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Name: ____________________________________________ Group: __________ Support activities – Second Year of Secondary Cycle Two ACTIVITY 34 ANSWER KEY Date: __________________ EST STUDENT BOOK: Chapter 8, pages 254–261 RELATED HANDOUT: Concept review 34 The biosphere: biogeochemical cycles 1. Complete the following sentences, using the words or groups of words in the box below. You may use some words more than once. • • • • • • • • • • • • • air algae ammonia ammonium atmosphere bacteria biogeochemical biogeochemical cycle biosphere calcium carbonate carbonate rock decomposed decomposers • • • • • • • • • • • • • • • • • • • • • • • • • • decomposition DNA eat erosion essential eutrophication fossil fuels fungi glucose herbivores hydrogen hydrosphere lithosphere live living organisms loops of recycling methane nitrates nitrogen-rich fertilizer oxidized phosphates photosynthesis plankton plant proteins respiration • rock • sediment • soap • solid • spread manure • sulphur • take in • teeth • temperature • volcanic eruptions © ERPI Reproduction and adaptation permitted solely for classroom use with Observatory. biosphere a) The ________________________ is the part of the Earth where human, animal or plant life solid is possible. It is composed of the lithosphere (the ________________________ outer hydrosphere covering of the Earth), the ________________________ (the layer of water) and the air atmosphere (the layer of ________________________ ). In other words, the biosphere living organisms ________________________ is the entire system of ________________________ and their habitats. essential b) The chemical elements ________________________ to life are found in the biosphere. biogeochemical loops of recycling They move in infinite ________________________ called “________________________ biogeochemical cycle cycles.” A ________________________ is a set of processes by which an element can pass from one environment to another and eventually return to its original environment. hydrogen sulphur Carbon, ______________________ , nitrogen, phosphorus and _______________________ are essential chemical elements because living organisms need to take in live _______________________ considerable amounts of them to _______________________ and grow. Observatory / Guide 11129-B 1 ANSWER KEY Support activities – Second Year of Secondary Cycle Two ACTIVITY 34 The biosphere: biogeochemical cycles Name: ____________________________________________ Group: __________ Date: __________________ c) Carbon is very important because it is a basic element in several complex substances, such proteins as ________________________ , lipids and carbohydrates. Carbon atoms are exchanged atmosphere between the ________________________ , the hydrosphere and the lithosphere. photosynthesis d) The carbon cycle can be described as follows: It starts with ________________________ ,a process by which plants capture carbon dioxide and transform it into glucose _______________________ . To take in the carbon they need, herbivores or carnivores eat respiration _______________________ plants or other animals. Through _______________________ , living organisms return the carbon they have ingested to the atmosphere. The rest of the decomposed carbon they have taken in is eliminated as waste and ________________________ by methane organisms called decomposers, producing carbon dioxide and _______________________ . Forest fires also release large amounts of carbon dioxide into the atmosphere. Part of the calcium carbonate carbon dioxide dissolved in water becomes ________________________ . On the ocean carbonate rock floor, this substance is changed and gradually forms ________________________ . At the surface, the rock can release part of the carbon it contains by melting on contact with volcanic eruptions Fossil fuels magma during ________________________ . ________________________ also provide an important supply of carbon dioxide. atmosphere e) The amount of carbon dioxide emitted in the ________________________ has increased rapidly since the beginning of the industrial era. Human activities have upset the natural balance of the carbon cycle, with the unfortunate consequences we know too well. proteins f) Nitrogen is essential in the formation of ________________________ and DNA. However, © ERPI Reproduction and adaptation permitted solely for classroom use with Observatory. living organisms cannot use it in the form of molecular nitrogen (N2), as it exists in the air. Bacteria ________________________ must first change it into ammonia (NH3), ammonium ________________________ (NH4+), nitrites (NO2–) or nitrates (NO3–). Nitrogen exchanges lithosphere take place between the atmosphere, the hydrosphere and the _______________________ . g) The nitrogen cycle can be described as follows: Certain bacteria in the ground or water ammonia capture nitrogen from the atmosphere and change it into ________________________ and ammonium. Bacteria also oxidize ammonium to form nitrites, which in turn can be oxidized ________________________ into nitrates. Then, plants can absorb ammonium and nitrates Herbivores from the soil and from water. ________________________ eat plants, and carnivores absorb nitrogen by eating herbivores and other animals. Certain bacteria and fungi ________________________ break down animal and plant waste, resulting in the transformation of nitrogen into ammonium. Finally, other bacteria convert nitrates ________________________ into molecular nitrogen, which returns to the atmosphere. Observatory / Guide 11129-B 2 ANSWER KEY Support activities – Second Year of Secondary Cycle Two ACTIVITY 34 The biosphere: biogeochemical cycles Name: ____________________________________________ Group: __________ Date: __________________ h) The nitrogen cycle can be disrupted by several natural factors, including temperature ________________________ , relative humidity and pH. Human activities have an impact nitrogen-rich fertilizer on this cycle through farming, when ________________________ is applied to the soil to increase productivity, and through industrial processes, when factories discharge ammonia in their wastewater. In the long term, this imbalance can interfere with plant growth. i) EST Phosphorus is also an essential element, especially as a basic component of DNA ________________________ . Many animals need it to form their bones, teeth ________________________ and shells. Phosphorus is exchanged between the lithosphere, the hydrosphere and living organisms in the form of phosphates ________________________ (PO43-). j) EST The phosphorus cycle can be described as follows: Erosion ________________________ of rocks by wind or rain wears away a part of the phosphorus in rocks, and it is changed into plants phosphates. The phosphates are absorbed by ________________________ , herbivores and carnivores. Some phosphates return to the soil in animal waste (feces and urine), and decomposition others are released through the ________________________ of dead animals and plants decomposers by ________________________ . These phosphates make their way into the oceans, plankton where some promote the growth of ________________________ and others contribute to © ERPI Reproduction and adaptation permitted solely for classroom use with Observatory. sediment sedimentation. Over time, ________________________ containing phosphates forms rock ________________________ , and phosphorus returns to its original state. k) EST Human activities also disrupt the phosphate cycle when farmers spread manure ________________________ that is rich in phosphates on their land or when people soap dispose of wastewater containing phosphate-laden ________________________ residues. algae An excess of phosphorus in lakes and rivers accelerates ________________________ eutrophication growth. This surplus can trigger ________________________ in aquatic environments. The affected bodies of water suffer an oxygen shortage due to the presence of organisms like algae that consume the dissolved gas. 2. Name two processes by which carbon dioxide is captured and used to produce other substances. Photosynthesis and calcium carbonate synthesis Observatory / Guide 11129-B 3 ANSWER KEY Support activities – Second Year of Secondary Cycle Two ACTIVITY 34 The biosphere: biogeochemical cycles Name: ____________________________________________ Group: __________ Date: __________________ 3. How have human activities contributed to disrupting the carbon cycle? Through the combustion of fossil fuels, used in cars, and through various industrial processes. 4. EST Which biochemical cycle or cycles are involved in each of the following situations? a) sheep grazing in fields The carbon, nitrogen and phosphorus cycles b) the dead leaves left on the lawn last fall The carbon, nitrogen and phosphorus cycles c) the fire of a charcoal barbecue The b) carbon Les cycle feuilles mortes laissées sur le gazon l’automne dernier. d) the steak atedufor supperdeyesterday Les you cycles carbone, l’azote et du phosphore. The carbon, nitrogen and phosphorus cycles b) Les feuilles mortes laissées sur le gazon l’automne dernier. © ERPI Reproduction and adaptation permitted solely for classroom use with Observatory. Les cycles du carbone, de l’azote et du phosphore. Observatory / Guide 11129-B 4 ANSWER KEY Support activities – Second Year of Secondary Cycle Two ACTIVITY 34 The biosphere: biogeochemical cycles