Bones that join together and are held in place with sheets of collagen between the bones are called , teeth held in sockets by a fibrous ligament are , and are found between most of the bones of the skull.

Bones JoinedPeriodontal ligamentSutures

Explanation:

Bones joined are the ones that join and held in place with threads of collagen, they are joined with cartilage between the ends, these are the most complex joints and are an important aid in body mobility.The periodontal ligament is the fibrous and connective tissue that joins the tooth to the alveolar bone or to the socket. The function of this ligament is supportive, sensory, and nutritive.All the bones of the cranium, excepting the mandible, are joined by a fibrous joint called a suture.  These sutures have the capacity to permit a small quantity of movement between the bones of the skull. Human cranium has around 20 sutures.

Ithink the dna sequences may vary but the amino acid sequences are identical. 

Carbon dioxide is the correct answer