Gas Exchange in Animals PDF

/.5 Gas exchange in animals Fas re To Se AEETo Li Abeeee BESE Ce...

/.5 Gas exchange in animals Fas re To Se AEETo Li Abeeee BESE Ce v Flipped classroom Gas exchange does not happen only in plants. It occurs in animals too. Watch a video B ~ Let us carry out Practical 7.12 and 7.13 to find out more about gas and answer the questions. exchange in animals. \ ® Practical 7.12 St ud yi ng up ta ke or re le as e of ca rb on di ox id e in animals Aim To find out the change in carbon dioxide content in a boiling tube with mealworms” ———— - I I ——— — Apparatus and materials per group boiling tube 2 forceps stopper 2 cotton thread a Nipiece 1 test tube rack 1 mealworm measuring cylinder (10 cm?) 1 hydrogencarbonate indicator f plastic vial with small holes 1 — RE - EC — ——— ——— ——— - po 1 Add 3 cm’ of hydrogencarbonate indicator to each of two boiling tubes (A and B). Record the colour of the indicator in each tube. 2 Use a pair of forceps to put some mealworms into a plastic vial with small holes. Put the plastic vial into tube A. Make sure the mealworms do not touch the indicator. plastic vial Caution with small WY Wear disposable gloves holes OT So ye AR when handling mealworms. mealworms CR Er hydrogencarbonate 3 Stopper the two tubes. Make sure there is no air RT indicator leakage. aed 4 Leave the set-up for one hour. Record the colour of the indicator in each tube. cont. LLL LL rT Tr EE E mealworm ZK £ a4?  Colour of hydrogencarbonate indicator Tr Yolo SRT TSE Discussion 1 What is the purpose of setting up tube B? Tube B® Ys coli) seT-up. IF makes sue fle resul 2 What can you tell about the gas exchange of the mealworms from the results? The indicator in tube A Wns Je (low while the indicator in tube B remains es. This shows that the mealworms 9 Ve owl carbon dioxide. 3 Suggest a reason for the change in carbon dioxide content in the two tubes (if any). The | in Tobe 7.13 \ Studying up ta ke or re le as e of o x y g e n in ® Practical animals (Teacher demonstration) Aim To find out the change in oxygen content in a boiling tube with mealworms Apparatus and materials per class boiling tube 2 capillary tubes fitted into stoppers wire gauze 2 (with colour marker inside the tubes) 2 ruler 1 mealworm soda lime 2 bags VRB a EE EE ES Do you remember that we used soda lime in Practical 7.7 (p. 29)? In this practical, we will use it to absorb carbon dioxide again. 48  Gas exchange in animals 1 Your teacher will set up the apparatus as shown below. wire gauze soda lime stopper capillary colour ruler tube marker mealworm boiling tube ? eo What is the purpose of. setting up tube B? 2 Measure the distance between the colour marker “— Wear safety spectacles! and the stopper in each tube using a ruler. Caution Record the results. e Wear disposable gloves when handling mealworms. 3 Leave the set-up for 20 minutes. Measure the distance e Soda lime is corrosive. between the colour marker and the stopper in each Avoid contact with skin. tube again. Record the results. Results Distance between the colour marker and the stopper (cm) Tube aa At the beginning After 20 minutes Discussion Why does the colour marker move in tube A? The mealworms carry out respiration. They take in MIL VXYqg~ aR EY nse (oxygen / carbon dioxide) and give out TLE dioxide (oxygen / carbon dioxide). The ca Din Aro x10. (oxygen / carbon dioxide) is absorbed by soda lime. e The decrease in oxygen inside the tube causes the gas pressure in the tube to Aozrenu (increase / decrease). The pressure becomes [ouwrey (lower / higher) than the atmospheric pressure. As a result, the colour marker is pushed towards the boiling tube. 49  Animals (like mealworms in Practical 7.12 and 7.13) exchange gases with the surrounding air. They take in oxygen for use in respiration. The carbon dioxide produced in respiration is released to the environment. Let us learn about gas exchange in humans in detail in the following sections. Gas exchange in humans 1 Comparing inhaled and exhaled air We breathe all the time. What are the differences between the air we breathe in (inhaled air”) and the air we breathe out (exhaled air’)? ® Practical 7.14 \ Comparing inhaled and exhaled air Aim To compare the oxygen content, carbon dioxide content and water vapour content of inhaled air and exhaled air Apparatus and materials per group gas jar with cover plate 4 forceps 1 pair measuring cylinder (10 cm’) 1 mirror 1 water trough 1 dry cobalt chloride paper 2 stopwatch 1 candle 2 rubber tubing 1 insulating mat 2 drinking straw 2 gas lighter 1 burning spoon 1 hydrogencarbonate indicator Part | Collecting inhaled and exhaled air 1 Cover two gas jars with cover plates. The two jars are filled with atmospheric air (i.e. inhaled air). Label them ‘inhaled air’. 2 Fill a gas jar with water in a water trough as shown below. gas jar gas jar completely filled with water trough water at LL LLL EL EE RE PEELE Ea pe SO inhaled air MARZER exhaled air "EH EYER  Gas exchange in animals 3 Insert a rubber tub ing wit h a cle an dri nki ng str aw into the gas jar as sho wn bel ow. Blow into the drinking straw slowly. Repeat several times until the gas jar is completely filled with exhaled air. Caution e Do not share the exhaled air drinking straw drinking straw. Blow slowly to avoid the water splashing out. water trough Students who are rubber tubing exempted from PE water lessons or who have symptoms of respiratory illness” should not do this step. 4 Cover the gas jar with a cover plate under water. Take the jar out and label it ‘exhaled air’. 5 Repeat steps 2 to 4 to collect another jar of exhaled air. Part Il Comparing oxygen content 1 Light a candle and fix it on a burning spoon. 2 Open the cover plate of a jar containing inhaled air. Immediately lower the burning candle into the jar. Record the time required for the candle flame to go out. ~~.) Wear safety spectacles! burning spoon burning candle A mat 3 Repeat steps 1 and 2 with a jar containing exhaled air. Results Type of air Time required for the candle flame to go out (s) Baie] Ts bianca shinai ods fal om) een] PTI rrr rr rR A EE AE RA EEE EEE EEE EEE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EE EYE] AEE EERE] RI ZEEE EE EE EE EE EE EE EE EE EEE EE - EA EE EE EE ER Ea PP FEE EEE ELL EA ad respiratory illness MIZFRFk A in  Discussion What do the results show? The candle burns for a longer time in the gas jar containing (inhaled / exhaled) air. Since oxygen supports burning, the results indicate that inhaled air contains (more / less) oxygen than exhaled air. Part lll Comparing carbon dioxide content 1 Slightly open the cover plate of a new jar containing inhaled air. Add 5 cm” of hydrogencarbonate indicator to the gas jar. Immediately cover the gas jar and shake it gently. Record the colour of the indicator. hydrogencarbonate § indicator 2 Repeat step 1 with a new jar containing exhaled air. Results Colour of hydrogencarbonate indicator Exhaled air Discussion What do the results show? The hydrogencarbonate indicator changes to yellow when it is shaken with the exhaled (inhaled / exhaled) air while its colour remains unchanged in the ) nhaled (inhaled / exhaled) air. This indicates that exhaled air contains MOK (more / less) carbon dioxide than inhaled air. 52  Gas exchange in animals Part IV Comparing water vapour content 1 Use a pair of forceps to take out a piece of dry cobalt chloride AK caution paper from the desiccator. Do not touch the dry cobalt chloride paper with bare hands. Otherwise, the moisture on your hands will change the colour of the paper. 2 Wipe a mirror with a piece of tissue paper to ensure it is dry. Rub the dry cobalt chloride paper on the mirror. Record the colour of the cobalt chloride paper. dry cobalt chloride paper mirror 3 Breathe onto the mirror for 10 seconds. Rub another piece of dry cobalt chloride paper on it. Record the colour of the cobalt chloride paper. Caution e Use a clean mirror. * Students with symptoms 3 mirror of respiratory illness should not do this step. e Wash the mirror with a suitable disinfectant and water after the ———— practical. ————— — Results te ———— What happens to the colour of the cobalt chloride paper after rubbing the mirror ——————— a before we breathe onto the mirror (step 2)? Tf Femarnb Sie b after we breathe onto the mirror (step 3)? blu 0 AN gu Discussion What do the results show? X a AlY conan Mert wo Vapour Ham Prhaled ar. 2% Bh AN 3  From Practical 7.14, we see that exhaled air contains less oxygen but more carbon dioxide and water vapour than inhaled air. To understand why there are such differences, we need to learn how gas exchange occurs in humans. 2 The human breathing system Humans have a well-developed breathing system” for gas exchange. Gas exchange ensures that there is a supply of oxygen to body cells for respiration and the carbon dioxide produced by body cells is removed. Let us learn about the main parts of the system in the activity below. R 4 Activity 7.2 The human breathing system 1 Your teacher will show you a human torso model or a computer model of the human breathing system. Identify the main parts of the breathing system. Label the diagram below using the words provided. 2 Draw arrows to show how air flows into and out of the system when we breathe in and breathe out. —— — air sac* bronchiole* bronchus diaphragm® intercostal muscle” lung * nasal cavity nostril” rib* trachea™ Aso Covi b 5 Chon not) d ; wr iifercostal mcs f : J LL LL rrr TTT rr rE Eh dd PA PRR EL 54 breathing system FFIRZ 4: air sac A 3 bronchiole /\X®% bronchus (pl. bronchi) XF#%E diaphragm t& IEE intercostal muscle BhfSUL lung ff nasal cavity BE nostril BFL rib B1® trachea |E  Gas exchange in animals In the lungs, there are millions of tiny cup-shaped structures called air sacs. Gas exchange takes place at air sacs. Their surfaces are covered with capillaries”. Capi loviet ca pi lay ics cap i (ices Capille yi€s Air from the atmosphere flows into the air sacs via a system of tubes. We can also breathe » When we breathe in, air flows through the nostrils and nasal cavity to proughiine mai the trachea. The trachea divides into two smaller tubes called bronchi. Inside the lungs, the bronchi further divide into bronchioles. The bronchioles end in the air sacs (Fig 7.20). trachea bronchiole bronchiole bronchi or.- * f _ air sacs AD v Ld ’ i capillary air sac Fig 7.20 The lungs and the air sacs oy hy,. ')pS € ; Au J E/ 5 (0). hy RL | WEgh! : N ) et 0. J h Laud & EOF 3 0 » :. X or Ye The diagram below summarizes the path of air flow when we breathe i in and breathe out: CLAIRE 1 : a) AX al AA of) ) path of air flow when we breathe in SdY Th sidih oo fo Co (oe (2 (EE wo 2 Re path of air flow when we breathe out ———— ry - - ¢essvanny ITE LPT LR Tr Lo atch hots echidna: & gir diate nbc ib tata bt sad ot oinih chit uit id 55 I FOF IE PURE or PE Ir IL Ppa er ry Prd Fr i ras Per rd Mr RUA PEE TEI capillary if iE. t nAL [ 1V) AY The lungs are protected by the rib cage”. The rib cage consists of the ribs, the backbone and the sternum’ (Fig 7.21). Intercostal muscles are present between the ribs. Below the lungs, there is a sheet of muscle called the diaphragm. The actions of the intercostal muscles and the diaphragm bring about breathing. ; 3 lungs trachea :.1 rib = £- L sternum > £4 intercostal ; muscle diaphragm Fig 7.21 The lungs are protected by the rib cage © Misconception (© As ‘ X The terms ‘breathing’ and ‘respiration’ describe the same process. a 5 V4 Breathing and respiration are two different a] processes. Breathing is the physical process SN of moving air into and out of the lungs. Respiration is the chemical process of releasing energy from food in cells. ® Practical 7.15 \ Dissection of pig lungs (Teacher demonstration) Aim To observe the structure of pig lungs — re—— { ee Apparatus and materials per class fresh pig lungs 1 pair air pump 1 dissecting board 1 beaker (glass or plastic) (500 cm?) 1 SCISSOrs 1 pair Caution e Cover any wounds with bandages. e Wear disposable gloves. * Wash your hands with soap and water thoroughly after the practical.. TTL LE ET TT PPP PY ELL Shh 56 ribcage fhE# sternum [3F  Gas exchange in animals 1 Your teacher will show you a pair of pig lungs. Identify the trachea and lungs. 2 Observe the colour of the lungs. tachea a What is the colour of the lungs? nls b Suggest a reason for the colour of the lungs. ungsS Np Tore sre 7 / Uy y PW ge-: Ls / U ” (/ 3 Press the lungs gently with your fingers. How do you feel? The lungs are Spongy (spongy / rigid). 4 Your teacher will pump air into the lungs with pig lungs an air pump. What happens to the lungs? The lungs increases in volume. 5 Your teacher will cut open the trachea and the bronchi. Observe how the trachea branches into two bronchi and how each bronchus branches into smaller tubes. 6 Your teacher will cut a piece of lung tissue and put it into a beaker of water. a What can you observe? The lung tissue + lols (floats / sinks). b Squeeze the lung tissue in water. What can you observe? Bubbles come out from the lung tissue. c¢ What do the results show? There is MI inside the lung tissue. SY)  3 Gas exchange at air sacs Extension Oxygen and carbon dioxide are exchanged between the air in the air sacs and the blood in the surrounding capillaries (Fig 7.22). e When we breathe in, inhaled air enters the air sacs. In the air sacs, oxygen in the inhaled air enters the blood in the capillaries. The blood then carries oxygen to the body cells for respiration. e Carbon dioxide is produced by the body cells during respiration. The blood carries carbon dioxide to the air sacs. Carbon dioxide then passes from the blood into the air sacs. It is removed from the body when we breathe out. carbon oxygen dioxide @ Inhaled air enters Carbon dioxide is removed the air sac. from the body when we breathe out. blood R The blood then fans OR [2 blood carries oxygen to Ba Be ody cells for 3 @ The blood carries 4 p. carbon dioxide from rend the body cells to the air sac. air sac capillary (2 Oxygen in the inhaled & Carbon dioxide then air enters the blood in passes from the blood the capillaries. into the air sac. Fig 7.22 Gas exchange at air sac In the air sacs, air is moistened by the water on the surface of the air sacs. It is also warmed by the blood in the capillaries near the air sacs. Therefore, the exhaled air contains more water vapour and is warmer than the inhaled air. OX Yejer» passes from the air sac into the blood V.% a joi - i | 1 :1 1 BE = } ba Ph coe “a Vwi EY, E: Rn in tho ~anillarioc 4 mma AINX 70. Naceee from the hlonad ; : La 4 veh rang. wv —r CT a”  Gas exchange in animals “Due to the process of gas exchange in air sacs (p. 58), the composition and temperature of inhaled air and exhaled air are different. These differences are highlighted in blue in the table below. | LA G fuateh ’ Ha. € Misconception (¢ X Inhaled air is oxygen and exhaled air is carbon dioxide. if Val Both inhaled air and exhaled Se 7 air contain oxygen and carbon ia ’ dioxide. The main difference is the percentages of these gases. : A TR - a 4 i So ‘4 ARTLINE Ry? Tre x gn coy —_— HA E- Shin gl eas es - Comp ith inhaled air, exhaled air. '. TE cena ie 1 { ELSt bk 3 ads al ho d :. Ra, ~ va eg eo contains les (mor / lesse ) oxygen; Sow PASAY 1 ar Write ‘T” for a tru e sta tem ent and ‘F’ for a fals e sta tem ent in the box es provided. 1 Exhaled air contains more carbon dioxide than oxygen. 2 Nitrogen is present in both inhaled and exhaled air. Check your answers (p. 88) 39  £Did you know?.(» } Total surface area of air sacs There are about 600 million air sacs in our lungs. Their total surface area is about 80 m* — almost the area of a badminton court®! The large total surface area increases the efficiency of gas exchange. Fig 7.23 A badminton court (Go further. (2 Gas exchange in other animals Different animals may use different structures for gas exchange. Some examples are shown below. Fish Gas exchange takes place in their gills. Some salamanders”® Gas exchange takes place in their external gills and through their skin. external gill Frogs Gas exchange takes place in their lungs and through their moist skin. Find out the structures used for gas exchange in some other animals on the Internet. Share the findings with your classmates. J LL LLL LLL LL Tr 60 badminton court FES salamander $247  Gas exchange in animals 4 Effects of smoking on gas exchange When people smoke, they are breathing in over 7000 chemicals. Some of these chemicals damage the breathing system and reduce the efficiency of gas exchange. & A ctivity 7.5 Effects of smoking on pig lungs Your teacher will show you a video. plastic box In the video, cigarette smoke is forced = cigarette — into and out of a pair of pig lungsto ~ demonstrate the effects of smoking. i \. \ to vacuum | \ |. pump ph { | Fig 7.24 The set-up of the experiment in the video Observe the differences between the ‘smoking’ and ‘non-smoking’ pig lungs shown in the video and answer the questions. 1 What are the differences between the colour of the two pairs of pig lungs? Le Lag : ’ SE , n | na Sm p1( 1S NL Age Fam fe néy\— Single. 2 What other differences can you observe between the tissue of the two pairs of pig lungs? Sot, brown subsume is prised nthe Toswe of He smoking py lungs Tt | 3 What are the differences between the tracheas of the two pairs of pig lungs? Tle hey ol] He 1 hed, oA le, "sms ra pig lands 1° Ark ened JA A SL 4 "ner 5 “ind P re. wine, 61  Tar® and some other chemicals in cigarette smoke reduce the Extension efficiency of gas exchange in the following ways: * Tar is deposited in the lungs (Fig 7.25). It covers some of the surface of the air sacs. As a result, the efficiency of gas exchange is reduced. non-smoker smoker | aod ec ia — v Y ¥ 1 » a ¥. - * po X BELENL 2? black tar +3 deposits Fig 7.25 Lung tissue of a non-smoker and a smoker e Carbon monoxide” reduces the oxygen-carrying ability of blood. Less oxygen in the air sacs can enter the blood. eo (Certain chemicals cause the walls of the air sacs to break down. The surface area for gas exchange becomes smaller. Go further. (¢ } Respiratory diseases caused by smoking Many smokers develop emphysema™ and chronic bronchitis*. In emphysema, the walls of air sacs are destroyed and become less elastic. In chronic bronchitis, the bronchi and bronchioles become narrower due to inflammation® and excess mucus” secretion (Fig 7.26). Fl e ; MAES D " Su “normal. - a Sa = PR bronchiole of an bronchiole «CSS [gW- San a person with a FAX vd S | chronic bronchitis  Gas exchange in animals 5 Effects of smoking on our health Apart from reducing the efficiency of gas exchange, smoking has many other effects on our health. For example, nicotine” in cigarette smoke is addictive”. Some other harmful effects of smoking are shown below. 954 legit einer three Harmful effects of smoking Smoking harms nearly every organ in our body. It is known to cause various diseases. For example: mouth cancer stroke™ | lung : hh nh 15 cancer bronchitis ™ heart 120 0585 * > feetatnnet About 8 million people around the world die from diseases related to smoking each year. This means about 15% of the deaths around the world are related to smoking. Studies found that life expectancy for smokers is at least 10 years shorter than for non-smokers. (Source: Website of Centers for Disease Control and Prevention — Health Effects of Cigarette Smoking, October 2021 & website of World Health Organization — Tobacco, May 2022) btdttittthbiididbbdbdidd ibid iddd iii tid idd ddd ad ddd ddd ddd ll Litt lid ddd add ddd edd dd idlad dit ldddidiad ddd adil tit AIT ltd adiAilid iT Tiill vet ye tere tr titra r at ree Ed ET EEE pO Seesnunnn nicotine ET addictive {# A FEB mouth cancer EC FEfE lung cancer fifif8 stomach cancer 8% stroke BE 65 bronchitis ZX RE 4 heart disease ‘EE Smoking also affects our looks. For example: ageing” of skin becomes faster :. breath smells bad ®+ +++ sseeeeeeees ® teeth turn yellow Gruss vans F IB Ve Ea * hair and clothes carry a bad smell of cigarette smoke * fingernails turn yellow So DO NOT SMOKE! (Go further. (2 Electronic cigarette An electronic cigarette® (e-cigarette) is a battery- powered device (Fig 7.27). It produces a vapour for the users to breathe in by heating a liquid. The liquid usually contains nicotine, flavourings and some other chemicals. There is evidence that using e-cigarettes is harmful to health. The selling of e-cigarettes is banned in Hong Kong. LETS STE —- a ea Fig 7.27 An e-cigarette ~ Learn more about the health effects of e-cigarettes on the Internet. electronic cigarettes health effects §O4  Gas exchange In animals 4 [ Fighting against smoking in Hong Kong In Hong Kong, many policies have been carried out to discourage smoking. These policies include: e Banning smoking in all indoor areas of restaurants, workplaces and public places, and some outdoor areas. e Requiring cigarette packets to show health warnings (Fig 7.28). e Banning cigarette advertisements®. e Increasing tobacco tax®. Fig 7.28 Health warnings on cigarette packets © After-class activity (5 } Search for more information about the long-term health effects of smoking on the Internet. Then design a poster or make a video clip to persuade smokers to quit smoking. smoking health effects (88 Sectionfsummaryk7:s. iF 1 Compared with inhaled air, exhaled air contains less oxygen, more carbon dioxide, more water vapour and has a higher temperature. 2 Gas exchange ensures that there is a supply of oxygen to body cells for respiration and the carbon dioxide produced by body cells is removed. 3 In humans, gas exchange takes place at the air sacs. ®@4 In the air sacs, e oxygen in the inhaled air enters the blood in the capillaries. Tea ary Tm e carbon dioxide passes from the blood in the capillaries into the air sacs. TY Na G5 Smoking reduces the efficiency of gas exchange. a 6 Smoking is harmful to health. It causes many diseases such as stroke, lung cancer and heart diseases. PE PT DT TT TT TT LL LLL rr rT rr EE EE ER EL LLL ARAL EAE itt TT LLL advertisement E4& tobacco tax EEF  SectionlexerciseR7.5, IF Questions 1 to 3: Write ‘T’ for a true statement and ‘F’ for a false statement in the boxes provided. 1 Exhaled air does not contain oxygen. « p. 59 2 Inhaled air mainly consists of oxygen and exhaled air mainly consists of carbon dioxide. | EF] €« p. 59 3 Gas exchange ensures there is a supply of oxygen to our body cells.