Darwin theorized that evidence for the evolution of new species can be found in homologous body structures. which observation supports this theory? a. the beaver and the capybara are similar species that inhabit similar environments in separate continents. b. the size, shape, and variety of squid, octopi, and chambered nautiluses have changed over time. c. the limbs of reptiles, bird, and mammals resemble the fins of the ancient lobe-finned fish. d. the embryos of many animals with backbones are very similar.

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.