Stimuli, Receptors, and Responses PDF

中/EN Stimuli, receptors and 16 responses Aristo 16.1 16.2 16.3 16.4 ◄ 1 ► 16.1 Irritability What is irritability (感應性)? the ability of organisms to detect stimuli (刺激) and produce responses (反應) enabl...

中/EN Stimuli, receptors and 16 responses Aristo 16.1 16.2 16.3 16.4 ◄ 1 ► 16.1 Irritability What is irritability (感應性)? the ability of organisms to detect stimuli (刺激) and produce responses (反應) enables organisms to escape from danger Aristo 16.1 16.2 16.3 16.4 ◄ 2 ► 16.1 Irritability What is irritability (感應性)? the ability of organisms to detect stimuli (刺激) and produce responses (反應) enables organisms to look for food and mates Aristo 16.1 16.2 16.3 16.4 ◄ 3 ► 16.1 Irritability What are stimuli? = changes in the environment detected by stimuli receptors (感受器) external = sensory cells (感覺細胞) internal group to form a sensory organ (感覺器官) Aristo 16.1 16.2 16.3 16.4 ◄ 4 ► 16.1 Irritability Four main types of receptors in humans Type of receptor Stimulus detected Sense organ(s) Photoreceptor light eye sound (a pressure ear Mechanoreceptor wave) touch (pressure) skin chemicals in the air nose Chemoreceptor chemicals in food tongue Thermoreceptor changes in temperature skin Aristo 16.1 16.2 16.3 16.4 ◄ 5 ► 16.1 Irritability Example of irritability in daily life detected by stimuli receptors hooting of the receptors in the boy’s ears approaching taxi Aristo 16.1 16.2 16.3 16.4 ◄ 6 ► 16.1 Irritability Example of irritability in daily life send nerve impulses (神經脈衝) to the brain coordinating systems receptors nervous system endocrine system the brain interprets the nerve impulses and produces the sensation (感覺) of hearing Aristo 16.1 16.2 16.3 16.4 ◄ 7 ► 16.1 Irritability Example of irritability in daily life send nerve impulses produce coordinating systems effectors responses (效應器) turn the boy’s head to look neck muscles at the source of the sound Aristo 16.1 16.2 16.3 16.4 ◄ 8 ► 16.1 Irritability Irritability is the ability of organisms to detect stimuli and produce appropriate responses. Aristo 16.1 16.2 16.3 16.4 ◄ 9 ► 16.2 Human eyes as the sense organs for detecting light The human eye Side view of the eye a spherical sense organ for detecting light situated in the orbit of the skull Aristo 16.1 16.2 16.3 16.4 ◄ 1 ► 16.2 Human eyes as the sense organs for detecting light The structures around the human eye Side view of the eye orbit encloses and protects all but the front of the eye Aristo 16.1 16.2 16.3 16.4 ◄ 2 ► 16.2 Human eyes as the sense organs for detecting light The structures around the human eye Side view of the eye eye muscles orbit attach the eyeball to the wall of the orbit Aristo 16.1 16.2 16.3 16.4 ◄ 3 ► 16.2 Human eyes as the sense organs for detecting light The structures around the human eye Side view of the eye eye muscles orbit contract and relax to allow the eyeball to rotate Aristo 16.1 16.2 16.3 16.4 ◄ 4 ► 16.2 Human eyes as the sense organs for detecting light The structures around the human eye Side view of the eye eye muscles optic nerve orbit leads to the brain Aristo 16.1 16.2 16.3 16.4 ◄ 5 ► 16.2 Human eyes as the sense organs for detecting light The structures around the human eye Front view of the eye eyebrow prevents sweat from entering the eye Aristo 16.1 16.2 16.3 16.4 ◄ 6 ► 16.2 Human eyes as the sense organs for detecting light The structures around the human eye Front view of the eye eyelashes trap dirt before it can enter the eye Aristo 16.1 16.2 16.3 16.4 ◄ 7 ► 16.2 Human eyes as the sense organs for detecting light The structures around the human eye Front view of the eye upper eyelid lower eyelid can close to protect the eye from foreign objects and strong light Aristo 16.1 16.2 16.3 16.4 ◄ 8 ► 16.2 Human eyes as the sense organs for detecting light The structures around the human eye Front view of the eye tear gland secretes tears : contain lysozyme which can kill bacteria keep the eye surface moist and clean Aristo 16.1 16.2 16.3 16.4 ◄ 9 ► 16.2 Human eyes as the sense organs for detecting light The structures around the human eye Front view of the eye drains tears to the nasal cavity tear duct Aristo 16.1 16.2 16.3 16.4 ◄ 10 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Outer layer sclera (鞏膜) cornea (角膜) Aristo 16.1 16.2 16.3 16.4 ◄ 11 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Outer layer sclera (鞏膜) a white, opaque, fibrous coat gives shape to the eyeball protects inner structures provides an attachment surface for eye muscles Aristo 16.1 16.2 16.3 16.4 ◄ 12 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Outer layer cornea (角膜) transparent to allows light to pass through refracts light into the eye Aristo 16.1 16.2 16.3 16.4 ◄ 13 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Middle layer choroid (脈絡膜) iris (虹膜) ciliary body (睫狀體) Aristo 16.1 16.2 16.3 16.4 ◄ 14 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Middle layer choroid (脈絡膜) contains blood vessels which supply nutrients to cells and remove wastes contains a black pigment which absorbs light to prevent the reflection of light in the eye Aristo 16.1 16.2 16.3 16.4 ◄ 15 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Middle layer a ring of muscular tissue that surrounds the edge of the lens contains ciliary muscles ciliary body (睫狀肌) which contract (睫狀體) and relax to change the shape of the lens Aristo 16.1 16.2 16.3 16.4 ◄ 16 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Middle layer lens (晶體) a transparent, elastic and biconvex structure consists of living cells refracts and focuses light onto the retina Aristo 16.1 16.2 16.3 16.4 ◄ 17 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Middle layer suspensory ligaments (懸韌帶) connect the lens to the ciliary body Aristo 16.1 16.2 16.3 16.4 ◄ 18 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Middle layer iris (虹膜) contains pigment which gives the eye its colour consists of circular muscles (環肌) and radial muscles (放射肌) Aristo 16.1 16.2 16.3 16.4 ◄ 19 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Middle layer central hole of the iris allows light to enter the pupil (瞳孔) eye size of the pupil and the amount of light entering the eye are controlled by circular muscles and radial muscles of the iris Aristo 16.1 16.2 16.3 16.4 ◄ 20 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye the colour of the iris varies among individuals Why does the pupil always appear black in colour? Aristo 16.1 16.2 16.3 16.4 ◄ 21 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Inner layer retina (視網膜) contains photoreceptors (light-sensitive cells) (感光細胞): rod cells (視桿細胞) and cone cells (視錐細胞) to detect light Aristo 16.1 16.2 16.3 16.4 ◄ 22 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye three layers of wall of the eyeball : Inner layer yellow spot (黃點) blind spot (盲點) Aristo 16.1 16.2 16.3 16.4 ◄ 23 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye yellow spot blind spot contains the region cone cells where the optic only nerve (視神經) leaves the eye contains no photoreceptors Aristo 16.1 16.2 16.3 16.4 ◄ 24 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye divided into two chambers anterior chamber posterior chamber Aristo 16.1 16.2 16.3 16.4 ◄ 25 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye divided into two chambers anterior chamber filled with aqueous humour (水狀液) : a clear, watery solution supplies nutrients and oxygen to the cornea and the lens Aristo 16.1 16.2 16.3 16.4 ◄ 26 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye divided into two chambers filled with vitreous humour (玻璃狀液) which is a clear jelly-like fluid posterior chamber Aristo 16.1 16.2 16.3 16.4 ◄ 27 ► 16.2 Human eyes as the sense organs for detecting light The internal structure of the human eye divided into two chambers anterior chamber the fluids inside both chambers can… maintain the shape of the eyeball refract and focus light posterior chamber Aristo 16.1 16.2 16.3 16.4 ◄ 28 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.1 Examination of a human eye model Procedure Examine a human eye model. Identify the various structures of the eye. Aristo 16.1 16.2 16.3 16.4 ◄ 29 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.1 optic nerve cornea eye muscle sclera Aristo 16.1 16.2 16.3 16.4 ◄ 30 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.1 iris pupil Aristo 16.1 16.2 16.3 16.4 ◄ 31 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.1 vitreous lens humour Aristo 16.1 16.2 16.3 16.4 ◄ 32 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.1 retina Aristo 16.1 16.2 16.3 16.4 ◄ 33 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video Dissection and examination of an ox eye In this practical, you will dissect an ox eye. An ox eye and the human eye have a similar overall structure. Aristo 16.1 16.2 16.3 16.4 ◄ 34 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video Dissection and examination of an ox eye By examining the anatomy of an ox eye, you can gain a better understanding of the structure and function of different parts of the eye. Aristo 16.1 16.2 16.3 16.4 ◄ 35 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video Procedure 1. Place an ox eye on a dissecting board. Examine the external structure of the eye. Locate and identify the eye muscles, the eyelashes, the eyelids (if still present), the sclera, the cornea and the optic nerve. Aristo 16.1 16.2 16.3 16.4 ◄ 36 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video 2. Remove the eyelids, the fat and the eye muscles around the eyeball with scissors. Be careful not to cut away the optic nerve. Wear a mask and disposable gloves. Scissors and scalpels are sharp. Handle them with care. Aristo 16.1 16.2 16.3 16.4 ◄ 37 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video 3. Make a small cut at the centre of the cornea with scalpel a scalpel. Then cut through the cornea twice diagonally with scissors. Note the liquid that flows cornea out when the cornea is cut open. This is the aqueous humour. Aristo 16.1 16.2 16.3 16.4 ◄ 38 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video 4. Spread out the four flaps of the cornea. Examine the iris and the pupil. pupil cornea iris Aristo 16.1 16.2 16.3 16.4 ◄ 39 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video 5. Cut through the iris and into the sclera to about half-way around the wall of the eye. pupil iris sclera Aristo 16.1 16.2 16.3 16.4 ◄ 40 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video 5. Locate and identify the lens, the suspensory ligaments, the ciliary body and the vitreous humour. lens suspensory ligament vitreous humour ciliary body iris Aristo 16.1 16.2 16.3 16.4 ◄ 41 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video Is it easy to cut through the sclera? Describe the texture of the sclera. No, it is not easy to cut through the sclera. The sclera is tough and strong. Aristo 16.1 16.2 16.3 16.4 ◄ 42 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video Compare the viscosity of the aqueous humour and the vitreous humour. The vitreous humour is more viscous than the aqueous humour./ The aqueous humour is more watery while the vitreous humour is more jelly-like. Aristo 16.1 16.2 16.3 16.4 ◄ 43 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video 6. Pick up the lens carefully with forceps and avoid making any scratches on the lens. Put it on a piece of newspaper with text printed on it. Observe what the text looks like through the lens. Squeeze the lens gently with your fingers and feel the texture of the lens. Aristo 16.1 16.2 16.3 16.4 ◄ 44 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video What is the shape of the lens? The lens is biconvex in shape. What do you observe when you look at the printed text through the lens? The printed text of the newspapers looks bigger through the lens. / The printed text is magnified. Aristo 16.1 16.2 16.3 16.4 ◄ 45 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video What is the texture of the lens when you squeeze it? The lens is elastic. Aristo 16.1 16.2 16.3 16.4 ◄ 46 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video 7. Empty out the jelly-like vitreous humour from the eyeball. Examine the retina and locate the blind spot. blind spot Aristo 16.1 16.2 16.3 16.4 ◄ 47 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video How can you locate the blind spot? The blind spot is located on the retina where the optical nerve leaves the eye. Aristo 16.1 16.2 16.3 16.4 ◄ 48 ► 16.2 Human eyes as the sense organs for detecting light Practical 16.2 Video 8. Lift up the retina with forceps and examine the choroid underneath. After the practical, dispose of the ox eye, the mask and the gloves as directed. collect the apparatus used for central sterilization by the technician. wash your hands thoroughly with soap and water. Aristo 16.1 16.2 16.3 16.4 ◄ 49 ► 16.2 Human eyes as the sense organs for detecting light How do we see? light rays from the object are refracted by… light ray from an object ❸ lens ❹ vitreous ❶ cornea humour ❷ aqueous humour Aristo 16.1 16.2 16.3 16.4 ◄ 50 ► 16.2 Human eyes as the sense organs for detecting light How do we see? focused on the retina to form an image retina Aristo 16.1 16.2 16.3 16.4 ◄ 51 ► 16.2 Human eyes as the sense organs for detecting light How do we see? object image on the retina The image formed on the retina is a real, vertically and laterally inverted image that is smaller than the object. Aristo 16.1 16.2 16.3 16.4 ◄ 52 ► 16.2 Human eyes as the sense organs for detecting light How do we see? light rays focused onto the retina stimulate the photoreceptors generate and send nerve impulses along the optic nerve to the visual centre of the brain Aristo 16.1 16.2 16.3 16.4 ◄ 53 ► 16.2 Human eyes as the sense organs for detecting light How do we see? the brain interprets the nerve impulses and produces vision upright image Aristo 16.1 16.2 16.3 16.4 ◄ 54 ► 16.2 Human eyes as the sense organs for detecting light What if the image is formed on the blind spot? layer of layers of neurones nerve fibres to image formed on the blind spot is photoreceptors not visible optic nerve cone cell rod cell no nerve impulses are choroid blind generated sclera spot X to brain No photoreceptors optic nerve blood vessels Aristo 16.1 16.2 16.3 16.4 ◄ 55 ► 16.2 Human eyes as the sense organs for detecting light Activity 16.1 Mini Lab Finding the blind spot There is a blind spot in each eye. Try this activity to find the blind spot in your right eye. Aristo 16.1 16.2 16.3 16.4 ◄ 56 ► 16.2 Human eyes as the sense organs for detecting light Activity 16.1 Mini Lab Hold your book at arm’s length. Close your left eye. Focus on the cross with your right eye and slowly move the book towards yourself. When the image of the dot falls on the blind spot, you will not see it. Aristo 16.1 16.2 16.3 16.4 ◄ 57 ► 16.2 Human eyes as the sense organs for detecting light ✗ No image is formed on the blind spot. ✓ An image is formed wherever incoming light rays meet on the retina, so it can be formed on the blind spot. However, images formed on the blind spot is not visible as there are no photoreceptors to detect light. Aristo 16.1 16.2 16.3 16.4 ◄ 58 ► 16.2 Human eyes as the sense organs for detecting light 1. Light rays that enter the eye are refracted by the cornea , the aqueous humour, the lens and the vitreous humour and focused retina on the. Aristo 16.1 16.2 16.3 16.4 ◄ 59 ► 16.2 Human eyes as the sense organs for detecting light 2. Photoreceptors detect light falling on them and send nerve impulses along the optic nerve to the visual centre of the brain. brain 3. The interprets the nerve impulses and vision produces. Aristo 16.1 16.2 16.3 16.4 ◄ 60 ► 16.2 Human eyes as the sense organs for detecting light Directions: Questions 1 and 2 refer to the diagram below, which shows a section of the human eye. 1 4 2 3 Aristo 16.1 16.2 16.3 16.4 ◄ 61 ► 16.2 Human eyes as the sense organs for detecting light 1. Refraction of light occurs at surface(s) A. 1. B. 1 and 3. C. 2 and 3. D. 1, 2 and 3. C Aristo 16.1 16.2 16.3 16.4 ◄ 62 ► 16.2 Human eyes as the sense organs for detecting light 2. Which of the following is/are the function(s) of structure 4? (1) to supply nutrients to the eyeball (2) to generate nerve impulses (3) to reduce reflection of light within the eye A. (1) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) B Aristo 16.1 16.2 16.3 16.4 ◄ 63 ► 16.2 Human eyes as the sense organs for detecting light What are rod cells and cone cells? rod cell cone cell Aristo 16.1 16.2 16.3 16.4 ◄ 64 ► 16.2 Human eyes as the sense organs for detecting light Comparison between rod cells and cone cells Rod cells Cone cells Shape rod-shaped cone-shaped Number more fewer Distribution evenly distributed most concentrated across the retina, at the yellow spot except at the yellow and none at the spot and blind spot blind spot Aristo 16.1 16.2 16.3 16.4 ◄ 65 ► 16.2 Human eyes as the sense organs for detecting light Comparison between rod cells and cone cells Rod cells Cone cells Sensitivity more sensitive less sensitive (presence of visual purple (視紫)) Stimulation by low light intensities by high light (work well under dim intensities light) (work well under bright light) Function black and white vision colour vision Aristo 16.1 16.2 16.3 16.4 ◄ 66 ► 16.2 Human eyes as the sense organs for detecting light Types of cone cells Blue Green Red cones cones cones 100 Sensitivity (percentage of light Each of the three types 75 of cone cells contains a different photosensitive absorbed) 50 pigment, which absorbs 25 light of different wavelengths, 0 corresponding roughly 380 450 500 550 600 650 700 750 to red, green and blue light. Wavelength of light (nm) Aristo 16.1 16.2 16.3 16.4 ◄ 67 ► 16.2 Human eyes as the sense organs for detecting light Types of cone cells the colours we see depend on the relative stimulation of the three types of cone cells Red Green Blue Colour we cone cells cone cells cone cells see ✔ red ✔ green ✔ blue ✔ ✔ yellow Aristo 16.1 16.2 16.3 16.4 ◄ 68 ► 16.2 Human eyes as the sense organs for detecting light Types of cone cells the colours we see depend on the relative stimulation of the three types of cone cells Red Green Blue Colour we cone cells cone cells cone cells see ✔ ✔ cyan ✔ ✔ magenta ✔ ✔ ✔ white black Aristo 16.1 16.2 16.3 16.4 ◄ 69 ► 16.2 Human eyes as the sense organs for detecting light 1. Rod cells can function in dim light and are responsible for black and white vision. 2. Cone cells function well in bright light and are colour responsible for vision. Aristo 16.1 16.2 16.3 16.4 ◄ 70 ► 16.2 Human eyes as the sense organs for detecting light Worked example 16.1 Figure 1 shows a horizontal section of the left eye. side of the head centre of the head 80° 80° 60° 60° 40° Y 40° 20° 20° X Figure 1 Aristo 16.1 16.2 16.3 16.4 ◄ 71 ► 16.2 Human eyes as the sense organs for detecting light Worked example 16.1 Figure 2 shows the densities of the two types of photoreceptors (rod cells and cone cells) in the X retina. 160,000 Number of photoreceptors rod cells 120,000 per mm2 80,000 40,000 cone cells 0 80° 60° 40° 20° 0° 20° 40° 60° 80° Figure 2 Y Aristo 16.1 16.2 16.3 16.4 ◄ 72 ► 16.2 Human eyes as the sense organs for detecting light Worked example 16.1 Use the information from Figures 1 and 2 to explain the following: (a) A person cannot see an object if its image falls on area X. (2 marks) Since there are no photoreceptors in area X, (1) no nerve impulses are generated to stimulate the visual centre of the brain. (1) Therefore, the image falling on area X cannot be seen. Aristo 16.1 16.2 16.3 16.4 ◄ 73 ► 16.2 Human eyes as the sense organs for detecting light Worked example 16.1 Use the information from Figures 1 and 2 to explain the following: (a) A person cannot see an object if its image falls on area X. (2 marks) No marks can be scored by simply stating that ‘X is the blind spot’ without reference to the distribution of photoreceptors. Aristo 16.1 16.2 16.3 16.4 ◄ 74 ► 16.2 Human eyes as the sense organs for detecting light Worked example 16.1 (b) It is easier to see a faint star if you look slightly to the side rather than looking directly at it. (4 marks) When looking slightly to the side of the star, its image falls on the periphery of the retina which has a higher density of rod cells than the central area. (1) Rod cells are stimulated by dim light to generate nerve impulses, so the star can be seen. (1) Aristo 16.1 16.2 16.3 16.4 ◄ 75 ► 16.2 Human eyes as the sense organs for detecting light Worked example 16.1 (b) It is easier to see a faint star if you look slightly to the side rather than looking directly at it. (4 marks) When looking directly at the star, its image falls on Y where there are only cone cells, no rod cells. (1) The light from the faint star is too weak to stimulate cone cells. (1) Aristo 16.1 16.2 16.3 16.4 ◄ 76 ► 16.2 Human eyes as the sense organs for detecting light Worked example 16.1 (b) It is easier to see a faint star if you look slightly to the side rather than looking directly at it. (4 marks) Rod cells are much more sensitive to light than cone cells, and can respond to lower light intensities. Aristo 16.1 16.2 16.3 16.4 ◄ 77 ► 16.2 Human eyes as the sense organs for detecting light How to control the amount of light entering the eye 1. In dim light Side view Front view radial muscles contract iris pupil dilates circular muscles relax Aristo 16.1 16.2 16.3 16.4 ◄ 78 ► 16.2 Human eyes as the sense organs for detecting light How to control the amount of light entering the eye 1. In dim light Side view stimulation of the photoreceptors to see in dim light more light enter the eye Aristo 16.1 16.2 16.3 16.4 ◄ 79 ► 16.2 Human eyes as the sense organs for detecting light How to control the amount of light entering the eye 2. In bright light Side view Front view radial muscles relax iris pupil constricts circular muscles contract Aristo 16.1 16.2 16.3 16.4 ◄ 80 ► 16.2 Human eyes as the sense organs for detecting light How to control the amount of light entering the eye 2. In bright light Side view prevents damage to the photoreceptors reduce amount of light enter the eye Aristo 16.1 16.2 16.3 16.4 ◄ 81 ► 16.2 Human eyes as the sense organs for detecting light ✗ When bright light shines into the eye, the pupil contracts. ✓ The pupil is a hole and cannot contract. It can only be constricted or dilated by the iris muscles. Aristo 16.1 16.2 16.3 16.4 ◄ 82 ► 16.2 Human eyes as the sense organs for detecting light 1. The circular muscles and the radial muscles of the iris can change the size of the pupil , thereby controlling the amount of light entering the eye. contract 2. In dim light, the radialrelax muscles and dilates the circular muscles. The pupil to increase the amount of light entering the eye. Aristo 16.1 16.2 16.3 16.4 ◄ 83 ► 16.2 Human eyes as the sense organs for detecting light 3. In bright light, the circular muscles contract and the radical muscles relax. The pupil constricts to reduce the amount of light entering the eye. Aristo 16.1 16.2 16.3 16.4 ◄ 84 ► 16.2 Human eyes as the sense organs for detecting light The graph below shows the changes in the diameter of the pupil of a person’s eye during a period of 30 seconds. pupil diameter X 0 10 20 30 time (s) Aristo 16.1 16.2 16.3 16.4 ◄ 85 ► 16.2 Human eyes as the sense organs for detecting light Which of the following combinations correctly states the change in light intensity and the type of iris muscles that begins to contract at X? Light intensity Iris muscles contracting A. increases circular muscles B. increases radical muscles C. decreases circular muscles D. decreases radical muscles D Aristo 16.1 16.2 16.3 16.4 ◄ 86 ► 16.2 Human eyes as the sense organs for detecting light What is eye accommodation? near require object more refraction divergent light rays distant object require less refraction parallel light rays Aristo 16.1 16.2 16.3 16.4 ◄ 87 ► 16.2 Human eyes as the sense organs for detecting light What is eye accommodation? adjust the amount of refraction require of light to focus light rays on the more retina refraction eye accommodation (視覺調節) by changing the require curvature of the elastic less lens of the eye refraction Aristo 16.1 16.2 16.3 16.4 ◄ 88 ► 16.2 Human eyes as the sense organs for detecting light How to focus on a near object 1 2 circular ciliary tension in suspensory muscles contract ligaments decreases 4 light rays light rays from focused on a near object the retina 3 lens becomes thicker due to its elasticity and refracts light more Aristo 16.1 16.2 16.3 16.4 ◄ 89 ► 16.2 Human eyes as the sense organs for detecting light How to focus on a distant object 1 2 circular ciliary tension in suspensory muscles relax ligaments increases 4 light rays from light rays a distant object focused on the retina 3 lens becomes thinner shape and refracts light less Aristo 16.1 16.2 16.3 16.4 ◄ 90 ► 16.2 Human eyes as the sense organs for detecting light 1. Eye accommodation refers to changing the shape of the lens to focus on objects at different distances. Aristo 16.1 16.2 16.3 16.4 ◄ 91 ► 16.2 Human eyes as the sense organs for detecting light 2. When focusing on a near object, the circular ciliary muscles contract ; the tension in the suspensory ligaments decreases ; the lens more becomes thicker ( convex) and light is refracted more. Aristo 16.1 16.2 16.3 16.4 ◄ 92 ► 16.2 Human eyes as the sense organs for detecting light 3. When focusing on a distant object, the circular ciliary muscles relax ; the tension of the suspensory ligaments increases ; the lens less become thinner ( convex) and light is refracted less. Aristo 16.1 16.2 16.3 16.4 ◄ 93 ► 16.2 Human eyes as the sense organs for detecting light HKDSEE Biology 2015 Paper 1 Section A Q27 (Refer to p.16-19) C Aristo 16.1 16.2 16.3 16.4 ◄ 94 ► 16.2 Human eyes as the sense organs for detecting light Eye defects short sight (近視) long sight (遠視) colour blindness (色盲) Aristo 16.1 16.2 16.3 16.4 ◄ 95 ► 16.2 Human eyes as the sense organs for detecting light What is short sight and its correction? see near objects more clearly than distant objects causes of short sight: eyeball is too long lens is too thick Aristo 16.1 16.2 16.3 16.4 ◄ 96 ► 16.2 Human eyes as the sense organs for detecting light What is short sight and its correction? Focusing on a distant object light rays from a distant object light rays focused in Blurred image front of the retina Aristo 16.1 16.2 16.3 16.4 ◄ 97 ► 16.2 Human eyes as the sense organs for detecting light What is short sight and its correction? Correction by wearing a concave lens light rays from a distant object diverged by a concave lens concave lens light rays focused on the retina Aristo 16.1 16.2 16.3 16.4 ◄ 98 ► 16.2 Human eyes as the sense organs for detecting light What is short sight and its correction? People with severe short sight have a higher risk for retinal detachment. This happens as the eyeball continues to lengthen, pulling the retina away from the choroid. Aristo 16.1 16.2 16.3 16.4 ◄ 99 ► 16.2 Human eyes as the sense organs for detecting light What is long sight and its correction? see distant objects more clearly than near objects causes of long sight: eyeball is too short lens is too thin Aristo 16.1 16.2 16.3 16.4 ◄ 100 ► 16.2 Human eyes as the sense organs for detecting light What is long sight and its correction? Focusing on a near object light rays from a near object light rays focused behind the retina Aristo 16.1 16.2 16.3 16.4 ◄ 101 ► 16.2 Human eyes as the sense organs for detecting light What is long sight and its correction? Correction by wearing a convex lens light rays from a near object converged by a convex lens light rays focused on the retina convex lens Aristo 16.1 16.2 16.3 16.4 ◄ 102 ► 16.2 Human eyes as the sense organs for detecting light What is long sight and its correction? Note the following when drawing ray diagrams: Use solid straight lines to present the light rays that enter the eyes and reach the retina. Light rays behind the retina should be drawn with dotted lines until they intersect. Light rays from a distant object should be parallel and the object should not be drawn. Light rays from a near object should be diverging from a single point. Arrowheads should be added to the light rays to indicate the direction in which the light is travelling. Aristo 16.1 16.2 16.3 16.4 ◄ 103 ► 16.2 Human eyes as the sense organs for detecting light What is colour blindness? inability to distinguish some or all colours due to the poor functioning or a deficiency of one or more types of cone cells an inherited eye defect no cure Aristo 16.1 16.2 16.3 16.4 ◄ 104 ► 16.2 Human eyes as the sense organs for detecting light What is colour blindness? e.g. red-green colour blindness cannot distinguish red and green poor functioning or a deficiency of red or green cone cells normal colour vision red-green colour blindness Aristo 16.1 16.2 16.3 16.4 ◄ 105 ► 16.2 Human eyes as the sense organs for detecting light 1. In short sight, the eyeball is too long or the lens is too thick , resulting in the image of distant objects being focused in front of the retina. It can be corrected by wearing concave lenses. Aristo 16.1 16.2 16.3 16.4 ◄ 106 ► 16.2 Human eyes as the sense organs for detecting light 2. In long sight, the eyeball is too short or the lens is too thin , resulting in the image of near objects being focused behind the retina. convex It can be corrected by wearing lenses. Aristo 16.1 16.2 16.3 16.4 ◄ 107 ► 16.2 Human eyes as the sense organs for detecting light 3. In colour blindness, one or more of the three types of cone cells function poorly or are deficient. There is no cure for colour blindness. Aristo 16.1 16.2 16.3 16.4 ◄ 108 ► 16.2 Human eyes as the sense organs for detecting light A person suffers from colour blindness and is unable to focus on distant objects. Which of the following can explain his conditions? A. deficiency of visual purple; lens too thick B. deficiency of visual purple; eyeball too short C. deficiency of cone cells; lens too thin D. deficiency of cone cells; eyeball too long C Aristo 16.1 16.2 16.3 16.4 ◄ 109 ► 16.3 Human ears as the sense organs for detecting sound The human ears sense organs for detecting sound Aristo 16.1 16.2 16.3 16.4 ◄ 1 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the human ear? auditory canal ear bones semicircular auditory canals nerve pinna cochlea oval window round window ear drum Eustachian tube outer ear middle ear inner ear (外耳) (中耳) (內耳) Aristo 16.1 16.2 16.3 16.4 ◄ 2 ► 16.3 Human ears as the sense organs for detecting sound Practical 16.3 Examination of a human ear model Procedure Examine a human ear model. Identify the various structures of the ear. Aristo 16.1 16.2 16.3 16.4 ◄ 3 ► 16.3 Human ears as the sense organs for detecting sound Practical 16.3 eustachian tube pinna auditory canal ear drum Aristo 16.1 16.2 16.3 16.4 ◄ 4 ► 16.3 Human ears as the sense organs for detecting sound Practical 16.3 auditory semicirular nerve canals ear bones cochlea Aristo 16.1 16.2 16.3 16.4 ◄ 5 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the outer ear? pinna a flap of elastic (耳殼) cartilage covered with skin collects sound waves Aristo 16.1 16.2 16.3 16.4 ◄ 6 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the outer ear? auditory canal (聽道) a passageway for sound from the pinna to the eardrum Aristo 16.1 16.2 16.3 16.4 ◄ 7 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the outer ear? thin, elastic membrane separates the outer ear from the middle ear converts sound eardrum waves into (耳膜) mechanical vibrations Aristo 16.1 16.2 16.3 16.4 ◄ 8 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the middle ear? an air-filled cavity ear bones (聽小骨) three ear bones amplify and transmit the vibrations from the eardrum to the oval window (卵圓窗) separating the middle ear from middle the inner ear ear Aristo 16.1 16.2 16.3 16.4 ◄ 9 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the middle ear? flexible membrane separating the middle ear from the oval window inner ear transmits vibrations from the ear bones to the inner ear middle ear Aristo 16.1 16.2 16.3 16.4 ◄ 10 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the middle ear? flexible membrane allow the release of pressure in the cochlea round window (圓窗) middle ear Aristo 16.1 16.2 16.3 16.4 ◄ 11 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the middle ear? connects the middle ear to the pharynx equalizes the air pressure on both sides of the eardrum Eustachian tube (耳咽管) middle ear Aristo 16.1 16.2 16.3 16.4 ◄ 12 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the inner ear? semicircular canals (半規管) fluid-filled tubes detect head movements and help us have a sense of balance inner ear Aristo 16.1 16.2 16.3 16.4 ◄ 13 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the inner ear? auditory nerve (聽神經) transmits nerve impulses to the auditory centre of the brain inner ear Aristo 16.1 16.2 16.3 16.4 ◄ 14 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the inner ear? semicircular auditory canals nerve a tube coiled into a spiral shape cochlea separated by (耳蝸) membranes into three liquid-filled canals for hearing inner ear Aristo 16.1 16.2 16.3 16.4 ◄ 15 ► 16.3 Human ears as the sense organs for detecting sound Cochlea upper canal filled with perilymph (外淋巴) central canal filled with endolymph (內淋巴) lower canal filled with perilymph auditory nerve Aristo 16.1 16.2 16.3 16.4 ◄ 16 ► 16.3 Human ears as the sense organs for detecting sound Cochlea the movements of the endolymph cause the hairs of membrane the sensory hair hair cells (感覺毛細胞) to bend sensory hair cell Aristo 16.1 16.2 16.3 16.4 ◄ 17 ► 16.3 Human ears as the sense organs for detecting sound What is the structure of the human ear? the sensory hair cells are stimulated send nerve impulses membrane along the auditory hair nerve to the auditory centre of the brain to auditory nerve sensory hair cell Aristo 16.1 16.2 16.3 16.4 ◄ 18 ► 16.3 Human ears as the sense organs for detecting sound How do we hear? 1 1 the pinna collects sound waves into the auditory canal Aristo 16.1 16.2 16.3 16.4 ◄ 19 ► 16.3 Human ears as the sense organs for detecting sound How do we hear? 2 2 the sound waves cause the eardrum to vibrate Aristo 16.1 16.2 16.3 16.4 ◄ 20 ► 16.3 Human ears as the sense organs for detecting sound How do we hear? 3 3 the ear bones amplify and transmit the vibrations from the eardrum to the oval window Aristo 16.1 16.2 16.3 16.4 ◄ 21 ► 16.3 Human ears as the sense organs for detecting sound How do we hear? 4 4 the oval window vibrates and causes wave movements of the perilymph in the upper canal of the cochlea Aristo 16.1 16.2 16.3 16.4 ◄ 22 ► 16.3 Human ears as the sense organs for detecting sound How do we hear? 5 5 the wave movements are transmitted to the endolymph in the central canal Aristo 16.1 16.2 16.3 16.4 ◄ 23 ► 16.3 Human ears as the sense organs for detecting sound How do we hear? 6 6 sensory hair cells are stimulated to generate and send nerve impulses Aristo 16.1 16.2 16.3 16.4 ◄ 24 ► 16.3 Human ears as the sense organs for detecting sound How do we hear? 7 7 nerve impulses travel along the auditory nerve to the auditory centre of the brain to produce the sensation of hearing Aristo 16.1 16.2 16.3 16.4 ◄ 25 ► 16.3 Human ears as the sense organs for detecting sound 1. The pinna of the outer ear collects and directs sound waves along the auditory canal to the eardrum, which converts sound waves to mechanical vibrations. amplify 2. In the middle transmit ear, the ear bones and the vibrations from the eardrum to oval window the. Aristo 16.1 16.2 16.3 16.4 ◄ 26 ► 16.3 Human ears as the sense organs for detecting sound 3. Vibrations of the oval window cause wave movement of the liquids in the cochlea. 4. Movement of the endolymph cause the hairs of sensory hair cells bend the in the cochlea to ; sensory hair cells nerve impulses are stimulated to send auditory nerve along the to the brain. Aristo 16.1 16.2 16.3 16.4 ◄ 27 ► 16.3 Human ears as the sense organs for detecting sound 5. Nerve impulses are interpreted by the brain to produce the sensation of hearing. Aristo 16.1 16.2 16.3 16.4 ◄ 28 ► 16.3 Human ears as the sense organs for detecting sound HKDSEE Biology 2013 Paper 1 Section A Q29 (Refer to p.16-29) C Aristo 16.1 16.2 16.3 16.4 ◄ 29 ►  16. Phototropic responses in plants 4 Irritability in plants plants can detect stimuli (e.g. light and water) respond by growing certain parts of their body (e.g. shoots and roots) Tropism (向性) Aristo 16.1 16.2 16.3 16.4 0  16. Phototropic responses in plants 4 Irritability in plants grows towards the stimulus positive response grows away from the stimulus negative response Aristo 16.1 16.2 16.3 16.4 0  16. Phototropic responses in plants 4 How do plants response to light? Phototropism (向光性) the directional growth movement of a plant part in response to unilateral light (i.e. light coming from one direction only) Aristo 16.1 16.2 16.3 16.4 0  16. Phototropic responses in plants 4 Practical 16.4 Vide o Investigation of the phototropic responses of shoots and roots Procedure. Set up the apparatus as shown below. Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Practical 16.4 Vide o light- proof box shoot light light cardboard root light light culture solution rotating stand clinostat Set-up A Set-up B Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Practical 16.4 Vide o Why are slits made on one side of the light- proof boxes? To provide unilateral light to the seedlings inside the boxes. Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Practical 16.4 Vide o Which set-up is the control? Explain its use in this investigation. Set-up B is the control. The rotation of clinostat cancels out the effect of unilateral light on the shoots and roots of the seedlings. This is to show that any changes in the appearance of the seedlings in the experimental set-up (set-up A) are due to unilateral light. Aristo 16.1 16.2 16.3 16.4 0  16. Phototropic responses in plants 4 Practical 16.4 Vide o 1. Observe and record how the seedlings have grown in the two set-ups after two days. Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Practical 16.4 Vide o Results Appearance of the seedlings Set-up Shoots Roots A bend towards light bend away from light grow vertically grow vertically B upwards downwards Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Practical 16.4 Vide o Discussion In set-up A, the seedlings are subjected to unilateral light. The shoots grow towards the light source, and the roots grow away from it. In set-up B, the effect of unilateral light is cancelled out by the rotation of the clinostat, and so the seedlings are equally illuminated on all sides. The shoots grow vertically upwards, and the roots grow vertically downwards. Aristo 16.1 16.2 16.3 16.4 0  16. Phototropic responses in plants 4 How do shoots response to light? positively phototropic growing towards unilateral light to obtain the maximum amount of light for photosynthesis Aristo 16.1 16.2 16.3 16.4 0  16. Phototropic responses in plants 4 How do roots response to light? negatively phototropic growing away from unilateral light ensures the roots grow downwards into the soil for anchorage Aristo 16.1 16.2 16.3 16.4 0  16. Phototropic responses in plants 4 Phototropism investigation a coleoptile is a protective sheath that covers the first leaf of a monocotyledonous seedling coleoptile coleoptile first leaf first leaf grain fast-growing easy to handle have simple structure for observation Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation Charles Darwin’s experiment coleoptile with opaque bending growth in the tip removed coverings region below the tip ligh t a b c d a b c d start results Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation unilateral light was detected by the tip of the coleoptiles ligh t a b c d a b c d start results Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation bending growth occurs in the region below the tip ligh t a b c d a b c d start results Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation some kind of signal must be transmitted from the tip to the lower part of the coleoptile ligh t a b c d a b c d start results Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation Boysen-Jensen’s experiment 1 a tip placed back on agar block b mica plate inserted below the tip ligh ligh t t agar mica block plate start start Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation Chemicals can diffuse through the agar block but not the mica plate. ligh ligh t t agar mica block plate start start Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation grew and bent towards the light no change a tip placed back on agar block b mica plate inserted below the tip ligh ligh t t agar mica block plate chemical signal is transmitted from the tip to the lower start result part of the coleoptiles start result Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation Boysen-Jensen’s experiment 2 a mica plate inserted on b mica plate inserted illuminated side on shaded side ligh ligh t t start produced the chemical result start result by the tip passes down the shaded side of the coleoptile Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation Frits Went ’s experiment 1 In darkness tip removed tip allowed to stand on agar block for several hours agar block Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation agar block Conclusion 1: the agar block contained the chemical produced by the tip of the coleoptile Conclusion 2: this chemical stimulated start result growth as it passed down a agar block placed on the decapitated coleoptile decapitated coleoptile Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation agar block Conclusion 3: higher concentration of the growth-promoting chemical on the one side causes bending on the other side start result b agar block placed on one side of decapitated coleoptile Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation Frits Went ’s experiment 2 X X Y Y ligh t X Y start result start result In darkness Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 Phototropism investigation shaded side had unilateral light had caused an a higher uneven distribution of the concentration chemical X X Y Y of the chemical ligh t X Y start result start result named as auxin (⽣長素) In darkness Aristo 16.1 16.2 16.3 16.4 0  16. Phototropic responses in plants 4 What are auxins? a group of plant hormones produced in the apical meristem at the tip of shoots and roots are then transported to the regions of elongation stimulate the cells to elongate promote growth Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 What are the effects of auxins on shoots and roots? 200 promote root growth but insufficient for shoot growth Percentage 150 shoots stimulation of growth (%) 100 roots 50 0 Percentage inhibition of 50 growth (%) 100 10- 10- 10- 10- 10- 10- 1 10 102 103 104 6 5 Concentration 4 3 of auxins 2 1(parts per million, ppm) Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 What are the effects of auxins on shoots and roots? 200 Percentage 150 promote both root and shoot growth shoots stimulation of growth (%) 100 roots 50 0 Percentage inhibition of 50 growth (%) 100 10- 10- 10- 10- 10- 10- 1 10 102 103 104 6 5 Concentration 4 3 of auxins 2 1(parts per million, ppm) Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 What are the effects of auxins on shoots and roots? 200 Percentage 150 shoots stimulation of growth (%) 100 inhibit root growth while roots promote shoot growth 50 0 Percentage inhibition of 50 growth (%) 100 10- 10- 10- 10- 10- 10- 1 10 102 103 104 6 5 Concentration 4 3 of auxins 2 1(parts per million, ppm) Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 What are the effects of auxins on shoots and roots? 200 Percentage 150 shoots stimulation of growth (%) 100 inhibit both shoot and root growth roots 50 0 Percentage inhibition of 50 growth (%) 100 10- 10- 10- 10- 10- 10- 1 10 102 103 104 6 5 Concentration 4 3 of auxins 2 1(parts per million, ppm) Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 What is the mechanism of phototropic responses? light from all directions evenly the shoot auxins distribution grows shoot of auxins straight up root auxins the root grows auxins are produced in the straight shoot tip and root tip down Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 What is the mechanism of phototropic responses? high auxin concentration stimulates shoot growth: on the shaded side the shaded side grows faster the shoot bends towards the light auxins unilateral unilateral light light shoot root auxins inhibits root growth: auxins are produced in the the shaded side grows more slowly shoot tip and root tip the root bends away from the light Aristo 16.1 16.2 16.3 16.4 0  16. Phototropic responses in plants 4. Phototropism is the directional growth movement of a plant part in response to unilateral light. Shoots are positively phototropic while roots are negatively phototropic. Aristo 16.1 16.2 16.3 16.4 0  16. Phototropic responses in plants 4. Phototropism is controlled by auxins. Auxins are produced in the apical meristems at shoot tips and root tips, and are transported to the regions of elongation where they affect growth. 3. High concentrations of auxins promote shoot growthinhibit but root growth. Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 1. HKDSEE Biology 2012 Paper 1 Section A Q30 (Refer to p.16-38) C Aristo 16.1 16.2 16.3 16.4 0 16. Phototropic responses in plants 4 2. HKDSEE Biology 2014 Paper 1 Section A Q36 (Refer to p.16-38) C Aristo 16.1 16.2 16.3 16.4 0