dolphins can not stay in water long time like most aquatic animals
Dolphins are marine mammals, zebras are terrestrial mammals. Zebras are herbivores, but dolphins are carnivores. Thus zebras are prey animals and dolphins are predators. But the biggest difference between these to animals is that they do not look the same.
Terrestrial animals can't just release sperm into their environment to fertilize eggs, where as some aquatic animals can, because sperm needs water to fertilize
Amphibians can live both on land and water
The respiratory system of most non-aquatic animals is entirely enclosed in the human body and connected with the lungs. Many aquatic animals have developed open respiratory systems that include features like the gills.
dolphins are mammals
a dorsal fin
It is not easy to compare terrestrial and aquatic systems because there is such on the similarities and differences between terrestrial and aquatic ecosystems.
A shark is considered a fish. A dolphin is a mammal. While both may be considered aquatic with living in water, both are different in that respect. The mammals breathe air and produce milk for their offspring.
An aquatic ecosystem is based on water, and a terrestrial ecosystem is based on land.
Ichthyology is the study of the group of animals called fish. Fish are a group of aquatic animals with fins. Fisheries are entities engaged in the controlled harvesting of fish, generally for food.
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A person can find pictures that show the difference between the genders of catfish in a book about catfish. It can also be found in a book about aquatic animals.