Chapter 33 Respiration Lecture Outlines by Gregory Ahearn University of North Florida Copyright 2011 Pearson Education Inc Chapter 33 At a Glance 33 1 Why Exchange Gases 33 2 What Are Some Evolutionary Adaptations for Gas Exchange 33 3 How Does the Human Respiratory System Work Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 1 Why Exchange Gases The act of breathing is called respiration The process of cellular respiration which converts the energy in nutrients into the ATP used by cells requires a steady supply of oxygen and generates carbon dioxide as a waste product Consequently the circulatory system works in close harmony with the respiratory system The circulatory system extracts oxygen from the air in your lungs carries it within diffusing distance of each cell and then picks up carbon dioxide for release from the lungs Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange Gas exchange in all organisms ultimately relies on diffusion Cellular respiration depletes CO2 levels creating a concentration gradient that favors the diffusion of CO2 out of cells and the diffusion of O2 into them Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange Although animal respiratory systems are amazingly diverse they all meet three requirements that facilitate diffusion Respiratory surfaces remain moist so that gases can diffuse across cell membranes The cells lining respiratory surfaces are very thin to facilitate diffusion of gases through them Respiratory systems have a sufficiently large area in contact with the environment to allow adequate gas exchange Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange Some animals in moist environments lack specialized respiratory structures For some animals that live in moist environments the outside of the body covered by a thin gas permeable skin provides an adequate surface area for the diffusion of gases If the body is extremely small and elongated as in microscopic roundworms gases need to diffuse only a short distance to reach all cells Alternatively an animal s body may be thin and flattened as in flatworms so that most cells are close to the moist skin through which gases diffuse Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange Some animals in moist environments lack specialized respiratory structures continued The relatively slow rate of gas exchange by diffusion may suffice for a larger thicker bodied organism if energy demands are sufficiently low as with sea jellies which can be quite large but require little O22 Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange Some animals in moist environments lack specialized respiratory structures continued Another adaptation for gas exchange involves bringing the watery environment close to each cell Sponges for example circulate seawater through channels within their bodies Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange Some animals in moist environments lack specialized respiratory structures continued For O2 delivery to cells some animals combine a large skin surface area with a well developed circulation For example in the earthworm gases diffuse through the moist skin and are distributed throughout the body by an efficient circulatory system Blood in the skin capillaries rapidly carries off O2 that has diffused through the skin maintaining a concentration gradient that favors the inward diffusion of oxygen The worm s elongated shape ensures a large surface area relative to its internal volume Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange Respiratory systems facilitate gas exchange by diffusion Most animals have evolved specialized respiratory systems that interface closely with their circulatory systems to exchange gases between their cells and the environment Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange Respiratory systems facilitate gas exchange by diffusion continued The transfer of gases between the environment and the body cells usually occurs in stages that alternate between bulk flow and diffusion During bulk flow liquids or gases move in bulk through relatively large spaces from areas of higher pressure to areas of lower pressure This contrasts with diffusion where molecules move individually from higher to lower concentrations Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange For animals with well developed respiratory systems gas exchange occurs in the following stages Air or water moves past a respiratory surface by bulk flow down a pressure gradient this is usually facilitated by muscular movements such as breathing O2 and CO2 are exchanged through the respiratory surface by diffusion O2 diffuse into the capillaries of the circulatory system and CO2 diffuses out Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange For animals with well developed respiratory systems gas exchange occurs in the following stages continued Gases are transported to between the respiratory system and the tissues by the bulk flow of blood as it is pumped throughout the body Gases are exchanged between the tissues and the circulatory system by diffusion at the tissues O2 moves out of the capillaries into tissues and CO2 moves from the tissues to the capillaries Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary Adaptations for Gas Exchange Gills facilitate gas exchange in an aquatic environment Gills are the respiratory structures of many aquatic animals The simplest type of gill found in amphibians consists of many thin projections of the body surface that protrude into the surrounding water Gills are elaborately branched or folded to increase their surface area and have a dense profusion of capillaries where gas exchange occurs Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 33 2 What Are Some Evolutionary
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