 As they evolved from lunged fish , amphibians had to make certain adaptations for living on land , including the need to develop new means of locomotion . In the water , the sideways thrusts of their tails had propelled them forward , but on land , quite different mechanisms were required . Their vertebral columns , limbs , limb girdles and musculature needed to be strong enough to raise them off the ground for locomotion and feeding . Terrestrial adults discarded their lateral line systems and adapted their sensory systems to receive stimuli via the medium of the air . They needed to develop new methods to regulate their body heat to cope with fluctuations in ambient temperature . They developed behaviours suitable for reproduction in a terrestrial environment . Their skins were exposed to harmful ultraviolet rays that had previously been absorbed by the water . The skin changed to become more protective and prevent excessive water loss . 
