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B14 Respiration and the Circulatory System.notebook
1
December 06, 2012
Some of the smallest and simplest life forms (the singlecelled organisms) respire directly through their cell membranes. Oxygen passes readily from the environment into these cells by simple . And because molecules always move from where they are concentrated to where they are concentrated, new oxygen from the environment constantly moves into the to replace oxygen that is used up.
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Many multicellular organisms also acquire oxygen through simple diffusion. Earthworms, for example, exclusively through their . However, because these animals have many layers of cells, many of which are far from the surface, they must have systems that pump blood through that are just one cell layer below the surface and then on to the innermost cells.
diffusion most least
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respire skin
circulatory capillaries
Despite its simplicity, a respiratory system that relies on diffusion through the skin is very limiting. For example, diffusion works well only when oxygen is in water, which is why earthworms and frogs are confined to environments. Skin respiration also limits an animal's . A hippopotamus, for example, could not possibly acquire enough through its skin because the ratio of its total volume is quite . This means that most of the hippo's cells are internal rather than on the surface. Skin respiration is simply too inefficient to supply oxygen to all of those internal cells.
size
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Respiration and the Circulatory System
http://www.teachersdomain.org/asset/tdc02_vid_circulator/
Gas Exchange in Smaller Organisms
B14 Respiration and the Circulatory System.notebook
2
December 06, 2012
Lungs and gills improve the efficiency of respiration by the surface area through which oxygen can diffuse. The human respiratory system, for example, again and again, with each tube leading to several smaller tubes and ultimately to a group of tiny air sacs called . The 300 million alveoli in a pair of human lungs provide a surface area of about 750 square feet about 40 times the body's surface area. In addition, surround each alveolus, just as they surround each filament in a fish's gills. This increases the of respiration by minimizing the distance across which oxygen must diffuse
maximizingbranches
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capillariesefficiency
http://www.youtube.com/watch?v=HiT621PrrO0&feature=related
Gas Exchange in Larger Organisms
B14 Respiration and the Circulatory System.notebook
3
December 06, 2012
http://www.youtube.com/watch?v=oHgVeY0Rlh4
Questions 1. Name 3 organs that are part of your respiratory system
3. How does Oxygen get into your blood stream?
4. Why are worms found in moist environments?
5. Why do humans have lungs?