Which is a characteristic of all vertebrates?

The presence of vertebral column or notochord at any stage of life in any organism is the characteristic of vertebrate.

Explanation:

An animal is vertebrate if it fulfils the following criteria:

Presence of vertebral column or notochord.

Presence of endoskeleton or backbone.

The spinal cord runs above the vertebral column.

Humans embryo has notochord which becomes a vertebral column.

The alimentary canals end in the anus.

Mouth is present ta the anterior side of the vertebrate.

Have legs, fins or wings for movement.

Presence of a nervous system and sensory organs.

Presence of skin, lungs or gills.

Presence of a circulatory system.

Vertebrates include fish, amphibians, reptiles, birds and mammals.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.