PLZ ANSWER ITS DONE TODAY NO ONE WOULD, The fossil record helps scientists identify a single species from which other organisms have descended. Which is used to refer to this single species?

parent organism
fossils
descendant
common ancestor HELP PLZ PLZ PLZ

You have just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals. what is the significance of this finding? it will be important to include cysteine in the diet of the mice. cysteine residues are required for the formation of α helices and β pleated sheets. cysteine residues are involved in disulfide bridges that form tertiary structure. cysteine causes bends, or angles, to occur in the tertiary structure of proteins.