CHAPTER 3 NOTES
ECOLOGY- FOOD WEBS
· Ecology studies interactions between organisms in a particular area (space).
· Evolution studies interactions between organisms over time.
Environmental factors in an ecosystem:
· Biotic: all the living organisms in an environment.
· Abiotic: all the non-living parts in an environment.
What is an ecosystem?
All of the biotic and abiotic factors in an environment.
· In an ecosystem, matter and energy flow and recycle continuously. Standard B1.44
· Sunlight is the main source of energy on Earth. Energy may also come from inorganic chemical compounds.
· The flow of energy is modeled through food chains (a series of steps in which organisms transfer energy).
Examples of food chains:
1st 2nd 3rd 4th
Algae à Herring à Squid à Shark
1st 2nd 3rd 4th
· The arrows represent the one way flow of energy.
· Each step in a food chain is called a trophic level.
· The first tropic level must always be an autotroph (producer).
· Energy is passed from autotrophs to heterotrophs (consumers) in a food chain.
· Examples of heterotrophs: herbivores, carnivores, omnivores and detritivores.
· Decomposers such as bacteria and fungus fit into the food chain at any trophic level.
· A food web links all of the food chains in an ecosystem together.
Energy pyramid Standard B1.37
· 90% of the energy is lost as heat to the environment at each trophic level.
· 10% of the energy is passed on to the next trophic level.
· Biomass is the total amount of living tissue.
· Represents the amount of potential food (in grams) available for each trophic level.
Pyramid of Numbers
· Based on the number of individual organisms at each trophic level.