Adaptation of vertebrates

Question

What are the various problems that vertebrates required to resolve to adapt to the terrestrial atmosphere as they came from aquatic habitat? How evolution does solve such problems?

Answer 1

The major problems vertebrates coming from water required to resolve to adapt to the terrestrial atmosphere were the following: the problem to evade dehydration; the problem of removal of wastes in a medium where water is less obtainable; the trouble of protection against nocent solar radiation; the difficulty of gamete locomotion in the atmosphere for fecundation; the problem of gas exchange, previously done by direct contact of water with gills; the trouble of body support, as it was water that played this function in fishes.

Solutions for the dehydration trouble: impermeable and thicker skin, to lose less water, or moist and permeable skin, similar to in amphibians. Answer for the excretion problem: excretion of urea (as well excreted by chondrichthyes) or uric acid, substances which require less water to be dissolved. Answers for the problem of protection against the radiation: skin pigments which filter injurious radiation, feathers, hair and carapaces. Answer for the gamete movement trouble: internal fecundation (apart from for most amphibians, that contain external fecundation). Answer for the gas exchange trouble: appearing of lungs and airways. Answer for the body support problem: further growth of muscular and bony structures such as claws and limbs.