What function does the skeletal system perform for defense?

Which describes the changes in the earths motion?

On his trip to the galapagos islands, darwin determined that animals on the islands

You are studying a protein that you call protein x. there is an aspartic acid at a key position in protein x which is important in the folding and stabilization of that protein. if this aspartic acid is changed to a different amino acid, which type of amino acid substitutions is most likely to allow the protein to fold normally?