There are various reasons living systems discharge liquids, such as to defend themselves, to avoid liquid buildup that can cause decay, to eliminate waste, or to dry off. Because liquids cannot be effectively moved through pushing, a different kind of force is needed to expel them. Creating that force requires energy, so living systems must have efficient strategies worth the energy investment or use an outside force (such as gravity). This typically entails strategies that build up pressure or use other forces to propel liquids away. An example of a living system that expels liquids is the scallop. This creature moves through water by clapping its shells together, generating a water jet that propels it in the opposite direction.
Class Reptilia (“creeping”): Lizards, crocodiles, turtles, snakes
Reptiles retain some of the key characteristics that first enabled vertebrates to live permanently on land. They have dry skin covered in scales made of keratin that help prevent water loss. (Amphibians still need to stick close to water to keep their skin moist.) Many reptiles reproduce by laying eggs that are watertight and have a yolk, so eggs can develop on land while staying moist and nourished. Reptiles are also ectotherms, meaning they don’t produce their own body heat. This means they burn through energy much more slowly than “warm blooded” creatures of the same size. It also means that they need to keep warm to keep active, which is why you might see them spending a seemingly inordinate amount of time simply basking in the sun.
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