When some amphibians mature they live on land because

They develop adaptive features like lungs, legs, skin etc.

Explanation:

Amphibians are one of the classes of animals. They are group of animals capable of living both in water and on land. During their early stage of growth as tadpoles, amphibians live in water using their gills to breathe. However, as they grow, they develop certain features like legs and lungs that enables them transit to living on land.

Amphibians start off their life in water and slowly get adapted to living on land as they mature. Most mature amphibians breathe through their lungs and skin, which they developed as time went by.

hydroxyl -oh

alcohols, always polar, can form hydrogen bonds with h2o molecules

carboxyl -cooh  

cargoxylic acids, has acidic properties which is a source of hydrogen ions, found in cells in ionized for with a charge of oh-1

carbonyl > co

ketone if within skeleton, aldehyde if group is at the end of skeleton, k & a may be structural isomers, it determines 2 sugars (ketose & aldose)

amino -nh2

amines, acts as a base, it can pick up h+ ions from surrounding solution, ionized with charge of 1+

methyl ch2

addition to rna/dna affects and gene expression

phosphate -opo3 ²⁻

organic phosphates, contributes to negative charge to, molecule that it is a part of, and potential to react with h20

sulfhydryl -sh

thiols, cross-linking stabilize the protein, and it is structure