Two species, a cactus and a Venus fly-trap, have a water intake system that's similar in function but not in structure. What type of structure is this?

The Structure of the two species are the cactus have  shallow root system and Venus fly traps are grown in indoors.

Explanation:

The Venus fly trap is very small in size whereas the cactus can grow to 50 feet tall and weighs up to 7 tones.

The cactus can store water from its unique design in which its skin can expand  to make large amounts of water. In fly traps there are leaves on the body called "Traps" they are used to catch insects and prey. the another difference between the two species is cactus does not have leaves.

The Venus flytraps do not have brains instead they have hormone associated with the feeding process.