Sunday, September 05, 2010

Why vertebrates don't have six legs like insects?

All vertebrates on Earth belong to the order chordates and come from a common ancestor.

Characteristics of vertebrates are, of course, the backbone and symmetrical body made up of head, body and tail.

In the order arthropod, in which insects, spiders and crustaceans belong, articulated organisms have been developed that have a couple of legs on each wrists (centipede is a good example).

Insects usually have six legs and it gives them good support for walking and, besides that, it does not require a common nervous system (which is anyway, less developed).

Terrestrial vertebrates, however, have much more developed brain that, during walking, is managing the movement of diagonal pairs of legs and thanks to that, four legs are sufficient.

Of course, for us humans, two legs are sufficient. :)

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