1. Communication Chapter 6: Animals that produce vibrations
also have organs to detect vibrations.

2. The use of sound for communication by animals
The reasons for producing sound are varied – coordination, contentment, distress, echolocation, fear, group cohesion, hunger, hunting, identification, illness, mating, migration, navigation, pain, predation, protection, thirst, warning, wooing… For example: cicadas produce sounds that are so loud that it can be painful to the human ear. The main purpose of their songs is to find a mate.

3. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
The ear is one of the most complex organs of the human body and yet it can be traced back to a simple organ in prehistoric creatures. Even in modern jellyfish it is an organ of balance. Although this is a secondary function of the ear today.

4. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
INSECTS Insects such as mosquitoes have tactile bristles on their cuticle and on their antennae which respond to low frequency vibrations. This form of communication brings the two insects closer together for mating. Many insects possess more specialised structures for hearing.

5. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
Crickets have a tympanum (drum) on each leg just below the knee. The tympanum is a cavity containing no fluid. It is enclosed by an eardrum on the outer side and a pressure release valve on the other. Nerve fibres are connected to the eardrum and pick up the vibrations directly. Female crickets are deaf to some frequencies and sometimes rely on the smell given off by the male as he raises his wing covers to make a call.

6. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
Both male and female cicadas possess organs for hearing despite the fact that it is only the males that sing. A pair of large, mirror-like membranes, the tympana, are connected to an auditory organ by a short tendon at the base of the abdomen. When a male cicada sings he crinkles his tympana to prevent deafening himself.

7. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
FISH The hearing abilities of fish vary between species. All fish have a lateral line sensory organ, a pronounced pair of sensory canals, which run the length of each side of the animal. Pressure waves in the surrounding water distort the sensory cells found in the canals, sending a message to the nerves.
The lateral line has the same type of hair cells and nerves that are found in the inner ear of humans.

8. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
Some fish actually perceive sound waves by possessing an inner ear that has a sensory chamber composed of passages called the labyrinth. It contains an otolith (ear stone) and is lined with hair cells. Auditory nerves detect the differences in vibrations between the hair cells and the otolith. This is recorded as a nerve impulse, which is carried to the brain.

9. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
The swim bladder may also play a part in transmitting vibrations to the sensory chamber. In many freshwater fish, such as carp, the transmission may be enhanced by a series of small bones, the ossicles, which connect the swim bladder to the sensory chamber.

10. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
MAMMALS There are many similarities in the basic hearing processes in marine mammals and terrestrial mammals. We will use the human ear as a model for terrestrial ears. Although there are differences among the ears of different species, the basic processes of hearing are the same.

11. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
The human ear is divided into three sections:
The outer ear which collects and directs sound
The middle ear filters and amplifies the acoustic energy to the inner ear
The inner ear transforms the acoustic energy to electrical signals that are processed by the brain.

12. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
Killer whales have an acute sense of hearing. Sound is received by the lower jawbone. This contains a flat-filled cavity which extends back to the auditory bulla (ear-bone complex).
Sound waves are received and conducted through the lower jaw, the middle ear, inner ear and the auditory nerve to the well- developed auditory cortex of the brain.

13. Detecting sound outline and compare the detection of vibrations by insects, fish and mammals
Dolphins close their canals when diving. They detect vibrations through special organs in the head and some low-frequency sounds through the stomach.

14. The range of frequencies detected by humans and two other mammals as sound process information from secondary sources to outline the range of frequencies detected by humans as sound and compare this range with two other mammals, discussing possible reasons for the differences identified
The frequency range of human hearing is limited to approximately cycles per second (Hz). The ability to hear high-pitched sounds decays throughout life. Mammals other than humans can detect sound frequencies lower than 20Hz and much higher than Hz. Dogs, for example, can easily detect sounds between 15Hz and Hz. They are able to hear a high-pitched dog whistle, which is inaudible to the human ears.

15. The range of frequencies detected by humans and two other mammals as sound process information from secondary sources to outline the range of frequencies detected by humans as sound and compare this range with two other mammals, discussing possible reasons for the differences identified
The frequency of sounds produced by dolphins ranges from 0.25Hz to Hz and takes the form of whistles and clicks. Their hearing range is Hz.
POSSIBLE REASON: Dolphins cant rely on vision all the times. They produce high-frequency, shorter sound wave in dark and murky water to locate objects and find food, and use low-frequency sounds known as whistles for communication. Lower-frequency sounds travel further in water.

16. The range of frequencies detected by humans and two other mammals as sound process information from secondary sources to outline the range of frequencies detected by humans as sound and compare this range with two other mammals, discussing possible reasons for the differences identified
Bats use a higher range of frequencies. Sounds produced are in the Hz Hz range. Their hearing extends from 1.0Hz Hz.
POSSIBLE REASON: Bats are crepuscular (active at dawn/dusk) or nocturnal (active in darkness). As a result they rely strongly on echolocation for navigation and detection of prey. The higher- frequency sound wave, being short, produces more detailed messages for the bat about its surroundings.

17. The range of frequencies detected by humans and two other mammals as sound process information from secondary sources to outline the range of frequencies detected by humans as sound and compare this range with two other mammals, discussing possible reasons for the differences identified
The flexibility of the basilar membrane limits the frequency range of human hearing. During the course of human evolution, the ability to modify the environment has resulted in less reliance on the sense of hearing for survival. Humans retain effective three-dimensional vision, which eliminated the need for echolocation.

18. The anatomy and function of the human ear describe the anatomy and function of the human ear, including: pinna, tympanic membrane, ear ossicles, oval window, round window , cochlea, organ of Corti, auditory nerve
THE EXTERNAL EAR
The external (outer) ear is comprised of the:
Pinna (pinnae is plural): the floppy bit
Meatus: the auditory canal
Tympanic Membrane: the outer layer of the eardrum
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19. The anatomy and function of the human ear describe the anatomy and function of the human ear, including: pinna, tympanic membrane, ear ossicles, oval window, round window , cochlea, organ of Corti, auditory nerve
THE MIDDLE EAR The middle ear is an air-filled cavity. It is separated from the external ear by the tympanic membrane and connected to the throat by the Eustachian tube. The middle ear opens into the inner ear through the oval window. Inside the cavity are three small bones, which are connected by true joints and form a system of levers. These bones are easily damaged by noises.
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The ossicles (small bones in the ear) are so small they could for into a 5 cent coin

20. The anatomy and function of the human ear describe the anatomy and function of the human ear, including: pinna, tympanic membrane, ear ossicles, oval window, round window , cochlea, organ of Corti, auditory nerve
THE INNER EAR
The inner ear is formed by a series of bony canals. It can be divided into three parts:
Vestibule (entrance)
Semicircular canals
The cochlea
The vestibule and the semi-circular canals play no part in hearing but are 3D sensors for balance. The cochlea is a spiral bony canal, which houses the organ of Corti.
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21. The anatomy and function of the human ear describe the anatomy and function of the human ear, including: pinna, tympanic membrane, ear ossicles, oval window, round window , cochlea, organ of Corti, auditory nerve
Each hair cell of the organ of Corti has a nerve fibre attached. These lead to the auditory nerve, which carries impulses to the hearing centres in the cortex of the brain.
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22. Eustachian tube outline the role of the Eustachian tube
The Eustachian tube helps to equalise air pressure on either side of the tympanic membrane by bringing in air from the mouth.
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23. Structure of the mammalian ear related to its functions gather, process and analyse information from secondary sources on the structure of a mammalian ear to relate structures to functions
Refer to table
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24. The external, middle and inner ear and energy transformations outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur
EXTERNAL EAR Sound is transmitted as a wave through air in the auditory canal to the outer layer of the tympanic membrane. Auditory Canal  Tympanic Membrane (Eardrum)
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25. The external, middle and inner ear and energy transformations outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur
MIDDLE EAR Vibrations from the tympanic membrane are conveyed through this air-filled chamber via the movement of the interconnecting ear ossicles to the oval window of the inner ear. Tympanic Membrane  Malleus (ossicle)  Incus (ossicle)  Stapes (ossicle)  Oval Window
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Ossicle = small bone

26. The external, middle and inner ear and energy transformations outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur
INNER EAR The stapes vibrates the oval window setting up a pressure wave in the perilymph of the upper canal of the cochlea. Stapes  Oval Window  Upper Canal (cochlea)
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Perilymph = liquid in cochlea (inner ear)

27. The external, middle and inner ear and energy transformations outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur
Reissner’s membrane
This causes Reissner’s (or vestibular) membrane to move, transferring the kinetic energy to the endolymph of the middle canal. This vibrates the basilar membrane stimulating the hair cells of the organ of Corti. Upper Canal  Reissner’s Membrane (Cochlea)  Middle Canal  Basilar Membrane  Hair Cells
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Perilymph = liquid in cochlea (inner ear)
Basilar membrane
Endolymph

28. The external, middle and inner ear and energy transformations outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur
The hair cells send messages along nerve fibres to the brain where they are interpreted. The pressure waves continue to the round window at the end of the lower canal. Hair cells (Organ of Corti)  Auditory Nerves  Brain
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29. The external, middle and inner ear and energy transformations outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur
ENERGY TRANSFORMATIONS
Sound waves pass in air along the auditory canal. Sound energy is converted to mechanical (kinetic) energy as the vibration is set up in the tympanic membrane. The mechanical energy is transmitted through the three ear ossicles to the oval window.
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30. The external, middle and inner ear and energy transformations outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur
As it passes into the perilymph, as a pressure wave, the mechanical energy is transferred via Reissner’s membrane to the endolymph to the organ of Corti. Mechanical energy is now converted to electrochemical energy as information is transmitted, as nerve impulses, from the hair cells by the auditory nerve to the brain.
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31. The external, middle and inner ear and energy transformations outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur
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32. The organ of corti and the detection of sound describe the relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of different frequencies
The organ of Corti rests on top of the basilar membrane. It is composed of supporting cells and about hearing receptor cells called cochlea hair cells. Unlike other cells of the body, there is a finite number and they are not replaced as they die.
Auditory tranduction

33. The organ of corti and the detection of sound describe the relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of different frequencies
There is one row of inner hair cells and three rows of outer hair cells sandwiched between the tectorial and basilar membranes of the cochlea. The fibres of the cochlea nerve are coiled around the bases of the hair cells. The cilia of the hair cells protrude into the potassium rich endolymph and the longest of them are embedded in the overlying gel of the tectorial membrane.
Coiling around the inside of the cochlea, the organ of Corti contains the cells responsible for hearing, the hair cells. There are two types of hair cells: inner hair cells and outer hair cells. These cells have stereocilia or "hairs" that stick out. The bottom of these cells are attached to the basilar membrane, and the stereocilia are in contact with the tectorial membrane. Inside the cochlea, sound waves cause the basilar membrane to vibrate up and down. This creates a shearing force between the basilar membrane and the tectorial membrane, causing the hair cell stereocilia to bend back and forth. This leads to internal changes within the hair cells that creates electrical signals. Auditory nerve fibre's rest below the hair cells and pass these signals on to the brain. So, the bending of the stereocilia is how hair cells sense sounds.

34. The organ of corti and the detection of sound describe the relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of different frequencies
Activation of the hair cells occurs at points of vigorous vibration of the basilar membrane. Hair cells nearest the oval window (base) are activated by the highest pitched sounds while those furthest away at the narrow end of the cochlea are stimulated by low frequency sounds.

35. The sound shadow cast by the head plays a part in the location of sound outline the role of the sound shadow cast by the head in the location of sound
The phenomenon caused by the obstruction or absorption of a sound wave by an object in its path is called a sound shadow. This is perceived as a reduction in amplitude or volume. The sonic shadow is the region which does not receive the direct sound as the head is blocking the vibration.
The effect will be greatest when the sound source, the absorbing object and the person hearing the sound are all aligned.

36. The sound shadow cast by the head plays a part in the location of sound outline the role of the sound shadow cast by the head in the location of sound
As humans are binaural (have 2 ears), the head creates a sonic shadow for the ear further away from the sound source. The head absorbs high- frequency sounds more readily than low- frequency sounds, and thus plays a role in locating a sound source.
Many humans will turn their head when trying to determine the source of a sound. This creates a sound shadow, increasing the difference in time of arrival of sound at each ear.
Visually impaired people use the sonic shadow effect, together with echolocation and other cues for orientation.

37. Hearing Aids and cochlear implants process information from secondary sources to evaluate a hearing aid and a cochlear implant in terms of: – the position and type of energy transfer occurring – conditions under which the technology will assist hearing – limitations of each technology
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