Balance of Oxygen and Carbon Dioxide in Nature PDF

Balance of oxygen andicarbon dioxide in Nature Legelbegin v, Flipped classroom The graph below shows the changes in the level of carbon dioxide Watch a video in...

Balance of oxygen andicarbon dioxide in Nature Legelbegin v, Flipped classroom The graph below shows the changes in the level of carbon dioxide Watch a video in the atmosphere over the past 2000 years. The level was relatively and answer the questions. constant before 1700s. But it has risen sharply in the last few hundred years. Do you know why? Level of carbon dioxide i t re ov st 2000 years 400 level of carbon dioxide (ppm) 350 300 250 year 0 500 1000 1500 2000 (Source: Website of CSIRO - Latest Kennaook / Cape Grim greenhouse gas data, February 2022) A Natural balance of oxygen and carbon dioxide Respiration and photosynthesis keep a balance of oxygen and carbon dioxide in Nature. Lok Lond E Ne Whenn living things carry out respiration, hagieteup OXY Salton.hs ! V4 the atmosphere. EL c oxygen'is replaced by theoxygen produced by Ii s things produce plants SR phbfodynthesis. At the same fine, liyin ln @ during respiration. The carbon dioxide isi taken up by plants for photosynthesis. As the result, there is a natural balance of oxygen and carbon dioxide in the atmosphere (Fig 7.29 on the next page). 67  photosynthesis of plants oxygen AAD i AIA) Fig 7.29 Natural balance of oxygen and carbon dioxide in the atmosphere Big science ideas Constancy of oxygen and carbon dioxide levels in air Oxygen taken up for respiration is replaced by the oxygen given out in photosynthesis. Carbon dioxide produced in respiration is taken up for photosynthesis. The amounts of oxygen and carbon dioxide in the atmosphere remain almost constant. B Disrupting the balance of carbon dioxide Since the Industrial Revolution in the late 1700s, the energy needs for transport, industrial activities or other purposes have increased greatly. To meet the increasing energy needs, large amounts of fossil fuels are burnt. The burning of fossil fuels releases a lot of carbon dioxide. Fig 7.30 Burning large amounts of fossil fuels in (a) motor cars, (b) power stations and (c) factories gives out a lot of carbon dioxide 68  Balance of oxydaen and carbon dioxide in Nature At the same time, large areas of forest have been cleared to obtain timber or land (Fig 7.31). As a result, less carbon dioxide is absorbed Skyrise greening by plants for photosynthesis. Skyrise greening* is the greening at cleared forest area buildings above the ground level. As plants take in carbon dioxide for photosynthesis, skyrise greening can help maintain the balance of carbon dioxide level in the atmosphere. It also helps reduce heat Island effect* in urban areas. 3 he * Fig 7.31 Forests are cleared to obtain timber or land ed ~ - Ho “ be | - ch ) ~ h ——— ye i : -~ oi poe Ph , “ - » : 5 J - LJ 1 ~~ J 5 i =) Te sant) BY 3 — These human activities caused the level of carbon dioxide in the = atmosphere to rise. The natural balance of carbon dioxide has been A rooftop rooftop garden gard disrupte J" oti dod s gnissoni onl Key point ~* Living things carry out. respiration. Plants carry out A Fey : | be Ro ee ph) ofp Syh floss. These two processes keep a balance of oxygen i and carbon dioxide in Nature. | : e Some human activities (e.g. burning fossil fuels and clearing : | forests) are disrupting the balance of carbon dioxide in Nature. o { : : 5 ft Sinai Sa 1 Effects of increasing carbon dioxide level in the atmosphere on the environment To understand the effects of increasing carbon dioxide level in the atmosphere on the environment, we have to learn about the greenhouse effect” first. RE ET LL LL LLL RE ER EE ELL EE LL REEL ER disrupt #@lL skyrise greening ®ZEA#{L heat island effect 245% greenhouse effect 382 ME 69  Some gases that are naturally present in the atmosphere (e.g. carbon dioxide) trap thermal energy in the atmosphere. This causes the Earth’s surface to warm up (Fig 7.32). This warming effect is called the greenhouse effect and the gases are called greenhouse gases’. 5 Some of the thermal energy 4 Some of the thermal energy is re-emitted towards the is absorbed by greenhouse Earth's surface. This makes gases and is re-emitted in all the Earth warmer. TT directions. 3 The Earth's surface warms up. It gives 1 Sunlight passes off thermal energy. through the atmosphere and reaches the Earth. 2 Some of the sunlight is absorbed by the Earth's surface. Fig 7.32 Greenhouse effect The greenhouse effect is an important natural process. It keeps the Earth's surface at a temperature suitable for life. The increasing amount of carbon dioxide in the atmosphere traps more thermal energy and enhances” the greenhouse effect. Scientists believe that this has caused the average temperatures of the Earth to increase (Fig 7.33). This is known as global warming’. +1.1 Key: — carbon dioxide level 410 y — global temperature change +0.9 390 global temperature +0.74 370 change relative to the carbon dioxide level average temperature 10.54 350 inthe atmosphere in the period (ppm) 1881-1910 (°C) +0.34 330 +0.1 310 —0.1 290 1880 1900 1920 1940 1960 1980 2000 2020 year (Source: Website of Climate Central — Yearly Carbon Dioxide Peak, May 2021) Fig 7.33 Changes in global temperature and carbon dioxide level in the atmosphere over the past 140 years ! BR LLL LL LL LTT EE py AALE LTT TTY TY TI AEE PRPpappapurpppippappappaapy LL © FL LE EE EE EE EEL Rh Ld 70 greenhouse gas JR ZS enhance MEJ global warming ZIkER{L  Balance of oxyden and carbon dioxide In Mature a PE © Did you know? (+ } Importance of greenhouse effect The Moon receives a similar amount of thermal energy from the sun as the Earth per unit surface. However, the average temperature of its surface is —=18 °C, which is much lower than that of the Earth's surface. One of the explanations for this is the Moon has a very thin atmosphere and thus very little greenhouse effect. Go further (2) Methane — another major greenhouse gas | also a major greenhouse 0s. One of its sources is rearing™ of animals such as cattle and sheep. Methane is produced and released to the environment when these animals digest food. As more of these animals are reared to meet the increasing demand for their meat, the amount of methane released from Fig 7.34 Rearing cattle and sheep these animals increases. This worsens releases a lot of methane global warming. into the atmosphere “Home lab 7.1 Be — SIE Modelling greenhouse effect We can use a model to demonstrate the greenhouse effect. Place a thermometer on a table Place another thermometer near the under the sun. Cover it with a first one. Are the temperatures of glass bowl. the two thermometers different half an hour later? da Under adult supervision EE EERE ELLER J hth ELL LL EE TT TRL LL LLL LLL TT IN rrr  2 Possible effects of global warming Scientists believe that the rise in global temperature will bring about climate change”. Climate change may lead to the following consequences: @ A warmer climate speeds up the 1980 2020 melting of ice in the Polar regions. This will lead to: a Living things in the Polar regions (e.g. Polar Bear) lose their habitats and die. b The sea levels rise, causing the flooding of low-lying areas. Ice covering the Arctic Ocean” was much smaller in 2020 compared with that in 1980. @ Unusual weather patterns may result, e.g. more typhoons”, hurricanes”, heat waves’, droughts” and flooding. @ Living things that cannot adapt” to the warmer climate may die. For example, the higher ocean temperature may cause corals” to die. Watch videos about the relationship between carbon dioxide level in the atmosphere, global warming and climate change. carbon dioxide global warming climate change video (2) Jretneen rin oe A To EE DE TT TT PSCC PU SPREE PPS PETRI PEP SISS SSP PRT SEL CEES S 72 climate change FR#{L Arctic Ocean Jbiki¥ typhoon B4@ hurricane BE heatwave BR drought 2K adapt i@fE coral Hi  Bra f Balance of oxygen and carbon dioxide in Mature tod Cae FF AL fat rn Global climate actions NSE: “E 3 R 7 % « 3 - : To deal with global warming, over 200 countries signed the Paris Agreement” in 2015. They 8 "” agreed to help limit the rise in global temperature below 2 °C from the pre-industrial® levels (i.e. the levels before the start of the Industrial Revolution). Many countries have plans to reduce the emission of greenhouse gases. Here are some of their actions. China e Increase the share of renewable energy sources (e.g. wind power and solar power) in producing electricity e Carry out large-scale afforestation”, e.g. in northern China Solar power stations are Trees are planted on set up barren mountains “United Kingdom § e Encourage switching to electric cars®, e.g. by installing more enpEN &