(Copyright 2000 McREL; Used with permission)

The simplistic image above is depicting energy flow from producers all the way up to tertiary consumers.  Also known as food web,  the arrows within are pointing toward organisms that consume the previous organism.  For instance, the Rattus norvegicus has three arrows pointing toward a fox, owl, and hawk.  These are considered  the predators or tertiary consumers.  On the other hand there is an arrow pointing toward the brown rat from a grasshopper making the brown rat a secondary  consumer.  This food web happens to take place in a terrestrial environment. 

The five trophic levels consist of primary producers, primary consumers, secondary consumers, tertiary consumers, and quarternary consumers.  Primary producers use photosynthesis  to create sugars and organic compounds which aid in cellular respiration for growth.  Primary consumer are herbivores that  eat plants and other primary producers; the flow of energy is then transferred from the primary producers to the primary consumer.  However, the organism on the receiving end will only obtain a portion of the energy.  According to the second law of thermodynamics, energy conversions can't be completely efficient; some of the energy is lost through heat. [2]  Furthermore, secondary consumers are carnivores that eat herbivores while tertiary consumers eat other carnivores.  Lastly, quarternary consumers eat tertiary consumers.   The flow of received energy through nutrients lessens as you move up the food chain.  The picture of the food chain for terrestrial and aquatic environments may help with clarity.



Food web










I found a video on showing the Rattus norvegicus being targeted as a food source by the Grey Heron.  Two species in their natural habitat both expressing transfer of Energy.  Ideally, Luck plays a role in living.  Grey Heron vs. Rattus norvegicus

Another video is an intense battle between the weasel and brown rat.  Survival of the fittest.  weasel vs. brown rat


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