5.1.9., & Communities and Ecosystems

5.1.9 State that light is the initial energy source for almost all communities. Sunlight is the initial source of energy for all vegetation. Since photosynthetic organisms occupy the first trophic level, sunlight is the initial energy source for almost all communities. However, some food chains can start without sunlight. E.g., deep sea hydrothermal vents provide chemical energy instead of light energy to start a food chain.

Explain the energy flow in a food chain.  Light energy is absorbed by producers  The chemical energy obtained by photosynthesis is available to the next trophic level  Energy is transferred from one organism to the next when carbohydrates, lipids or proteins are digested.

FOR EXAMPLE… When cows eat grass, chemical energy from the grass is transferred to the cow. (If a clump of grass dies without being grazed on, decomposers such as fungi will use the energy it has to offer.) Inside the cow, the chemical energy is used for cellular respiration. If the cow is eaten, some of the chemical energy in its body can be passed on to the next trophic level. If it dies and is not eaten, detrivores and decomposers will use its available energy.

State that energy transformations are never 100% efficient. Chemical energy is the only energy that can be used by the next trophic levels, and only a small amount of the energy that an organism absorbs is converted into chemical energy. No organism can ever use 100 percent of the energy from the food it eats, usually only percent. The reasons why this is the case are as follows:  Not all of the eaten some parts are abandoned and will decay  Not all of the food swallowed can be absorbed and used in the body  Some organisms die before being eaten by an organism from the next trophic level  There is a lot of heat loss because of cellular respiration