The stomata of leaves are surrounded by guard cells. The guard cells help the leaves to regulate the rate of transpiration of water from the leaves by opening and closing the stomata. When water enter the guard cells, they swell and bulge and this makes the stomata to open. So, with high water pressure, the guard cells will stimulate the stomata to open. The reverse will be the case if the water pressure is low.
Calcium is a chemical element with symbol Ca and atomic number 20. Calcium is a soft gray Group 2 alkaline earth metal, fifth-most-abundant element by mass in the Earth's crust. The ion Ca2+ is also the fifth-most-abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate.[5] Free calcium metal is too reactive to occur in nature. Calcium is produced in supernova nucleosynthesis.
Answer. They are the “last trophic level” in some hierarchies because they feed on everything (National Geographic). However, according to the strict trophic level definition they would be primary consumers.
