9.5 Option - Communication
1. Humans, and other animals, are able to detect a range of stimuli from the external environment, some of
which are useful for communication.

Identify the role of receptors in detecting stimuli
A receptor is a specialized structure that can detect a specific stimulus and initiate a response. The stimulus
may come from the external environment (e.g. light intensity, sound) or may come from the internal
environment (e.g. hormone levels, arrival of food).
There are many type of receptors:


Proprioreceptors in muscles, tendons and joints

Mechanoreceptors respond to stretching, movement, touch, pressure and gravity

Chemoreceptors respond to chemicals

Photoreceptors detect light

Thermoreceptors detect heat and cold

Electroreceptors detect electrical energy
Explain that the response to a stimulus involves:

Stimulus

Receptor

Messenger

Effector

Response
Any information that can provoke a response from us is called a stimulus. Our environment contains many
stimuli and we have special receptors to detect them and send information about conditions to control
centers of the body. This can initiate a response. Responses are brought about by effector organs, which
are usually muscles or glands. The messenger that travels from the receptor to the effector may be nervous
or hormonal.
In summary, the pathway from stimulus to response is as follows:
Stimulus  receptor  messenger  effector  response

Identify data sources, gather and process information from secondary sources to identify the range
of senses involved in communication
Communication is the ability to perform an act that will change the behavior of another organism. The
methods of communication involve all the senses - sight, sound, touch, taste and smell. Each species has
developed its own methods of communicating information, which relate to its lifestyle. Humans rely mostly
on visual and auditory signals.

Chemical signals
o Pheromones - chemicals released by an organism into the external environment that
influence the behavior or development of other members of the same species.
o
Common among mammals and insects.
1
o
Examples: female insects produce pheromones to attract males of the same species, ants
will follow a pheromone trail, in bees, queen bee secretes an ‘anti-queen pheromone’ which
inhibits worker from raising a new queen.
o
o

Many species mark out territories with urine.
Blowflies fly towards chemical odour of decaying meat.
Visual signals
o
Many species use different postures for communication and many use colourful displays to
attract a mate (eg peacocks).
o
Honeybees have a sophisticated form of communication: a ‘dance’ to indicate the direction
and distance of a source of nectar relative to the hive. Close food supplies are shown by a
‘round dance’ ‘Waggle dance’ gives the angle of the food source relative to the sun and the
hive.
o

Male fireflies use flashing lights as a visual signal to attract female fireflies.
Sound signals
o Birds sing either to attract a mate or establish their own territory.
o
The sound of beating wings of a female mosquito attracts the male mosquito.
Refer to white sheet “Stimuli and receptor” and “Methods of communication”
2. Visual communication involves the eye registering changes in the immediate environment

Describe the anatomy and function of the human eye, including the:

Conjunctiva

Cornea

Sclera

Choroids

Retina

Iris

Lens

Aqueous and
vitreous
humor

Ciliary body

Optic nerve
2
Parts
Structure
Function
Conjunctiva
Thin, clear membrane covering the front
of the eye and the inner eyelids
Protect the front part of the eye against
infection
Produce mucous that helps lubricate the
eye
Cornea
Transparent, dome-shaped window
A powerful refracting surface providing 2/3
covering the front part of the eye
of the eye’s focusing power
Bend light rays as they pass through and
helps it to focus
Sclera
“The white of the eye”
The eye’s protective outer coat
Tough, white outerback part of they
eyeball
Choroid
Lies between the retina and sclera
Absorbs and prevents light scattering to
A dark pigmented layer containing many
prevent false images forming on the retina
blood vessels
Retina
Film of the eye
Converts light rays into electrical signals
The innermost layer of the eye, contains
the light sensitive cells or photoreceptors
and sends them to the brain through the
optic nerve
(rods and cones) and fibres
Contain fovea
Iris
Lens
Aqueous humor
Coloured part of the eye
Contracts and expands, opening and
A ring of muscle fibres
closing the pupil in response to the
brightness of surrounding light
A transparent, biconvex protein disc
Focuses light rays onto the retina
behind the pupil
Refractive media and has a role in
accommodation
A thin, watery fluid that fills the space
Nourished the cornea and the lens and
between the cornea and the iris
Continually produced by cilliary body
gives the front of the eye its form and
shape
Refractive media
Vitreous humor
A thick, transparent jelly-like substance
that fills the center of the eye
Composes mainly of water giving the eye
its forma nd shape
Bends rays of light as they pas through
Refractive media
Cilliary body
Connects the choroids with the lens and
Alters the shape of the lens -
contains the cilliary muscles and
suspensory ligaments that hold the lens in
accommodation
position
Optic nerve
The optic nerve connects the eye to the
Transmits electrical impulses form the
brain
retina to the brain
The region where it leaves - blind spot
because it has no photoreceptors and
therefore cannot produce an image
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
Identify the limited range of wavelengths of the electromagnetic spectrum detected by humans and
compare this range with those of other vertebrates and invertebrates
Energy from the sun reaches Earth as waves of electromagnetic radiation. The electromagnetic spectrum
has a range of waves of different wavelengths. Light is one form of electromagnetic radiation and makes up
a part of the spectrum. The shortest wavelengths are gamma rays and in order of increasing wavelengths,
X-ray, UV, visible light, infra-red, microwaves, TV and radio waves.
Only a limited range of these wavelengths can be detected by humans. This range is called the visible
spectrum - from 380 to 750 nm. Different wavelengths correspond to different colours.
UV and infra-red are outside the human range but other animals can detect them. For example, bees and
many other insects can see well into the UV range and can navigate to pollen and nectar in flowers by
following UV landing strips on petals.

Plan, choose equipment or resources and perform a first-hand investigation of a mammalian eye to
gather first-hand data to relate structures to functions
Refer to print outs on “cow-eye”

Use available evidence to suggest reasons for the differences in range of electromagnetic radiation
detected by humans and other animals
Range of EMR detected
Animal
Range
Reasons
Humans
380 - 750 nm
Active during the day, colour vision important to distinguish
food and to gain information about the environment
Pit viper
400 - 850 nm
Relies on infra-red to locate prey in dark burrows
Deep sea fish
450 - 500 nm
Little light penetrated to the depth at which they live, use
bioluminescence to communicate: can only detect blue light
Honeybee
300 - 650 nm
Some flowers have ultraviolet markings on them which bees
use to find pollen
3. The clarity of the signal transferred can affect interpretation of the intended visual communication

Identify the conditions under which refraction of light occurs
Light travels in a straight line and is bent or refracted when it moves from one medium to another with
different densities. Refraction occurs when the wave changes speed and direction. A ray of light moving into
a more dense medium is refracted towards the normal: a ray of light moving into a less dense medium is
refracted away from the normal. Light is not refracted if it hits the boundary of 90 degrees.
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
Identify the cornea, aqueous humor, lens and vitreous humor as refractive media
Refraction is very important in the eye. As light passes into the eye it is refracted by four different
transparent media. These are:

The cornea, which causes most of the refraction

The aqueous humor

The lens, which fine focuses the image onto the retina
 The vitreous humor
They are called refractive media because light bends as it passes through them

Identify accommodation as the focusing on objects at different distances, describe its achievement
through the change in curvature of the lens and explain its importance
Accommodation is the ability to focus objects at different distances through a change in the curvature of the
lens by the contraction of the ciliary muscles. It is the way our eye adjusts so that the light is always focused
on the retina. It is important to allow clear vision. Without accommodation the eye would have a fixed focus
and would not be able to change focus from distant to close objects, which will appear to be blurred.
The ciliary muscles control the thickness of the lens and attached to these muscles are suspensory
ligaments. The ciliary muscles change the curvature according to the distance of the object to be focused.
When the ciliary muscles contract, the ligaments loosen and the lens bulges outwards and becomes more
rounded that is curvature increases. This focuses light from objects that are close. On the other hand, when
the ciliary muscles relax, the ligaments tighten and the lens pulls inwards and flattens that is the curvature
decreases. This focuses light coming from distant object

Compare the change in the refractive power of the lens from rest to maximum accommodation
At rest, the ciliary muscles relax, the suspensory ligaments are taut and the lens is flattened. Vision would
be focused on far objects and the refractory power would be at minimum
At maximum accommodation, the ciliary muscles contract, the suspensory ligaments that hold the lens are
released and the lens become more rounded. This is fully accommodated and maximum refraction of light.
Near object would be in focus.
Eye
Shape of lens
Suspensory
Ciliary
ligaments
muscles
Focus
Focal
Refractive
length
power
At rest
Flattened
Taut
Relaxed
Far objects
Long
Low
Full
Bulging and
Relaxed
Contracted
Near
Short
High
accommodation
rounded
objects
Refer to accommodation drawings

Distinguish between myopia and hyperopia and outline how technologies can be used to correct
these conditions
Sight defects are very common and can be caused by many situations. In normal vision the image is
focused when it lands on the retina. If the light rays coming into the eye are not focused onto the retina then
the image will be blurred.
5
Two common refractive problems with eyes are conditions:

Myopia (Short-sightedness) - can see close objects clearly but distant objects are out of focus image is focused in front of the retina

Hyperopia (Long-sightedness) - can see objects in the distance but close objects are out of focus -
image is focused behind the retina
Several technologies used to correct these conditions include:

Glasses and contact lenses
There are two types of lenses:
o concave lens - light passing through diverges (spreads out) - correct myopia
o

convex lens - light passing through converges to a focal point - correct hyperopia
Explain how the production of two different images of a view can result in depth perception
Depth perception is the ability to judge the distance between objects. Depth perception required the ability
to see depth in our three dimensional world usually called binocular vision or sometimes even referred to as
stereoscopic vision. Depth perception results from having forward facing eyes. This produces an overlap
between the view from left and the view from the right eye. The images formed by both eyes are sorted in
the brain that a three dimensional picture is formed.

Plan, choose equipment or resources and perform a first-hand investigation to model the process of
accommodation by passing rays of light through convex lenses of different focal lengths
Refer to macquarie study guides page 106

Analyse information from secondary sources to describe changes in the shape of eye’s lens when
focusing on near and far objects

Process and analyse information from secondary sources to describe cataracts and discuss the
implications of this technology
Cataracts
The word cataract comes from the Latin word ‘cataracta’ that means waterfall. Cataract is the term given for
the gradual clouding of the lens in the eye that would normally be clear or transparent. In a normal eye, light
passes through the transparent lens to the retina where nerve signals are sent to the brain. In order to
receive sharp images, the lens must be clear. However in an eye that is developing cataract light does not
pass through the lens as well due to the cloudiness and vision is affected. The images seen would be
blurred. Cataracts if left untreated may eventually lead to blindness.
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Causes and risk factors
The most common cause of cataracts is the ageing process although they can develop any age even
infancy. As we age, the lenses in our eyes become less flexible, less transparent and thicker. The lens is
made mostly of water and eye proteins. As the eyes get older, certain eye proteins such as alpha-crystalline
fail to function properly. Alpha-crystalline is important in protecting other lens proteins. If they fail to work,
normal clear lens proteins would clump together and lose their transparency clouding some part of the lens
(cataract develops). Alpha-crystalline can also be damaged by highly charged, unstable molecules known
as free radicals that may have resulted from smoking and exposure to UV light.
Although ageing is the primary risk factor for developing cataracts, there are several other causes and risk
factors such as:

Fetal exposure to infection such as rubella, radiation, steroids, alcohol and other substances during
pregnancy can lead to cataracts developing on the fetus inside the mother’s womb. This type of
cataract is called congenital cataract.


Family history of cataracts
Medical disorders such as diabetes increases risk of developing cataracts at some stage in life. In
the case of diabetes high blood sugar levels react with eye proteins forming a by products that
accumulate in the lens.

Eye Injuries - Any accidents or play injuries results in trauma to the eyes. This can lead to cataracts
developing years later.

Eye diseases - Certain eye diseases such as glaucoma, eye inflammation are associated with

cataracts.
Steroid use - Long term use of high dose of steroids (taken by mouth, inhalation, eye drops etc)

also increases the risk of cataracts
Smoking - It is linked to the formation of cataracts. The eye can be damage by certain chemicals

from cigarette. Also it is a source of free radicals that destroy eye protein called alpha-crystalline.
Exposure to sunlight and high levels of radiation - exposure to UV radiation (UVA and UVB) can
lead to cataracts. The longer the exposure, the greater the risk. UV exposure is also a source of
free radicals.
On the whole cataracts are probably cause by a combination of the ageing process and the environment.
Symptoms of the presence of cataracts
Cataract is usually painless and develops slowly. It starts out only affecting small area of the lens. At this
point, the person is unaware of cataract development. Gradually, the cloudiness of the lens grew larger and
visions are greatly affected
Symptoms of cataract include:
 Cloudy or blurry vision - lead to an overripe cataract where it becomes completely white


Colours seem faded - everything seen may have a yellowish or even reddish tinge
Glare. Headlights, lamps, or sunlight may appear too bright.

A halo may appear around lights


Poor night vision
Double vision or multiple images in one eye

Frequent prescription changes in your spectacles or contact lenses -index myopia
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Comparison of 3 different surgical procedures to treat cataracts
When cataract reaches the stage where it is interfering with our vision and our everyday activities such as
driving, working or reading, it is best to consider surgery for removal. Cataract surgery nowadays is
believed to be one of the safest surgeries and most commonly performed around the world including
Australia.
There are three basic types of surgical procedure for cataracts removal:

Intracapsular cataract extraction
With this type of surgical procedure, the entire cataract and its surrounding capsule are removed.
An incision is made in the upper part of the eye and the cornea is gently folded back. A freezing
probe is used to freeze the lens and capsule to make extraction easier and minimize bleeding
during the surgery. Fine stitches were done to close the incision. Main advantage of this method
would be that every bit of lens tissue and capsule tissue have been removed so that no future
cataract can develop. However, the disadvantage of this method would be that the lens capsule
was taken out leaving space for the vitreous humor to move forward where it does not belong and

this could result in some problem. This procedure is very rare today.
Extracapsular cataract extraction.
This surgical procedure is similar to intracapsular method of cataract extraction. Except that in
extracapsular method, the lens capsule is left in place. An incision was made about three eights
(3/8) of an inch in the upper lid just as it would in intracapsular method. The surgeon opens the lens
capsule and the harder central part of the lens was removed by gently squeezing it. The softer part
is left for vacuum with a suction instrument. An advantage of this method of cataract extraction is
that the lens capsule is left intact providing support for the lens implant, an intraocular lens (IOL)
that is made of plastic, acrylic or silicone. However the disadvantage of leaving the capsule would
be that months after surgery it could cloud up once again reducing vision. If this occurs, the capsule
can be opened with a laser beam, neodymium YAG laser.

Phacoemulsification
Phacoemulsification is the newest type pf extracapsular technique developed in 1970s. An incision
was made on the side of the cornea. In this procedures the incision is smaller, about one eight (1/8)
of an inch. A special probe, a phacoemulsifier was used to break up the cataract (make into an
emulsion) using ultrasonic energy so that it can be suctioned out. Due to smaller incision, healing
process becomes very fast. Like general extracapsular surgery, the clouded lens will be replaced
by an artificial intraocular lens. Today, phacoemulsification is the most common way cataracts are
removed today.
Possible side effects and complications of cataract surgery today, compared with that in the past
Cataract surgeries are generally safe to perform and are usually a highly successful procedure. However,
no surgical procedures come with 100% guarantee. In fact nearly with all surgeries/operations, possible
complications and side effects are possible. The risk of infection is very low but unpredictable complications
can and do occur although rarely.
Possible side effects - the unwanted temporary effects of treatment:
 Nausea
8

A significant increase in eye redness

Blurry vision for a few days
Aching of the eye


Bruising behind the eye
These side effects should stop after approximately 10-14 days.
On rare occasions some experience further mild complications of cataract surgery, which can be treated.
They include:





Persistent internal eye inflammation called iritis
Infection - rare possibility
Bleeding - can occur every time an incision is made
Problems with the retina such as retinal detachment, rare but potential blinding complication

Macular edema caused by microscopic amounts of fluid pooling in the center of the retina
Corneal clouding caused by the depletion of cells, which keep the cornea clear

Glaucoma

Second cataract - can be treated with laser treatment
For vast majority of patients, serious complications are rare and the benefits of clear sight outweigh the
risks of surgery.
Due to advanced technology, side effect and complications such as painful stitches can be avoided due to
the small incision made and fast healing process. Today’s side effects and complications are mostly
treatable unlike in the past, untreatable.
Discuss the implications of cataract surgery for society
Cataract surgery with an artificial lens implant has become one of the greatest successes in all medicine
and surgery. Benefits obtained from cataract surgery include the improvement of eyesight, improved color
vision and night vision, improved functional abilities for reading, driving and occupational task, less frequent
need to change eyeglasses’ prescription in the future and a permanent end to worsening vision caused by
cataracts.
In past years, removal of cataract was a big ordeal to a lot of people. This is because they would have to
stay in hospital for several days; painful stitches in the eye and a recovery spent lying on hospitals bed.
However things have changed dramatically due to the advancement of technology in cataract surgery.
Advanced cataract surgical techniques have eliminated sutures, anesthetic, injections and eye handbags.
Process of surgery and also recovery has become much faster, safer and easier today.
Doctors used to prescribed strong, thick and positive glasses for cataract treatment for their patient. This is
not a very convenient method. The development of the intraocular lens implant in 1970s replaces early
cataract treatment techniques. Today through surgery cataract lens can be replaced with an artificial, clear,
plastic intraocular lens.
Visions are greatly improved through cataract surgery. This surgery has been very successful in restoring
vision. More than 90% of people who have a cataract-removed end up with better vision. It has been
reported that not only better vision was obtained but also a reduction in the power of their eyeglasses’
prescription and thus improved their functional abilities; reading and driving.
9
In conclusion there are many benefits that society obtained from cataract surgery. This outweighs some of
the risks that people considered when having the surgery.
4. The light signal reaching the retina is transformed into an electrical impulse

Identify photoreceptor cells as those containing light sensitive pigments and explain that these
cells convert light images into electrochemical signals that the brain can interpret
The retina is a thin sheet of cells that contains photoreceptor cells. Photoreceptor cells are those containing
light-sensitive pigments. They convert light images into electrochemical signals that the brain can interpret.
The photoreceptors contain photopigments, which are coloured proteins that absorb light and undergo
structural changes that lead to the production of action potentials and the start of a nerve impulse.
There are two types of photoreceptors in the retina:


Rods - most numerous at the periphery of the retina and detect shape, movement and light and
dark changes.

Cones - sensitive to three different colours - green, red and blue
Describe the differences in distribution, structure and function of the photoreceptor cells in the
human eye
Description
Rods
Cones
Shape
Usually narrower, longer and
straighter than cones
Conical
Number of discs containing
pigment
More than cones
Shape of disc region
Rod like
Arrow like
Type of pigment
Rhodopsin or visual purple
Photopsin - green, red and
blue
Location in retina
Spread across the retina,
Spread across, but usually in
more dense on the edges
groups at center - fovea
Number in human eye
125 million rods
6 or 7 million cones
Type of vision
Night vision
Day vision
Dim light
Detects movement
Fine focusing - visual acuity
Colour vision
Good for peripheral vision
Illustration, labelled
10

Outline the role of rhodopsin in rods
Rhodopsin is a photosensitive pigment. It consists of two molecules joined together; they are retinal (a
derivative of vitamin A) and opsin. When light falls on rhodopsin a series of chemical reactions break the
molecule rhodopsin into retinal and opsin. This generates electrical impulse that is transmitted to the bipolar
cells, the ganglion cells and then through the optic nerve where the signal is interpreted by the brain. The
molecules then reform as rhodopsin again and the process is repeated.

Identify that there are three types of cones, each containing a separate pigment sensitive to either
blue, red or green light
Humans have three types of cone cells which mean they can detect the full visible spectrum. These are:


Red cones (contain erythrolabe) type L - these respond to long wavelengths of light (red at 564 nm)

Green cones (contain chlorolabe) Type M - these respond to the middle wavelengths of light (green
at 533nm)

Blue cones (contain cyanolabe) Type S - these respond to short wavelengths of light (blue and
violet at about 435 nm)
Explain that colour blindness in humans results from the lack of one or more of the colour-sensitive
pigments in the cones
Colour blindness or more correctly, colour vision deficiency, describes a number of problems in identifying
various colours and shades, which can range from only a slight difficulty distinguishing among different
shades of the same colour to the rare inability to distinguish any colours at all.
Colour blindness can result from the absence or impairment of one or more of the types of cones.

Process and analyse information from secondary sources to compare and describe the nature and
functioning of photoreceptor cells in mammals, insects and in one other animal

Simple eyes (called ocelli) are found in worms, mollusks and crustaceans. Eyes that are located in
a hollow are called a cup eye. These eyes do not detect colour and only give information on the
direction of light source

Compound eyes made up of a large number of separate light receptors called ommatidia. Insects
have compound eyes and they have three colour vision including the ultraviolet range spectrum.
Each ommatidium has its own cornea and a lens made up of a crystalline cone. Compound eyes
can have high flicker speeds for detecting movement, can detect ultraviolet light and the
polarization of light

Single lens eye is a more complex camera type of eye found in mammals, all vertebrates and
cephalopods. These eyes can focus and form an image. There are three different types of
receptors found in the eye: colour vision, visual acuity and night vision. Having two eyes depth
perception can be achieved
11
Group
Examples
Visual system
Nature of
Vision
photoreceptor /
photopigment
Flatworm
Planaria
Cup eye with no lens
Rhodopsin located
No image formed - only detects
presence and direction of light
in simple cup eye
Direction of light
Photocells are called ocelli, which
produce an impulse when light
falls on them
Insect
Bee
Compound eye consisting of
many ommatidia made up of a
Rhodopsin located
in compound eyes
Colour vision, depth
perception, detection of
cornea and a lens made of
crystalline cone
that consist of
individual
movement
Receptor cells produce an
ommatidia
electrical impulse when light falls
on them
Mammal
Human
Single-lens eye forming an image
Rhodopsion, rod
and cone cells
Depth perception,
colour vision, detection
of movement, night
vision

Process and analyse information from secondary sources to describe and analyse the use of colour
for communication in animals and relate this to the occurrence of colour vision in animals
Animals that use colours to communicate include fish, amphibians, reptiles and birds.
Animals use colour communication for a variety of reasons including:

To signal their availability to mate and other kinds of reproductive behaviour like coutship

To warn off predators

Protective coloration and camouflage
Examples of colour communication:

Camouflage - hiding by blending into the environment. Some animals can change the colour of their
skins to match wherever they are - e.g. chameleons and the octopus

Mimicricy - many animals that are poisonous advertise this by having striking colouration. Others
who are not poisonous evolved the same colouration to fool predators into not attacking them - e.g.
Monarch butterfly and Viceroy butterfly, same appearance although only monarch has a bad taste

Sexual dimorphism - different appearance between the sexes. Males and females can be
distinguished by their colours or sizes - e.g only male lion develops the mane, in birds often male is
brightly coloured while female is plain

Warning colours - some animals change colours to give warning that they are about to attack - e.g.
blue ringed octopus when threatened blue rings appear all over the surface of the skin

Breeding colours - many birds take o different colours during breeding season - e.g. male puffin
during breeding season the bands on the beak are bright while outside season the bands fade.
12
5. Sound is also a very important communication medium for humans and other animals

Explain why sound is a useful and versatile form of communication
Sound is a form of energy that travels in waves. Sound waves can be compared by determining their
frequency. Sound requires a medium such as solid, liquid or gas through which to travel. It cannot travel
through a vacuum.
Sound is a useful for communication to many because of the enormous variety of sounds that can be
produced. Sound is useful both day and night. It travels over long distances and can go around corners.
Sound is also versatile because variation can occur in the actual sound or the loudness of the sound, and
the pitch and duration of a message can be readily changed
Advantages of sound communication:


A variety of sounds can be made by an individual

Sound travels well in both air and water

The sender does not have to be visible to the receiver

It is useful at night and in dark environments

Sound can go around objects

It provides directional information

It works over long distances
Explain that sound is produced by vibrating objects and that the frequency of the sound is the same
as the frequency of the vibration of the source of the sound
Sound is a form of energy that requires a medium. It cannot travels in a vacuum. It is a longitudinal wave
where the particles move backwards and forwards in the direction of the wave. Sound is a form of energy
produced by an object that vibrates. The vibrating object causes nearby air molecules to vibrate back and
forth, and these molecules causes other to vibrate at the same frequency. This results in a compression
wave, which travels through a medium. The frequency of the vibration of air molecules is the same as the
frequency of the vibrating object.

Outline the structure of the human larynx and the associated structures that assist the production
of sound
The larynx or voice box lies directly below the tongue and
soft palate. Inside the larynx are the vocal cords, which
consist of muscles, which can adjust pitch by altering their
position and tension. Together, the larynx, tongue and hard
and soft palate make speech possible. When air passes over
the vocal cords in the larynx, they produce sounds that can
be altered by the tongue, together with the hard and soft
palate, the teeth and the lips
Refer to cream sheet
13

Plan and perform a first-hand investigation to gather data to identify the relationship between
wavelength, frequency and pitch of a sound
Sound waves can be investigated by using a cathode ray oscilloscope (CRO), which displays sound waves
on a screen.
Pitch and frequency are closely related. Pitch depends on the frequency that is the number of vibrations per
second measured in Hertz. As the frequency of waves increases the pitch increases. This means that high
frequency is the same as high pitch and low frequency is the same as low pitch.
N.B. High frequency sounds (high pitch) have a short wavelength; low frequency sounds (low pitch) have a
long wavelength. The number of vibrations per second is measured in Hertz. The amplitude or height of a
wave determines the loudness of a sound.

Gather and process information from secondary sources to outline and compare some of the
structures used by animals other than humans to produce sound
Animals use a range of structures to produce sounds. They use sounds for a variety of purposes. These
include attack, escape, identification, warn off predators, mark territory, attract mated and for locating each
other.
Animal
Description of structure used to produce sound
Bats
Ultrasonic signals form the bat’s larynx
Grasshoppers
Friction of the back legs or rubs the veins on the wings
together (stridulating)
Frogs
Male frogs vocalize by squeezing their lungs while shutting
their nostrils and mouth, air flows over their vocal cords and
into their vocal sacs
Fish
Some fish vibrate their swim bladders to create sound
6. Animals that produce vibrations also have organs to detect vibrations

Outline and compare the detection of vibrations by insects, fish and mammals
Insects, fish and mammals detect vibrations using different organs.

Insect
Insects have hearing organs in many different parts of their bodies. Three main types of sound
detection organs in insects are:
o
Tympanic organs - consists of a membrane stretched across an air sac. In grasshoppers,
tympanic organs are located on the legs. When sound waves reach the tympanic organ the
membrane vibrates and this stimulates the hair cells and a message is sent via nerve to the
brain.
o
Auditory hairs - Many insects are covered with auditory hairs that are sensitive to sound
waves. These hairs have different lengths and stiffness and respond to vibrations at
different frequencies. The hairs are particularly abundant on the antennae and legs.
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o
Vibration receptors - Insects that fly at night have adaptations that can detect ultrasonic
sound produced by bats. Hawk moths can hear ultrasonic sound through two sets of
modified mouthparts.

Fish
Fish have several organs to detect sound waves. These include:
o
Internal ears - Fish have an ear but unlike mammals, there is no external opening or an
eardrum. Otoliths and the labyrinth make up the inner ear of fish. The movement of otolith
across sensory hair cells is interpreted as sound by fish.
o
o
Lateral line organ - visible line along the body of fish. It consists of fluid-filled canals that are
collections of sensory hairs called neuromasts. These respond to low frequency sound. The
neuromast consists of hair cells that detect vibration in the surrounding water
Swim bladder - primarily responsible for equalizing pressure between the surrounding
water and the fish. It acts as an amplifier to any sound, passing the vibrations directly onto
the inner ear.

Mammals
Mammals have ears to detect sound. Sound enters the ear, and travels along the auditory canal. It
then causes the tympanic membrane to vibrate at the same frequency as the sound waves. In the
middle ear the ossicles transfer and amplify the sound vibrations to the oval window. It then
transfers the sound vibrations to the fluid-filled cochlea. Inside the cochlea is the organ of Corti,
which has rows of hair cells that respond to different frequencies, convert vibrations into an
electrochemical impulse and transfer the message to brain via the auditory nerve.
Structures used
to detect
Insects
Fish
Mammals
Tympanic membrane
Sensory hairs
Internal ear
Lateral line system
Cochlea
vibrations
Receptor cells
Swim bladder
Mechanoreceptor
cells
Hair cells in the inner
ear
Hair cells in the organ
of Corti
Neuromasts in the
lateral line

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
15
The anatomy of the ear can be divided into three sections:

Outer ear - pinna and ear canal ending at the tympanic membrane (eardrum)

Middle ear - air-filled chamber with ear ossicles (3 small bones - hammer, anvil and stirrup) and
ending at the oval and round window

Inner ear - cochlea and three semicircular canals
Structure
Anatomy
Function
Pinna
Freshly external organ
consisting of a flop of cartilage
Collects sound and directs into
the ear canal
and skin
Tympanic membrane
(eardrum)
Ear ossicles
Oval window
Round window
Thin membrane between the
external ear and the middle
Vibrates when sound waves
reach it; transfers the vibration
ear
to the hammer
Three tiny bones located in the
middle ear; hammer, anvil and
Magnify and transfer vibrations
from the tympanic membrane
stirrup
to the oval window on the
cochlea
Flexible membrane between
Transfers vibrations from the
the middle and inner ear
stirrup to the fluid in the
cochlea
Flexible membrane between
the middle and inner ear
Bulges outwards (into the
middle ear) to allow
displacement of fluid when
vibrations are transferred to
the cochlea
Cochlea
Fluid-filled spiral tube that
contains the organ of Corti
Detects different frequencies
of sound -high pitch sounds
are detected at the start of the
cochlea and low pitch sounds
at the end of the spiral
Organ of Corti
Auditory nerve

Consists of hair cells on the
Hair cells translate vibrations
basilar membrane
into electrochemical signals
Consists of the axons of the
Transfers the impulse from
hair cells and lead from the
cochlea to the brain
hair cells to the brain
Outline the role of the Eustachian tube
The Eustachian tube connects the middle ear with the back of the throat. It is filled with air and responds to
changes in pressure. The role of the Eustachian tubes is to keep the pressure in the middle ear and the
throat and therefore the outside atmosphere equal and to drain the middle ear. It also replaces the air in the
middle ear after it has been absorbed.
16

Outline the path of sound wave through the external, middle and inner ear and identify the energy
transformations that occur
When sound waves enter the pinna they travel along the auditory canal and cause the tympanic membrane
(eardrum) to vibrate. These vibrations are carried and amplified by the ossicles in the middle ear. The
ossicles are three tiny bones also known as the malleus (hammer), the incus (the anvil) and the stapes (the
stirrup). The ossicles join the inner ear at the oval window. The cochlea is a snail-shaped, fluid-filled
structure in the inner ear. Inside the cochlea is another structure called the organ of Corti. Inside the organ
of Corti there are hair cells located on the basilar membrane. These are in contact with the tectorial
membrane. When vibrations reach the hair cell the message is converted into an electrochemical response,
which travels via the auditory nerve to the brain.

Describe the relationship between the distribution of hair cells in the organ of Corti and the
detection of sounds of different frequencies

Frequencies of sounds are detected in the organ of Corti. This has three main components: the
basilar membrane, hair cells and the tectorial membrane.

The basilar membrane is composed of transverse fibres of varying lengths. Vibrations received at
the oval window are transmitted through the fluids of the cochlea causing the transverse fibres of
the membrane to vibrate at certain places according to the frequency.

High frequency sounds cause the short fibres of the front part of the membrane to vibrate and low
frequency sounds stimulate the longer fibres towards the far end.
17

As the basilar membrane vibrates, the hairs of the hair cells are pushed against the tectorial
membrane. This causes the hair cells to send an electrochemical impulse along the auditory nerve
to the brain

Outline the role of the sound shadow cast by the head in the location of sound
Humans and other animals use two methods to locate the source of sound: the difference in time between
the sound arriving at each ear, and the difference in the intensity of the sound arriving at each ear. These
differences occur because the head casts a sound shadow that causes one ear to receive less intense
sound than the other. Humans usually trace the location of a sound by turning their heads until the intensity
of the sound is equal in both ears; at this point people should be looking in the direction of the source of the
sound. Other animals have more mobile ears, rather than their heads, to pick up a sound

Gather, process and analyze information from secondary sources on the structure of mammalian
ear to relate structures to functions
Refer to the table above

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
Humans can hear in the range 20 to 20000 Hz. Younger children can hear frequencies up to 25000 Hz but
this ability decreases with age. Human hear best from about 2000-4000 HZ because this is the range in
which human speech falls.
Bats produce sound in 2000 to 110000Hz range through their mouths or through elaborate nose organs.
The insect-catching bats use echolocation to locate their prey in mid air. To do this they send out high
frequency sound (ultrasonic) and then interpret the echo that bounces back. This gives them information on
the distance and the direction of movement.
Dolphins belong to the toothed whales group, which have a very high frequency hearing range between 75
to 150000 Hz. They have specialized inner ears. They have more nerve endings than terrestrial animals.
Dolphins have adaptations for very high frequency sound detection such as a thick basilar membrane and
bony supports for the cochlea.
Sound becomes important in environments where visual information is limited. It plays an important role in
finding mates, prey and avoiding predators. Bats use sound to navigate in dark environments to avoid
objects and to locate prey. They use high frequency sound, which is only useful over short distances.
Dolphins have high frequency hearing. High frequency sound is used over short distances to locate prey.

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
18
Hearing aid is an electronic battery-operated device that amplifies and changes sound to allow for improved
communication
A cochlear implant is a small, complex electronic device that can help to provide a sense of sound to a
person who is profoundly deaf or severely hard of hearing.
Position
Hearing Aid
Cochlear Implants
“In the ear” types are made of
Consists of internal and
moulded plastic and fit in to
the outer ear (used for mild to
external parts. The internal
parts are placed surgically in
severe hearing loss).
the bone behind the ear and
the inner eat. The external
parts can be detached at any
time.
Type of Energy Trnasfer
Hearing aids receive sound
Sound is detected by a
through a microphone, which
microphone. Transmits sound
then converts the sound
waves to electrical signals.
to speech processor which
codes the sounds
The amplifier increases the
loudness of the signals and
electronically and transmits
them via a wire to the
then sends the sound to the
ear through a speaker.
transmitting coil which sends
the messages through the skin
via radio waves to the
receiver/simulator which sends
the sound as electrical signals
which stimulate particular
nerves to send the messages
to the brain.
Conditions under which they
help
Patients that have residual
hearing loss. Hearing aids are
Patients who are profoundly
deaf but still have enough
particularly useful for those
patients that have
surviving auditory nerve fibres.
Mostly used in young children
sensorineural hearing loss
(caused by aging, noise,
(aged 2 and up) who will gain
no advantage from the use of
illness etc). They aid in
hearing aids
improving speech
comprehension and general
hearing
Limitations
“In the Ear” types can’t be
The Cochlear implant does not
used for children because they
fully reproduce the sounds
have to be remodeled to fit
inside the ear as the child
hear by someone with normal
hearing. It enables patients to
grows so it isn’t practical. They
can also be damaged by
have about 80% speech
recognition.
earwax and ear drainage.
Hearing aids will not restore
normal hearing or eliminate
background noise. They can
also be difficult to adjust to suit
19
varying noise conditions. They
are also battery operated, so if
the battery runs put they won’t
work.
7. Signals from the eye and ear are transmitted as electrochemical changes in the membranes of the optic
auditory nerves

Identify that a nerve is a bundle of neuronal fibres
A nerve is a bundle of axons or neuronal fibres bound together like wires in a cable.
Neurons or nerve cells are the functional units of the nervous system. They are specialized cells that
transmit signals from one location in the body to another location by electrochemical changes in their
membranes.
Neurone consists of three main parts:

Cell body - contains the nucleus and other cell organelles. High level of cellular activity - means
there is a large amount of endoplasmic reticulum - secretes protein visible in cytoplasm

Dendrites - pick up messages using their extensive branches to increase the surface area of the
‘receiving end’ of the nerve cell

Axon - conducts messages away from the cell body. The axon has many vertebrates surrounded by
schwann cells (supporting cell that forms insulating layer of myelin sheath)

Identify neurons as nerve cells that are transmitters of signals by electrochemical changes in their
membranes
A neurone is a nerve cell that transmits a signal or impulse from one part of the body to another by
electrochemical changes in the membrane.
A nerve impulse can be detected as a change in voltage. The impulse is transmitted as a wave of electrical
changes that travel along the cell membrane of the neurone.
The electrical changes are caused as sodium ions move into the neurone. Thus the signal is described as
an electrochemical impulse
After the signal has been transmitted, potassium ions move to the outside of the cell to restore the original
charge of the neurone.

Define the term ‘treshold’ and explain why not all stimuli generate an action potential
Treshold is the minimum stimulation required to create an action potential in a nerve cell. The minimum
amount is usually a change in membrane potential difference of at least 12 mV. Not every stimulus
generates an action potential because insufficient change in membrane potential difference occurs.
20
Need to refer to action potential in depth, if possible put a diagram.
Need more info

Identify those areas of the cerebrum involved in the perception and interpretation of light and sound
Refer to the diagram of the cerebrum


Parietal lobe - at the top of the head towards the back - this area is important for interpreting
sensory signals including sight and sound

Occipital lobe - located at the back of the head - concerned with vision as well as perception such
as touch, pressure temperature and pain - site of visual cortex

Temporal lobe - located at the side of the head above the ears - interprets the impulses from the
ears and give meaning to information - important region for the sense of hearing.
Explain, using specific examples, the importance of correct interpretation of sensory signals by the
brain for the coordination of animal behaviour

The environment in which an organism lives is constantly changing. Sense organs such as the ear
and the eye detect these changes and send information to the brain. The brain then interprets the
information and sends an impulse to an effector organ such as a muscle. It is essential that the
brain interpret signals from the sense organs correctly.

The cerebral cortex is the most important association centre of the brain. Information comes to this
area from our senses and the brain sorts it out in the light of past experiences. As a result, motor
impulses are sent along the nerves to cause an appropriate action to take place.

For example, the eyes and ears, receptors in muscles and tendons, pressure sensors on the feet all
provide signals about the position of the body in space. The cerebrum of the brain interprets all of
these signals and sends messages to various effectors to balance the body in space.

Walking involves several receptors, including the eyes, gravity receptors in the ears, pressure
sensors in the feet and position receptors in the joints. These receptors are connected to the brain
by neurones and the brain interprets the signals it receives. The brain sends messages to the
muscles and other effectors to coordinate the process of walking.
21

The importance of the brain in the coordination of animal behaviour is highlighted when parts of it
are damaged. The paralysis that follows a stroke, or the shaking movements of people with
Parkinson’s disease, are signs of damage to the brain. In people with these conditions, muscular
contractions are no longer coordinated by the brain

Perform a first-hand investigation using stained prepared slides and/ or electron micrographs to
gather information about the structure of neurons and nerves
Refer to page 124 of Macquarie Biology study guides

Perform a first-hand investigation to examine an appropriate mammalian brain or model of a human
brain to gather information to distinguish the cerebrum, cerebellum and medulla oblongata and
locate the regions involved in speech, sight and sound perception


This activity requires the examination of the brain of a mammal, which can be obtained from a local
butcher. Alternatively, you can examine a model of a human brain.

Perform a first-hand investigation by examining the brain so that hazards are minimized. Identify
and use safe work practices during this investigation.

Draw a diagram to show the various structures you observe.

Use the diagram below to identify the cerebrum, cerebellum and medulla oblongata.

Prepare notes to explain how you minimised hazards, disposed safely of any waste materials.

Note that the cerebrum or cerebral cortex is involved in thinking and reasoning, as well as the
perception of the senses, including speech, sight and sound perception.
Present information from secondary sources to graphically represents a typical potential action

The action potential of a neurone can be
graphically represented by the graph below.
22