they obtain some of the energy that is “lost” in each energy transfer by consuming the energy in the “leftovers” that might not otherwise be eaten.Since they don’t pass energy on to higher levels of the pyramid, they are not shown in the pyramid (nor in food chains or food webs)
15Why do some ecosystems have more extensive food webs and species richness than others? Species Richness (Biodiversity) = # of different species in an area.The species richness in an ecosystem is entirely dependent upon the producersIf conditions (temperature, sunlight, water, etc.) are good there will be many producers and high primary productivity (large mass of producers)More producers = more energy available for consumers = more consumers=high species richnessTropical rainforests and estuaries have high productivity and species richness, while deserts and temperate grasslands have much lower values
17Think of how the primary productivity of these areas compare.
18More on Species Richness Species richness is not only affected by primary productivity. It is also affected by:AreaHabitat destruction and/or fragmentation reduces species richness“Key stone” PredatorsIf certain predators are removed or low in numbers it reduces species richness in the lower trophic levels.Introduction of “foreign” speciesBy either competing with endemic species or preying upon them, some endemic species go extinct and/or their populations are drastically reduced.
19Reintroduction of Gray Wolves led to increased species richness