Ch. 5 - How Ecosystems Work

3.1 Energy Flows in Ecosystems

• Sunlight is the source of energy for almost all producers in almost all ecosystems.  The provides the energy used by produces to make fook the sun is also the indirect source of energy for nearly all consumers.

Organisms classified on how they obtain their enegy

• Life on Earth could not exisit without producers.  With no producers, consumers and decomposers would run out of food soon and die off, all live would die off without the energy of producers.
• Consumers
  • Herbivores eat only plants, ominvores eat both plants and animals. EX: grasses, trees, ect.
  • Carnivore eats only other consumers. EX: Lions, hawks
  • Ominvore eats both producers and consumers. EX: bears, people
  • Decomposer  breaks down dead organisms in an ecosystem, returning nutrients to the soil or wate 
• In a food web an organism could be both predator and prey.
• More people could be supported by eating only plants than eating both plants and animals. 90 percent of the energy is lost in each step of the food chain, and since plants are the 1st step, humans would recieve more energy and be able to feed more people by eating only plants.
• Energy is lost at each trophic level, organisms at higher trophic levels need more food to suport themselves than do organisms at lower trophic levels.
  • Prodcuers at the bottom of an energy pyramid have 1000 times more energy than a hawk (teriary consumer) at the top of the pyramid
• Each trophic level can support fewer organisms than the level below it.