Scientists used radiometric dating and other fossil evidence to look for the Tiktaalik fossils. They already had prior knowledge that the aquatic vertebrates first moved to land between 380 to 363 million years ago. They looked for sedimentary rock layers that match this age and started the search for the fossils from there.
The molecule that would be affected by 'limited nitrogen' is the myofibrillar proteins in muscle. Explanation: The myofibrils of the muscle have a number of protein molecules.
