They have a back bone
They are cold-blooded
Breathes through skin
(extras)
they go though metamorphosis
and they hatch from eggs! <span />
<span>Pleural sac is a two
layered membrane formed when a serous membrane known as pleura folds back onto
itself. Thus, the pleura invest the lungs and line the walls of the thoracic
cavity. However, the potential volume of the thoracic cavity increases during
inhalation.</span>
