The basic cycle of energy shows how energy decreases as it moves through higher trophic levels in an ecosystem. In the first level, the primary organisms (such as plants) utilize energy from the sun to generate biomass through photosynthesis. In the second level, the organisms exploit primary trophic level organisms as food sources and thus obtain energy. Finally, in the third level, carnivores eat the herbivory organisms to obtain energy. At each trophic level, an important part of the energy is lost as metabolic heat; however, this energy can not be reused, this principle is known as the 'law of conservation of energy'.
Depending on the stimulus, graded potentials can be depolarizing or hyperpolarizing. Action potentials always lead to depolarization of membrane and reversal of the membrane potential. Amplitude is proportional to the strength of the stimulus. ... Duration of graded potentials may be a few milliseconds to seconds.
