1. Humans, and other animals, are able to detect a range of stimuli from the external environment, some of which are useful for communication

DP1 “identify the role of receptors in detecting stimuli” A stimulus is a change in the environment. Examples of stimuli include light,

sound, temperature, pressure, pain and certain chemicals. A receptor is a specialised cell that detects a stimulus. As a result a nerve

impulse may be generated or a hormone produced. There is a range of receptor cells adapted to detecting specific stimuli, e.g. rods and cones in the eye. Sometimes receptors are distributed all over the body, such as touch receptors in the skin. In other cases, particular receptors are concentrated in an organ, such as the eye, or an endocrine gland such as the adrenal gland.

DP2 “explain that the response to a stimulus involves:” stimulus receptor messenger response

SC DP1 “identify data sources, gather and process information from secondary sources to identify the range of senses involved in communication”

2. Visual communication involves the eye registering changes in the immediate environment

DP1 “describe the anatomy and function of the human eye, including the:” conjunctiva cornea sclera choroid retina iris lens aqueous and vitreous humor ciliary body optic nerve

DP2 “identify the limited range of wavelengths of the electromagnetic spectrum detected by humans and compare this range with those of other vertebrates and invertebrates”

Limit of human wavelength is 380nm to 780nm Invertebrates:

Bees can see in UV but humans cannot. Vertebrates:

Birds can see in UV but humans cannot. UV light

- Vertebrates- Goldfish, salmon- Zebra, finches (Birds)

Infra-red:- Vertebrate- Australian Pythons

SC DP1 “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”

SC DP2 “use available evidence to suggest reasons for the differences in range of electromagnetic radiation detected by humans and other animals”

3. The clarity of the signal transferred can affect interpretation of the intended visual communication

DP1 “identify the conditions under which refraction of light occurs” Light rays travel in straight lines. However, if a light ray passes from one

medium to another at an angle other than 90 º, the ray is bent. This bending, as light passes from one medium to another, is called refraction.

Refraction of light occurs when light passes from one substance to another.

DP2 “identify the:”Cornea, aqueous humor, lens and vitreous humor as refractive media.

DP3 “identify accommodation as the focusing on objects at different distances, describe its achievement through the change in strength of the lens and explain its importance”Accommodation is the focusing of the eye on objects at different distances. Accommodation is achieved through the change in curvature of the lens, to either elongated (taut, ligaments rested) or highly convex (slackened, ligaments contracted). Accommodation is important because it allows the eye to focus on distant objects then the ability to change focus to a close object very quickly without straining the eye.

DP4 “compare the change in the refractive power of the lens from rest to maximum accommodation”When the lens is rested it has minimum accommodation because it is ready to look at an object in the distance not needing to bend the light rays. But, when it needs maximum accommodation it has to look at a near by-object which means it needs to refract the light rays the most because they are entering at acute angles.

DP5 “distinguish between myopia and hyperopia and outline how technologies can be used to correct these conditions”Feature Myopia HyperopiaCause of condition The ciliary muscles do

not relax enough causing the lens to be not fully elongated causing too much refraction

The ciliary muscles does not contract enough, leaving the lens still elongated, causing not enough refraction.

Where image focuses Too short of the retina Past the RetinaWhich objects focus correctly

Close Objects Distant Objects

Diagram of lens used for correction

Concave Lens Convex Lens

DP6 “explain how the production of two different images of a view can result in depth perception”Some animals have forward facing eyes. This means that there is considerable overlap between the views on the left and the right. Because the two eyes are a few centimetres apart, each eye sees a slightly different view of an object. The images formed by each eye are superimposed by the brain, and because each view is slightly different, objects appear to have depth as well as height and breadth, that is we see in three dimensions. This is known as stereoscopic or binocular vision. This type of vision also makes it possible to judge distances of near objects. Climbing animals such as monkeys and predators such as cats have forward facing eyes, but grazing animals such as horses have eyes on the side of the head so they have a wider field of view.

SC DP1 “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”A biconvex lens is shaped as shown in the diagram below. Convex lenses magnify images by causing rays of light to converge.The lens in the human eye is a convex lens. When parallel rays of light are passed through a convex lens, they will converge at a point, known as the focal point.The focal length of a lens is the distance of the focal point from the centre of the lens.

Convex Lens

SC DP2 “analyse information from secondary sources to describe changes in the shape of the eye’s lens when focusing on near and far objects”

SC DP3 “process and analyse information from secondary sources to describe cataracts and the technology that can be used to prevent blindness from cataracts to discuss the implications of this technology for society”A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light. Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated. The condition usually affects both the eyes, but almost always one eye is affected earlier than the other.

Cataracts mostly affect the elderly as they are the majority getting cataract surgeries. There are no known causes of cataracts and research is still going on to find a cause, but for now they only have suggestions. Such as people who have:

A family history of the eye condition Diabetes An injury to the eye Exposed their eyes to sunlight without protection over a long term Smoked for a period of time

There are some technologies that can be used to fix this problem. Initially glasses, strong bifocals, magnification, appropriate lighting or other visual aids may be able to improve your vision. But, eventually surgery will be the only option because the cataracts will spread and blindness will eventually occur.

Surgery is only recommended when your cataracts have progressed enough to seriously impair your vision and affect your daily life. Many people consider poor vision an inevitable fact of aging, but cataract surgery is a simple, relatively painless procedure to regain vision.

The most common surgery, is where the surgeon will remove your clouded lens and in most cases replace it with a clear, plastic intraocular lens (IOL). New IOLs are being developed all the time to make the surgery less complicated for surgeons and the lenses more helpful to patients. Presbyopia-correcting IOLs potentially help you see at all distances, not just one. Another new type of IOL blocks both ultraviolet and blue light rays, which research indicates may damage the retina.

Another least commonly used surgery is called Phacoemulsification, which is a modern cataract surgery in which the eye's internal lens is emulsified with an ultrasonic handpiece to break up the protein that causes the cataract.

The Fred Hollows Foundation was started by Fred Hollows (1929-1993). Fred was an eye doctor, a skilled surgeon of international renown, a champion of the right of all people to good health and a strong advocate for social justice.

The Fred Hollows Foundation was established in 1992 to continue the work of Professor Fred Hollows.

The Foundation works internationally on comprehensive quality eye care, with a focus on cataract. In Australia, The Foundation is committed to roles as both partner and advocate of effective health programs for Indigenous Australians.

4. The light signal reaching the retina is transformed into an electrical impulse

DP1 “identify photoreceptor cells as:”Cells containing light sensitive pigments and explain that these cells convert light images into electrochemical signals that the brain can interpret.

DP2 “describe the differences in distribution, structure and function of the photoreceptor cells in the human eye”Photo-receptor Cell

Distribution Structure (description and diagram)

Pigment Function Colour and wavelength of light to which cell is sensitive

Rods Evenly distributed across most of the retina, but are absent from the fovea.

The outer segment is long and narrow.

Rhodospin Responsible for most peripheral vision, including the detection of movement

Sensitive to low-light (night vision)

Cones Distributed in groups throughout the retina, but there are fewer around the periphery of the retina.

Have a shorter outer segment that is cone-shaped

Iodopsins Responsible for colour vision

Less sensitive to light, they require larger quantities of light to stimulate or bleach them

DP3 “outline the role of rhodopsins in rods” Rhodopsin is a 2 part molecule, containing a protein molecule called opsin

and a light absorbing molecule called retinal. The main function of the photochemical pigments rhodopsin is to absorb

light. The light activates the retinal which allows the retinal molecule to split

away from the opsin molecule. The activated pigment causes a change in electrical charges of the

membrane of the rod (changing the language of light energy into a type of language the brain can process which is electrical energy).

Electrical impulse cannot jump from axon branch to axon branch at the synapses (which is an insulator) so an chemical, which has to be created which is called a neurotransmitter chemical to allow the electrical impulse to keep continuing along the axon, there is a short delay when this happens (the less stops the quicker the impulse can travel to the brain).

DP4 “identify that there are three types of cones, each containing a separate pigment sensitive to either blue, red or green light”Rhodopsin and other opsinsBecause all rods have only one type of pigment, rhodopsin, they are not sensitive to different colours. Rhodopsin is a broad spectrum pigment. Its peak sensitivity is in the 500 nm wavelength region of the visible spectrum, but rods do not allow us to perceive any colour. Vision involving rhodopsin in rods allows us to see in shades of black, white and grey.Each cone contains one of three types of iodopsin pigments and is therefore most sensitive to light in one of three wavelengths. These pigments result in cone cells being sensitive to:

n the short wavelengths of blue light, peak sensitivity being at approximately 455 nm; orn the medium wavelengths of green light, peak sensitivity being at approximately 530 nm; orn the long wavelengths of red light, peak sensitivity being at approximately 625 nm.

However, the sensitivity of a particular cone cell allows it to detect light to some extent on either side of these peak sensitivities, giving an overlap in some of the colours detected. 'Red' cones are actually more sensitive to yellow light (560-565 nm) than to red light, but they respond to red light before any of the others do, therefore behaving as red receptors. Therefore light of a particular wavelength may stimulate more than one cone. By comparing the rate at which various receptors respond, as well as the overlap in colours detected, the brain is able to interpret these signals as intermediate colours. This allows us to 'see' a variety of colours.

DP5 “explain that colour blindness in humans results from the lack of one or more of the colour sensitive pigments in the cones”

Cones detect colour, any defect or damage to the cones will affect the ability of the eye to perceive colour.

Humans have three different forms of opsins present in cones, each coded for by one gene.

A mutation in a gene that codes for a cone pigment leads to the inability of this pigment to function correctly. As a result, the person is unable to perceive colour in the normal trichromatic matter and is said to be either colour deficient or colour blind, depending on how the mutation affects the pigment.

In humans red/green pigments are located on the X chromosome. Mutations in the gene for the blue cone pigment are extremely rare.

SC DP1 “process and analyse information from secondary sources to compare and describe the nature of photoreceptor cells in mammals, insects and in simple light receptors in one other animal”Animal No. of eyes Type of

Photoreceptor cell

Description of Photoreceptor cell

Pigment Colour Vision

Mammal – Human

2 Rods and Cones Rods for peripheral and nighttime vision. Cones for colour and clarity.

Rhodospin and Iodopsins

Yes

Insect – Fly

Each compound eye is made up of about 8000 units called ommatidia

Ommatidia Registers vision for a different part of the environment. The result is an image that is a pattern of dots.

Rhabdom Yes

SC DP2 “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”

Many animals use colour to communicate a variety of types of information. The effectiveness of this communication depends on the animals that they are sending this information to, having colour vision to detect it. Fish, amphibians, reptiles and birds have well-developed colour vision, but humans and other primates are among the minority of mammals that can see colour.

Animals may use colour to signal their availability to mate, to indicate their suitability as a potential parent, to hide from predators or to warn of their unpalatability as prey. Some species mimic other unpalatable or poisonous species by using colour.

Human have 10,000 cones per square millimetre compared to some birds that have up to 120,000 per square millimetre. Birds who feed in the daylight see colours very clearly, for example hummingbirds can spot red flowers from over a kilometre away.

5. Sound is also a very important communication medium for humans and other animals

DP1 “explain why sound is a useful and versatile form of communication” Sound is used for:

- Mating behaviour- Warning of predators- Feeding patterns- Social activities

Survival can depend on the ability to relate to each other, establish territory, defend territory, obtain food and reproduce.Sound not light dependentCan travel through solids, liquids and gases.Most animals can produce and detect sound.

DP2 “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 produced by an object that vibrates, moving backwards and forwards. The vibrating object causes nearby air molecules to vibrate back and forth, and these molecules cause others to vibrate.

This results in a compression wave travelling through the air. The frequency of the vibration of air molecules is the same as the

frequency of the vibrating object.

DP3 “outline the structure of the human larynx and the associated structures that assist the production of sound”The frequency of sound generated by the larynx is the same frequency that the medium vibrates and the same frequency that the ear detects.

The human larynx produces sound by using muscles to change the shape of the vocal cords or folds and pass air over them to make them vibrate.The vocal folds are located in the larynx, which is found at the top of the trachea. It is a tubular organ made of cartilage, held in place by ligaments and muscle.

When the vocal cords are pulled tight, they vibrate at a high frequency and when there is less tension they vibrate at a lower frequency. Speed of opening and closing also affects frequency. Vocal cords open and close more frequently for high pitched voices.

SC DP1 “plan and perform a first-hand investigation to gather data to identify the relationship between wave-length frequency and pitch of a sound”

Used the Cathode Ray Oscilloscope (CRO)

SC DP2 “gather and process information from secondary sources to outline and compare some of the structures used by animals to produce sound”

Adult female mosquitos beat their wings, emitting low-frequency sounds (200-400 Hz).

Male frogs croak, the sound is generated in their vocal sacs and mouth cavities.

A snake or a turtle will hiss, a gecko chirp and a crocodile produce a wide variety of sounds.

6. Animals that produce vibrations also have organs to detect vibrations

DP1 “outline and compare the detection of vibrations by insects, fish and mammals”

DP2 “describe the anatomy and function of the human ear, including:”

DP3 “outline the role of the Eustachian tube”The role of the Eustachin tube is to equalise the pressure between the outer ear and the inner ear. This is so the tympanic membrane remains intact. The tube is able to do this as it connects the inner ear with the outside air in the pharynx. Under normal circumstances, the canal of the tube is closed, but yawning, coughing and swallowing opens the canal briefly and equalises the pressure.

DP4 “outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur”

DP5 “describe the relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of different frequencies”The detection of sounds of different frequencies is made possible by two features. The first is that vibrations of a certain frequency cause the next structure to vibrate at the same frequency. The second feature is that the similar membrane of the organ of corti is made up of fibres or hairs of varying lengths. Each of these lengths vibrates at a different frequency.The hair cells are arranged along the basilar membrane from those stimulated by low frequency at the apex, to those stimulated by high frequency at the base.

DP6 “outline the role of the sound shadow cast by the head in the location of sound”Sound waves reach both ears with equal intensity when the sound is directly in front or behind you. However, mostly sound reaches one ear with greater intensity then the other. The head casts a shadow which blocks some of the intensity in the ear furthest from the source, as the sound bends around the head. The difference in intensity is reflected in the signal that is sent to the brain via the auditory nerve. This is processed to provide the location of the sound.

SC DP1 “gather, process and analyse information from secondary sources on the structure of a mammalian ear to relate structures to functions”

SC DP2 “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”Mammal Lowest Frequency

Detected(Hz)Highest Frequency Detected(Hz)

Human 20 20000Dolphins 20000 80000Kangaroo Rat 30 50000SC DP3 “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

Hearing aids and cochlear implants are both devices designed to improve deafness. A hearing aid is an electronic, battery-operated device that amplifies and changes sound to allow for improved communication. Hearing aids receive sound through a microphone, which then converts the sound energy to electrical energy. The amplifier increases the loudness of the signals and then converts the electrical energy back to sound. This sound leaves the hearing aid through a speaker which directs the sound down the auditory canal. Most hearing aids are placed in or near the external auditory canal.

Hearing aids are particularly useful in improving the hearing and speech comprehension of people with sensorineural hearing loss. Sensorineural hearing loss develops when the auditory nerve or hair cells in the inner ear are damaged by aging, noise, illness, injury, infection, head trauma, toxic medications, or an inherited condition. Hearing aids will not restore normal hearing or eliminate background noise.

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. It bypasses damaged parts of the inner ear and electronically stimulates the auditory nerve. Part of the device is surgically implanted in the skull behind the ear and tiny electrode wires are inserted into the cochlea. The other part of the device is external and has a microphone, a speech processor (to convert sound into electrical impulses), and connecting cables. An implant does not restore or create normal hearing. Instead, it can give a deaf person a useful auditory understanding of the environment and help him or her to understand speech. Unlike a hearing aid which amplifies sound, cochlear implants compensate for damaged or non-working parts of the inner ear. It electronically finds useful sounds and then sends them to the brain.

A person with a cochlear implant must learn to interpret the sounds created by an implant. This process takes time and practice. The person may also have to use the implant in conjunction with lip reading. It has been shown that individuals who receive the implant after they have learnt to speak perform better than those who have never spoken. The implant is also very expensive.

7. Signals from the eye and ear are transmitted as electro-chemical changes in the membranes of the optic and auditory nerves

DP1 “identify that a nerve is a bundle of neuronal fibres”

DP2 “identify neurones as nerve cells that are the transmitters of signals by electro-chemical changes in their membranes”

DP3 “define the term threshold and explain why not all stimuli generate an action potential”Resting Potential

– No impulse generated– -70 mV

Action Potential- An impulse has been generated- +34 mV

Threshold- Minimum amount of change in charge needed to generate the impulse- -50 mV When a neurone fires it is known as the 'all or none' response or the 'all

or nothing' response. The reaction either occurs at the maximum or does not fire at all.

The point of excitation that causes the neurone to fire is called the threshold of reaction.

The intensity of the stimulus is recorded by the firing of all neurones not in a greater or lesser action potential of an individual cell.

DP4 “identify those areas of the cerebrum involved in the perception and interpretation of light and sound”

DP5 “explain, using specific examples, the importance of correct interpretation of 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. 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.

SC DP1 “perform a first-hand investigation using stained prepared slides and/or electron micrographs to gather information about neurones and nerves”

SC DP2 “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”

SC DP3 “present information from secondary sources to graphically represent a typical action potential”