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Hearing apparatus of mammals and insects - Coggle Diagram
Hearing apparatus of mammals and insects
Mammals
Vertebrate ears
Speculated
have taken their first evolutionary steps in semiaquatic tetrapods
Straddled the aquatic-terrestrial shoreline.
Acanthostega
Parmastega aelidae
Glimpse of these aquaticterrestrial transitional forms of vertebrates.
Frequency range of their
balance organs
The first was a lack of structures
Tympani (ear drums) to capture sound energy
Form of sound pressure differences.
The second was a lack
of structures (a middle ear))
To transmit any airborne sound
energy to their internal balance organs
Impedance transformers because air-borne sound must be converted
Into vibrations of the high impendence
Balance organs
Perfectly sufficient to detect the footfall of predators
Competing conspecifics through surface-borne ground vibrations
Fossil evidence
Internalized mechanoreceptor
Vertebrate armored “fish” creature—the Ostracoderm Protopteraspis micra
Embedded in the skull
Bilateral labyrinths
Resembling basic acceleration or balance organs
Insects
Their descendants went onto evolve acoustic
communication
Earliest proof of insects producing sound
is from a Permian insect
Permostridulus brongniarti
Existed∼260 MYA
This is based on its specialized
grooved veins under the wing
Modern day crickets rub this vein along its other wing to stridulate and produce mating calls
The ability to produce sound does not necessarily imply the ability to hear
Tympanal membranes on forelegs
Found in Triassic and Jurassic fossils
Most modern-day Orthoptera that stridulate
have ears
Insect ears
Evolved from proprioceptors littered throughout their body
Lack a distinct middle ear
Nonethe-less exploited biomechanical first-order levers to enhance sound detection
Dedicated head-based
mechanosensory
First of two major milestones
Evolution of vertebrate hearing
Took place in a purely
aquatic environment.
Evolution
Sculpt this prototypical mechanoreceptive organ to fulfill the selective pressures
Vertebrates to hear as they diversified into terrestrial niches