Interesting question. Mean time can somebody explain why we have such unwanted organ in our body. It create gall bladder stones etc. Is that evolutionary mistake?

Dear collègues,

The specific organise lack in plant, for exemple of leaves or roots is a good known phenomenon. Not very good study ? - Yes. So, I thing for animals, having métamorphoses, it not exist all organe, witch wille présents in maturity...

See:

Phylogenic Studies on the Olfactory System in Vertebrates - NCBI - NIH

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4108759/

TANIGUCHI - ‎2014 - ‎ - Schematic drawings of the phylogenic tree of the vertebrates showing the presence (O) or absence (X) of the vomeronasal organ.

Best

For the evolutionary perspective of a lack of defect of organs in some individuals, it could be that, due to variation in genetime and subsequent phenotype, there is always a monority in the population that develops no/defect organs, unless they still viable.

I thing to the question accurately it would be better to give a "scale" for this phenomenon: for example, among vertebrates (between species), among individuals of the same species, or in a lifetime like the case of methamorphosis

idk

All know the fact of conservation of DNA during the process of evolution. The 100% of the DNA codes are not processed, similarly in the course of evolution the percentage of DNA code activation might be less or more. The internal physiology and also the external factors are responsible. this will lead to either loss of some organs in organisms, prominently seen in vertebrates..

Adaptação a uma nova situação ecológica. Segundo Gould, o processo evolutivo é marcado por catástrofes e novos arranjos geobiológicos, seguidos de longos períodos de estase evolutiva. Em um ambiente mais árido certos grupos de vertebrados, alguns orgãos desaparem pela seleção natural.

If we slightly recollect the functions of gall bladder, then we would find that its main objective is to store bile which is essential for lipid digestion in the intestine. However, when one sees the feeding habits of rat then one would find that the intestine of Rat produces lipases which are more potent than bile in digesting lipids.

Evolution or mutation depends which organ is absence.