Why are open circulatory systems advantageous to some animals?
they use less metabolic energy.
they the animal move faster.
they do not need a heart.
they large insects develop.

Open circulatory systems are advantageous to some animals because they use less metabolic energy.

Explanation:

Open circulatory systems are also known as lagoon circulatory systems. In this systems the blood is not necessarily always inside the blood vessels; It leaves the heart and will directly irrigate the organs and then return by other means or mechanisms.

So that it can be understood more easily, it is necessary to think about this system acting in organisms much smaller and less complex than mammals or any other vertebrate of greater size. As this animals doesn't have a great size, they need to use less metabolic energy than more developed organisms, so this system allows them to save metabolic energy to be used in other living functions.

lizards have adapted to life in the desert. some desert lizards have toes with spiny scales to them run across the sand without sinking. some use the sand to hide from predators, or to search for small animals that they prey upon.

not sure if this what   you'r looking for would be percent composition