Gas Exchange in Animals PDF

7.5 Gas exchange in animals.5 ¥ g Fu *..s o R...

7.5 Gas exchange in animals.5 ¥ g Fu *..s o R T R - e Ny e s B Q Flipped classroom Gas exchange does not happen only in plants. It occurs in animals too. Watch a video.E - Let us carry out Practical 7.12 and 7.13 to find out more about gas and answer the questions. exchange in animals. \ ‘ Practical.12 Studying uptake 6r release of carbon dioxide Aim To find out the change in carbon dioxide content in a boiling tube with mealworms™ - - - — —_— _— - Apparatus and materials per group ‘ boiling tube 2 forceps § stopper 2 cotton thread pe r A.piece 1 test tube rack 1 mealworm ; measuring cylinder (10 cm?) 1 hydrogencarbonate indicator plastic vial with small holes 1 — —_— N —_— = —e e 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 Wear disposable gloves holes 2 when handling mealworms. e mealworms o oy 3 Stopper the two tubes. Make sure there is no air hydrogencarbonate MO st indicator leakage. [ gt | 4 Leave the set-up for one hour. Record the colour of the indicator in each tube. cont. oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo mealworm Z K £ 47  Colour of hydrogencarbonate indicator At the beginning — felo pit o €1 L fipd w1 gy Discussion 1 Whatis the purpose of setting up tube B? Tube B ¥s WJLPO) 59%’&{'3 VMLes SULe He resul 2 What can you tell about the gas exchange of the mealworms from the results? The indicator in tube A Wrns e (\ow while the indicator in tube B remainS 1o. This shows that the mealworms gi 3 omL carbon dioxide. 3 Suggest a reason for the change in carbon dioxide content in the two tubes (if any). The | ,G»‘ILLJM,/X 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 A e R L s ool Lo b 2 L e AR R O i o T e N AR e ool i e o 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 ? e 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 Avioid coftact withskin. tube again. Record the results. Results Distance between the colour marker and the stopper (cm) Tube S At the beginning After 20 minutes Discussion Why does the colour marker move in tube A? e The mealworms carry out respiration. They takein adse VXYqgg,~ LOJHON (oxygen / carbon dioxide) and give out Maw Jioxfaiq, (oxygen / carbon dioxide). The ca f,gm A.‘o ;qb\Q (oxygen / carbon dioxide) is absorbed by soda lime. e The decrease in oxygen inside the tube causes the gas pressure in the tube to JW (increase / decrease). The pressure becomes /awfl/ (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’)? “ Pracfical 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 completely gas jar filled with water trough water at ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo SO inhaled air RARZER exhaled air "EHEYZER  Gas exchange in animals 3 Insert a rubber tub ing wit h a clea n 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 sulating 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) Bt ] e e s Dol sbixoi nodhes (ol \ o) __ o] e e R R A A R R R R R R R R YY) LA EE R ERE R Rl A R R R R R e oo R T R R R e e P L LR L L L A R A A g PP respiratory iliness MR ip R A  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 Il 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 xhaled (inhaled / exhaled) air while its colour remains unchanged in the ) r\ka,\e)» (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 A 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. e Students with symptoms }' mirror of respiratory illness should not do this step. e \Wash the mirror with a suitable disinfectant and water after the practical. Results What happens to the colour of the cobalt chloride paper after rubbing the mirror a before we breathe onto the mirror (step 2)? I'f remarns l)’uw b after we breathe onto the mirror (step 3)? MWL ‘{o F.}\k = ‘ ‘ - Discussion What do the results show? = X aJ AlY w’fM‘M Mmert hnk"' Vapouwr 'H‘fl”‘ l"\;\al&l aur. 2% B AL J3  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. ‘ ACtiVity 7.2 Thé 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 i nasal cavity™ nostril* rib* trachea™ C rached d br‘or\Ckw : S llk 0 NronCn10I|¢ h 15 ALY SoL oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo 54 breathing system MEAR Z4%: airsac RE bronchiole NXRE bronchus (pl. bronchi) X®/E diaphragm f&iRAR intercostal muscle BhfSUL lung f5 nasal cavity &2 nostril #fL rib B1® trachea |E  Gas exchangde 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 Wlth capillaries*. Car)i//afi(", (n/u‘//flyic', r:izl/)"//(f,;/;}“z, L,"fl/)/'//fuf'/"(; o 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 RAreOgh e o) 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 & * f v air sacs -y......... capillary air sac Fig 7.20 The Iungs and the air sacs Ay R -‘/. -. KON P N 3 \") ™~ : J\\Cfi& '{\rlc_)“ 3{ Q‘VM‘ K@ Ay The diagram below summarizes the path of air flow when we breathe LA 5 ‘c‘;( P in and breathe out: \ \ ‘ , J‘\J‘\i\') Wit (O path of air flow when we breathe in | a8 “ \ hC (/0 N ;}—, bronchloles a|r cs sa o) L \\° W\ ! U ¢ U O/\r \VNU ) ‘ ‘Ny\-_,é\ Q path of air flow when we breathe out r :;%J;\ | \ ‘(\%\‘O}w \ 10 Al '\ R --------- oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo 55 capillary £ &  , ( nAL (’l) -“’\,'J' The lungs are protected by the rib _cgge,*. 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. trachea lungs rib )' ‘ ;. | /4 t sternum intercostal - ‘ muscle diaphragm Fig 7.21 The lungs are protected by the rib cage & Misconception () ' X The terms ‘breathing’ and ‘respiration’ describev”. *. G cns : the same process. S / Breathing and respiration are two different AN processes. Breathing is the physical process R of moving air into and out of the lungs. Respiration is the chemical process of releasing energy from food in cells. O Practical 7.15 \ Dissection of pig lungs (Teacher demonstration) Aim To observe the structure of pig lungs. ———————— l 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 Wear safety spectacles! —- _— —_— Caution () e Cover any wounds with bandages. e Wear disposable gloves. * Wash your hands with soap and water thoroughly after the practical.. oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo 56 ribcage fhB# sternum 3%  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. irdchas a What is the colour of the lungs? i') Mlé b Suggest a reason for{ tbe colour of the lungs. ungs 2 N TI—(A'Q’M‘Q/ ; /“” 477\1(’/“0-/7 /”/' % 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 Iungs an air pump. What happens to the lungs? The lungs inreas®s 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 + ‘ochS (floats / sinks). b Squeeze the lung tissue in water. What can you observe? Bubobles come out from the lung tissue. ¢ What do the results show? There is MY inside the lung tissue. 37  3 Gas exchange at air sacs 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. @ °* Carbondioxide 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 r.Animation? R T body when we breathe out. carbon oxygen dioxide fi Inhaled air enters e Carbon dioxide is removed the air sac. from the body when we breathe out. blood R The blood then s 90 carries oxygen to n The blood carries :cha p l?;(:i);zell ; s ¥ carbon dioxide from e the body cells to the air sac. air sac capillary Oxygen in the inhaled e 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. oy ¢1 BNEE | PR Yol | 35 el o ai o g ek Rk Iag i K 1 n - the (E?a;;aaflfl_lrau_u:@fi,, (drpen MOXIAQ passes from the blood 1n the ;‘Jow]?ssnix‘cf:t into the air sac o~ 5‘." ,-—'4 - :_—'J'b o | -‘r— n] ¢ :—" Y e 58  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. T T T A W ) o fif&&f@f&}\ & Misconception (o 7 5 ’ X Inhaled air is oxygen and exhaled air is carbon dioxide. ] | / Both inhaled air and exhaled 7 air contain oxygen and carbon i dioxide. The main difference is. the percentages of these gases. R ] : e it gl et e M P o et o Co ith inhaled air,e aled ek PR air & i e e contains___lees 552N 1 (mo/ r lesse ) oxygen; Y v 3 I L s ityg;?'h-” |. ] ' ; o~ & "o r ‘ 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) 29  £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 SfuGorther.(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. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 60 badminton court SFJEHS 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 -~ z into and out of a pair of pig lungsto demonstrate the effects of smoking. > - \‘;"’n 1 to vacuum | \ | pump | 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? - /\9/ & S s 3 910 i 5 0’&» F' A AT 7‘}% fJ/\Q/ £ WU SW i fog 2 What other differences can you observe between the tissue of the two pairs of pig lungs? Sowt._browr substunge, is prtsint nthe fisswe of A smolking o9 lungs Tt 3 What are the differences between the tracheas of the two pairs of pig lungs? Tle ey wu“ ‘}’Zc 'IL hed, J"f '/Lc/hbma ) pig lungs 12 Aok ened “//‘5/ fld"c &L -;L!g: fm\vfifiil‘fi‘? 'filz /%fl; £ #{hlé, 61  Tar” and some other chemicals in cigarette smoke reduce the 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 black tar 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. e Certain chemicals cause the walls of the air sacs to break down. The surface area for gas exchange becomes smaller. 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). bt -normal. bronchlole of 10 bronchiole. aperson with chronic bronchitis narrower due to inflammation €XCesSSs mucus Fig 7.26 A normal bronchiole and a bronchiole of a person with chronic bronchitis The efficiency of gas exchange is lowered in people with these diseases. Can you explain why? \ : Smokmg reduces the eff1c:1en‘ 62 tar 51 carbon monoxide —4& Lk emphysema i@ chronic bronchitis 8 XREX inflammation 24 mucus $4&  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. ?7 "’{%d’ I‘Qr"\(cn\&?er’ ‘HW‘Q/Q/ Harmful effects of smoking Smoking harms nearly every organ in our body. It is known to cause various diseases. For example: mouth 5 cancer stroke™ ! lung 2 191 C);‘v{/l’l; 15 cancer bronchitis™ ED ;L 2oL\ 4D hgart * A n3e5 Le A diseases”™ ° fiftnnanee 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) oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo oooooooooooooooooooooooooooooooooooooooooooooooooo......... ooooooo nicotine E™R T addictive (& A FFBAY mouth cancer A &3 lung cancer fitifE stomach cancer B & stroke & 65 bronchitis X R &4 heart disease /&  Smoking also affects our looks. For example: e ageing” of skin becomes faster ™ breathsmensbad @cccrceccccccssscscccce ® teethtumyellow Pk W% B BRI AR NE B * hair and clothes carry a bad smell of cigarette smoke * fingernails turn yellow So DO NOT SMOKE! ({Gofuither.(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. s SR R LI R == _7,,-7;;_':‘? Fig 7.27 An e-cigarette - Learn more about the health effects of e-cigarettes on the Internet. electronic cigarettes health effects £O4 64 ageing Z{t electronic cigarette &F1&  v Gas exchange In animals ¢ 3 |o 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 ({84 ¥SectionfsummarnyR7:s. 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. on | mencmd b e carbon dioxide passes from the blood in the capillaries into the air sacs. 290