Study Guide for Chapter 48

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Biological Sciences
Mary Olaveson

Chapter 48 Gas Exchange in Animals -Respiratory gases: oxygen and carbon dioxide -Diffusion- is the only method of exchanging gases through internal body fluids - random motion of molecules( area of high [C] to an area of low [C]) -No means of active transport necessary to transport gases cross biological membranes Ficks Law of Diffusion- describes the rate at which a substance will diffuse through a concentration gradient. Q = DA (P -P 1 2 L) - Q = the rate at which a gas such as oxygen diffuses between two locations - D = is the diffusion coefficient, which is a characteristic of the diffusion substance, the medium and temp - A = is the cross-sectional area through which the gas is diffusing - P1and P =2are the partial pressures of the gas at the two locations - L = is the path length, or distance between the two locations. -Air is a better respiratory medium than water so oxygen can be obtained more easily than water for these reasons: - The oxygen content of air is much higher than the oxygen content of an equal volume of water - Oxygen diffuses about 8000 times more rapidly in air than in water - More energy is required to move water than to move air because water is 800 times more dense and 50 times more viscous then air -Oxygen availability decreases with altitude for air breathers and rise in temperature reduces the supply of oxygen available to water breathers -The direction and rate of diffusion of respiratory gases depend on the partial pressure gradients of the gases. External gills- are highly branched folds of extensions of the body surface that provide a large surface area for gas exchange in water. - Found in larval amphibians Internal gills- are found in many mollusks and arthropods, and in fishes - Protective body cavities have evolved due to that external gills usually were susceptible to damage Lungs- has internal cavities for respiratory has exchange with air. - Lungs have a large surface area because they are highly divided, and they are elastic so that they can be inflated and deflated with air. Tracheae- the most abundant air-breathing invertebrates are insects, which have a respiratory gas exchange system consisting of a network of air-filled tubes called tracheae that branch through all tissues of the insects body. -Partial pressure gradients drive diffusion across gas exchange surfaces. These gradients can be maximized in several ways: Minimization of path length- very thin tissues in gills and lungs reduce the diffusion path length
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