Two species have a relationship with one another in an ecosystem. Suppose one of these two species goes extinct. Which type of relationship did the two have if the surviving species population increases after the other goes extinct?

Commensalism

Explanation:

Commensalism - relationship in which one organism benefits while the other is neither helped nor harmed.

Because there were two species we can see that there was not a harmful (parasitism) relationship, nor Mutualism because when one species died the other remained safe.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.