When the cell increases in size, the volume increases faster than the surface area, because volume is cubed where surface area is squared. When there is more volume and less surface area, diffusion takes longer and is less effective.
<span>The water molecule, as a whole, has 10 protons and 10 electrons, so it is neutral.In a water molecule, the oxygen atom and hydrogen atoms share electrons in covalent bonds, but the sharing is not equal.In the covalent bond between oxygen and hydrogen, the oxygen atom attracts electrons a bit more strongly than the hydrogen atoms.The unequal sharing of electrons gives the water molecule a slight negative charge near its oxygen atom and a slight positive charge near its hydrogen atoms.When a neutral molecule has a positive area at one end and a negative area at the other, it is a polar molecule.<span>Water molecules attract one another based on the attraction between the positive end of one water molecule and the negative end of another.</span></span>
Answer:
Dicot stems have their vascular bundles in a ring arrangement. Monocot stems have most of their vascular bundles near the outside edge of the stem. Monocot roots, interestingly, have their vascular bundles arranged in a ring. Dicot roots have their xylem in the center of the root and phloem outside the xylem.
External exchange of gases
Well the main purpose of xylem is to transfer sap from the roots to the leaves and phloem typically transports sugars from leaves to sink tissue. Xylem only travels up from the roots but phloem can have either travel up or down. The outside cells of xylem are dead and the the cells that make up phloem are the sieve elements, which are supported by companion cells.
