Green-eyed tree frog
Frogs are born with legs that are good for hopping and special pads on their toes to help them climb. In comparison, toads have shorter legs, drier skin, and are less likely to live near water. Most frogs and toads are responsible for controlling the Earth's insect population, since their diet consists mostly of insects and spiders. However, the green eyed-tree frog is also a carnivore. As a tadpole, the frogs mostly consume algae and plants. Frogs have a moist and permeable skin layer covered with mucous glands, which enables them to breathe through their skin, not just their lungs. The layer of mucus that covers them also acts as a shield, protecting them from scratches. The reason frogs have large and protruding eyes is to make up for their lack of a neck. This eye feature allows them to see everything around them. The color scheme of the green-eyed tree frog is to camouflage them from predators. Frogs with bright colors are alerting predators of their poisonous nature.
Tetrapod
Although air-breathing fish can absorb oxygen through their lungs, the lungs tend to be ineffective for discharging carbon dioxide. In tetrapods, the ability of lungs to discharge CO came about gradually, and was not fully attained until the evolution of amniotes. The same limitation applies to gut air breathing (GUT), i.e., breathing with the lining of the digestive tract. Tetrapod skin would have been effective for both absorbing oxygen and discharging CO, but only up to a point. For this reason, early tetrapods may have experienced chronic hypercapnia (high levels of blood CO). This is not uncommon in fish that inhabit waters high in CO.
According to one hypothesis, the "sculpted" or "ornamented" dermal skull roof bones found in early tetrapods may have been related to a mechanism for relieving respiratory acidosis (acidic blood caused by excess CO) through compensatory metabolic alkalosis.