Chapter 45: How Ecosystems Work

The Flow of Energy

Ecosystem Function

1. Energy moves thought ecosystems in a one-way flow. It must constantly be replenished.
2. Nutrients cycle and recycle in a continuous flow

Autotrophs: "self feeders", producers, plants
Heterotrophs: "other feeders", consumers, animals

The amount of life an ecosystem can support is determined by the energy captured by the producers

Net primary productivity -- measured in calories or biomass

The more sunlight & water, the more plants, the more animals etc

Trophic level - the level at which an organism feeds

Primary consumers (herbivores)
Secondary consumers (carnivores)
Tertiary consumers (carnivores that eat other carnivores)
Quaternary consumers (eat tertiary consumers)

Organisms can move from one trophic level to another, by eating different types of things.

Food Chains and Food Webs illustrate feeding relationships in ecoysystems

Detritus feeders: decomposers, feed on refuse and return nutrients to the cycle

Energy Pyramids illustrate how energy is transferred between trophic levels.

Energy is lost as you move up.

An ecosystem can support more primary consumers than it can secondary consumers

Biological Magnification - toxins build up to higher levels as you move up in the food chain. (Example: DDT)

Biogeochemical Cycles (Nutrient Cycles)