Where does all life on Earth get energy from? SBI4U RHSA

 All energy for life on Earth comes from the Sun.  The First Law of Thermodynamics states that “Energy cannot be created or destroyed, it can only change form.”  Only about 1% of the sunshine that reaches Earth is captured by plants. This heat and light energy is converted to chemical energy, in the form of glucose, by photosynthesis.  Where does most photosynthesis occur?

In marine ecosystems! It’s the phytoplankton.

 The organisms that capture sunshine energy are called producers or autotrophs, which means “self food”.  Producers are almost always the first trophic level of any food chain.  The word troph derives from the Greek word for food.  -wheatley-holding-tree-planting-event-to- reduce-carbon/

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 All other organisms are heterotrophs and get energy by consuming other organisms.  All herbivores, omnivores, carnivores and decomposers are heterotrophs.  Herbivores, also called primary consumers, must always be at the second trophic level, as they eat plants.  Secondary consumers could be carnivores or omnivores and are at the third trophic level.

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 Decomposers are often hard to place in a food chain as they consume detritus from multiple trophic levels.  Fungi, worms, and many species of bacteria recycle large organic molecules into small organic molecules that can be reabsorbed.  The flow of energy is considered to be an open system as there is always more energy arriving at Earth and some heat energy always leaving Earth.  This is the opposite of the nutrient cycles like nitrogen which are part of a closed system.

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