Understanding Amphibians: Characteristics and Classification

Study Notes

Anfíbios are vertebrates that live in aquatic and terrestrial environments.
Anfíbios maintain strong ties to water and do not stray far from it, as they need to keep their moist skin.
Fertilization in anfíbios usually occurs externally, and is most commonly found in water.
The anfíbios' respiratory system consists of three parts: lungs, skin, and the mucosa of the mouth and stomach.
The anfíbios' respiratory system is closed and the blood circulates in two loops.
The anfíbios' heart is divided into three chambers, and due to the presence of only one ventricle, the blood rich in oxygen has contact with the blood rich in carbon dioxide, making the circulatory system incomplete.
The anfíbios' skin is smooth, vascularized, and permeable. They do not absorb water, which is obtained through the skin through gas exchange.
The anfíbios' reproductive system is sexuado, and fertilization usually occurs externally. The female expels the eggs into water and the male deposits the sperm over them.
The anfíbios have three groups of animals: anuros, ápodes, and urodelos.
Anuros, when adults, lack legs and have a tail, for example, snakes, lizards, and turtles.
Urodelos have cylindrical bodies and lack legs, for example, snakes, lizards, and turtles.
Apodes have bodies that are elongated and lack legs, for example, cobras-cegas, which live buried in the ground and are more active at night.
The anfíbios have an excretory system with the presence of kidneys. Many anfíbios excrete ammonia when in their aquatic phase and change their excretion behavior when in the terrestrial environment, excreting urea.