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How do organisms get the energy needed for metabolism?

 Recall that all organisms require energy.  Organisms use this energy for metabolism. Metabolism is why organisms can grow and develop.

 Producers can make their own food.  Most producers get their energy directly from the sun.  They use a process called photosynthesis to generate food using this energy.  Some producers use chemical reactions instead.

 Producers are the cornerstone of all food chains and webs, because they are the only organisms that can make their own food.  Producers are also known as autotrophs.

 All other organisms must consume something to get energy. Thus, we call them consumers.  Consumers are also known as heterotrophs.

 Herbivores ONLY eat plants.  Carnivores ONLY eat other animals.  Omnivores can eat plants AND other animals.  Detrivores ONLY eat dead organisms.

 Decomposers break down organic matter into smaller pieces.  This is critical for recycling matter!

 Energy ALWAYS moves in one direction. ◦ From the sun to consumers.  A food chain shows how energy moves through several organisms.

 A food chain ALWAYS starts with a producer.  The organism that eats that producer is called a primary consumer.  The next organism in the chain is called a secondary consumer.  And, the next (and usually last) link is a tertiary consumer.

 Each step or link in a food chain or web is also called a trophic level.  For example, these food chains have six trophic levels.

 However, most ecosystems are so wide that a simple food chain fails to show all energy flow.  A food web shows ALL of the potential food chains for any one ecosystem.

1. What do we call organisms that make their own food? 2. True or false: Detrivores are heterotrophs. 3. True of false: Herbivores are autotrophs. 4. In which direction does energy move in a food chain? 5. Does a food chain show biotic or abiotic factors?

In all food webs, a large population of producers and primary consumers is needed to supply enough food to support a much smaller population of tertiary consumers. Why do you think this is? Write a paragraph explaining your reasons.

 Consumers are at a great disadvantage compared to producers.  Since producers make their own food, they can store as much energy as they need.  However, consumers use most of the energy they obtain from food for metabolism, or release it as heat.  Consumers can only store 10% of the energy they acquire!

To recap:  If consumers only get 10% of the energy from what they eat…  Primary consumers can get 10% of the energy that producers had.  Secondary consumers get 10% of the 10% that the primary consumer had, or a total of 1%.  How much energy would tertiary consumers have?  Producers = 100% of the available energy.  Primary Consumer = 10% of the available energy.  Secondary Consumer = 1% of the available energy.  Tertiary Consumer = 0.1% of the available energy.

 We can show this loss of energy through an energy pyramid.  Note that because so much energy is lost toward the top of the pyramid, only a few top predators can be supported in each ecosystem!

 Recall that all living organisms also require matter. We call this matter biomass.  A biomass pyramid shows the matter available to each organism in each trophic level.

 Keep in mind that energy and biomass are NOT the same.  In a marine environment, the biomass pyramid MAY be inverted…  However, the energy pyramid is NEVER inverted.

1. How many trophic levels are shown in this pyramid? 2. What organism gets 0.1% of the original energy? 3. How much energy (in kcal) would be available for the kangaroo rat?

 Biomagnification is the principle where toxins become more concentrated higher up in the food chain.  This means that organisms in higher trophic levels are much more vulnerable to toxins and their harmful effects.

1. What happens in biomagnification? 2. What trophic level is the most affected by biomagnification?