Energy Losses in Food Chains (HL IB Environmental Systems & Societies (ESS))

Energy Losses in Food Chains

• The total organic matter transferred from one trophic level to the next is never 100% because:

  1. Not all the food available to a given trophic level is harvested

  2. Of what is harvested, not all is consumed

  3. Of what is consumed, not all is absorbed

  4. Of what is absorbed, not all is stored

• For example, if we take the example of caterpillars (the primary consumer) eating the leaves of an oak tree (the producer):

  1. The caterpillars do not eat every leaf available to them (there may simply be too many leaves, not enough caterpillars, or some leaves may be in locations that are difficult for the caterpillars to access)

  2. The caterpillars may not eat the entire leaf (they might eat only the softer, more nutritious parts and leave behind tougher portions or parts with toxins)

  3. Once the caterpillars eat the leaves, not all of the nutrients are absorbed by their bodies (some parts of the leaves may be indigestible or contain compounds that the caterpillars cannot process, which are then egested by the caterpillars)

  4. When the caterpillars digest the leaves and convert the nutrients into energy, not all of the energy from the leaves is stored for growth and development, as some of that energy is lost as heat during cellular respiration