Chapter 1.2 – How energy is transferred in the biosphere Pages 16 – 27 in your text

Ecosystems have relationships based on energy and matter exchange. To describe these we use: Food chains Food webs Ecological pyramids

Trophic levels describe: where an organism feeds in the ecosystem how many energy transfers an organism is from its original energy source (ie. the Sun) How many trophic levels does this food web have?

Autotrophs “self feeders”: Can produce own food. Photosynthetic or chemosynthetic Also called producers. They make up 99% of all biomass.

obtain their energy from autotrophs or by eating another heterotrophs also called consumers Primary consumers feed directly on producers. They are also called herbivores. Secondary consumers feed on primary consumers. They may be omnivores or carnivores.

Higher levels include: tertiary or quaternary consumers also called top order consumers Decomposers: are heterotrophs include bacteria and fungi extract energy from dead organisms recycle nutrients

The laws of thermodynamics 1st Law: energy can neither be created nor destroyed, only changed in form. 2nd Law: with each energy change, some useful energy is lost as heat.

The Rule of 10: Only about 10% of available energy can be passed up a level in the food chain. What does this suggest about the number of organisms at the top trophic levels?

Trophic levels are described 3 ways: food chains food webs ecological pyramids: pyramid of numbers pyramid of biomass pyramid of energy

Food chain: linear series of feeding relationships. Disadvantages: Simplistic; show only one predator- prey relationship. do not illustrate rule of 10

Food Web: series of interconnected feeding relationships Disadvantages: do not illustrate rule of 10 can get complicated

Pyramid of Numbers: producers at the bottom population numbers at each trophic level are drawn to scale aren’t always pyramid shaped.

Pyramid of Biomass: shows the mass(kg) of living material at a trophic level.

Pyramid of Energy: shows the amount of energy (J) available at each trophic level.