Animals maximize their survival chances because any departure from symmetry affects locomotion. If one leg is shorter than the other you limp and become prey to predators. Birds could not fly nor fish swim if they were not evenly balanced. Their equilibrium would be affected.
And symmetry breeds success…I understand that perfect symmetry helps horses win races.
So most animals are bilaterally symmetrical and their bodies are divided equally into left and right sides. There are always exceptions. (sponges have an asymmetrical body plan).
As I look out at the trees from my window, I notice that they too have approximate symmetry even though they are not going anywhere. Pines are perfectly balanced but in most trees the two sides do not match exactly, branches may protrude. But I imagine that they too are shaped so that they do not topple over.
Of course fruit and flowers have perfect radial symmetry as we can see if we cut an apple or an orange in half. Bees are said to have imperfect vision but they are drawn to flowers because of their symmetry. So this seems like an evolutionary advantage. And the fruit is probably prevented from falling prematurely because its weight is even.
Our bodies are also approximately symmetrical. We too have two legs, hands, ears etc. But then why do we have only one heart, liver and pancreas? Why do we favor one hand over the other? (and why is it usually the right hand?)
In arguments we like to assign sides by saying: on the one hand, on the other hand, yes or no, true or false, something or nothing. So if we were a millipede would we see one thousand alternatives to every question?
(next time, more symmetrical thinking)