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| regulation of a solute concentration and water balance by by a cell or organism |
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| the diffusion of water across a selectively permeable membrane |
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| a spontaneous movement of a substance down its concentration gradient, from a region where it is more concentrated to a region where it is less concentrated |
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| solute concentration expressed as molarity |
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| an animal that is isoosmotic with its environment (does not regulate its internal osmolarity) |
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| an animal whose body fluids are not isoosmotic with its environment (regulates its internal osmolarity) |
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| a dormant state involving loss of almost all body water |
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| one or more layers of specialized epithelium cells that regulate solute movements |
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| Animals excrete nitrogenous wastes as ammonia, urea, or uric acid. these forms vary significantly in their toxicity and the energy costs in making them. |
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when proteins and nucleic acids are broken down for anergy or converted to carbohydrates of fats, enzymes remove nitrogen in the form of ammonia.
-very toxic
-most common in aquatic species |
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Produced in the vertebrate liver, urea is the product of a metabolic cycle that combines ammonia with carbon dioxide.
-main advantage: low toxicity
`animals can transport in the circulatory system and store in high concentrations
`less water is lost in comparison to excretion of ammonia
-main disadvantage: animals must expend energy to produce urea form ammonia |
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readily non toxic, does not readily dissolve in water.
incests, many reptiles and birds
Main advantage: very little water loss; can be excreted in a semisolid paste
Main disadvantage: most energetically expensive, requires considerable ATP for synthesis. |
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is a passive biological system that removes excess, unnecessary or dangerous materials from an organism, so as to help maintain homeostasis within the organism and prevent damage to the body. It is responsible for the elimination of the waste products of metabolism as well as other liquid and gaseous wastes.
4step process: 1)filtration 2) reabsorption 3)secretion 4)excretion. |
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the extraction of water and small solutes, including metabolic wastes including body fluids.
the excretory tubules collect a filtrate from the blood. Water and solutes are forced by blood pressure across the selectively permeable membranes if a cluster of capillaries and into the excretory tubules.
(step 1 of excretory system) |
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the transport epithelium reclaims valuable substances from the filtrate and returns then to the body fluid
(step 2 of excretory system) |
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Other substances such as toxins and excess ions are extracted from body fluids and added to the contents of the filtrate.
(step 3 of excretory system) |
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(step 4 of excretory system)
the altered filtrate (urine) leaves the system and the bod. |
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