Feeding Relationships and Trophic Levels All Life Needs a Source of Energy

Feeding Relationships and trophic levels All life needs a source of energy. • Therefore, the life in an ecosystem need energy too! • The sun provides that energy. • The sun’s energy is not DIRECTLY usable by most organisms. • Only organisms called autotrophs (like plants) can DIRECLTY use the sun’s energy so we call these organisms “producers”. (They produce for everyone else!) Producers are the first living thing to provide energy in an ecosystem. • Producers are also called autotrophs because they make their own food. Processes done by producers. • Photosynthesis is done by many producers to make their own energy from sunlight and carbon dioxide. • Chemosynthesis is done by some bacteria to make their energy from chemicals in their environment. • We focus on those producers who use the sun! carbon dioxide + water + hydrogen sulfide + oxygen sugar + sulfuric acid But what if you can’t make your own food? • Many living things are not able to photosynthesize or chemosynthesize so what about them? If you can’t make your own energy from the sun, or chemicals you are called a consumer. • Consumers are organisms that get their energy by eating other living or once-living things. • Consumers are also called heterotrophs because they eat other things. Think-Pair-Share • Think about these words: – Heterotroph – Autotroph – Chemotroph • What does the suffix TROPH mean? Consumers are not all alike. – Herbivores eat only plants. – Carnivores eat only animals. – Omnivores eat both plants and animals. – Decomposers are organisms that break down dead or once living organic matter into simpler compounds. carnivore decomposer The names for different consumers are based on their diets. We call these trophic levels. – Primary consumers are herbivores that eat producers. – Secondary consumers are carnivores that eat herbivores. – Tertiary consumers are carnivores that eat secondary consumers. – Quaternary consumers eat tertiary consumers and producers. • Specialist consumers are organisms that primarily eat one specific organism or a very small number of organisms. • Generalist consumers are organisms that have a varying diet. Think-Pair-Share • Think of an example of a specialist. • Think of an example of a generalist. • Are specialists or generalists more likely to survive a change in the environment? Why? Putting it all together • Producers and consumers are all connected in ecosystems as they all depend on each other for survival. • Therefore, we an draw diagrams of those connections. Those diagrams are called food chains and food webs. Food chains and food webs show the flow of energy in an ecosystem and relationships between organisms. Food chains show specific relationships and are linear: • Notice we start with a producer. • Which way does energy flow? GRAMA GRASS DESERT COTTONTAIL HARRIS’S HAWK A food web shows complex feeding relationships and many food chains. • A food web emphasizes complicated feeding relationships and energy flow in an ecosystem. Pyramids model the distribution of energy and organism’s numbers in an ecosystem. The pyramid is used as it is big on the bottom and smaller on the top. • The most abundant organisms are on the bottom and the least abundant are on the top. • This is true for available energy too. • Between each tier of an energy pyramid, up to 90 percent of the energy is lost into the atmosphere as heat. • Only 10 percent of the energy energy at each tier is lost transferred from one energy transferred trophic level to the next. Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms. • Biomass is a tertiary 75 g/m2 measure of the consumers total dry mass of organisms in 150g/m2 a given area. secondary consumers • Notice the numbers as we primary consumers 675g/m2 go up or down the pyramid, producersproducers 2000g/m2 Think-Pair-Share • Explain why a pyramid must be used and not a square or circle to represent numbers of organisms and energy amounts. .

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