Trophic Structure of Ecosystems – V2

Where does all life on Earth get energy from?

SBI4U RHSA – Ellen Murray

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.

In which ecosystem does most photosynthesis occur?

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

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 non-photosynthetic 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

On the food web circle an autotroph and draw a square around a secondary trophic level organism.Review as many lecture terms as you can using this food web diagram!

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. Trace one food chain on this food web.

Decomposers are often hard to place in a food chain as they consume detritus from multiple trophic levels. Identify decomposer trophic levels as one more than the organism being consumed.

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

What is the most important difference between energy and nutrients in this 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.