2007-03-24 13:31:53 · 7 answers · asked by Ernest p 1 in Science & Mathematics ➔ Zoology
All animals are bilaterally symmetric, this means they are equal on both sides of their bodies. If they had three legs there would be a difference in their body plan, thus they would not be symmetrical and would undoubtedly have difficulty walking, climbing, etc.
Look at animals like star fish which can have 5 "legs" they are very slow moving, they are marine, and they are not quite mobile.
Hope this helps!
2007-03-24 13:44:29 · answer #1 · answered by Anonymous · 2⤊ 1⤋
Evolution has done this so creatures can achieve balance which most creatures need to run from thier predator.
It's the same reason why no creatures have one eye, because they would have poor eyesight.
2007-03-24 13:37:07 · answer #2 · answered by Anonymous · 0⤊ 0⤋
It's easier to walk straight when left and right match. Besides vertebrate anatomy is pretty much bilaterally symmetric.
2007-03-24 13:35:42 · answer #3 · answered by Kuji 7 · 0⤊ 0⤋
because they wouldn't be able to run properly adn plus that's just the way god made them. don't question his judgement.
he could have made you to have 3 legs. wow that would be really ugly. just except things as they are.
2007-03-24 13:37:48 · answer #4 · answered by Anonymous · 0⤊ 1⤋
Ask Darwin.
No, seriously, nature seems to love symmetry.
2007-03-24 13:35:58 · answer #5 · answered by Anonymous · 0⤊ 1⤋
balance in nature
2007-03-24 13:33:39 · answer #6 · answered by T Time 6 · 0⤊ 0⤋
They would walk in circles.
2007-03-24 13:39:50 · answer #7 · answered by tasgunter 3 · 0⤊ 0⤋