Food Web and Ecological Pyramid.

Recap on Food Chains: The energy flow from one trophic level to the other is known as a food chain A food chain is simple and direct It involves one organism at each trophic level Primary Consumers – eat autotrophs (producers) Secondary Consumers – eat the primary consumers Tertiary Consumers – eat the secondary consumers Decomposers – bacteria and fungi that break down dead organisms and recycle the material back into the environment

Short Food Chain

Long Food Chain

L O N G F D C H A I

Food Web Most organisms eat more the JUST one organism When more organism are involved it is know as a FOOD WEB A food web is a graphical description of feeding relationships among species in an ecological community, that is, of who eats whom. It is also a means of showing how energy and materials flow through a community of species as a result of these feeding relationships. Typically, species are connected by lines or arrows called "links“.

Food Web

Food Web Food webs are more complex and involve lots of organisms Notice that the direction the arrow points  the arrow points in the direction of the energy transfer, NOT “what ate what”

Food Web

TASK: Draw a short and Long food chain from each of the following habitats. Desert Arctic Ocean Savannah Draw a food web from any ONE habitat of YOUR choice.

Ecological pyramids

Ecological pyramid Pyramid diagrams show food chains in a different way . There are three different types: Pyramid of Number Pyramid of Biomass Pyramid of Energy The Pyramid shows which level has the most energy and the highest number of organisms

Most ecological pyramids are large at the base and narrow at the top. This is because every time that an organism is eaten by the next trophic level, some of the energy is lost as heat. More Energy Less Energy

Pyramid of Numbers: Illustration of the number of organisms at each level

Pyramid of Biomass Illustrates the amount of biomass in each trophic level

Pyramid of Energy: Most of the energy available to the community is in the 1st trophic level. Only 10-20% of the energy is available to the next trophic level (≈ 90% lost)

Transfer of Energy When a zebra eats the grass, it does not obtain all of the energy the grass has (much of it is not eaten) When a lion eats a zebra, it does not get all of the energy from the zebra (much of it is lost as heat)

Transfer of Energy The two (2) previous examples of energy transfer show that no organism EVER receives all of the energy from the organism they just ate Only 10% of the energy from one trophic level is transferred to the next – this is called the 10% law

Task: Create a 3D pyramid model depicting all the three types of pyramids (Pyramid of Numbers, Biomass and Energy) How to make a 3D pyramid: http://www.youtube.com/watch?v=YqnT-_QRRbM