Terrestrial Vs Aquatic Organisms

One obvious problem that terrestial organisms, not aquatic ones, would suffer from, would be the simple imperative of finding water. All living things need water to survive, but for animals trapped on land, its not always available. An Aquatic creature, however, is never lacking in water. Unless it has been removed from its environment, in which case, it is most likely dead or dying. One evolutionary adaptation of terrestial animals to overcome this disadvantage is an acute sense of smell. many animals can use their sense of smell, which is on average far greater than that possessed by human beings, in order to help them find both food and water. 

Another problem afflicting only terrestrial organisms would be weather. Animals on land have to adapt their day to day activities in accordance with the weather. Aquatic organisms, on the other hand, have the rather constant tides, and no real weather to speak of. An evolutionary method for overcoming terrestrial animals need to find shelter from nature is fur, or some other kind of protective and insulating outer coating, such as feathers on birds and scales on reptiles. 

A third problem that would affect terrestrial animals and not aquatic would be temperature. The seasons shift on land, changing the weather, which raises and lowers the temperature, which changes migration patterns, as well as the lands usefulness. Terrestrial animals have to be able to change from season to season, adapting their daily routine to the differing temperatures. Aquatic organisms, on the other hand, only experience major shifts in temperature when they go to areas of the ocean which hold at different temperatures than they are used to. As with weather, fur and other outer coverings are evolutionary tools to overcome this disadvantage.