OPTION – COMMUNICATION

Humans are social animals and, as such, are in constant communication with others. Many animals have an extensive range of communication strategies that include both visual and vocal signals. Learning these signals relies heavily on the involvement of all the sensory organs as well as the brain.

While the full range of senses can be involved in communication, the relative importance of each of the sense differs from animal to animal. This module focuses on the two senses that are important for many vertebrate and invertebrate animals – sight and hearing.

Human cultural development exploded with the development of speech and concurrent increasing complexity of communication. For some people, however, communication signals are not identified effectively because of faults in the sending, receiving or deciphering of some of the signals. With increasing advances in technology, assistance for people with difficulties in communicating continues to improve.

Identify the role of receptors in detecting stimuli.Things to consider: What does identify mean? What is a receptor? Be succinct

The roles of receptors are to detect stimuli within the surrounding environment. Once a stimulus has been detected by the organism it will respond. For example if the thermoreceptors on your skin detect cold air you will begin to shiver to maintain your body heat.Receptors are also classified on the basis of their function, they are as follows:Chemoreceptors: detect chemicals.Electromagnetic receptors: change in electromagnetic field, E.G. light receptors in eye.Mechanoreceptors: detect mechanical features such as pressure, touch, stretch.Pain receptors: detect pain.Thermoreceptors: detect change in temperature.

Explain that the response to a stimulus involves:- stimulus- receptor- messenger- effector- response

Things to consider: What does explain mean? Be succinct.

A stimulus is something that produces a response in the organism. For example if you were suddenly exposed to bright light (stimulus) the photo - receptors in the eye (receptor) send a message to the central nervous system (CNS - messenger) which then in turn sends a message to the muscles in the eye (effector) for the muscles to contract which then elicits the response of blinking (response). This process applies to all stimulus/response actions.

Identify data sources, gather and process information from secondary sources to identify the range of senses involved in communication.

Things to consider: What does identify, gather and process mean? What are the main senses used in communicating? Underline key words, be succinct

There are five main senses which are involved in communication, which are seeing, hearing, touch, taste and smell.Seeing (OCCULAR): or sight involves the use of an eye. An eye contains many structures which allow certain amounts of light as well as different electromagnetic waves to pass in and out of the eye. The organism reacts to these changes by relaying a message via the optic nerve to the brain to either allow more or less light/electromagnetic waves into the eye. Hearing (AUDITORY): involves the use of ears. The ear contains many structures which allow certain frequencies of noise to enter the ear and to be deciphered by the brain. Touch (SOMATOSENSORY SYSTEM): involves the use of mechanoreceptors, pain receptors and thermoreceptors. These receptors are usually found on the skin of the organism and enable the organism to enjoy certain stimulus and to avoid certain stimulus.Taste (GUSTATION): refers to the ability of being able to taste foods and chemicals entering the mouth. Taste involves the use of chemoreceptors which detect chemicals within the food. There is said to be 4 aspects of taste; sweet, sour, salty, bitter. Smell (OLFACTION): smell is the ability of an organism to perceive odours or smells. Chemoreceptors are found in the nose which has the ability of detecting these smells.

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

Things to consider:- What does describe mean?- Ensure you can label the diagram without using your textbook.- Include the function of each highlighted structure.

PART OF EYE

STRUCTURE FUNCTION

Conjunctiva A delicate membrane that covers the surface of the eye and the inside of the eyelids.

Protects the front part of the eye.

Cornea The front part of the eyeball which is transparent and quite thick.

Refracts light rays as they pass through it.

Sclera Continuous with the cornea but not transparent, it forms the tough, white outer back part of the eyeball.

Protects the eye and helps maintain eye shape.

Choroid The choroid lies on the inside of the sclera. It is a thin black layer which contains many blood vessels.

The pigment absorbs stray light preventing stray images.

Retina The innermost layer of the eye. It lines the back of the eyeball with a network of photoreceptors and nerve fibres.

Receives the light images and translates this into electrical impulses which are sent to the brain and deciphered.

Iris The coloured part at the front of the eye containing many fibrous muscles.

Regulates the amount of light entering the eye.

Lens A transparent biconvex protein disc behind the pupil.

Refracts and bends light rays towards the retina.

Aqueous and Vitreous Humor

Aqueous humor a vitreous substance fills the front chamber of the eye. Vitreous humor a jelly – like substance fills the back chamber of the eye.

Keeps the eyeball in shape as well as refracts light towards the retina.

Ciliary Body

Connects the choroid with the lens. It contains suspensory ligaments as well as ciliary muscles.

Holds the lens in place as well as altering the shape of the lens depending on the distance of an object.

Optic Nerve Connects the eyeball to the brain. Where the optic nerve connects to the brain is known as the blind spot as no image can be made or processed due to the lack of photoreceptors.

Carries nerve impulses to the visual cortex of the brain so images can be translated.

(HEINEMANN BIOLOGY 2nd EDITION)

Identify the limited range of wavelengths of the electromagnetic spectrum detected by humans and compare this range with those of other vertebrates and invertebrates.

Things to consider:- What does identify and compare mean?- Ensure you include other vertebrates AND invertebrates.

The electromagnetic spectrum is a range of energy forms which all travel at the speed of light. However these energy forms vary in wavelength and frequency. Humans detect visible light which ranges from 400nm to 700nm. This means that humans can only see objects within this wavelength. In comparison snakes use infrared light to detect prey and to avoid predators. Infrared light falls between 750nm to 1mm. Bees use ultraviolet light to detect petals on plants. This leads the bees to a food source (nectar). U.V. light ranges from 10nm to 400nm.

Use available evidence to suggest reasons for the differences in range of electromagnetic radiation detected by humans and other animals.

Things to consider:- Understand what the question is asking before you answer.- Be succinct- This question is almost a discussion so provide points for and/or against the differences in

range of electromagnetic radiation.

There are many different reasons as to why humans detect a different range of the electromagnetic spectrum in comparison to that of other animals. The reasons are as follows: Many organisms live in different niches. These niches produce different obstacles for the

organism. Each organism needs to detect predator and prey within their environment to survive. This may come in the form of a different electromagnetic field.

For example electric eels emit an electric field within their environment. Any disturbance to this environment such as that by prey is detected by the eel. Subsequently the prey is consumed. Eels use this form of electromagnetic radiation as vision within a water environment is quite poor.

The platypus has electromagnetic receptors in its bill. This helps the platypus to detect prey which produces an electric field. Platypuses use these receptors as vision within a water environment is quite poor.

Snakes use infrared light to detect predators and prey. This is due to the fact that snakes are largely found on the ground and in the underbrush of bushland. Snakes rarely use normal vision due to the lack of periphery on the ground.

Bees use ultraviolet light in detecting the nectar on flowering plants. This form of electromagnetic radiation is an advantage as the bee is able to quickly and efficiently detect a food source.

Humans use two single lens eyes to detect visible light. Humans have many photoreceptor cells of different pigment which detect the various colours of the spectrum. This form of electromagnetic radiation enables humans to produce sharp images of various objects.

It is evident that depending on the organism and its environment organisms have adapted various electromagnetic fields to detect predators and prey.

Identify the conditions under which refraction of light occurs.

Things to consider:- What does identify mean?- Be succinct- Understand key concepts before writing an answer.

Light refraction occurs when a light wave travels from a higher density to a lower density or a lower density to a higher density. An example of refraction is light waves travelling from air to water.

Identify the cornea, aqueous humor, lens and vitreous humor as refractive media.

Things to consider:- What does identify mean?- What is refraction?- Keep your answer simple.

Refraction occurs in the eyeball where light waves are bent towards the retina to from an image. This refraction occurs with the use of refractive media. The refractive media in the eye include:

- cornea- aqueous humor- lens- vitreous humor

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.

Things to consider:- What does identify, describe and explain mean?- Underline key words.- Ensure you answer all aspects of the dot point.- Be succinct

Accommodation is the process by which the lens changes shape according to the distance of an object of which it is focusing on. This process is possible due to the lens altering its curvature. If an object is less than six meters away the ciliary body will contract causing the lens to bulge. This in turn will cause the lens to refract the light at a greater angle. The effect of this is a greater sharper image. In contrast if you were to look at an image one hundred meters away the ciliary body relaxes, this cause the lens to elongate, this causes the lens to refract the light at a smaller angle. The effect of this process allows for a sharper image. Therefore accommodation allows humans to focus on objects at varying distances.

Compare the change in the refractive power of the lens from rest to maximum accommodation.

Things to consider: What does compare mean? What is refractive power? What is accommodation?

DISTANT OBJECT CLOSE OBJECT Light reaches eye in parallel rays. Lens is quite flat/elongated and at resting

state. Ciliary muscles relax. Low refractive power. This means that there

is very little to low levels of refraction occurring.

Light reaches eye as diverging rays. Lens becomes convex, that is bulging out.

This is due to the ciliary muscle contracting. High refractive power. This means that there

is a high level of refraction occurring.

Analyse information from secondary sources to describe changes in the shapes of the eye's lens

when focusing on near and far objects.

Things to consider: What does analyse mean? What does describe mean? Use diagrams to illustrate your answer.

Accommodation is the process by which the lens changes shape and curvature due to the distance of an object the person is looking at. In general a distant object causes the ciliary muscles to relax. This in turn causes the lens to elongate. The refraction index is low. This is due to the fact that if we focus on a distant object the light rays are coming in parallel lines. This means that the refractive media within the eye do not have to work as hard to refract the light to produce an image. When we refer to a close object the eye has to work harder in order to refract the light rays. Light rays at a close object are generally diverging, meaning they are splitting in an outwards direction. This causes the ciliary muscles to contract in turn causing the lens to bulge and refract the light at a higher index. An example of accommodation taking place when focusing on a distant and close object is illustrated below: (NOTE THE SIZE OF THE LENS. THIN = FAR OBJECT, THICK = CLOSE OBJECT.)

http://upload.wikimedia.org/wikipedia/commons/thumb/8/81/Focus_in_an_eye.svg/325px-Focus_in_an_eye.svg.png

Distinguish between myopia and hyperopia and outline how technologies can be used to correct

these conditions.

Things to consider: What does distinguish mean? What does outline mean? Be succinct. Ensure you know the technologies used.

Myopia commonly known as short sightedness, usually results from an elongated eyeball. Close objects can be viewed with no difficulty due to accommodation by the lens. However distant objects appear to be blurred due to the light rays being refracted in front of the retina. To correct this condition a concave lens is used either as spectacles or contact lenses. As you can see below the top diagram indicates myopia, as the light is focused before the retina. Through the use of the concave lens, which diverges the light rays, the focal point hits the right spot on the retina. (Fovea)

Figure 1: Myopia – illustrating refraction and the effect the concave lens has on the focal point.

http://upload.wikimedia.org/wikipedia/commons/1/13/Myopia.png

FIGURE 2: A TYPICAL IMAGE SEEN BY A PERSON SUFFERING FROM MYOPIA

http://www.psych.ucalgary.ca/PACE/VA-Lab/AVDE-Website/Assets/Barn%20Scene

%20Myopia.jpg

Hyperopia is commonly known as long sightedness. The condition occurs from either a short eyeball or poor accommodation ability by the lens. Distant objects can be viewed easily where as close objects appear blurry. This is due to the fact that the focal point for close objects is behind the retina, indicated below in figure 3. To correct this convergent or convex lenses are used in the form of spectacles or contact lenses, see figure 3.

Figure 3: Hyperopia - illustrating refraction and the effect the convex lens has on the focal point.

http://upload.wikimedia.org/wikipedia/commons/thumb/6/60/Hypermetropia.png/250px-Hypermetropia.png

FIGURE 4: A TYPICAL IMAGE SEEN BY A PERSON SUFFERING FROM HYPEROPIA

http://www.bausch.com/en_US/images/concern_full_img/farsightedness.jpgOther technologies that are used to correct myopia and hyperopia include radial keratotomy and photo – refractive keratectomy. Both of these technologies involve a surgical procedure which reshapes the cornea in order to alter the refractive power. In radial keratotomy fine surgical instruments shave small amounts of corneal tissue off the eye while in photo – refractive keratectomy a computer controlled laser is used to remove thin slices of corneal tissue.

Plan, choose equipment or resources and perform a first – hand investigation of a mammalian eye to gather first hand data to relate structures to its function.

Things to consider:- What does plan, choose equipment and resources mean? Ensure you write an experimental

procedure similar to the one on page 502 of the text book.- The experimental procedure, results, discussion and conclusion needs to be handed up to me

by the end of the lesson.

MODELLING ACCOMMODATION USING CONVEX LENSES

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.

Things to consider:- The dot point says to plan so you need to complete a detailed write up of this experiment. - Ensure you learn the detailed method as you could be asked to reproduce the method in the

HSC exam.- Refer to page 503 of your text book.

AIM:To model the process of accommodation by passing rays of light through convex lenses of different thicknesses.

MATERIALS/EQUIPMENT: One thin convex lens, one thick convex lens. A lens holder. A sheet of white cardboard or paper clipped on to a solid support; this acts as a screen where the

object is focused. A metre ruler. A small lamp.

METHOD:1. Darken the room and set up the thin lens in the holder as shown in figure 12.1. (Page 503 of

text book)2. Move the lens forwards and backwards to find a position that produces a clear focused

image of the light source on the screen.3. Describe the image and measure and record the distance of the image from the lens.4. Keep the lens holder the same distance from the screen and change the lens to the thick lens.5. Observe the screen and note the appearance of the image. Record it.6. Move the light source until the image is focused again.7. Measure and record the distance from the light source to the lens.8. Answer the questions.

RESULTS:LENS THICKNESS DISTANCE OF FOCAL

POINT (cm)Thin 28Thick 13

The image is a clear/white dot on the white screen. Some of the spectrum can be seen. When changing the lens from thin to thick the image became unfocused, larger in size and

blurred.

DISCUSSION/QUESTIONS: (Page 503 of text book)1. In this experiment the lens represents the lens in our eye, the distance from the lens to the

screen represents the focal length and the screen represents our retina.2. a.) The image on the screen was a small round white dot. As it was a perfect circle it did not

matter if it was inverted.b.) If we had an image in front of the light it would have produced a shadow, which could have been our object. If this occurred the shadow should have appeared upside down on the screen of paper. This relates to our eye as when we first look at an image it is shown upside down on our retina. Our brain turns the image the right way around.

3. A thin lens gives a clear focus on a far object. This is illustrated by the results as the lens was 28cm away from the screen, compared to the thick lens which was 13cm. This indicates that a thinner lens accommodates best when focusing on a distant object.4. A thick lens gives a clear focus on a near object. This is illustrated by the results as the lens was 13cm away from the screen, compared to the thin lens which was 28cm. This indicates that a thick lens accommodates best when focusing on a near object.5. Through this experiment links can be drawn between the results and how the human eye works. Through accommodation the human eye is able to see distant and near objects with precision. This is largely due to that fact that the lens is able to change shape or accommodate according to the distance of the object it is looking at. When we look at a distant object our ciliary muscles relax and lens becomes thinner, this was also illustrated by the experiment and our results. When we look at near objects the ciliary muscles contract causing the lens to bulge and become more convex, this was also illustrated by our results.6. This model differs from the eye in the following ways. The focal length in the human eye will be a lot shorter. The size of the lens is controlled by ciliary muscles in the eye. The human eye contains other refractive media such as the cornea, aqueous humor and vitreous humor which also affects the amount of refraction.7. This model is similar to what happens in the eye in the way the lens refracts the light to a central point. In this experiment the light was refracted to one point on the screen while in the human eye light is refracted to the retina.8. Models help to explain key concepts in science on a larger scale. Their disadvantage is that they can not include all relevant data and concepts.

CONCLUSION:In this experiment we were able to model the concept of accommodation. This was evident in the refraction taken out by the different sized lenses and their focal lengths on the screens.

Process and analyse information from secondary sources to describe cataracts and the technology that can be used to prevent blindness from cataracts and discuss implications of this technology for society.

Things to consider:- What does analyse, describe and discuss mean?- Break the question up, firstly describe what cataracts are, secondly describe the technology

and thirdly discuss how this technology affects society.

BACKGROUND:A normal human adult lens should be transparent to allow light to flow through to the retina. The transparency is due to structural and biochemical factors. The lens consists of many folded fibres called crystallins. The way these fibres are arranged makes the lens transparent. Lens fibres are capable of producing energy for the lens. Like all fibres and tissue, lens fibres need to be replaced making the lens become thicker and less elastic over time.

When the lens thickens or becomes cloudy the vision of the person decreases. This condition is known as cataracts. It is believed that the cause of cataracts is the insufficient nutrients in the lens fibres due to the density of these fibres. The crystallin proteins are then oxidised which then in turn causes the fibres to clump together producing a cloudy thickened lens.

Cataracts can come in many forms including age – related cataracts (old age), radiation – induced cataracts (U.V. light) and infectious cataracts (rubella virus causing cataracts). The simple type of technology used in preventing these types of cataracts is the use of sunglasses to prevent U.V. light damaging the lens and an adequate diet high in anti – oxidants which destroy free radicals. However in some circumstances the cataracts are well developed causing blindness to the patient. In this case a surgical procedure known as phakoemulsification must take place. During this procedure a small chisel – like instrument is inserted into the lens. The content of the lens is sucked out while the lens cavity is filled with a fluid to prevent damage to the cavity and loss of vitreous humor which will cause the retina to detach from the eyeball. A contact lens is then placed in the lens cavity. This is performed by folding the contact lens and inserting it into the eye via a straw. Once inside the cavity the lens unfolds and remains there for the rest of the patient’s life restoring their vision. The contact lens is known as an interocular lens (IOL) which resists U.V. light and is accepted by the body due to its plastic nature.

Phakoemulsification is a surgical technique which has greatly implicated society. The procedure itself takes very little time, is performed under a local anaesthetic and can be performed almost anywhere around the world. Phakoemulsification has revolutionised how doctors treat cataracts as it prevents unnecessary blindness especially third – world countries. Phakoemulsification is a safe, precise and successful technique available to thousands of people in developed and developing countries. The late Fred Hollows, who was responsible for restoring sight to many people in third world countries, set up a factory which made interocular lenses for only 10 cents. This made the process even affordable for the poor. It is through phakoemulsification, a huge advance in technology, cataracts are easily and successfully treated.

Figure 1: Person suffering from cataracts

http://www.ehponline.org/docs/2005/113-3/eye.jpgFigure 2: Simple process of phakoemulsification

http://www.med.umich.edu/1libr/aha/phacoext.gif

Explain how the production of two different images of a view can result in depth perception.

Things to consider:- What does explain mean?- What is depth perception?- Be succinct.

The ability to judge the distance of an object from our eyes is called depth perception. Depth perception relies on many factors. Firstly as humans we have binocular vision meaning we see through two eyes. The eyes are separated horizontally which enables humans to have stereoscopic vision (3D). So when we look at an object with both eyes two different images are formed on both retinas. This is due to the fact that the object we are looking at is at a different distance compared from one eye to the next. The brain interprets these two images produced by both eyes and fuses the images together to ascertain a general perception about the depth of the object.

Experience is an important factor relating to depth perception. Through our life we learn how tall certain objects are, this also helps us to perceive the depth of an object because we also know that distant objects appear to be small. So when we look at an object the size of the image on the retina is interpreted as being close or distant depending on the size of the object.

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.

Things to consider:- What does identify mean?- What does explain mean?- What are photoreceptors?- Relate to brain and electrochemical signals.

Photoreceptor cells are special types of neurons which are sensitive to light. In a human eye there are two types of photoreceptors rods which contain the light sensitive pigment rhodopsin and cones which contain the light sensitive pigment photopsin.

These photo-sensitive pigments are responsible for changing light signals into electrochemical signals which are interpreted by the brain as a certain image. When light enters the eye it is focused onto the retina. Rods and cones are not in the first layer of the retina. The light or collection of light known as photons pass through the layer of the ganglion cells, then the bipolar cells and then finally reach the rods and cones. In the rods the rhodopsin absorbs the light causing the retinal part of the molecule to change shape. This change in the rhodopsin molecule causes a change in the opsin molecule which then activates a relay molecule known as transducin. This results in less inhibitory neurotransmitter being released between the synapses between the rods and bipolar cells and the bipolar cells and ganglion cells, (enables messages to pass through). The electrochemical signal is passed through the rods to the bipolar cells, then from the bipolar cells to the ganglion cells, then from the ganglion cells to the optic nerve which delivers the electrochemical signal to the brain for interpretation.

Describe the difference in distribution, structure and function of the photoreceptor cells in the human eye.

Things to consider:- What does describe mean?- Differences only- What are photoreceptor cells?

CONESDISTRIBUTION STRUCTURE FUNCTION

6 Million cones in the human eye.

Cones are largely concentrated around the fovea where most of the daylight is focused.

Elongated cells with a synaptic terminal and an outer terminal containing discs. Similar to the basic structure of a nerve cell.

Provide sharp images. Not sensitive to light. Images are NOT sharp

during night time due to the lack of light.

Can distinguish colour.

RODSDISTRIBUTION STRUCTURE FUNCTION

125 Million rods in the human eye.

They are largely concentrated around the surface of the whole retina.

Elongated cells with a synaptic terminal and an outer terminal containing discs. Similar to the basic structure of a nerve cell.

Rods are very sensitive to light.

Responsible for night vision seeing black and white.

Outline the role of rhodopsin in rods.

Things to consider:- What does outline mean?- What is rhodopsin?- You can use point form for this answer.

Rhodopsin is a light absorbing pigment found in the rods of the human eye. Composed of a derivative of vitamin A called retinal bonded to a protein called opsin. Retinal part of the rhodopsin molecule is responsible for the initial absorption of light. Different opsin molecules affect the light – absorbing ability of the retinal. Rhodopsin is sensitive to lower wavelengths in the visible spectrum, (blue – green). Rhodopsin is more active during duller light or darkness.

Identify that there are three types of cones, each containing a separate pigment sensitive to either blue, red or green light.

Things to consider:- What does identify mean?- Keep your answer simple, be succinct.

There are three types of cones found in the human eye which are all sensitive to different wavelengths of the visible spectrum. This is due to the type of opsin molecule which best absorbs that certain colour. The opsin molecule and its absorbing wavelength are as follows:

- Blue region, maximum of 420 nanometres.- Green region, maximum of 530 nanometres.- Red region, maximum of 560 nanometres.

These cones are responsible for all the colours of the spectrum which we see.

Explain that colour blindness in humans results from the lack of one or more of the colour sensitive pigments in the cones.

Things to consider:- What does explain mean?- What are colour sensitive pigments?- Be succinct.

Colour blindness, a sex – linked condition often occurring in males, is the deficiency in distinguishing between certain colours. There are three types of colour blindness. The most common is referred to as red – green colour blindness. With this condition individuals either lack the red pigment or green pigment in their cones. This results in the other two cones, which are present, seeing all the colours of the visible spectrum. However as a result the individual is easily confused when distinguishing between red and green or they can not see red or green properly.

The second rarer type of colour blindness is blue – yellow colour blindness. These individuals lack the blue pigment in their cones. This results in confusion between blue and yellow, or the colours of blue and yellow are difficult to see.

The third and extremely rare condition of colour blindness is the total absence of cones. These individuals have no cones which means they have no colour – sensitive pigments. This results in the individual only seeing in black and white.

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.

Things to consider:- What does compare and describe mean?- Understand what the question is asking.- Ensure you use a mammal example, an insect example and another animal example.- Pages 479 – 481

MAMMAL (Human) INSECT (Fly) OTHER ANIMAL (Planarian Worm)

Evolved single – lens eyes to see.

Each eye contains a retina which is composed of many differing cells. In particular photoreceptor cells known as rods and cones.

Rods and cones contain visual pigments that absorb light.

This in turn causes the light signal to be changed by the photoreceptors into an electrical impulse which is eventually interpreted by the brain.

Evolved a compound eye which contains thousands of light detecting units called ommatidium.

Each ommatidium contains a lens which focuses the light on the light absorbing pigments.

The cells are arranged in a stack formation called a rhabdom.

Each photoreceptor alters the light signal to an electrochemical signal which is interpreted by the brain.

Insects see different coloured dots through each ommatidium. A change in shade or colour could mean that there is a predator present.

Evolved an eye cup which holds many photoreceptor cells.

These photoreceptors are stimulated by light and send a nerve impulse to the brain for interpretation.

The planarian worm has two eye cups. When the brain registers the strength and direction of the light the worm moves to an area of lower light intensity.

The resulting darkness helps the worm steer clear of predators.

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.

Things to consider:- What does process, analyse and describe mean?- Understand what the question is asking.- Be succinct- Refer to page 479.

The animal kingdom heavily relies on vision as a means of communication. In particular is the use of colour vision. Each organism varies in its capabilities of seeing certain objects. In order to have colour vision an organism must have cones, a photoreceptor found in the retina of the eye. Bees are an example of an organism which uses colour vision as a means of communication. Bees can see the ultraviolet end of the spectrum which enables the bees to see certain patterns on flowers. This results in the bee distinguishing between which plants to access its food from.

Many members of the five classes of animals; amphibians, fish, reptiles, birds and mammals can see using colour vision. This adaptation enables the organism to communicate within its environment, aid in reproduction as well as reproductive behaviour and eat certain foods which they are attracted to due to the colour of the food. For example many primates can detect the ripeness of the food they eat based on the colour of the food.

Nocturnal animals do not rely on colour vision. Nocturnal animals are largely active during the night and hence have a larger number of rods in their eye structure. This enables the nocturnal organism to see sharper images during the night time.

Birds use colour vision as a means of communicating with other birds and detecting food. Birds are strongly attracted to the colour red. To enable birds to see the red colour more readily they have a higher concentration of red pigment photoreceptors in their eye. The result of this is that birds can see red more readily then any other colour resulting in finding food at a much more efficient rate.

Ultimately colour vision is a useful tool for all organisms in communicating within their own environment.

Explain why sound is a useful and versatile form of communication.

Things to consider:- What does explain mean?- What is communication?- Be succinct

Sound is a useful and versatile form of communication as it is used by many organisms for socialising, mating behaviours, feeding patterns, the avoidance of prey and overall an effective communication tool.

Sound is an advantageous form of communication. Sound does not need light in order to be heard. Sound can travel through solids, liquids and gases. This means that sound can be used in dense environments. For example birds could call out to warn other animals of approaching predators.

Sound is used to send and receive messages. Humans and other mammals use vocal chords, fish use swim bladders and insects such as cicadas use a tympanal membrane to produce a “chirping” noise. Sound by organisms is detected by the ear.

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.

Things to consider:- What does explain mean?- What is frequency, how is it measured?- Be succinct

Sound is always produced by a vibrating object. For example when humans speak their vocal chords vibrate in order to produce the sound. In birds their vocal chords vibrate to produce a squawking noise. These vibrations produced by different organisms result in the same frequency of vibrations in the medium for which the sound is travelling through. For example if I say the word “biology,” at 80 Hertz (Hz) this will result in the word “biology,” being transferred through the medium (air) at 80Hz.

Another example in the text book states that if a tuning fork vibrates at 256Hz it sets the air particles through which it is travelling at 256Hz also. Outline the structure of the human larynx and the associated structures that assist the production of sound.

Things to consider:- What does outline mean?- What is the larynx?- Be succinct

The larynx is a complex structure located at the front of the throat - neck. The larynx is part of the trachea a passageway surrounded by rings of cartilage which is connected to the oral cavity and the lungs. The major function of the larynx is to produce sound. Sound is produced through many different structures which make up the larynx. The larynx is made up of nine different cartilages. The vocal chords are connected to some of these cartilages and extend across the tracheal opening. These vocal chords are made up of elastic fibres. As air rushes up from the lungs the vocal chords vibrate which results in the production of sound. The vocal chords and larynx surround a narrow

opening of the trachea called the glottis.

Speech involves the passage of air passing through the glottis. The pitch of the sound is altered by the length and tension of the vocal chords as well as the degree of the opening of the glottis. High pitched noises are due to the following structural characteristics; tense short vocal chords, vocal chords that vibrate at a fast rate and the glottis forming a narrow passage for air to pass through. Low pitched noises are due to the opposite; relaxed long vocal chords that vibrate at a slow rate with the glottis forming a large passage for air to pass through.

Louder noises are produced by the amount of air being forced through the and across the vocal chords.

Gather and process information from secondary sources to outline and compare some of the structures used by animals other than humans to produce sound.

Things to consider:- What does gather process, outline and compare mean?- Understand what the question is asking before you answer the question.- Underline key words- Be succinct.

A comparison showing various organisms and the means of their sound production is outlined below:

FROGS REPTILES BIRDS Male frogs produce a

croaking noise for various forms of communication, for reproduction or the marking or territory by various males.

The croak is generated by vocal sacs and their mouth cavity.

Sound is produced by forcing air out of the lungs across the vocal chords causing them to vibrate. Muscles in the surrounding trunk area contract to expel the large amounts of air to produce a croaking noise.

Croaking is species – specific meaning that each individual species produces a croak at a different frequency compared to that of different male frogs.

Reptiles produce sound for various forms of communication such as for reproduction or warning off other predators.

Sound is produced similar to that of the frog. Depending on the size and shape of the vocal chords air is expelled from the lungs to produce a sound. For example a snake will “hiss” to scare off predators, a gecko will “chirp” to call other geckos and a crocodile can produce a variety of sounds including “roar,” “hiss,” and “bark.”

Birds produce various calls or songs to warn others of predators or for calling a mate.

To produce these calls birds have a special structure known as a syrinx.

The syrinx is generally located at the base of the trachea.

The rings of cartilage the surround the bronchi and trachea are modified in the syrinx. They have partially become muscular in nature which results in the “bird call.”

Different vibrations of the membranes and the amount of air expelled causes different sounds produced by different birds.

Plan and perform a first hand investigation to gather data to identify the relationship between wavelength, frequency and pitch of a sound.

Things to consider:- What does plan mean? You will have to recall how you performed this experiment.- Ensure you understand the process of the experiment.- Be succinct.- What are wavelength, frequency and pitch?

- Fill in results table.- Answer questions 1 – 5 page 504.- Answer questions 1 – 4 page 505.- Where necessary write a conclusion to these experiments.

Outline and compare the detection of vibrations by insects, fish and mammals.

Things to consider:- What does outline mean?- What does compare mean?- What would be a good way of recording this information?- Be succinct

Sound is produced by the vibration of certain structures within an organism. These vibrations are received by other organisms using various sound detecting structures. A comparison of how different organisms detect sound is outlined below:

INSECTS FISH MAMMALS Insects such as mosquitoes

have tiny hairs on their body (mainly on the antennae) which detects sound emitted by the female mosquito beating her wings. This form of communication brings the two insects closer for mating.

Other insects such as grasshoppers contain a tympanic membrane. This membrane is stretched over an air chamber which in turn vibrates when sound is produced. This produces a response in the insect.

To detect vibrations within their ecosystem fish use their lateral line. The lateral line is used to detect the fish’s movement through the water, the direction and flow of the current, pressure waves from other objects such as predator and prey and in the detection of low frequency sound.

The lateral line works similar to that of the mammalian ear. (Sound detected, bends hair cells, nerve impulse sent to the brain.)

Fish also have an inner ear which detects high pitched sound.

To detect vibrations within their ecosystem mammals use a structure known as the ear. The vibration of air particles causes the membranes, bones, fluid and hair cells to vibrate within the inner ear. This in turn causes a nerve impulse to be sent to the brain and the sound or message is interpreted.

Organisms such as bats, whales and dolphins use echolocation to determine the distance and size of an approaching object.

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

ALSO

Gather process and analyse information from secondary sources on the structure of a mammalian ear to relate structures to functions.

Things to consider:- What does describe, gather, process and analyse mean?- What would be the best way to illustrate this answer? Table (Structure/function)?- Be succinct.

STRUCTURE DESCRIPTION FUNCTIONPinna The outer cartilage of the ear. Round in shape which causes

sound to enter the ear.Tympanic Membrane (eardrum)

A thin type of membrane located in the outer ear. Also known as the eardrum.

The tympanic membrane or eardrum separates the outer ear from the inner ear. The membrane vibrates in the presence of a sound which initiates the process of hearing.

Ear Ossicles The ear ossicles consist of three small bones, located in the middle ear known as the malleus (hammer), incus (anvil) and the stapes (stirrup).

The ear ossicles vibrate at the same frequency as the ear drum in the presence of a noise. These vibrations are passed on to the inner ear.

Oval Window The oval window is a membrane which separates the middle ear from the inner ear.

This membrane passes the frequency from the middle ear to the inner ear into the cochlea. (Same vibration.)

Round Window The round window is a membrane similar to that of the oval window which adjoins the inner ear and the cochlea.

Similar tot eh oval window this membrane passes the frequency from the inner ear to the cochlea. (Same vibration.)

Cochlea Main part of the inner ear involved in the hearing process. It is a coil like structure.

The cochlea contains 3 chambers. These chambers contain fluids which vibrate at the original frequency.

Organ of Corti The cochlea duct contains the organ of corti which contains the receptor cells responsible for detection of sound.

Organ of corti contains hair cells which eventually convert the vibrations into electrical signals which connect to the auditory nerve.

Auditory Nerve The auditory nerve is a bundle of sensory neurones located next to the cochlea.

Responsible for the transmission of electrical impulses to be interpreted by the brain as sound.

Outline the role of the Eustachian tube.

Things to consider:- What does outline mean?- Where is and what is the Eustachian tube?- Be succinct.

Our body is unique as everything in some manner is connected. The tube that connects the middle ear to the nose and throat is known as the Eustachian tube. By connecting to an air filled space such as the nose and throat the Eustachian tube is able to equalise the pressure between the eardrum and the middle ear. Equalising the pressure often happens when a person swallows or opens their mouth wide enough in time to equalise the pressure.

Outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur.

Things to consider:- What does outline and identify mean?- Figure 9.7.2 on page 485 will be very useful in answering this dot point.- Ensure you include the energy transformations that occur.

The following is an outline illustrating the hearing process.1. Sound is emitted causing the air to vibrate.2. These vibrations in the air travel to the outer ear and strike the eardrum (tympanic

membrane).3. The eardrum begins to vibrate at the same initial frequency.4. Sound energy is then transferred from the eardrum to the ear ossicles. The three ear ossicles

vibrate and transfer these vibrations to the oval window.5. When the oval window is pushed in by the ear ossicles a pressure wave is produced through

the fluids in the cochlea.6. As the pressure wave passes through the cochlea fluid it reaches the round window whereby

the round window is pushed in the opposite acting as a pressure release valve.7. The pressure wave also acts on the cochlea duct, the basilar membrane, the tectorial

membrane and eventually the organ of corti as a whole.8. The “push” from the pressure wave causes the hair cells in the organ of corti to bend. This in

turn causes the hair cells to release neurotransmitter into the synapses, between the hair cells and the neurones which carry the message to the auditory nerve.

9. An action potential is created by these hair cells and the message is delivered to the cerebral cortex for interpretation.

Basically the energy transformations that occur in the hearing process are sound waves into pressure waves which are eventually converted into nerve (electrical) impulses and are interpreted by the brain.

Describe the relationship between the distribution of hair cells in the organ of corti and the detection of sounds of different frequencies.

Things to consider:- What does describe mean?- Underline key words.- Understand what the question is asking before you write an answer.

The distribution of hair cells in the organ of corti cause different interpretation of sound. Firstly we know that when sound enters the ear at a certain frequency it will cause the eardrum and ossicles to vibrate at that frequency. Once the vibration has been passed through the ear and it reaches the cochlea as a pressure wave an ingenious set of hairs in the organ of corti determine the frequency of the original sound. This originally begins in the basilar membrane. The fibres in the basilar membrane are of different lengths. Each of these different length fibres vibrate at a certain frequency. Hair cells run along the basilar membrane so that when a certain fibre is triggered by a certain frequency that group of hair cells will begin to bend. Thus different frequencies of sound will activate different areas of the basilar membrane in turn causing different groups of hair cells to bend.

If we observe the cochlea like a piano the hair cells are arranged according to the level of the frequency they detect. Low frequencies are detected at the apex of the membrane while high frequencies are detected at the base.

The hair cells, neurones, the auditory nerve and the brain all work in tandem to determine the frequency of the noise. Different neurones are produced when the hair cells bend causing the nerve impulses to travel to different areas of the cerebral cortex resulting in the interpretation of different frequencies of noise by the brain.

Therefore hair cells are arranged to detect different frequencies of noise working in tandem with the brain to interpret these frequencies.

Outline the role of the sound shadow cast by the head in the location of sound.

Things to consider:- What does outline mean?- What is a sound shadow?- Be succinct.

The ears are placed on either side of the human head. If a noise or sound is coming from the right it reaches the right ear first. For the sound to reach the left ear it must travel around the head or through the head to reach the left ear. The head absorbs high frequencies much more easily then low frequencies causing a sound shadow to be cast over the ear furthest away from the sound source. The sound shadow in turn enables humans to determine the direction of the 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.

Things to consider:- What does process, outline, compare and discuss mean?- Best way to represent this information? Table?- Ensure you can identify the frequency at which humans hear best.

HUMANS DOLPHINS KANGAROO RAT The range of sound that can

be detected by humans is about 0.02 kHz – 20 kHz or 20 – 20000 Hz.

The range that humans are most sensitive at is approximately 2 – 4 kHz or 2000 – 4000 Hz.

Humans are capable of very finely discriminating between different frequencies and intensities.

This means that humans can accurately identify the differences and loudness of sounds.

This adaptation is believed to be handed down by the primates whereby humans developed dialogue and the ability to distinguish between a moderate frequency range.

This adaptation has also enabled humans to detect different frequencies and the direction of the sound.

The range of sound that dolphins can detect lies between about 1 kHz – 100 kHz.

The range that dolphins are most sensitive at lies between 20 – 80 kHz.

The lower range frequencies represent what a dolphin “usually” hears, while the high range of frequency is used in the process of echolocation.

Echolocation is used to determine the distance, size, speed, shape and texture of an approaching object.

This is a valuable asset for the dolphin as it enables it to survive within its environment.

The range of sound that a kangaroo rat can detect lies between about 0.03 kHz – 50 kHz.

The range that the kangaroo rat is most sensitive at lies at about 1 kHz.

Kangaroo rats are most sensitive at low frequency sounds as it enables them to detect predators which emit low frequency sounds such as the slithering of a snake or the wings beating of an owl.

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.

Things to consider:- Important dot point as it is secondary source. Could be a 6 – 7 marker in the HSC.- What does process and evaluate mean?- Ensure you answer the question properly.

HEARING AID COCHLEAR IMPLANTPosition on the body.

A hearing aid can be attached to the body in a variety of ways. Firstly the behind the ear (BTE) hearing aid consists of a hard plastic case worn behind the ear and is connected to a plastic ear mould which sits inside the outer ear. The second type of hearing aid is the “in the ear,” (ITE) hearing aid. This hearing aid as it suggests is a tiny mould which sits directly in the ear canal.The third type of hearing aid is a canal hearing aid and as the name suggests this small type of hearing aid sits in the ear canal.

The cochlear implant as the name suggests has to be implanted into the patient’s ear. There are external parts to the cochlear implant as well as internal parts. The external parts consist of a microphone which sits behind the users ear, a thin chord which connects the microphone to the speech processor, a speech processor which deciphers noise which is a small device usually in the users pocket or attached to their waste and the transmitting coil which usually is attached to the behind to ear on the users scalp. The internal parts consist of receiver/stimulator which sits just inside the skin and on top of the skull and the electrode array which is implanted into the cochlear.

Type of energy transfer.

The type of energy transfer that takes place in a hearing aid includes:A sound is produced in the external environment. This sound reaches the hearing aid. The hearing aid uses this sound and converts it into an electrical signal. This electrical signal is then turned into amplified sound in which the person wearing the hearing aid can hear.

The type of energy transfer that takes place in a cochlear implant is as follows: sounds are detected by the microphone which amplifies the sound. The sound waves are sent to the speech processor which converts the sound into an electrical signal. The electrical signals are sent to a transmitter which turns the electrical signals into radio waves. The transmitter sends these radio waves to the receiver/stimulator which converts the radio waves into electrical signals. These electrical signals go to the electrodes fitted to the cochlear and excite the auditory nerve. The brain receives these electrical impulses via the brain and interprets them as sound.

Conditions under which the technology

The purpose of a hearing aid is to make sound louder and audible for a person who is suffering from hearing loss. A hearing aid can work in quiet as well as

The cochlear implant works considerably differently from a hearing aid. A cochlear implant is implanted into a patient if they suffer from

will assist hearing.

noisy areas. Ultimately the use of a hearing aid is to amplify sound, and it can be used in all conditions.

deafness. Depending on the patient a cochlear implant can be very helpful. Usual sound is picked up by the person with the implant; however some sounds are hard to distinguish in a noisy environment.

Limitations. Hearing aids can be somewhat expensive to buy and maintain depending on the patients economic status.

Hearing aids can be uncomfortable to wear.

The voice of the person using the device may seem a lot louder to them then usual.

Hearing aid users may get feedback from their device such as a whistling noise.

Hearing aid may pick up background noise which may give the patient some difficulty in distinguishing between people and sounds within a room or area.

Some hearing aid users may get a buzzing noise when they use a mobile phone.

Surgery and the cost of a cochlear implant may be somewhat expensive depending on the patient’s economic status.

The device as a whole can be uncomfortable.

A person who has not developed speech will be at a far greater disadvantage then a patient who becomes deaf at a later date in their life.

Sound in noisy areas can be somewhat hard to distinguish.

Sound can be unclear. Full hearing potential is not reached

with a cochlear implant.

http://www.nidcd.nih.gov/health/hearing/coch.asphttp://www.nidcd.nih.gov/health/hearing/hearingaid.asphttp://www.science.org.au/nova/029/029box01.htm

COCHLEAR IMPLANT

Identify that a nerve is a bundle of neuronal fibres.

Things to consider:- What does identify mean?- Understand the difference between the words nerve and neurones.

As the question states a nerve is a bundle of nerve fibres also known as neurons. These neurons all have specific structures including:

- Nucleus to control the function of the neuron.- Dendrites to provide a larger surface area for the collection of nerve signals.- Cell body to provide nutrients as well as maintain metabolism in the neuron.- Axons to convey signals along the neuron. Axons can be covered in myelin sheath, which is

made by Schwann cells. The myelin sheath insulates the axon. In between each Schwann cell is a gap called the node of ranvier. This gap allows fast and efficient signalling through the nerve.

- Synapse or synaptic knob is a gap between neuron to neuron.

http://training.seer.cancer.gov/module_anatomy/images/illu_neuron.jpg

Identify neurones as nerve cells that are the transmitters of signals by electro – chemical changes in their membranes.

Things to consider:- What does identify mean?- Understand what the question is asking before you answer it.

Neurons are transmitters of electrical signals. However when the electrical signal reaches the axon terminals it somehow has to jump across the synapse from one neuron to the next neuron. How does it do this? This action is performed through the use of neurotransmitters (chemical). Neurotransmitters are released from the axon branches into the synaptic space. Once in the synapse the neurotransmitter will travel to the dendrites of the next neuron. There the neurotransmitter will stimulate the dendrites membrane to become permeable to sodium ions. This therefore initiates a nerve impulse (action potential) in the next neuron and hence the message is passed on.

Define the term threshold and explain why not all stimuli generate an action potential.

Things to consider:- What does define and explain mean?- Two parts to your answer. Ensure you answer both.

The threshold is the value that must be reached usually in the vicinity of -50mV, -55mV. This value is reached depending on the strength of the stimulus acting on the neuronal membrane. If these values are reached an action potential will occur.

The stronger the stimulus the more likely it will change the membrane potential towards the threshold value. Once the threshold is reached the action potential occurs. Action potential occurs in an all or nothing phase which means if the threshold is reached it will occur and if the threshold is not reached it will not occur.

Some stimulus however will not cause the membrane to become permeable to sodium ions therefore causing the threshold not to be reached in turn causing no action potential.

Identify those areas of the cerebrum involved in the perception and interpretation of light and sound.

Things to consider:- What does identify mean?- Ensure you can identify these areas if given a brain model.

LIGHT (VISUAL AREA) SOUND (AUDITORY AREA) Interpretation and perception of light

(vision) is located in one of the largest sensory areas of the brain which is the occipital lobe. (Back of the brain)

Two parts – the primary visual cortex which synthesises images from both the left and right eye to gain an overall image. The visual association area of the brain associates with images we have seen before, for example someone you have met before or a “familiar face.”

Interpretation and perception of sound (auditory) is located in the temporal lobe. (Above the ear.)

Two parts – the primary auditory cortex, through the natural function of the ear interprets different electrical impulses and converts them into sound. The auditory association area which recognises sounds or voices from previous experience.

http://sehati.org/neurosurgicalprocedures/images/craniotomy/craniotomy1.jpg

Explain, using specific examples, the importance of correct interpretation of sensory signals by the brain for coordination of animal behaviour.

Things to consider:- What does explain mean?- What is coordination?- Relate findings to the actual brain and its structures.

It is very important for all organisms to interpret stimulus in a way that enables them to respond in an appropriate way in order to survive. For example if we look at human beings. Our behaviour is coordinated as a result of the signals coming to our brain and our correct interpretation of these signals. For example if we were to cross a road and as we were crossing we did not notice a truck coming towards us at a high speed. Many signals enter the brain and are integrated into one conclusion – get out of the way. These sensory signals enable humans to respond to their environment in a coordinated way which leads to survival of the species.

Another example is the migratory patterns of birds and whales. It has been shown through various studies that birds and whales can perceive, store, process and use the information obtained by vision and hearing to behave in a manner that is advantageous for them. Whales and birds rely on the storage of certain data to enable them to migrate accordingly every year. This unique ability illustrates that by interpreting these sensory signals, storing these signals and reusing these signals birds and whales are capable of coordinating in their behaviour in such a way that enables them to find exact locations hundreds to thousands of kilometres away.

Perform a first hand investigation using stained prepared slides and/or electron micrographs to gather information about the structure of neurones and nerves.

Things to consider:- This is an experiment using a light microscope. Recall how to draw a field of view. Ensure

you include a title, total magnification and relevant labels to what you are viewing.- Refer to the diagram of a neuron on page 489 of the text book to assist you in how you label

your neuron(s)- Refer to page 510 of the text book, which outlines the experimental procedure.- Answer questions 1 – 4 on page 510 and conclude your experiment.

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.

Things to consider:- Ensure you make a good observation of the brain. In the HSC they could possibly give you a

diagram of the brain and you have to indicate the areas involved in speech, sight and sound perception.

- For revision of this experiment please refer to the experimental procedure, diagrams and pictures on pages 508 – 510.

Present information from secondary sources to graphically represent a typical action potential.

Things to consider:- What does present mean?- Ensure you can explain the parts of the graph.

http://gargoyle.arcadia.edu/psychology/blustein/neuro/Lecture_Notes/Week_1/Week_2/Action_Potential.jpg

STEP 3 = FULL ACTION POTENTIAL