What would an evolutionary advantage be to having a metamorphosal development?

Question

I'm trying to understand why so many amphibians have evolved to metamorphose from a larval to an adult form. Why do they do it? It seems to take so much energy and they are so vulnerable as babies!

Answer 1

I don't think it's necessarily evolutionarily an advantage, nor a detriment.  They continue to survive just like the fish who are born in water and continue to live in water do, by laying multiple eggs.  It would seem that this phase remained from when they were strictly water beings.  If it made a difference, they would more likely have evolved to lay their eggs on land rather than do away with the metamorphic stage.

Answer 2

It's called resource partitioning - the young live and feed in one environment and the adults in another. This way young and adults are not competing with each other for the same resources. Couple this with their high rate of fecundity (each female might lay hundreds or thousands of eggs), and the dangers of the metamorphic process (to the individual) are not as costly as the advantages are to the population. Remember that individuals do not evolve, populations do - look for advantages at the population level not the individual.

Answer 3

You're asking the wrong question. It's not, why did so many evolve to metamorphose from a larval to an adult form? Its, did they evolve?

The answer to that is no. Evolution is a world view that has been around for many thousands of years. It became popular in our time and culture through Darwin and his contemporaries. Since the mid-1800's, everything in science and especially biology has been interpreted under evolution's moral law. When we see amphibians and insects go though metamorphosis, we should appreciate God's wonderful creation. We should reflect on His personality and wondrous creative ability. What we see is that He has made an enormous amount of variation in His creation. Plants and animals that cover a huge diverse biosphere, each having specialized abilities and functions.

If a person wants to believe that a caterpillar somehow evolved the ability to make a cocoon, dissolve its entire body and reform it into a different specialized creature with entirely different parts and systems, that would be that persons religious faith based convictions and not part of observable testable science.