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Name: Joseph
Status: Other
Grade:  Other
Location: IL
Country: United States
Date: March 2005

Since dogs are mammals with virtually all the same organs as humans, why do they age so quickly in comparison?

In general, the smaller the mammal, the shorter the life span, for example rats live only 2-3 years before they die of old age. I've never heard a good theory to explain this but it might have something to do with their metabolic rates. The smaller the animal, the higher the metabolic rate or calories burned per hour per gram of body weight. One of theories of ageing is that free radicals like atomic Oxygen or H2O2 (peroxide) cause chemical damage to essential enzymes and DNA, and the higher the metabolic rate, the more free radicals are produced per unit time.

Ron Baker, Ph.D.

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