Chapter 1: Stimuli and Responses PDF

THEME 1 Maintenance and Continuity of Life Humans, animals and plants depend on stimuli and responses for survival. Name the organs or parts involved in the stimuli and responses based on the photographs shown. Why...

THEME 1 Maintenance and Continuity of Life Humans, animals and plants depend on stimuli and responses for survival. Name the organs or parts involved in the stimuli and responses based on the photographs shown. Why is it healthier for us to exercise during the day than at night? 1 Chapter Cha Chapter Chapte hapte apte ter te er Stimuli and 11 Responses What do you know about the human nervous system? How are stimuli related to responses in humans? How are stimuli related to responses in plants? What is the importance of responses to stimuli in animals? Let’s study Human nervous system Stimuli and responses in humans Stimuli and responses in plants Importance of responses to stimuli in animals 2  Science Gallery Loudspeaker Time measuring device The sprint event in international sports competitions such as the Olympics uses loudspeakers and time measuring devices as shown in the above photograph. The time measuring device measures the time interval between the sound from the loudspeaker and the first push exerted by the runner’s foot against the time measuring device. This time interval is known as the reaction time. In the 100 m sprint event at the 2016 Olympics, the reaction time of the gold medal winner, Usain Bolt, was 0.155 s. If the measured reaction time of a runner is less than 0.1 s, the runner will be disqualified from competing. Why? Keywords Stimulus Voluntary action Hydrotropism Response Involuntary action Thigmotropism Spinal cord Photoreceptor Nastic movement Peripheral nerve Taste bud Stereoscopic vision Affector Optical illusion Monocular vision Effector Geotropism Stereophonic hearing 3  1.1 Human Nervous System In a game of badminton… 2 The brain interprets the impulse, estimates the speed 1 The movement of of the shuttlecock and determines the direction and the shuttlecock the pattern of body serves as a stimulus movement. that is detected by the eye. An impulse is triggered and 3 The brain then sends sent to the brain. impulses to the hand and leg muscles to respond. The human nervous system is an important control system in body coordination. Other than sight, thinking and body movement, the human nervous system also controls and coordinates organ functions in the body and maintains a balanced internal environment through a process. What is this process? Structure of the Human Nervous System Look at Figure 1.1. The human nervous system consists of: Brain Cranial nerves Peripheral nervous Central system nervous Spinal nerves system Spinal cord Peripheral nervous system consists of: t

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nerves connecting the brain to the sensory and internal 5 organs *( t

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: nerves connecting the spinal cord to the , skeletal muscles. 7( Figure 1.1 Human nervous system 4 1.1.1  Chapter 1: Stimuli and Responses Functions of the Human Nervous System The human nervous system controls and coordinates organs and parts of the body. The human nervous system: detects stimuli sends information in the form of impulses interprets impulses produces appropriate responses Photographs 1.1, 1.2 and 1.3 show examples of daily activities that involve detection of stimuli and production of responses to the stimuli detected. State the stimulus and response in each of the daily activities shown. Photograph 1.1 Collecting garbage Photograph 1.2 Sneezing Photograph 1.3 Surfing the Internet 1.1.1 5 Voluntary and Involuntary Actions The responses of the human body to stimuli can be divided into voluntary actions and involuntary actions. Observe the examples of responses of the human body in Figure 1.2. RAFIQ (a) Reading a book (b) Withdrawing hand from (c) Peristalsis in oesophagus a hot object Figure 1.2 Examples of responses of the human body Based on Figure 1.2, which response is a voluntary action and which is an involuntary action? Voluntary Actions Voluntary actions are conscious actions and conducted under one’s will. All voluntary actions are controlled by the brain. Examples of voluntary actions include reading, writing, speaking, eating, drinking, walking, running and exercising. Figure 1.3 shows the pathway of impulse in a voluntary action. Affector (receptor) Stimulus ne r v in human ear e im puls e Phone rings e puls e im Effector ne r v Response (muscle or gland) Brain Touch the screen Direction of the pathway of impulse from the affector (receptor) to the effector Figure 1.3 Pathway of impulse in a voluntary action Let us learn more on voluntary actions by carrying out Activity 1.1 on page 7. 6 1.1.2  Chapter 1: Stimuli and Responses Activity 1.1 Inquiry-based activity Measuring the reaction time by catching a free-falling ruler (voluntary action) Aim: To measure reaction time Apparatus Half metre rule Instructions 1. Work with a partner. 2. Ask your partner to hold the end of a half metre rule as shown in Figure 1.4. Safety 30 Precautions 50 48 46 44 40 42 38 Make sure that the hand used 36 34 32 30 to catch the ruler remains 28 26 24 stationary on the table. 22 18 20 16 Be careful when releasing or 14 12 10 catching the ruler. 8 6 4 2 0 Table Figure 1.4 3. Place your hand at the end of the ruler close to the zero mark without touching it as shown in Figure 1.4. 4. Your partner will release the ruler without warning and you must try to catch the ruler as quickly as possible. 5. Record the distance the ruler fell, x, that is, the scale on the ruler when you catch it. The distance, x, is the measurement of your reaction time. 6. Repeat this activity four times. Then, calculate the average distance, xaverage. Questions 1. In this activity, state the stimulus and its response. Is the response a voluntary action or an involuntary action? Explain. 2. Why is the distance the ruler fell considered as the reaction time? 3. Explain the difference in the reaction time among the students in the class. 4. What is the importance of reaction time in our daily life? Conclusion Draw a conclusion on the reaction time of the students in your class. 1.1.2 7  Involuntary Actions SCIENCE INFO Involuntary actions are actions that occur immediately without conscious control or prior thoughts. Involuntary actions can be classified into two. Involuntary actions Medulla oblongata Involving medulla Involving spinal cord Spinal cord oblongata (reflex actions) Heartbeat Withdrawing hand Breathing when it accidentally touches a hot object Peristalsis Withdrawing foot when it accidentally steps on a sharp object Secretion of saliva Sneezing when dust enters the nose Affector (receptor) Hot object Spinal cord Effector Direction of impulse Direction of impulse from the affector (receptor) to the effector Figure 1.5 Pathway of impulse in an involuntary action (reflex action) Let us learn more on involuntary actions by carrying out Activity 1.3 on page 9. Activity 1.2 To create a presentation on: the parts involved in the transmission of impulse from the affector ICS to the effector Innovation- based activity the pathway of impulses in voluntary and involuntary actions Instructions 1. Work in groups. 2. Each group is required to create a presentation to illustrate the following: The parts involved in the transmission of impulse from the affector to the effector The pathway of impulses in voluntary and involuntary actions 8 1.1.2  Chapter 1: Stimuli and Responses Activity 1.3 Inquiry-based activity Detecting changes in the size of the pupil in the eye towards light intensity (involuntary action) Aim: To observe changes in the size of the pupil of the eye towards different light intensities Apparatus Mirror and lamp Instructions 1. Identify the pupil of the eye in Figure 1.6. Pupils Figure 1.6 2. Observe the pupil using a mirror in bright light. Sketch the size of the pupil. 3. Observe the pupil in dim light. Sketch the size of the pupil. 4. Compare and contrast the size of the pupils in bright and dim lights. Questions 1. In this activity, state the stimulus and its response. Is the response a voluntary or an involuntary action? Explain. 2. What is the relationship between the size of the pupil and light intensity? 3. What is the importance of this response? Conclusion Draw a conclusion about the changes in the size of the pupil towards light intensity. SCIENCE INFO The pupil in the human an eye is circular. Is the pupil in other animals’ an eye circular as well? (a) Goat: (b) Stingray: (c) Crocodile: (d) Squid: Rectangular Crescent Vertical slit W-shaped 1.1.2 9  BRAIN Importance of the Network of Human TEASER Nervous System in Daily Life Other than the nervous system, The network of the human nervous system controls and what other body systems help in body and internal organ coordinates the organs and parts of the body to carry movements? out processes in the body such as breathing and body movements. A damaged nervous system normally causes a person to become temporarily, partially or completely paralysed. For example, if the nerves in the muscles of a leg or hand - Science, Technology, Engineering, Mathematics are injured, the person will face difficulty in moving his leg or hand. In the case of a more serious problem, he might Humanoid robot have to depend on machines to carry out his physiological 5 processes such as breathing or heart beating. *( : Humans are blessed with a nervous system, so they should use and take good care of it. ,.      7( Photograph 1.4 Partially- Photograph 1.5 Patient using a breathing paralysed individual machine Formative Practice 1.1 1. State two main parts of the human nervous system. 2. (a) What is voluntary action? Give one example of a voluntary action. (b) What is involuntary action? Give one example of an involuntary action. 3. What happens if a person has brain injury? 4. What is the importance of the network of human nervous system in life? 10 1.1.3  Chapter 1: Stimuli and Responses 1.2 Stimuli and Responses in Humans Humans face constant changes in surroundings. These changes are called stimuli. Examples of stimuli include light, sound and chemical substances. Humans use their sensory organs to detect stimuli. Humans have five sensory organs: eyes, ears, nose, skin and tongue as shown in Photograph 1.6. Which sensory organ is the largest? Eyes (sense of sight) Ear (sense of hearing) Nose (sense of smell) Tongue (sense of taste) Skin (sense of touch) Photograph 1.6 Human sensory organs Eye Study Figure 1.7. Can you identify the parts of the eye? Let us learn more about the parts of the eye by referring to Figure 1.8 on page 12. Sclera Iris Pupil Figure 1.7 Front view of the eye 1.2.1 11  Ciliary muscle Eye lens Sclera Choroid 12 Muscle that changes Transparent and Strong layer that maintains Black layer that prevents the thickness of the elastic convex the shape of the eye reflection of light in the eye and eye lens through lens which and protects it. supplies oxygen and nutrients Suspensory contractions focuses light to the eye. ligaments and relaxations. onto the retina. Strong fibres which hold the Retina eye lens in its Layer containing position. photoreceptors which detects light and produces nerve impulses. Cornea Transparent layer which refracts and Yellow spot focuses light onto Part of the retina which is the retina. most sensitive to light as it has many photoreceptors. Iris The coloured part of the eye which controls Optic nerves the size of the pupil. Nerve fibres which carry nerve impulses from the Pupil retina to the brain to be Opening in the interpreted. centre of the iris which controls the Aqueous humour Vitreous humour Blind spot quantity of light entering the eye. Transparent fluid which Conjunctiva Transparent jelly-like substance Part of the retina which is not maintains the shape of Transparent membrane which maintains the shape of sensitive to light as there are no the eyeball and focuses which protects the front the eyeball and focuses light photoreceptors and an exit point for light into the eye. part of the sclera. onto the retina. all optic nerve fibres. 1.2.1 Figure 1.8 Parts of the human eye and their functions  Chapter 1: Stimuli and Responses What is the Colour of the Object Seen? The retina has two types of photoreceptors: rod cells and cone cells as shown in Figure 1.9. Rod cells are sensitive to different light intensities including faint light but are not sensitive to the colours of light. Cone cells are sensitive to the colours of light under bright conditions. There are three different types of cone cells, where each is sensitive to red light, green light and blue light. Rod cell Light Cone cell Vitreous humour Sclera Retina Choroid Figure 1.9 Photoreceptors – rod and cone cells Ear What are the parts of the ear and their functions? Study Figure 1.10 and Table 1.1 on page 14. Outer ear Middle ear Inner ear Ossicles Semicircular canals Auditory nerve Cochlea Earlobe Ear canal Eardrum Oval Eustachian tube window Figure 1.10 Parts of the human ear 1.2.1 13  Table 1.1 Functions of the parts of the human ear Part of ear Structure of ear Functions Earlobe Collects and directs sound waves into the ear canal Outer ear Ear canal Directs sound waves to the eardrum Eardrum (thin Vibrates according to the frequency of the sound waves membrane) received and transfers the vibrations to the ossicles Ossicles (made up of Amplify sound vibrations and transfer them to the three small bones) oval window Middle ear Oval window Collects and transfers sound vibrations from the ossicles to the cochlea Eustachian tube Balances the air pressure on both sides of the eardrum Cochlea (contains fluid) Detects and converts sound vibrations into nerve impulses Semicircular canals Detect the position of the head and help to balance the Inner ear (contain fluid) body Auditory nerve Sends nerve impulses from the cochlea to the brain to be interpreted Nose What are the parts of the nose? Study Figure 1.11. Nerve Nerves to the brain Nasal cavity rs ente Air Sensory cells for smell (smell receptors) Nose Sensory cells for smell Mucus Tongue Nostrils Figure 1.11 Parts of the human nose 14 1.2.1  Chapter 1: Stimuli and Responses Structure of the Nose The nose is the sensory organ of smell. Smells are chemical BRAIN substances present in the air. About 10 million sensory TEASER cells for smell are located at the roof of the nasal cavity Why is a person suffering from flu as shown in Figure 1.11. normally unable to detect smells? Function of Sensory Cells for Smell Sensory cells for smell are tiny and covered with a layer of mucus. Chemical substances in the air will dissolve in this layer of mucus and stimulate the cells to produce nerve impulses. The nerve impulses are then sent to the brain to be interpreted to determine the type of smell. Tongue What are the parts of the tongue? Study Figure 1.12. Pore Supporting cell Taste receptor Nerves to the brain Papillae on the tongue Taste bud on the papillae Tongue Figure 1.12 Parts of the human tongue Structure of the Tongue The tongue is the sensory organ of taste. Observe the SCIENCE INFO surface of your tongue using a mirror. There are tiny Umami is classified as a basic nodules known as papillae on the surface of the tongue. taste because there are taste The surface of a papillae is covered by hundreds of taste receptors that can only detect buds. Each taste bud contains 10 to 50 taste receptors. umami taste. This is the same as These taste receptors can detect five types of basic tastes other basic tastes such as sweet, which are sweet, salty, sour, bitter and umami. salty, sour and bitter. Umami taste is related to delicious tastes such Function of Taste Buds as the taste of meat in soups or the taste of fermented foods such When food is chewed, part or all the chemical substances as cheese and mushrooms or in the food dissolve in the saliva. These dissolved chemical monosodium glutamate (MSG). substances will diffuse into the taste buds through their pores and stimulate the taste receptors in them to produce nerve impulses. These nerve impulses are then sent to the brain to be interpreted as sweet, salty, sour, bitter, umami tastes or a combination of the basic tastes. 1.2.1 15 Skin What are parts of the skin? There are five types of receptors found in the skin. What are their functions? Study Figure 1.13. Pain receptor Cold receptor Detects stimuli that Detects cold stimuli causes pain Hair Oil gland Epidermis Heat receptor Detects heat stimuli Dermis Touch receptor Detects touch stimuli Fat layer Nerve Pressure receptor Detects pressure exerted Figure 1.13 Parts of the human skin The skin is the largest sensory organ in the human BRAIN body. The human skin is made up of a thin outer layer TEASER known as epidermis and an inner layer known as dermis. How does the skin function as a The skin has five types of receptors at different positions sense of ‘sight’ for the blind? to detect different stimuli as shown in Figure 1.13. State the five types of stimuli which can be detected by the receptors in the skin. When the receptor in the skin is stimulated, nerve impulses are produced and sent through the nervous system to the brain to be interpreted and to produce an appropriate response. 16 1.2.1  Chapter 1: Stimuli and Responses Mechanism of Hearing How do we hear? Study Figure 1.14. Ossicles Brain Auditory nerve Cochlea Earlobe Ear Ear canal Eardrum Oval window Direction of sound sound sound vibrations Source Ossicle Earlobe Ear canal Eardrum of sound bones Earlobe e receives rec Ear canal channels thee The vibrations ns are and gathers sound waves to the amplified by the vibrations sound waves. eardrum causing it to ossicles and then vibrate. sent to the cochlea through e ova the oval window. nerve nerve impulses impulses vibrations Sound is Auditory Oval Brain Cochlea interpreted nerve window The nerve rve im impulses are then sent through the auditory en se audi Nerve cells in n the cochlea convert the nerve to the brain to be interpreted. sound vibrations to nerve impulses. Figure 1.14 Mechanism of hearing in humans Activity 1.4 To study the mechanism of hearing using a model CPS, ICS Instructions Innovation- 1. Work in groups. based activity 2. Each group is required to present the mechanism of hearing using a model prepared by the teacher. 3. Construct a flow chart that shows the direction of sound in the mechanism of hearing. 1.2.2 17 Mechanism of Sight How do we see? Study Figure 1.15. Ciliary muscle Vitreous humour Light rays Retina from an object Cornea Brain Aqueous humour Eye lens Optic nerves Light rays from an object enter the eye through the cornea, aqueous humour, eye The light rays stimulate The brain interprets the lens and vitreous humour before reaching photoreceptors to nerve impulses. The the retina. These parts of the eye focus the produce nerve impulses smaller inverted image light rays from the object onto the retina. that are sent to the on the retina will then The object appears smaller and inverted. brain. appear upright. Figure 1.15 Mechanism of sight in humans Activity 1.5 To study the mechanism of sight using a model CPS, ICS Instructions Innovation- 1. Work in groups. based activity 2. Each group is required to present the mechanism of sight using a model prepared by the teacher. 3. Construct a flow chart that shows the direction of light in the mechanism of sight. Photograph Ph t h 11.77 A human h eye model dl 18 1.2.2  Chapter 1: Stimuli and Responses Sensitivity of the Skin on Different Parts of the Body towards Stimuli Photograph 1.8 shows a few examples of daily activities of humans which make use of the sensitivity of skin on different parts of the body towards different stimuli. Photograph 1.8 Sensitivity of the skin on different parts of the body Why are the daily activities shown in Photograph 1.8 carried out on different parts of the body? Let us investigate this in Activity 1.6. Activity 1.6 Inquiry-based activity To investigate the sensitivity of the skin on different parts of the body towards the touch stimulus Material Cellophane tape Apparatus Ruler (30 cm), toothpick and handkerchief (or blindfold) Instructions 1. Work in pairs. 2. Set up the apparatus as shown in Figure 1.16. Toothpick 2 Ruler             Cellophane tape Toothpick 3 Toothpick 1 Figure 1.16 Using the cellophane tape, attach: Toothpick 1 on the 0 mark of the ruler. Toothpick 2 opposite the first toothpick on the ruler. Toothpick 3 on the 0.5 cm mark of the ruler. 1.2.3 19  3. Cover your partner’s eyes with a handkerchief. 4. Prick the back of your partner’s hand with one or two toothpicks as shown in Figure 1.17. Hold the sharp end of the toothpick with care. Do not press the sharp end of the toothpick too hard onto the skin. Throw away all used 0 1 2 3 4 5 6 7 8 9 10 11 toothpicks into the rubbish bin. Figure 1.17 Ask your partner if he or she feels it as one or two toothpicks. 5. Mark ‘’ if the answer is correct and ‘×’ if the answer is wrong in the table below. 6. Repeat steps 4 and 5 three times. 7. Repeat steps 4 to 6 on different parts of the body such as the tip of the index finger, elbow and arm. Touch stimulus by using one toothpick two toothpicks Part of Body 1st 2nd 3rd 1st 2nd 3rd attempt attempt attempt attempt attempt attempt Back of the hand Tip of the index finger Elbow Arm Questions 1. At which part or parts of the body is the skin most sensitive to touch stimulus? Explain your observation. 2. At which part or parts of the body is the skin least sensitive to touch stimulus? Explain your observation. 3. Which type of receptor is stimulated in this activity? 4. State two factors that affect the sensitivity of skin on different parts of the body towards touch stimulus. The sensitivity of skin towards stimuli depends on the number of receptors and the thickness of the skin epidermis. For example, the tip of the finger is very sensitive towards touch because at the tip of the finger, there is a large number of touch receptors and the epidermis is thin. The tongue, nose and lips are also very sensitive to touch. The elbow, the sole of the foot and the back of the body are less sensitive to touch. Why? 20 1.2.3  Chapter 1: Stimuli and Responses Sensitivity of the Tongue towards Different Taste Stimuli The tongue can detect five types of tastes which are sweet, salty, sour, bitter and umami. Each type of taste is detected by a different receptor. Let us investigate the areas of the tongue that detect different tastes in Activity 1.7. Activity 1.7 Inquiry-based activity To show that the sensitivity of the tongue towards taste stimuli is related to the number of receptors Materials Do not taste any chemical Sugar solution (sweet), salt solution (salty), lime juice substance in the laboratory (sour), strong coffee without sugar (bitter), mushroom without your teacher’s permission. soup (umami) and distilled water Apparatus Drinking straw, handkerchief (or blindfold) and six cups Instructions 1. Work in pairs. Your teacher will provide each pair of students with five solutions of different tastes which are sweet, salty, sour, bitter and umami, in different cups. 2. Cover your partner’s eyes with a handkerchief. 3. Ask your partner to gargle with distilled water. 4. Using a drinking straw, place a drop of sugar solution Photograph 1.9 on part A of his tongue as shown in Figure 1.18. 5. Ask your partner to identify the taste of the solution without pulling the tongue back into the mouth. E 6. Mark ‘’ if your partner correctly identifies the taste of C C the solution and ‘×’ if your partner incorrectly or fails D to identify the taste of the solution in a table as shown B B below. A 7. Repeat steps 3 to 6 on parts B, C, D and E. 8. Repeat steps 3 to 7 using the four other solutions provided. Figure 1.18 Type of taste Part of the tongue Sweet Salty Sour Bitter Umami A B Questions 1. Why does your partner have to gargle each time before tasting the solutions? 2. Which part of the tongue is able to identify all the tastes of the solutions? 3. Which part of the tongue is most sensitive to taste? Explain your observation. 4. Which part of the tongue is least sensitive to taste? Explain your observation. 5. What conclusion can you draw from this activity? 1.2.3 21  Different Areas of the Tongue are More Sensitive to Specific Taste KEY: Areas of the tongue are sensitive to all five tastes. Bitter However, different areas of the tongue have different sensitivities towards specific taste. For Sour example, the area in front of the tongue is more Sweet sensitive to sweet taste whereas the sides are more sensitive to sour and salty tastes. The area at the Salty back of the tongue is more sensitive to bitter taste. The area at the centre of the tongue, however is Umami more sensitive to umami taste. Study Figure 1.19. Figure 1.19 Different areas of the tongue BRAIN are more sensitive to specific taste TEASER Nowadays, there is a toothbrush equipped with a tongue cleaner. Does the use of the tongue cleaner reduce the sensitivity of the tongue? Combination of the Sense of Taste and the Sense of Smell Look at Photograph 1.10. Can the child enjoy the fried chicken? Does the sense of smell play a role when a person tastes food? Let us investigate this matter in Photograph 1.10 Food eaten Activity 1.8. without smelling Activity 1.8 Inquiry-based activity To investigate the relationship between sense of taste and sense of smell Materials Cordial drinks of different flavours (grape, orange, mango, strawberry) and distilled water Apparatus Handkerchief (or blindfold) and cups Instructions 1. Work in pairs. Your teacher will provide each pair of students with cordial drinks of different flavours such as grape, orange, mango and strawberry in different cups. 2. Cover the eyes of your partner with a handkerchief and ask him to pinch the nose as shown in Photograph 1.11. 3. Give your partner a cup of distilled water and ask him to gargle. 22 1.2.3  Chapter 1: Stimuli and Responses 4. Give your partner a cup of grape-flavoured cordial drink and ask him to identify and state the flavour of the cordial in the given cup. 5. Mark ‘’ if your partner answers correctly and ‘×’ if your partner is unable or fails to answer correctly in a table as shown below. 6. Repeat steps 3 to 5 using cordial drink of other flavours. 7. Repeat steps 2 to 6 without pinching the nose. Condition Flavour of cordial drink of the nose Grape Orange Mango Strawberry Photograph 1.11 Pinched Without being Make sure your partner is not pinched allergic to all the flavours of the cordial drinks investigated. Questions 1. Under what condition is your partner able to identify the flavours of the cordial drinks more easily, with his nose pinched or not being pinched? 2. State one inference based on your answer. 3. Why should your partner’s eyes be covered in this activity? 4. Why does hot food taste better? Case Study 1. The judges in a cooking competition as shown in Photograph 1.12 use several types of senses. (a) State the types of senses used by the judges to carry out their evaluation. (b) What sensory organs are related to the sense of taste? Photograph 1.12 2. Have you ever carried out the daily activity as shown in Photograph 1.13? (a) What is the combination of senses used in this activity? (b) What is the importance of the combination of sensory organs in carrying out this activity? Photograph 1.13 1.2.3 23 How do Limitation of Senses, Defect in Sensory Organs and Ageing Affect Human Hearing and Sight? Audio visual which combines the senses of hearing and sight, plays an important role in daily life. Let us investigate SCIENCE INFO how limitation of senses, defect in sensory organs and Audio visual refers to the use ageing affect the sensitivity of hearing and sight of humans. of two components, sound component (audio) and graphic component (visual). Limitations of Sight Limitation of sight is the limitation in the ability of the eye to see objects. We cannot see very tiny objects such as microorganisms as well as very distant objects such as planet Jupiter. Limitations of sight include optical illusions and blind spot. Optical Illusions P R X Y Q S (a) Which line is longer? (b) Which spot in the (c) Are the sides of the square centre is larger? straight or curved? Figure 1.20 Optical illusions Look at Figure 1.20 and answer the questions given. Check your Optical illusion Without optical illusion answer using a straight ruler. Is your P R P R answer correct or wrong? Why? Optical illusion occurs when an object that is seen differs from its actual state. Optical illusion occurs because the brain is unable to Q S Q S accurately interpret the object seen by With distractions around Without distractions around the eye due to distractions around the straight lines PQ and RS straight lines PQ and RS object. Look at Figure 1.21. Figure 1.21 Factor causing an optical illusion 24 1.2.4  Chapter 1: Stimuli and Responses Blind Spot Refer to the blind spot shown in Figure 1.8 on page 12. Why are images that fall on the blind spot invisible? We are unaware of the presence of the blind spot in the eye because it is not possible for the image of the same object to fall on the blind spots of both eyes simultaneously. Carry out the following simple activity to investigate the blind spot. Figure 1.22 Investigating the blind spot Instructions 1. Hold this book with your right hand and straighten your arm. 2. Cover your left eye and look at the cat in Figure 1.22 with your right eye. 3. Move this book slowly towards your eyes. Does the bird disappear from your sight at a certain position? Why? Photograph 1.14 shows examples of various devices used to overcome the limitations of sight. Name these devices. Gather information on the use of these devices from the Internet, magazines, books, newspapers and other sources. Discuss the information gathered. Present the findings of your discussions collaboratively using multimedia presentation. Binoculars Light microscope Scanning electron microscope Ultrasound machine X-ray machine Photograph 1.14 Examples of devices to overcome limitations of sight 1.2.4 25  Defects of Sight and Ways to Correct Them Defects of sight include short-sightedness, long-sightedness and astigmatism. How can these defects of sight be corrected? Study Table 1.2. Table 1.2 Defects of sight and ways to correct them Defect of sight How it is corrected Short-sightedness (a) Inability to see distant objects clearly. Short-sightedness can be corrected using (b) Distant objects appear blurry because the concave lens. image is focused in front of the retina. (c) This defect is caused by the eye lens being too thick or the eyeball being too long. Eye lens too thick Distant object Distant object Image formed Concave lens Image formed in front of the retina on the retina Eyeball too long Distant object Distant object Long-sightedness (a) Inability to see near objects clearly. Long-sightedness can be corrected using (b) Near objects appear blurry because the image convex lens. is focused behind the retina. (c) This defect is caused by the eye lens being too thin or the eyeball being too short. Eye lens too thin Near object Near object Image formed Image formed Convex behind the retina on the retina lens Eyeball too short Near object Near object 26 1.2.4  Chapter 1: Stimuli and Responses Defect of sight How it is corrected Astigmatism Astigmatism can be corrected using cylindrical (a) Seeing part of an object clearer than the rest lenses. of the object. (b) This defect is caused by the uneven curvature of the cornea or eye lens.          Cylindrical lens    Figure 1.23 Test your eyes by looking at Figure 1.23. Can you see all the lines clearly? If you cannot, you have astigmatism. Today in history Limitations of Hearing Limitations of hearing are limitations in the ability of the ear to hear sound. We can only hear sounds of frequencies between the range of 20 Hz to 20 000 Hz. The ears are unable to detect sounds which lie outside this frequency range. The frequency range of hearing of every individual is different. When a person gets older, the frequency range The first stethoscope made of of his hearing gets narrower as his eardrum becomes less wood was invented by Rene elastic. Examples of devices invented and used to overcome Laennec at Necker-Enfants the limitations of hearing are shown in Photograph 1.15. Malades Hospital, Paris in 1816. A loudspeaker amplifies sound so that it can be heard from far away. Stethoscope helps us to listen to the heartbeats. Photograph 1.15 Examples of equipment used to overcome limitations of hearing 1.2.4 27  Defects of Hearing and Ways to Correct Them Defects of hearing occur when the sense of hearing of a person does not function well. Defects of hearing are normally caused by damage to the ear due to infection by microorganisms, injury, ageing process or continuous exposure to loud sounds. Damages to the outer ear and middle ear can be corrected easily. For example, the clearing of foreign objects in the ear canal. Punctured eardrum and damaged ossicles can also be corrected using medicine or surgery. Damage to the inner ear is more difficult to correct. A damaged cochlea can be corrected using a cochlear implant but a damaged auditory nerve cannot be corrected using medicine or surgery. Photograph 1.16 shows how innovation and technology are applied to invent smaller and more sophisticated hearing aids. Photograph 1.16 Advancements in hearing aids The Five Senses – a Gift The five senses is a gift from God that we should appreciate. However, unhealthy lifestyles and high risk careers can affect the sensitivity of the sensory organs. Based on Photographs 1.17 and 1.18: name the sensory organ whereby the sensitivity is affected in each situation describe how each situation can affect the sensitivity of the sensory organ h h 1.17 Unhealthy Photograph h l h lifestyle lf l what are the devices or safety measures taken to maintain the safety and health of the sensory organ in each situation? Photograph 1.18 High risk careers 28 1.2.5  Chapter 1: Stimuli and Responses Activity 1.9 Instructions 1. Work collaboratively in groups. CPS, ISS, ICS 2. Each group is assigned by your teacher to create a multimedia Technology- presentation such as MS PowerPoint or animation on one of the based activity following topics: Optical illusion and blind spot Various types of audio visual defects such as short-sightedness, long-sightedness, astigmatism and defects of hearing Correction of audio visual defects using concave lenses, convex lenses and hearing aids Examples and effects of unhealthy lifestyles or high risk careers that can affect the sensitivity of the sensory organs The five senses – a gift and the importance of practising safety and healthcare of the sensory organs Formative Practice 1.2 1. Complete the following mechanism of sight. Light (a) Aqueous Humour (b) Eye lens Vitreous Humour (c) Optic nerve (d) 2. Which structure of the ear, if damaged, will not influence the mechanism of hearing? 3. Where is the sensory cell for smell located? 4. State the five tastes that can be detected by the tongue. 5. State two factors that influence the sensitivity of the skin to stimuli. 6. (a) State the type of stimulus that can be detected by the tongue. (b) Explain how the stimulus in question 6(a) can be detected. 29  1.3 Stimuli and Responses in Plants After a week… Will a plant grow faster Hello plant, please grow faster! Why is the stimulus given if we talk to it? not effective? Like humans and animals, plants can also Responses Res onses of Responses sponses of plants plants lants detect stimuli and respond to them. The stimuli that can be detected by plants include light, water, gravity and touch. The responses of plants can be divided into two as shown in Tropism Nastic movement Figure 1.24. Figuree 1.24 Respon Responses nses of plants to stimuli Tropism Tropism is a directional response of plants to stimuli such as light, water, gravity and touch coming from a certain direction. A certain part of a plant will grow towards or move away from the detected stimulus. The part of a plant which grows towards a stimulus is known as positive tropism whereas the part of a plant which grows away from a stimulus is known as negative tropism. The directional response of plants normally occurs slowly and less significantly. Let us carry out Experiment 1.1 to determine the direction of response of plants to light, water, gravity and touch. Experiment 1.1 A Response of plants towards light or phototropism Aim: To study the response of plants to light Problem statement: Which part of plants responds to light? Hypothesis: Shoots of plants grow in the direction of light. Variables (a) manipulated variable : Direction of light towards the shoots of the seedlings (b) responding variable : Direction of growth of the shoots of the seedlings (c) constant variables : Seedlings of the same type and height, volume of water 30 1.3.1 1.3.2 1.3.3  Chapter 1: Stimuli and Responses Materials Green pea seedlings, soil, water and three boxes (one box with an opening at the top and two other boxes with openings at the side) Apparatus Three beakers Procedure Light Green pea seedlings Light Light Beaker Beaker Beaker Box A Box B Box C Figure 1.25 1. Set up the apparatus as shown in Figure 1.25. 2. Observe and sketch the positions of the shoots of the seedlings in boxes A, B and C. 3. Keep all three boxes in the laboratory for five days. Keep the soil moist by watering it with the same amount of water daily. 4. After five days, observe and sketch the positions of the shoots of the seedlings in boxes A, B and C. Conclusion Is the hypothesis accepted? What is the conclusion of this experiment? Questions 1. What is the stimulus used in this experiment? 2. State the part of the plant that responds to the stimulus. 3. Does the part of the plant in question 2 show positive or negative phototropism? Explain your answer. B Response of plants to gravity or geotropism Aim: To study the response of plants to gravity Problem statement: Which part of plants responds to gravity? Hypotheses: (a) Roots of plants grow in the direction of gravity. (b) Shoots of plants grow in the opposite direction of gravity. Variables (a) manipulated variable : Position of the seedlings relative to the direction of gravity (b) responding variable : Direction of growth of the roots and shoots of the seedlings (c) constant variables : Presence of water, absence of light, seedlings with straight roots and shoots Materials Green pea seedlings with straight roots and shoots, moist cotton wool and plasticine 1.3.1 1.3.2 1.3.3 31 Apparatus Petri dish Procedure 1. Set up the apparatus as shown in Figure 1.26. Make sure that the green Petri dish pea seedlings are arranged in different Moist cotton wool positions in the Petri dish. 2. Observe and sketch the position of the Seedlings with shoots and roots of the seedlings in the straight roots and Petri dish. shoots 3. Keep the apparatus in a dark cupboard forr two days. 4. After two days, observe and sketch the Plasticine position of the shoots and roots of the seedlings in the Petri dish. Figure 1.26 Conclusion Are the hypotheses accepted? What is the conclusion of this experiment? Questions 1. Why is the apparatus kept in a dark cupboard? 2. Based on your observations, state the direction of growth of the: (a) shoots of the seedlings (b) roots of the seedlings 3. Do plants show positive geotropism or negative geotropism? Explain your answer. C Response of plants to water or hydrotropism Aim: To study the response of plants to water Problem statement: Which part of plants responds to water? Hypothesis: Roots of plants grow in the direction of water. Variables (a) manipulated variable : Presence of a source of water (b) responding variable : Direction of growth of roots of seedlings (c) constant variables : Gravity, absence of light and seedlings with straight roots Materials Green pea seedlings with straight roots, moist cotton wool and anhydrous calcium chloride Apparatus Rough wire gauze and two beakers Procedure 1. Set up the apparatus as shown in Figure 1.27. 2. Observe and sketch the positions of the roots of the seedlings in beakers X and Y. 3. Keep both beakers X and Y in a dark cupboard. 4. After two days, observe and sketch the positions of the roots of the seedlings in beakers X and Y. 32 1.3.1 1.3.2 1.3.3  Chapter 1: Stimuli and Responses Moist cotton wool Seedlings with straight roots Wire gauze Water Anhydrous calcium X chloride Y Figure 1.27 Conclusion Is the hypothesis accepted? What is the conclusion of this experiment? Questions 1. What is the stimulus used in this experiment? 2. State the part of the plant that responds to the stimulus. 3. What is the function of the anhydrous calcium chloride in beaker Y? 4. Does the part of the plant in question 2 show positive or negative hydrotropism? Explain your answer. Plants need to be responsive towards stimuli such as light, gravity and water so that they can respond appropriately to ensure their sustainability and survival. Why do plants need light and water? Name one stimulus that can be detected by plants but not investigated in Experiment 1.1. Phototropism Source of light Phototropism is the response of plants Grow towards light towards light. Shoots of plants show positive phototropism which is growth towards the direction of light (Photograph 1.19). As plants need light to carry out photosynthesis, positive phototropism ensures that shoots and leaves of plants obtain enough sunlight to make food through photosynthesis. Photograph 1.19 Shoots of plants show positive phototropism Hydrotropism Hydrotropism is the response of plants towards water. Roots of plants show Water positive hydrotropism which is growth Moist towards the direction of water (Figure 1.28). soil Positive hydrotropism allows roots Positive of plants to obtain water to carry out hydrotropism photosynthesis and absorb dissolved (Grow towards mineral salts to stay alive. water) Figure 1.28 Roots showing positive hydrotropism 1.3.1 1.3.2 1.3.3 33  Geotropism Positive geotropism Geotropism is the response of plants towards gravity. (Grow in the Roots of plants show positive geotropism which is direction of downward growth towards the direction of gravity. gravity) Negative geotropism Positive geotropism allows the roots of plants to grow (Grow in deep into the ground to grip and stabilise the position the opposite of the plant in the ground. On the other hand, shoots direction of of plants show negative geotropism which is upward gravity) growth in the opposite direction of gravity. Negative geotropism allows the shoots and leaves of plants to Figure 1.29 Roots show positive grow upwards to obtain sunlight for photosynthesis geotropism whereas shoots show (Figure 1.29). negative geotropism Thigmotropism Thigmotropism is the response towards touch. Tendrils or twining stems show positive thigmotropism when they cling onto whatever objects or other plants they come into contact with (Photograph 1.20). This response enables plants to grow upwards to obtain sunlight and grip objects to obtain support. Roots show negative thigmotropism since they avoid any object that obstructs their search for water. (a) Cucumber plant has tendrils that twine (b) Morning glory plant has stems that twine around objects in contact with it around objects in contact with it Photograph 1.20 Tendrils and stems which twine around objects show positive thigmotropism Nastic Movement Nastic movement is the response towards a stimulus such as touch but does not depend on the direction of Nastic movement 5 the stimulus. What are other stimuli that can cause nastic *( of the Mimosa sp. : movement? Why is nastic movement not a type of tropism? Nastic movement occurs more rapidly than tropism. For ,.      7( example, the Mimosa sp. responds to touch by folding its leaves inwards when touched as shown in Photograph 1.21. This nastic movement serves as a defence of the Mimosa sp. against its enemies and strong wind. 34 1.3.1 1.3.2  Chapter 1: Stimuli and Responses Photograph 1.21 Nastic movement of a leaf of Mimosa sp. Activity 1.10 To investigate responses of plants in different situations CPS The responses of plants towards Earth’s gravity and Inquiry-based the period of exposure to sunlight in a day activity influence the growth of shoots and roots of plants. These ensure the sustainability and survival of the plants. At the International Space Station (ISS), scientists investigate the growth of plants in the following situations: (a) No gravity (b) Period of exposure to sunlight Instructions Photograph 1.22 A scientist carrying 1. Work in groups. out investigations at the ISS 2. Gather information on the results of the investigations of the scientists on the growth pattern of shoots and roots of plants towards stimuli (gravity and sunlight). 3. Present the outcome of the discussion of each group using multimedia presentation. Formative Practice 1.3 1. (a) What is tropism? (b) State the type of tropism towards the following stimuli: (i) Touch (ii) Gravity (iii) Light 2. (a) Which parts of a plant show: (i) positive phototropism? (ii) positive geotropism? (iii) positive thigmotropism? (b) What is the importance of hydrotropism to plants? 3. State one similarity and one difference between the responses of tropism and nastic movement. 1.3.1 1.3.2 1.3.3 35  Importance of Responses to Stimuli in 1.4 Animals Stereoscopic and Monocular Visions What is the importance Study Figure 1.30 to understand of the location of eyes to stereoscopic and monocular visions. humans and animals? Table 1.3 shows the characteristics and importance of stereoscopic and LIM monocular visions in animals. t
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monocular vision. Large Small overlap overlap Field of monocular vision Field of monocular vision Field of stereoscopic vision Field of stereoscopic vision (a) Stereoscopic vision (b) Monocular vision Figure 1.30 Stereoscopic and monocular visions 36 1.4.1  Chapter 1: Stimuli and Responses Table 1.3 Differences between stereoscopic and monocular vision Stereoscopic vision Monocular vision Both eyes located in front of the head. Both eyes located at the sides of the head. A narrow field of vision. A wide field of vision. Fields of vision overlap to a great extent. Fields of vision do not overlap or overlap only Overlapping fields of vision produce vision slightly. in three dimensions. Three dimensional images formed in the Two dimensional images formed in the non- overlapping fields of vision allow the distance, overlapping fields of vision prevent the distance, size and depth of objects to be estimated size and depth of objects from being estimated accurately. accurately. The ability to estimate distance accurately helps A wide field of vision helps animals to detect their animals to hunt. enemies coming from any direction. Humans and most predators have stereoscopic Most prey have monocular vision. vision. Stereophonic Hearing What is the importance of having a Source of sound pair of ears to humans and animals? Stereophonic hearing is hearing using both ears. Stereophonic hearing allows us to determine the direction of the sound accurately. Look at Figure 1.31. The importance of stereophonic hearing to humans is to determine Figure 1.31 Stereophonic hearing the location of a source of sound. Stereophonic hearing helps predators to determine the location of their prey. Conversely, stereophonic hearing also helps prey Based on the above to determine the location of their diagram, the ear which is LIM predators and to escape nearer to the source of from them. sound (right ear) receives sound earlier and louder than the other ear. BRAIN The difference in time and loudness of the TEASER sound received by both ears is detected by the brain which then allows us to determine How does the ear function as a the direction of the source of sound which is sense of ‘sight’ for the blind? from the right. 1.4.1 37 Hearing Frequencies of Animals I CAN Different animals can hear sounds of different frequencies REMEMBER! as shown in Figure 1.32. Frequencies of sounds that can be detected by the human ear are limited to the range of 20 Hz to 20 000 Hz. Sea lion 450 – 50 000 Hz Rat Dolphin 200 – 80 000 Hz 40 – 100 000 Hz Frequencies of hearing range Bat Elephant 2 000 – 110 000 Hz 16 – 12 000 Hz Dog 67 – 45 000 Hz Figure 1.32 Frequencies of hearing range of different animals Activity 1.11 Instructions 1. Work collaboratively in groups. CPS, ISS, ICS Technology- 2. Each group will be assigned by your teacher to create a based activity multimedia presentation such as MS PowerPoint or animation on one of the following topics: (a) Stereoscopic and monocular visions in animals (b) Stereophonic hearing (c) Different hearing frequencies for different animals 38 1.4.1  Chapter 1: Stimuli and Responses Sensory Organs Ensure the Survival of MARVELS OF Animals on Earth SCIENCE Animals such as ants, snakes, Responses to stimuli ensure the survival of animals on frogs and birds are believed to Earth. The sensory organs and responses of several animals be able to predict earthquakes. are shown in Photograph 1.23. Carry out Activity 1.12 to Scientists are investigating the investigate the sensory organs and responses of several types of stimuli detected by these other animals. animals before earthquakes occur. Sensory organ: Response: Lateral line Lateral Secretion of line Websites pheromone Electric field of an electric eel http://links.andl17.com/BT_ Science_39 Response: Producing electric field Photograph 1.23 Sensory organs and responses of animals Activity 1.12 To explain the sensory organs and responses of other animals on Earth ICS Discussion Instructions activity 1. Work in groups. 2. Each group is required to gather information on how responses of animals in Photograph 1.23 are able to ensure their survival on Earth. 3. Discuss the information gathered. 4. Present the outcome of the discussion of each group in class using multimedia presentation. Formative Practice 1.4 1. State two types of vision of animals. 2. State the factor that determines the type of vision of animals. 3. What is the type of vision of a primary consumer? Give your reasons. 4. What is the importance of stereophonic hearing? 5. In the dark, Azman can determine the location of a mewing cat. Explain how Azman is able to determine the location of the cat. 1.4.2 39  Summary 40 Stimuli and responses in Humans Plants Other animals are controlled by such as such as Human nervous system Sensory organs Tropism Nastic Stereoscopic Monocular Stereophonic movement vision vision hearing consists of such as that includes – Central Eye, ear, nose, Phototropism, in in which nervous system skin, tongue geotropism, – Peripheral hydrotropism, Predators Prey Uses both nervous system sensitive to stimuli thigmotropism ears such as responses through to hear to Voluntary action, Light, sound, smell, Light, gravity, Sounds with involuntary action touch, taste water, touch different frequency ranges for through different Sensitivity to stimuli animals Mechanism of hearing and mechanism related to of sight Number Combination of of receptors sensory organs  Chapter 1: Stimuli and Responses Self-reflection After studying this chapter, you are able to: 1.1 Human Nervous System Describe the structures and functions of human nervous system through drawings. Make a sequence to show the pathway of impulses in voluntary and involuntary actions. Justify the importance of human nervous system in life. 1.2 Stimuli and Responses in Human Draw the structures of sensory organs and explain their functions and sensitivities towards stimuli. Explain the mechanism of hearing and sight through drawing. Relate human sensory organs to the sensitivity towards various combination of stimuli. Explain through examples how the limitation of senses, defect in sensory organs and ageing affect human hearing and sight. Justify how innovations and technologies can improve the ability to sense in sensory organs. 1.3 Stimuli and Responses in Plants Describe the parts of a plant that are sensitive towards stimuli. Justify how responses in plants ensure their sustainability and survival. Carry out experiments to study responses in plants towards various stimuli. 1.4 Importance of Responses to Stimuli in Animals Explain with examples the types of sight and hearing in animals. Communicate how sensory organs ensure the survival of animals on Earth. Summative Practice 1 Answer the following questions: 1. Mark ‘✓’ for the correct statement and ‘×’ for the incorrect statement about the human nervous system. (a) The peripheral nervous system is made up of nerves connecting the brain with the spinal cord. (b) Without a functioning brain, voluntary actions cannot be carried out. (c) Playing badminton is an involuntary action. (d) Impulses can only be interpreted by the brain. 41 2. Figure 1 shows structures P, Q and R of the human nervous system. P: Q: R: Figure 1 Label P, Q and R in Figure 1. 3. Figure 2 shows responses A and B of the eye. Response A Response B Figure 2 (a) State the responses shown in Figure 2. (b) State the stimuli that cause these responses. (c) How do the stimuli cause these responses? (d) These responses protect the eye especially the retina by preventing light of excessive intensity from entering the eye. During the solar eclipse, explain why we should observe this event on the water surface in a basin of water. 4. In a science class, Azura studies the mechanisms of hearing and sight. (a) Draw one flow chart that shows the pathway of sound from a source of sound entering the ear. (b) Draw one flow chart that shows the pathway of light from an object entering the eye. 42  Chapter 1: Stimuli and Responses 5. Figure 3 shows the structure of thee human skin. skin. Y: X: Figure 3 (a) Label X and Y in Figure 3. (b) Explain why the fingertip and not the palm of the hand is used to detect Braille symbols. (c) Mazlan classifies the tongue as skin that possesses taste receptors. Do you agree with the classification of the tongue as skin? Explain your answer. 6. (a) What is the importance of the sense of smell when we are in the science laboratory? Give one example. (b) Why are dogs in police units trained to detect the presence of drugs kept in bags? 7. (a) State two responses in plants that help photosynthesis. (b) How do the two responses of plants in question 7(a) help photosynthesis? 8. (a) Name the type of vision of an eagle. (b) What is the importance of the type of vision in question 8(a) to the survival of the eagle? Focus on HOTS HOTS 9. Pak Dollah who is long-sighted forgot to bring his glasses during breakfast in a restaurant. You are required to invent a lens to enable Pak Dollah to read the newspaper. Your invention must make use of the materials shown in Figure 4. Transparent Water plastic bottle Figure 4 43