Discuss the problems that animals had to overcome to adapt to the land environment. How did they ...

Because animals evolved in a moist environment, they had to adapt to the drying effects of
the atmosphere by acquiring an outer covering for protection. They also had to develop a
means to extract oxygen from the atmosphere by lungs rather than from water by gills.
Because animals need mobility to find food, they also had to develop a means of locomotion
on land by foot rather than locomotion in water by fins. And, animals need to overcome the
effects of gravity with a skeletal structure for support. Their reproductive strategy moved
toward internal fertilization since gametes were no longer dispersed in water, and they had to
combat the problems of desiccation of unprotected eggs with the evolution of the amniote
egg.