All chordates have a hollow nerve cord, a notochord, and pharyngeal slits. Lateral line fish heart and liver Fish have a lateral line that serves as a sensory organ. They practice external fertilization in wetland areas. Amphibians are experiencing hardship due to environmental problems. Atrazine is an endocrine disrupter in frogs, and methoprin, a mosquito spray, is killing them.
Frogs develop missing limbs and also extra limbs.
UV-B rays, pollution, acid rain, over harvesting, and parasite relationships are also harming frog and toad populations.