Trophic Structure of Ecosystems

Where does all life on Earth get energy from?

SBI4U RHSA

http://www.nrri.umn.edu/worms/forest/ecosystems.html

Energy flows to and from the Earth.Nutrients cycle within Earth.

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?

Most photosynthesis occurs in marine ecosystems! It’s the phytoplankton.

http://thomsenlab.com/home/

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.http://ckdp.ca/2009/10/29/two-creeks-in-wheatley-holding-tree-planting-event-to-reduce-carbon/

http://schoolworkhelper.net/2011/01/energy-movement-in-ecosystems-trophic-energy-pyramid/

1st trophic level

2nd trophic level

3rd trophic level

4th trophic level

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.

http://www.docbrown.info/ks3biology/8DmcHP6.htm

A food chain is one path through a food web. The arrows must always start with the producers at the first trophic level and go “up” the chain. Review as many lecture terms as you can using this food web diagram!

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.

http://www.sciencelearn.org.nz/Contexts/Future-Fuels/Sci-Media/Images/Simple-ecosystem-diagram

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.