Chapter 35: Respiratory Systems AP Curriculum Alignment Cells are restricted in size by the necessity of maintain a large surface area to volume. The cells of the alveoli, which are the functioning units of the human lungs, are illustrative examples in Big Idea 2for increasing surface area without increasing the volume of a cell. Chapter 35 explains how gas exchange occurs in alveoli and in simpler animals that use diffusion across their body surface for gas exchange. The various mechanisms in invertebrates and aquatic animals are explained in detail. Big Idea 2 states that homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments. The countercurrent gas exchange that occurs in gills is such an adaptation. Chapter 35 describes in detail the specialized organs of several different types of gas exchange systems and how they function. The exchange of gases appears as an illustrative example in Big Idea 4. ALIGNMENT OF CONTENT TO THE CURRICULUM FRAMEWORK Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis. Enduring understanding (EU) 2.A: Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Essential knowledge (EK) 2.A.3: Organisms must exchange matter with the environment to grow, reproduce and maintain organization. b. Surface area-to-volume ratios affect a biological system s ability to obtain necessary resources or eliminate waste products. Evidence of student learning is a demonstrated understanding of each of the following: 1. As cells increase in volume, the relative surface area decreases and demand for material resources increases; more cellular structures are necessary to adequately exchange materials and energy with the environment. These limitations restrict cell size. To foster student understanding of this concept, instructors can choose an illustrative example such as: Root hairs Cells of the alveoli Cells of the villi Microvilli Enduring understanding (EU) 2.D: Growth and dynamic homeostasis of a biological system are influenced by changes in the system s environment. Essential knowledge (EK) 2.D.2: Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments. b. Organisms have various mechanisms for obtaining nutrients and eliminating wastes. Mader, Biology, 12 th Edition, Chapter 35 497
To foster student understanding of this concept, instructors can choose an illustrative example such as: Gas exchange in aquatic and terrestrial plants Digestive mechanisms in animals such as food vacuoles, gastrovascular cavities, one-way digestive systems Respiratory systems of aquatic and terrestrial animals Nitrogenous waste production and elimination in aquatic and terrestrial animals Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties. Enduring understanding (EU) 4.A: Interactions within biological systems lead to complex properties. Essential knowledge 4.A.4: Organisms exhibit complex properties due to interactions between their constituent parts. b. Interactions and coordination between systems provide essential biological activities. To foster student understanding of this concept, instructors can choose an illustrative example such as: Respiratory and circulatory Nervous and muscular Plant vascular and leaf Enduring understanding (EU) 4.B: Competition and cooperation are important aspects of biological systems. Essential knowledge (EK) 4.B.2: Cooperative interactions within organisms promote efficiency in the use of energy and matter. a. Organisms have areas or compartments that perform a subset of functions related to energy and matter, and these parts contribute to the whole. 2. Within multicellular organisms, specialization of organs contributes to the overall functioning of the organism. To foster student understanding of this concept, instructors can choose an illustrative example such as: Exchange of gases Circulation of fluids Digestion of food Excretion of wastes Concepts covered in Chapter 35 also align to the learning objectives that provide a foundation for the course, an inquiry-based laboratory experience, class activities, and AP exam questions. Each learning objective (LO) merges required content with one or more of the seven science practices (SP), and one activity or lab can encompass several learning objectives. The learning objectives and science practices from the Curriculum Framework that pertain to respiratory systems are shown in the table below. Note that other learning objectives may apply as well. 498 Mader, Biology, 12 th Edition, Chapter 35
LO 2.25 The student can construct explanations based on scientific evidence that homeostatic mechanisms reflect continuity due to common ancestry and/or divergence due to adaptation in different environments. LO 2.26 The student is able to analyze data to identify phylogenetic patterns or relationships, showing that homeostatic mechanisms reflect both continuity due to common ancestry and change due to evolution in different environments. LO 2.27 The student is able to connect differences in the environment with the evolution of homeostatic mechanisms. LO 4.8 The student is able to evaluate scientific questions concerning organisms that exhibit complex properties due to the interaction of their constituent parts. LO 4.9 The student is able to predict the effects of a change in a component(s) of a biological system on the functionality of an organism(s). LO 4.10 The student is able to refine representations and models to illustrate biocomplexity due to interactions of the constituent parts. LO 4.18 The student is able to use representations and models to analyze how cooperative interactions within organisms promote efficiency in the use of energy and matter. Key Concepts Summary Respiratory systems in animals Respiration is the gas exchange between an organism s body and the environment. Respiration includes three steps: ventilation, external exchange of gases, and internal exchange of gases. Gas exchange depends on diffusion and for external respiration to be effective, the gas-exchange region must be (1) moist, (2) thin, and (3) large in relation to the size of the body. Some small animals conduct gas exchange over the surface of their bodies, but most have specialized tissues or organs for gas exchange. o Aquatic invertebrates and aquatic vertebrates have gills that extract oxygen from a watery environment. Fish use countercurrent exchange to transfer oxygen from the surrounding water into their blood. Water and blood flow in opposite directions. With countercurrent flow, as blood gains oxygen, it always encounters water having even higher oxygen content. o Insects have a system of air tubes called tracheae through which oxygen is delivered directly to the cells without entering the blood. o Terrestrial vertebrates usually have lungs, which are vascularized outgrowths from the lower pharyngeal region. The lungs of birds and mammals are elaborately subdivided into small passageways and spaces. Mader, Biology, 12 th Edition, Chapter 35 499
Human respiratory system In humans, air moves through the nose, the pharynx, trachea, and bronchi to the lungs. Lungs terminate in an elongated space enclosed by a multitude of air pockets called alveoli, which fall the internal region of the lungs and are the location of the gas exchange. In the nose, hairs and cilia act as a screening device. In the trachea and the bronchi, cilia beat upward, carrying mucus, dust, and occasionally small bits of food that went down the wrong way back into the throat, where the accumulation may be swallowed or expectorated. The respiratory center in the medulla oblongata of the brain automatically sends out impulses by way of a spinal nerve to the diaphragm (phrenic nerve) and intercostal nerves to the intercostal muscles of the rib cage for respiration to occur. Oxygen is brought into the body by the respiratory system but is then transferred to the blood so that it can be transported through the rest of the body by the circulatory system. Key Terms alveoli aortic bodies asthma bicarbonate ion bronchi bronchioles carbonic anhydrase carotid bodies countercurrent exchange cystic fibrosis diaphragm emphysema epiglottis expiration external respiration gills glottis hemoglobin (Hb) inspiration internal respiration larynx lung cancer lungs partial pressure pharyngitis pharynx pneumonia pulmonary fibrosis pulmonary tuberculosis respiration respiratory center trachea tracheae ventilation Teaching Strategies Class time: Two 45-minute class periods Day 1: Lecture on respiration and gas exchange across animal phyla 35 minutes Demonstrate a model of human lungs 10 minutes Day 2: Activity 1, modeling respiration 45 minutes 500 Mader, Biology, 12 th Edition, Chapter 35
Suggested Approaches As with most topics, a mix of hands on experience and the use of models and lectures increases concept understanding. To demonstrate how a human lung works, a model may be purchased or borrowed from as association like the American Lung Association, the Cystic Fibrosis Foundation, or local pulmonary physician. Student Misconceptions and Pitfalls Most students do not make the connection between metabolism, energy requirements for life, and respiration. The connection can be made clearer as students learn about the simple gas exchange of planarians that are so small and have small energy needs. Movement across land takes more energy than movement in the water due to buoyancy. Most students have experienced this. Suggested Activities Activity 1: Modeling Respiration In this activity, students will build a model of human lungs. They will use their model to answer questions about the human respiratory system. See student worksheet below. Mader, Biology, 12 th Edition, Chapter 35 501
Modeling Respiration Materials: String Pair of latex gloves Rubber band Clear 2-liter plastic soda bottle Scissors or knife Y-tubes Instructions: 1. Cut two fingers off the glove. These will represent the lungs. 2. Tie the fingers to the ends of the Y-tube. 3. Cut the bottom off the soda bottle. 4. Ask your leader to punch a hole in the bottle cap. 5. Place the Y-tube with the fingers attached into the bottle through the bottom. 6. Place the cap on bottle so that the Y-tube sticks through it out of the top of the bottle. 7. Cut a circle from the palm of the glove. 8. Stretch the circle over the bottom of the bottle and secure it with a rubber band. 9. Push up and pull down on the latex on the bottom of the bottle. What happens? Questions: 1. In what ways does the model you built do a good job of representing the lungs? 2. In what ways could your model be improved? 3. Research asthma and emphysema. Develop a new model that shows the effect of one of these respiratory diseases on lung functioning. 502 Mader, Biology, 12 th Edition, Chapter 35
Student Edition Chapter Review Answers Answers to Assess Questions 1. a. external respiration; b. CO2; c. CO2; d. tissue cells; e. internal respiration; f. O2; g. O2; 2. b; 3. c; 4. c; 5. f; 6. c; 7. a; 8. d; 9. d; 10. b; 11. b; 12. b; 13. c; 14. c; 15. d; 16. a; 17. c Answers to Applying the Big Ideas Questions 1. Animal respiratory systems achieve maximum surface area for gas exchange. For example, human lungs have a total surface area which is about 50 times the surface area of the skin. a) Describe the specialized structure of the alveoli of lungs. b) Explain how cell size and shape affect the overall rate of nutrient absorption and waste elimination. Essential Knowledge Science Practice Learning Objective 2.A.3: Organisms must exchange matter with the environment to grow, reproduce and maintain organization. 6.2: The student can construct explanations of phenomena based on evidence produced through scientific practices. 2.7: Students will be able to explain how cell size and shape affect the overall rate of nutrient intake and the rate of waste elimination. 3 points maximum. Explanations for how cell size and shape affect the overall function of the lungs may include: Descriptions of villi and Explanation of related function (1 microvilli (1 point each) Alveoli are numerous air pockets located at the terminus of bronchioles in the internal region of the lungs. point each) Through the multitude of alveoli, the surface area of the lungs is increased, increasing the capacity of the lung to perform gas exchange across membranes. Alveoli are surrounded by a capillary network. Ventilation causes the alveoli of the lungs to have a different partial pressure than the nearby capillary. This accounts for the exchange of gases between the alveoli and surrounding capillary network as the gasses diffuse from higher to lower pressure. Mader, Biology, 12 th Edition, Chapter 35 503
2. Organisms exhibit complex properties due to interactions between their constituent parts. Cooperation between the respiratory and circulatory systems ensures an effective gas exchange. Predict the effect on the circulatory system for each of the following malfunctions of the respiratory system: a) Alveoli burst and fuse into enlarged air spaces. b) Alveoli fill with pus and fluid. c) Airways are inflamed due to irritation or infection. Essential Knowledge Science Practice Learning Objective 4.A.4: Organisms exhibit complex properties due to interactions between their constituent parts. 6.4: The student can make claims and predictions about natural phenomena based on scientific theories and models. 4.9: The student is able to predict the effects of a change in a component(s) of a biological system on the functionality of an organism(s). 2 points maximum. Predicted effects of a malfunction in the respiratory system may include (1 point each): a) The surface area for gas exchange with capillaries is reduced, and less oxygen reaches the heart and brain. b) This makes breathing more difficult for the individual, making gas exchange with capillaries more difficult and often leading to cardiac disease. c) This makes gas exchange with capillaries more difficult and often leads to cardiac disease. Answers to Applying the Science Practices Questions Think Critically 1. most likely Subject C because his or her hemoglobin content of the blood is the lowest 2. most likely Subject B because the oxygen content of Subject B s blood in the arteries is the lowest (except for Subject C, whose low oxygen content is due to another reason) 3. most likely Subject E because the difference between the oxygen content of his or her arteries and veins is the smallest 504 Mader, Biology, 12 th Edition, Chapter 35
Additional Questions for AP Practice 1. How is carbon dioxide moved through the body and eventually expelled from the body? 2. Explain what alveoli contribute to the respiratory function. Mader, Biology, 12 th Edition, Chapter 35 505
Grid-In Questions 1. Most adults have a resting breathing rate of 12 to 20 ventilations per minute, assuming an average ventilation rate per minute, how may ventilations occur in one hour? 2. The skeletal muscles use more oxygen during heavy physical exercise than when a body is at rest. If person s skeletal muscles uses 0.23 L of oxygen per minute at rest, and 3.1 L of oxygen per minute during heavy exercise, how much more oxygen do a person s muscles need during 15 minutes of heavy exercise versus 15 minutes of rest? Round your answer to the nearest liter. 506 Mader, Biology, 12 th Edition, Chapter 35
Answers to Additional Questions for AP Practice 1. During external respiration in the lungs, carbon dioxide (CO2) leaves blood, and oxygen (O2) enters blood. During internal respiration in the tissues, oxygen leaves blood, and carbon dioxide enters blood. 2. Terrestrial vertebrates have lungs with a large total external respiration surface. Alveoli increase the surface area of the lungs and increases the speed and efficiency of gas exchange. Answers to Grid-In Questions 1. 960; (12+29) 2 = 16 vvvvvvvvvvvv mmm 60 mmmm hr = 960 vvvvvvvvvvvv/hr 2. 43; 0.23 L O2 mmm 15 mmm = 3.45 L O2 nnnnnn aa rrrr 3.1 L O2 mmm 15 mmm = 46.5 L O2 nnnnnn dddddd heeee eeeeeeee 46.5 3.45 = 43.050 mm mmmm Mader, Biology, 12 th Edition, Chapter 35 507