Gas Exchange in Plants and Animals PDF

N Living Things and Air Gas exchangein P 7.4 Jants and animals bm gy :. fro enersgi i on to rehleitiosse mhe ati respirirat out ry car Plants and ZOXY e e, their own food _by p e mak nts pla en Gre food. y8! of carbon dioxide an ge han exc e olv inv ses proces ion, let us learn i z animals living things and their environment. In this section, and animals. about gas exchange in plants [} Gas exchange in plants 7 . ge ini plants ini Experii men t7.7 Let us first look at the gas exchan L ymmtm—- Experiment video ev07s7 Gas exchange in plants Material and apparatus green leaf e boiling tube aluminium foil thread measuring cylinder (10 cm?) table lamp In this experiment, we O stopper test tube rack use 2 hydrogencarbonate indicator hydrogencarbonate indicator to show any change in carbon dioxide content. The indicator shows different colours in different carbon dioxide contents. 0.03% > U Yellow gas exchange $893%H% =0.03% (in normal air) <0.03% Red Purple o Procedure 1. Add 3 cm’ of hydrogencarbonate indicator to each of four boiling tubes and set up the apparatus as shown below. Put all four boiling tubes in bright light for about one hour. « Tip The distance between the lamp and each boiling tube aluminium foil should be the same. thread leaf hydrogencarbonate indicator 2. Record the colour of the hydrogencarbonate indicator in each tube in the table below. Results Colour of the hydrogencarbonate indicator At the beginning | After one hour Which tubes are the control set-ups? Discussion 1. Compare the results in tube A and tube B. What do the results show? 2. Compare the results in tube C and tube D. What do the results show? & Living Things and Air 1. Net gas exchange in plants Plants can carry out photosynthesis and respiration. Net gas exchange in plants depends on the relative rates of photosynthesis and respiration (Fig. 7.16). photosynthesis & S « respiration = COjou 1 In the daytime, both photosynthesis and respiration At night, photosynthesis stops. Only respiration take place. takes place. Rate of photosynthesis > Rate of respiration e ® Net uptake of carbon dioxide ® ® Net release of oxygen Fig. 7.16 Net release of carbon dioxide Gas exchange in plants Active learning In o exchange (Neto gas in plants) respiration. Since the rate of photosynthesis is higher than the rate simulation IE Net uptake of oxygen the e daytime, X of respiration, there plants carry out is a net uptake both photosynthesis e of carbon dioxide and and a net release of oxygen. At night, photosynthesis stops and only respiration Therefore, there is a net uptake of oxygen takes place. and a net release of carbon dioxide by plants. Now, can you explain the results of Experiment 7.7? Net gas exchange in plants depends photosynthesis and respiration. on the relative rates of 2. Role of stomata Gas exchange in plants is carried out through the tiny pores on the leaf epidermis. These pores are called stomata (singular: stoma). \ Surrounding each stoma are two guard and closing of the stoma. In the daytime, the guard cells are full of water. They open the stoma. The plant takes in carbon dioxide from the air for photosynthesis, and gives out the through the stoma. oxygen pig,7.17 produced A stomaonthe lower epidermis of aleaf (400X) NOISN3LX3 cells. The guard cells control the opening At night, the guard cells shrink as they lose water, and so the stoma closes. guard cells guard cells (swollen) (shrunken) stoma open stoma closed (in the daytime) (at night) chloroplast cell wall stoma Fig. 7.18 Open stoma and closed stoma Stomata are very small a microscope. In in size. They can Experiment 7.8, we will only be observed use using a microscope to observe stomata. Gas exchange in plants is carried out through the on the leaf epidermis. stoma 517, Suard cell 3B epidermis JRE 35 Living Things and Air ‘ Experiment7.8 Experiment video av ] ev07s8 Observing stomata under a microscope Material and apparatus prepared slide of leaf epidermis 1 microscope 1 e Procedure Your teacher will give you a prepared slide of leaf epidermis. 2., Examine the slide under a microscope. Can you find the stomata? Observe them and make a biological drawing of a stoma and guard cells B e 1. you have observed. Are the stomata open or closed? & \4 ( Checkpoint 7.5 ‘ e-Checkpoint T A cpo7ss (a) Plants do not carry out respiration in the daytime. (b) At night, there is a net uptake of oxygen by plants. H(c) 2. Ood Write ‘T’ for a true statement and ‘F’ for a false statement. 1. Leaf epidermis has stomata, where gas exchange takes place. Study the experimental set-up on the right. (a) What is the colour of hydrogencarbonate indicator after two hours? hydrogencarbonate b (b) The leaf carries out both (i) (i), W_——— gl indicator Explain the result of (a). and (i). is higher than the rate of (iv). - The rate of . There is a net of carbon dioxide. Thus, the indicator turns (Vi) . Living Things and Air \ Experiment 7.10 Experiment video af ! ev07s10 Comparing the water vapour content of inhaled air and exhaled air Material and apparatus dry cobalt chloride paper forceps 2 1 pair mirror tissue paper 1 Procedure 1. Use a pair of forceps to take out a piece of dry cobalt chloride paper from the desiccator. Hold it against a dry mirror. Breathe onto the mirror 10 times. dry cobalt chloride paper D Caution Every student should use a clean * * mirror for this step. Students who have symptoms of respiratory illnesses should not perform this step. Wash the mirror with soap after the experiment. What happens to the colour of the cobalt chloride paper? Wipe the surface of the mirror with tissue paper to make it dry. Then, use a pair of forceps to place another piece of dry cobalt chloride paper on the dry mirror. Observe any colour change of the paper for five minutes. dry cobalt chloride paper e Does the cobalt chloride paper show any colour change? If yes, does the change occur more slowly or quickly than that in Step 17 Conclusion Inhaled air contains —___________ water vapour than exhaled air. Experiment 7.11 Experiment video af ! ev07s1 Comparing the temperature of inhaled air and exhaled air Material and apparatus thermometer 1 boiling tube bendable straw 1 cotton wool test tube rack 1 1 Procedure 1. Measure the room temperature with a thermometer. This is the temperature of inhaled air. Record the reading in the table below. 2. Set up the apparatus as shown on the right. thermometer cotton wool bendable straw boiling tube test tube rack 3. Blow gently into the boiling tube through the straw 10 times. Record the reading of the thermometer. & Caution « * Every student should use a new straw. Do not share a straw for this step. Students who are exempted from P.E. lessons for medical reasons or have symptoms of respiratory ilinesses should not perform this step. Results Inhaled air Temperature (°C) Conclusion The temperature of inhaled airis ________ than that of exhaled air. ¢ Exhaled air e Living Things and Air Think about o A comparison between inhaled air and exhaled air: If an accident happens, an injured personm: K‘;mmfum,,m?us s stop breathing. To save the injured person, trained first-aiders will blow air into the lungs of the Inhaled air Exhaled air Oxygen 21% (more) 16% (less) Carbon dioxide 0.03% (less) 4% (more) . Water vapour variable (less) saturated (more) Temperature lower higher - injured person. This is called artificial respiration. How does artificial respiration save a person’s Jife? Carbon dioxide is produced during respiration and is removed from our bodies through gas exchange. Therefore, the carbon dioxide content in exhaled air is higher. How about other animals? Let us find out in the following experiment. Experiment 7.12 Experiment video ev07s12 Studying the gas exchange in mealworms Material and apparatus boiling tube 2 test tube rack 1 1 stopper 2 measuring cylinder (10 cm?) wire gauze 2 hydrogencarbonate indicator mealworm about 10 procedure 1. Set up the apparatus as shown below. Record the colour of the hydrogencarbonate f indicator in the table on the next page. /b { Caution Wear protective gloves when handling mealworms. mealworm . wire gauze wire gauze 3cm’of 3om®of hydrogencarbonate hydrogencarbonate indicator indicator artificial respiration A\ TS5 =N What is the purpose of setting up boiling tube 87 2. Record the colour of the hydrogencarbonate indicator after 30 minutes. Results Colour of hydrogencarbonate indicator s oiling tube At the beginning Mealworms giveout —_in 30 minutes Jater gas exchange. & w [ Checkpo?nt 7.6 Study the experimental set-up below. Soda lime absorbs carbon dioxide in air. — — air to vacuum pump soda lime limewater A (a) When the vacuum mouse B pump c is turned on, what happens limewater D to the limewater in flask B and flask D? Limewater in flask B: Limewater in flask D: (b) Explain the result of (a). Soda lime in U-tube A absorbs carbon dioxide in air so that air flowing into flask B does not contain )~ (i) . Limewater .The mouse in flask B thus in bell jar C gives out (i), g Living Things and Air 2. Human breathing system Humans have a breathing system for gas exchange. Gas exchange two different processes. allows of oxygen of drawing air in and expelling respiration, so that energy stored in food can be released for use by air out of the lungs. the body. At the same time, carbon & Breathing and respiration are Breathing is a physical process Respiration Is @ chemical process carried out inside body cells to release energy ., from food, our body cells to have a continuous supply dioxide produced during respiration will not build up and it will be removed from the body. Now, we will learn about the human breathing system. Identifying the main parts of the human breathing system Your teacher will show you a human torso model. Identify the main parts of the breathing system. Label parts (a) to (i) in the diagram below with the words provided. ﬂ» lung— diaphragm intercostal-musele __rib trachea bronchus air sac —nasatCavity u bronchiale Active IearmnSI 3D model (a) @ breathing system IFIRFEH rib BB tung B bronchus XK diaphragm B8 nasal cavity B® Intercostal muscle BIMEEL trachea $i§ alrsac fifE bronchiole /\TSEF (Human breathing system) for When we breathe in, air enters our nasal cavity. The air then passes down the trachea. The trachea divides into two bronchi (singular: bronchus). smaller bunch Inside branches the called lungs, each bronchioles. bronchus further Each bronchiole of air sacs. Air sacs are surrounded divides into ends in a by many small blood vessels called capillaries. Gas exchange takes place at the air sacs. = Ltrachea ] =) monchi ] e g Lbronchioleﬂ =) Fig. 7.19 The pathway of air flowing through the breathing system Fig. 7.20 below illustrates the structures of some parts of the breathing system. blood flows away from blood flows to the lungs the lungs air sac @ trachea % Fig.7.20 apillary e junction between @ airsac (200X) tracheaand bronchi pies Structures of some parts of the breathing system B Living Things and Air Experiment video ﬁ & Observing the structure of pig’s lungs ev07s13 couti aution * Material and apparatus 1 pump i i [flssm i beaker (250 cm®) 1 hend tens ! i pig's lungs . 1 pair carry germs. ) After the experiment, clean the bench with disinfectant and wash your hands thoroughly with soap. Procedure 1. Wear protective gloves as animal specimens may Your teacher will show you a pair of pig’s lungs. Identify the trachea, the bronchi, the left and right lungs. 2. Observe the colour of the lungs. What is the colour of the lungs? 3. Press the lungs gently and feel their texture. What is the texture? Theyare_ 4. (hard/soft) and have a texture. Press the trachea and feel its hardness. Is the trachea hard or soft? _ 5. Pump air into the lungs by using the air pump. How does the volume of the lungs change? When air is pumped into the lungs, the volume of the lungs 6. Cut a small piece of lung tissue and put it into water. (a) Doesitfloatorsink? (b) Use a hand lens to observe the lung tissue carefully. Explain your observation in (a)- o Gas exchange allows a continuous supply of oxygen to the body cells for respiration, and removal of carbon dioxide from the body. o Gas exchange in humans takes place at the 3. Gas exchange at the air sacs Inside the lungs, the air sacs are surrounded by capillaries. Gas exchange takes place between the air in the air sacs and the blood in the surrounding capillaries: Oxygen passes from the air sacs into the blood capillaries. The blood then carries the oxygen to the body cells for respiration. Carbon dioxide is produced during respiration. It is carried by blood flowing to the lungs. Carbon dioxide passes from the blood into the air sacs. It is then breathed out. blood to body cells » high oxygen content and low carbon dioxide content blood from body cells . [ » high carbon dioxide content and low oxygen content blood capillary > E Active learning Animation ‘E (Gas exchange in air sacs) pig. 7.21 Gas exchange between the air sac and the surrounding blood capillaries point Gas exchange at the air sacs: o passes from the air sacs into the blood e passesfrom the blood into the air sacs How large is the total surface area of our lungs? There are millions of air sacs in our lungs. Their total surface area is about the size of a tennis court. This provides a large surface area for gas exchange to take place. SN LRV =« Living Things and Air T ecneckpant ) (Checkpo’nt 7.7 iz I The drawing below represents the lungs of a frog. Study it carefully. NOISN3LX3 air sacs Compare the structure of the frog’s lungs with that of human lungs. In which lungs do you think gas exchange is more effective? Explain your answers. is more effective. This is because Gas exchange in (a) many more (b). at the ends of the there are (c). Effects of smoking on gas exchange in humans Do you know how smoking affects gas exchange? Let us learn more in this section. Qil‘ Experiment 7.14 Demonstration Experiment video af ! ev07s14 Observing how smoking affects the pig’s lungs Material and apparatus vacuum pump scissors 1 pair transparent box clgarette pig's lungs 12 packs 2 pairs cigarette holder beaker (250 cm’) gas lighter 48 [ rubber tubing b Caution * Wear protective gloves as animal specimens may carry germs. * After the experiment, clean the bench with disinfectant and wash Yyour hands thoroughly with soap. = Procedure 1. Your teacher will use a pig’s lungs to set up the following model. This model simulates the smoking process by the lungs. . ; transparent box pump <— = r.l rubber tubing 1 t} beaker 2. Caution Perform this experiment in a fume cupboard. cigarette pig's lungs to vacuum B Tip Make sure the box is airtight. Light the cigarette and turn on the vacuum pump. Turn off the pump when the lungs are inflated. NOISN3LX3 cigarette holder 3. Keep turning on and off the pump until the cigarette has burned completely. 4. Light 20 more cigarettes by repeating Steps 2-3. 5. Take out the lungs from the box carefully. Compare them with the pair of non-smoking lungs in the following ways: (a) Cut open the trachea and observe the inner wall. (b) Observe the colour of the lungs. (c) Cut a piece of lung tissue and observe its colour. Record your observations in the table below. Results Smoking lungs Non-smoking lungs Inner wall of the trachea Colour of the lungs ﬁolour of the lung tissue ¢ In Experiment 7.14, the colour change of the lungs is caused by tar in cigarette smoke. Tar is a sticky substance that deposits in the lungs and other parts of the breathing system when a person smokes. It therefore affects gas exchange. Let us look further into this on the next page. tar Sl 49 Living Things and Air In a healthy person, the airway all along the trachea, bronchi and some larger bronchioles mucus-secreting cells and ciliated cells: nasal are cavity, lined with e The mucus-secreting cells secrete mucus which traps particles and bacteria entering the breathing system. dust o The ciliated cells have tiny hairike cilia (singular: cilium) on their surfaces. The cilia move back and forth to sweep out the NOISN3ILX3 mucus in which the dust particles and bacteria are trapped. ciliated cell ©®—— dust particle mucus-secreting cell [ Key: —> Fig. 7.22 direction of mucus flow How mucus and cilla work to remove dust particles and bacteria Inside the airway of a smoker, the tar in cigarette smoke causes the cilia to stick together, and also increases mucus production. Mucus builds up in the airway, making the airway narrower. It is more difficult for air to pass into and out of the lungs. The mucus may also block the air sacs, making gas exchange even more difficult. Smoking makes gas exchange in humans more difficult. 4. Effects of smoking on health Cigarette smoke substances, contains such as many tar, harmful nicotine and carbon monoxide. These substances have many harmful (Table 7.3). effects Flg. 7.23 on our health Harmful substances in cigarette smoke can kill, mucus-secreting cell $572 cillated cell #E4n5 clia 8% 4AE nicotine BT carbon monoxide —&ALE % - Ljving Things and Air Activity 7.6 Tolbe STALISHo 195 up ot o tire ard TOUTH [ Quit smoking! Sroking Imagine you are a graphic designer working in the Department smokers of Health. Design to quit smoking. Some a poster to persuade references are shown on the right. ESN Srseme Electronic cigarettes Electronic cigarettes (e-cigarettes) do not burn tobacco. These | devices run with batteries. They work by heating up a flavoured l i solution, which vaporizes and therefore the user can inhale. This creates a feeling like smoking. E-cigarettes have different flavours such as soft drink, fruit and chocolate. Most not manufacturers addictive. solution claim that e-cigarettes are harmless However, studies show and that the flavoured and the vapour formed contain harmful chemicals. e-cigarettes Some people also doubt whether e-cigarettes are safe to use as some cases of e-cigarette explosion E-cigarettes have become have been reported. more popular. Some people urge the government to regulate their sale in order to protect public health. However, some claim e-cigarettes can help smokers quit smoking. Search the Internet for more information and discuss whether their sale should be regulated by the government. \4 ( Checkpoint 7.8 . «e-Checkpoint Eex Write ‘T’ for a true statement and ‘F for a false statement. (a) Cigarette smoke contains only three harmful substances. [ (b) Tar in cigarette smoke stimulates mucus production in the airway. ‘ M () Tiny hairike cilia along the airway helps remove dust particles and bacteria. tobacco & vaporize {t, sz Living Things and Air N 3. When the gas jar is filled with your exhaled air, cover it with a cover plate under water. Take the gas jar out of the water and label it ‘exhaled air’. cover plate cover plate <& insert 4. Use the same method to collect another jar of exhaled air. 5. Leave another two gas jars open to air for a moment and then cover each of them with a cover plate. Label them as ‘inhaled air’. Part B: Comparing 6. (a) the oxygen content Put a burning splint into a jar of exhaled air. Record the time taken for the flame of the burning splint to go out in the table on the next page. Wear safety goggles. Start timing (b) Repeat Step 6(a) with a jar of inhaled air. Stop timing [ Gas exchange in animals 1. Comparing inhaled air and exhaled air We need to take in oxygen from the air and remove carbon dioxide from our bodies. There is gas exchange between our bodies and the environment. By comparing the composition of the air we breathe in (inhaled air) and the air we breathe out (exhaled air), we can find evidence for this gas exchange. Experiment video af ! ev07s9 Comparing the oxygen and carbon dioxide contents of inhaled air and exhaled air Material and apparatus gas jar 4 bendable straw 2 stopwatch 1 cover plate 4 wooden splint 2 measuring cylinder (10 cmz) 1 water trough 1 gas lighter 1 hydrogencarbonate indicator Procedure Part A: Collecting inhaled air and exhaled air 1. Fill a gas jar with water in a water trough as shown. Then, place it upside-down. gas jar completely filled with water 2, Insert one end of a bendable straw into the gas jar. Take a deep breath and then blow slowly through the straw. Repeat until the gas jar s filled with exhaled air. b Caution * * Every student should use a new straw, Do not share a straw for this step. Students who are exempted from P.E, lessons for medical reasons or have symptoms of respiratory illnesses should not perform this step. Inhaled alr MARIZSR erhaled air BRIV =N Exhaled air Inhaled air |‘(Time taken for the flame of lﬁurning splint to go out (s) Conclusion Exhaled air contains Part C: Comparing 7. (@ Add 5 cm® oxygen than inhaled air. the carbon dioxide content of hydrogencarbonate indicator to a jar of exhaled air. Cover the jar immediately and shake it gently. Record any colour change of the indicator in the table below. (b) Repeat Step 7(a) with a jar of inhaled air. () hydrogencarbonate indicator Exhaled air Inhaled air Colour change of the hydrogencarbonate indicator Conclusion Exhaled air contains —___ carbon dioxide than inhaled air. Refer to p.32 for the colours of the hydrogencarbonate indicator in different carbon dioxide contents.

Gas Exchange in Plants and Animals PDF

Document Details

Tags

Related

Summary

Full Transcript

Upgrade to continue