Short answers, pulled from the story.
The human ear has three parts: the outer ear, the middle ear, and the inner ear. The outer ear includes the auricle and ear canal, the middle ear holds the tympanic cavity and three ossicles, and the inner ear sits in the bony labyrinth and contains the semicircular canals, utricle, saccule, and cochlea.
The stapes, one of the three ossicles in the middle ear, is the smallest named bone in the human body. The ossicles, the malleus, incus, and stapes, work together to amplify sound waves by nearly 15 to 20 times as they transmit vibration from the eardrum to the inner ear.
The ear provides balance through the vestibular system, handling static balance and dynamic balance. Static balance comes from the utricle and saccule, where shifting otoliths of calcium carbonate bend filaments, while dynamic balance comes from the three semicircular canals, which sense acceleration through fluid pressure on the cupula.
The human ear can generally hear sounds with frequencies between 20 Hz and 20 kHz, known as the audio range. Sounds below 20 Hz are infrasound and sounds above 20 kHz are ultrasound.
Conductive hearing loss results from injury or damage to the outer ear or the ossicles of the middle ear, such as a canal blocked by earwax or holes in the eardrum. Sensorineural hearing loss results from damage to inner ear structures such as the cochlea, auditory nerve, and potentially the vestibulocochlear nerve.
Ears are individually almost unique, with very low odds of two people having matching ears, and their proportions are normally retained for life. Because of this, ears have been employed for forensic identification since the 1950s.
Only vertebrate animals have ears, though many invertebrates detect sound using other sense organs. Insects use tympanal organs, the female cricket fly Ormia ochracea hears with linked organs on her abdomen, and Monarch butterfly caterpillars respond to vibration through 450 micrometre long hairs called trichoid sensilla.