A vertebrate-animal embryo gives rise to the centrum. The centrum is a bone that is part of the vertebral column. It is the hollow space within the vertebra that protects and contains the spinal cord. Within this hollow area are several nerves that send impulses to the brain enabling the organism to function and be at its homeostasis.
The answer: ribonucleic acid (RNA)
Explanation: RNA was the first molecule of heredity, so it evolved all the essential methods for storing and expressing genetic information before DNA came into the scene.
Bird skeletons are very delicate, and therefore, difficult to be preserved. The bones of the birds are soft. The small animals are very prone to physicochemical as well as biological decay. This is why the fossil record of bird is incomplete and well-preserved fossils of birds are rare to find, except at a few unusual sites.
Answer:
All arthropods have an exoskeleton.
Explanation: