Final answer:
The lateral line sense organ is the structure in fish that contributes to hearing by detecting vibrations in the environment. It senses changes in water pressure and movement, enabling the fish to hear without external ears.
Step-by-step explanation:
In fish, the structure that is analogous to the ossicles in mammals and contributes to hearing by sensing vibrations is the lateral line system. Unlike mammals, which have external ears that collect sound waves and transmit these waves via a set of bones in the middle ear to the inner ear, fish lack external ears and therefore rely on this different mechanism for hearing.
The lateral line sense organ consists of a series of fluid-filled canals lying beneath the skin and running along the sides of the fish's body. This system is sensitive to changes in water pressure and movement, allowing the fish to detect vibrations and even the direction from which they come. The lateral line plays a crucial role in the fish's ability to hear and respond to environmental cues, making it a fundamental sensory organ for survival in an aquatic habitat.