Over 90% of all parasympathetic fibers are derived from the cranial nerve X, which is the vagus nerve.
The vagus nerve influences most organs below the neck. The activation of this nerve affects heart rate, blood pressure, production of stomach acid, movement of food through the intestines and breathing.
The independent variable is the amount of water consumed by the football players.
The dependent variable is the football players' endurance, measured by how many times they can run up and down the bleachers before catching their breaths.
The coach's hypothesis was that the more water consumed, the more endurance the players will have.
There is not a control group present in this experiment, but it would be the set of players who did not drink a bottle of water before practice.
The experimental group is the set of players who did drink a bottle of water before practice.
The constants in the experiment are the operational definitions of endurance (how he measures their endurance), the amount of water each player drinks throughout the week, and the players used in the experiment.
The lack of a set control group poses a threat to the accuracy of the experiment's results.
The amount of total energy at each trophic level decreases as it moves through, so 90% is lost at each level. This means that only 10 percent of the energy at any trophic level is transferred to the next level; and the rest is lost as heat.
In this case, if a plant ecosystem has 3000000 kilocalories (kcal) of energy, about 300000 kcal will be transferred to primary consumers (for example grass hoppers). If the red-tailed hawks are tertiary consumers, they will get 3000 kcal of energy.
