Which of the following four statements, if any, is true regarding essential elements and living organisms?
1. the elements carbon, hydrogen, nitrogen, and oxygen make up 20-25% of living mass.
2. given their low concentrations in nature, the toxicity of some elements is generally not a factor in the evolution of biological communities.
3. although all forms of life require iron, other elements are required only by certain species.
4. all organisms require 25 of the 92 naturally occurring elements to survive.
5. all of the listed responses are correct.

What is the 77 element on the periodtic table

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.

The tubes transporting minerals and water upward are called ?