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Which is the chordate class considered an evidence of the transition of the vertebrates from the aquatic to the dry land environment?

The amphibians are totally aquatic in the larval stage and partially terrestrial animals as adults and for these facts they are considered intermediate beings in the evolutionary passage of vertebrates from the aquatic to the dry land habitat. Amphibians are also the first tetrapod animals, i.e., the first with two pair of limbs, a typical feature of terrestrial vertebrates. The name “amphibian” comes from the double life (aquatic as larvae and partially terrestrial as adults) of these animals.

What are the amphibian features that make them dependent on water to survive?

Permeable skin, body subjected to dehydration, external fecundation, eggs without shells and larval stage with branchial respiration are features that make amphibians dependent on water to survive.

Do amphibians have direct development?

In amphibians the embryonic development is indirect (there is larval stage).