HSC Biology: Communications

4.1.1) List the stimuli that can be detected by humans.

Light, sound, heat, pressure and certain chemicals

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4.1.1) What is a receptor?

A specialised nerve cell that sends a nerve impulse or releases a hormone as a result of detecting a specific stimulus

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4.1.1) What role do receptors play in detecting stimuli?

Receptors are specific to a stimuli and respond to it.

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4.1.2) What are the steps involved in the response to a stimulus?

1: A change in the environment, 2: Specific receptor detects the stimulus, 3: Receptors start a nerve impulse/messenger, 4: Effector receives the message and responds

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4.1.2) What are the range of senses involved in communication?

Visual (sight), Olfactory (smell), Auditory (hearing), Tactile (touch), taste.

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4.2.1) Describe the conjunctiva

Fine transparent membrane covers & protects cornea

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4.2.1) Describe the cornea

Transparent front window which light enters through. Does initial focusing of the image.

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4.2.1) Describe the sclera

White of the eye. Tough outer layer, protects eyeball.

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4.2.1) Describe the choroid

Underneath sclera. A sheet of blood vessels that carry oxygen & nutrients, remove C02 & wastes. Prevents light in the eye from reflecting internally.

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4.2.1) What is a photoreceptor

Specialised neurones that respond to a specific range of wavelengths of light and produce a nerve impulse that allow us to see shape, movement & colour

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4.2.1) Describe the retina

Complex structure of photoreceptors (rods & cones) on back of eye. Retinal nerve cells convert incoming light into nerve impulses.

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4.2.1) Describe the iris

Coloured part of eye. Ring of muscle with hole in middle (pupil). Controls amount of light entering eye. Dim light= iris relaxes & pupils dilate to allow more light in. Bright light= iris tightens & pupil contracts

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4.2.1) Describe the lens

Behind iris, focuses light onto photoreceptors

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4.2.1) Describe the aqueous & vitreous humor

Clear jelly that fills two pressurised chambers. Give eye spherical shape.

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4.2.1) Describe the ciliary body

Circular, muscular rings that focuses lens

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4.2.1) Describe the optic nerve

Contains a million nerve fibres that conduct the nerve impulses to the vision centres in the brain

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4.2.2) What is the electromagnetic spectrum?

Range of radiation that travels through space. Includes light, infra-red radiation & ultraviolet light

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4.2.2)Describe the range of the electromagnetic spectrum can be detected by human ?

Between 380-750 nm (nanometres). Called "visiable light". Comprised of the colours red, orange, yellow, green, blue, indigo & violet. Most effective wavelengths are blue-green (500nm). Less effective are red & violet light.

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4.2.2) How does the range of the electromagnetic spectrum detected by humans compare with that of other vertebrates?

All have different ranges and are more sensitive to different ends of the spectrum. Eg. bees are less sensitive to higher (red) wavelengths. Many are not able to distinguish different colours.

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4.2.2) Why would it be an advantage for a nocturnal animal to detect infra-red light?

Help animals to "see" the heat coming from other organisms that could be predator or prey

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4.2.2) Why would some nectar-feeding birds benefit from seeing either ultraviolet light or infra-red light in addition to to visible light?kg

To guide the bird to the flowers and give it a better chance in the competition for the food source as some flowers emit this wavelength.

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4.2.2) Why would bees benefit from seeing ultraviolet light?

See patterns on flowers that humans cannot see to guide them to the pollen & nectar source in the flower.

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What is the fovea?

A small depression in the retina of the eye where visual acuity is highest. The center of the field of vision is focused in this region, where retinal cones are particularly concentrated

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4.3.1) What is refraction? What causes it?

Refraction is the bending of light when it changes speed as it moves from one medium to another of different density. It occurs when light passes through a denser medium because the speed is slowed down

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4.3.2) What part of the eye causes the greatest refraction?

The cornea because light leaves air and enters the cornea.

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4.3.2) Why is the lens an important refracting part of the eye?

Because the ciliary muscles can change the shape of the lens, the amount that the lens refracts the light varies which enables focusing on objects at different distances.

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4.3.3) How is accommodation achieved in the eye?

By changing the lens shape to focus images from objects at different distances onto the retina

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4.3.3) Why is accommodation important?

So a clear image of an object at different distances can be seen

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4.3.3) What is the shape of the lens when focused on a nearby object?

It is round. The ciliary body squeezes until the lens is short and dense & have a greater curvature. Refractive power of the lens is at the maximum.

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4.3.3) What is the shape of the lens when focused on a distant object?

It is longer & thinner. The ciliary muscles relax, allowing lens to become long and thin.

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4.3.4) How does the refractive power of the lens change from rest to maximum accommodation?

Refractive powers of lenses compares using SI unit diopter. The larger the number of diopters, the less the refraction. The relaxed eye is approx. 60 diopters. To read at a distance of 30cm 3 diptors of refractive power is needed.

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4.3.4) What is accommodation?

The ability of the eye to focus on objects at different distances.

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4.3.4) How can you model accommodation?

Tracing light rays of through lenses of different thickness and comparing focal lengths

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4.3.5) What is myopia?

Short sightedness, when the distance between the lens and the retina is too great or the lens is too strong, so the image will be increased in front of the retina which makes it blurry

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4.3.5) How is myopia corrected?

A concave lens that increases the focal length of the eye

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4.3.5) What is hyperopia?

Far sightedness, when the distance between the lens and the retina is too short or the power of the lens is too weak, so light rays coming into the eye from a near object will be focuses on an imaginary spot behind the retina making it blurry

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4.3.5) How is hyperopia corrected?

A convex lens that increases refraction to form a clearer image

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4.3.5) What are cataracts?

A condition where the lens grows cloudy and eventually becomes opaque. This prevents light from reaching the retina and the person becomes blind.

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4.3.5) How can blindness from cataracts be prevented?

Cataract microsurgery which involves replacing the damaged or cloudy lens with an intraocular lens

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4.3.5) How has society benefited from current technology to remove cataracts?

Millions of people throughout poorer nations have had their eyesight restored. In some countries, people die within four years of becoming blind so this has helped that.

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4.3.6) How do we perceive distance?

Because our brain processes two slightly different images, one from each eye. Having our eyes at the front of our face but further apart allows for depth perception.

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4.4.1) Why are photoreceptor cells important for vision?

They convert light images into electrochemical signals that the brain can then interpret.

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4.4.2) What are the two types of photoreceptor cells in the human eye?

Rods and cones

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4.2.2) What are the structure, function and distribution of rods in the human eye?

Densely concentrated at the edges of the retina. Function in dim light, allow us to discriminate between light and dark. Responsible for the formation of an image.

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4.2.2) What are the structure, function and distribution of the cone cells in the human ee?

Densely concentrated in the central fovea. Stimulated by bright light, specific for colour vision and visual activity. Responsible for formation of an image

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4.2.2) What is the nature of photoreceptor cells in mammals?

Rods for detection of low light. Primates have 3 types of cones & rods for colour vision. Many mammals only have 2 types of cones and don't have full colour vision.

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4.2.2) What is the nature of photoreceptor cells in insects?

Located at the base of the ommatidia (mini-eyes) that make up their compound eyes. May contain different pigments which make them sensitive to certain wavelengths eg. ultraviolet.

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4.2.2) What is the nature of photoreceptor cells in an animal other than a mammal or insect?

A flatworm has a patch of light-sensitive cells that help distinguish light, dark & movement.

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4.4.3) What are rhodopsins?

A photosensitive pigment in a rod. Highly sensitive to light (low levels of light). Specialised for night vision.

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4.4.3) What is the function of rhodopsins in rods?

Detects low levels of light by breaking into two molecules, initiating a nerve impulse.

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4.4.4) How do the three types of cone cells differ?

Each cone cell contain a separate pigment sensitive to red, blue & green. Similar to rods, but they need bright light.

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4.4.5) What causes colour blindness in humans?

Lacking one or more of the colour-sensitive pigments in cones. Most common is red-green.

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4.4.5) What groups of animals have good colour vision?

Bony fish, frogs, turtles, lizards & birds.

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4.4.5) In what ways does colour vision support communication in animals that see colour?

To distinguish male from female, signal breeding times, camouflage, & threat signals.

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4.5.1) Briefly describe the properties of sound

Longitudinal wave that must travel through a medium. Can reflect of surfaces & refract. Can travel through solids, liquids & gasses at varying speeds.

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4.5.1) Why is sound so useful in communication?

Can signal both day & night. Travel over distances when animals cannot see, smell or touch each other. Varies in pitch & dynamic and can convey different meaning.

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4.5.2) How is sound produced?

By vibrating objects. The vibrations are transferred along adjoining molecules.

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4.5.2) How is the frequency of sound determined?

The frequency of the sound is the same as the frequency of the vibration of the source of the sound.

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4.5.2) What is a cathode ray oscilloscope?

A device that converts sound waves into electronic signals to visually display the characteristics of sound waves.

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4.5.2) What is the relationship between wavelength and frequency of sound?

As the frequency goes higher, wavelength gets shorter.

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4.5.2) What is the relationship between frequency and pitch of sound?

Sounds with a short wavelength have a higher frequency (higher pitch). Sounds with long wavelengths have a low frequency (lower pitch)

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4.5.2) Outline how you determined the relationship between frequency, pitch & wavelength of sound in a first-hand investigation

Attach an audio oscillator to the cathode ray oscilloscope. A.O produces sounds of varying frequencies that can be heard and their wavelength displayed on the screen of the C.R.O.

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4.5.3) How is the structure of the larynx related to its function?

Has vocal chords (flexible chords of muscle & ligament). Air passes through the lungs, they vibrate producing sound. Frequency of vibration will determine pitch, rate of flow of air determines volume.

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4.5.3) How is sound modified after being produced in the larynx?

Nasal cavity is responsible for the unique voice. Different speech sounds ("uh", "a", "ph", "t", "g") produced by movement of the tongue, lips & jaw.

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4.5.3) Compared with humans, what structures are used by other animals to produce sound?

Fish produce sound by rubbing their fins/gils together or by vibrating their swim bladder. Male grasshoppers & crickets rub veins on the base of their forewings & inner surfaces of their hind legs.

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4.6.1) How do insects detect vibrations?

Crickets (ears on legs), grasshoppers & cicadas (ears on abdomen). Tympanum: thin, circular membrane stretched across an air space. Connection to nervous system relays impulse.

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4.6.1) How do fish detect vibrations?

1) Labyrinth (series of tunnels in inner ear, contain sound receptors. 2) Visible lateral line, runs along body & has receptors sensitive to surrounding water disturbance. Fish have no middle hear cavity or cochlea.

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4.6.1) How do mammals detect vibrations?

Organs in the head. Bats, toothed whales & dolphin navigate & hunt prey by echolocation (sending out sound impulse and listening for echo that bounces off objects)

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4.6.2) Describe the pinna (the flap)

Collects sound waves from a wide area and funnels the sound into the external ear passage.

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4.6.2) Describe the Tympanic membrane (ear-drum)

Stretched across end of auditory canal. Separates outer ear & middle ear. Sound waves cause it to vibrate. Then conveyed to oval window by ear ossicles.

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4.6.2) Describe the ear ossicles

3 intricately formed bones (the hammer, anvil & stirrup), transmit the sound waves to inner ear (sound travels well through bones)

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4.6.2) Describe the oval window and round window

2 thin membranes. Sound reaches inner ear at oval window. Pressure then transmitted in the fluid to tympanic canal. Pressure causes round window at other end to bulge out. Helps amplify pressure of sound vibrations.

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4.6.2) Describe the cochlea (snail like spiral coiled tube in the inner ear)

Has receptors for sound and vestibular apparatus associated with balance. As a result of the round window bulging out, fluid in the cochlear tubes vibrate.

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4.6.2) Describe the organ of corti

Contains auditory receptor cells

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4.6.2) Describe the auditory nerve

Transmits sound vibrations to brain

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4.6.3) What is the Eustachian tube?

Connects middle ear to the pharynx (chamber at the back of the mouth & nose). Usually closed but can be opened by yawning or swallowing.

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4.6.3) What function does the Eustachian tube perform?

To equalise the pressure on the two sides of the ear-drum.

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4.6.4) Explain the pathway of sound through the external & middle ear

External ear (ear canal & ear drum/ tympanic membrane) -> middle ear (vibrations transmitted by ear ossicles [hammer, anvil, stirrup] -> sound reaches inner ear...

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4.6.4) Explain the pathway of sound through the inner ear ear

Sound reaches inner ear at oval window (vibrations transmitted through oval window to round window through the spinal cochlea, containing fluid and nerve endings) -> impulse to auditory nerve -> auditory area of the cerebrum

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4.6.4) Identify what energy transformations occur with the passage of sound through the ear and where they occur

Sound energy is transferred to the tympanic membrane where transformed into movement (mechanical) energy of ossicles. Movement energy transferred to hair cells in organ of Corti, then transformed into electrochemical energy

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4.6.5) Describe the sound receptors in the organ of Corti

Hair cells. Move in response to pressure variations in the fluid-filled tympanic and vestibular canals. Distributed along basilar membrane which follows the spiral of the cochlea.

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4.6.5) What are the high and low frequency sounds detected by the organ of Corti

HF sounds selectively vibrate the basilar membrane of the inner ear near entrance (oval window). LF travel further along membrane before triggering hair cells.

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4.6.5) What is the range of frequency detected by a normal human ear?

20-20,000 Hertz (Hz)

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4.6.5) How does the range by detected by humans compare with to other animals?

Bats: 100,000-120,000 Hz. Marine Mammals: Some whales can hear sounds as low as 20 Hz, some dolphins can hear sounds as high as 150,000 Hz. Porpoise's range 50-150,000 Hz

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4.6.5) What are the possible advantages of the range of sound frequency detected by mammals other than humans?

Bats' range of sound allows for precise echolocation. Marine animals communicate long distances, very low sounds travel a long way.

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4.6.6) What is a sound shadow?

A result of one ear being closer to the sound source. This ear receives slightly more sound than the other.

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4.6.6) How does the sound shadow help humans locate the direction of a source of sound?

Brain interprets sound from each ear and we turn our heads to the source of the sound.

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4.6.6) Describe the conditions under which a hearing aid helps hearing impaired people

Amplify sounds. Fit into the hollow of the ear canal. Consists of a microphone to capture sound & amplifier to magnify it. Assists in conditions where conduction deafness is caused by damage to the outer or middle ear.

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4.6.6) What are the advantages and disadvantages of hearing aids?

Advantages: Improved hearing. Disadvantages: Must provide enough amplification without being painfully loud, so models do not fit everyone. Do not assists in nerve damage to the inner ear/brain/cochlea/auditory nerve

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4.6.6) Describe the conditions under which a cochlea implant helps hearing impaired people

Helps those who are profoundly deaf & have damage to the inner ear or auditory nerve.

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4.6.6) What are the advantages and disadvantages of cochlea implants?

Advantages: Hearing. Disadvantages: Cost, need for operation, need to wear sound processor & microphone.

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4.7.1) What is a nerve?

A bundle of neuronal fibres (neurones)

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4.7.1) Describe an axon.

An axon branches off a neurone to join with dendrites of other neurones at synapses/

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4.7.2) What is a neurone?

Single nerve cell made of dendrites, body cell with nucleus & axon. Transmit signals by electrochemical changes (detected in voltage) in their membrane. Signals travel like wave from dendrites through cell body to axon to other neurones.

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4.7.2) How can the observation of stained prepared slides or electron micrographs assist the understanding of nerves & neurones?

Demonstrating the variety & arrangement of different nerve structures in the body that have different jobs.

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4.7.3) What is a nerve threshold?

The minimum stimulus required to generate a response in the nerve cell.

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4.7.3) Describe a typical action potential.

At rest, ions is balanced. When a sufficient stimulus is received the membrane changes its permeability and the threshold is achieved. Allows a rapid flow of ions, action potential initiates. Travels as wave along membrane from point of stimulus.

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4.7.4) What is the position and role of the primary visual area and visual association area?

PVA: Located at optical lobe at near of brain. Detects simple visual stimuli. Perceives light. VAA: Located above visual cortex. Complex processing of visual info. Interprets light.

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4.7.4) What is the position and role of the primary auditory area and auditory association area?

PAA: Located temporal love at lover side of brain. Detects sound (loudness + tone), perceives sound. AAA: Behind auditory cortex. Complex processing of auditory info. Interprets sound.

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4.7.4) What is the position and function of the cerebrum in speech, sight & sound perception?

Folded large part of brain, encases other parts at the top. Has a role in memory, attention, perceptual awareness, thinking, language, consciousness. Responsible for speech, sight, sound & perception.

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4.7.4) Describe the position and function of the cerebellum.

Located at lower rear section of brain behind brain stem. Coordinates movement, posture & balance.

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4.7.4) What is the position and function of the medulla oblongata?

Upper extension of spinal chord located in front of cerebellum. Responsible for basic functioning like breathing.

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4.7.5) Give an example to identify the importance of correct interpretation of signals by the brain for the coordination of animal behaviour.

"Lo" moth virtually invisible when resting b/c camouflage. If predator approaches, it displays an eye pattern on its hind legs by vigorously drawing forward its forewings, making it appear large or dangerous, giving an opportunity to escape.

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HSC Biology: Communications

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