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Chapter%203%20part%202 - Physical Development Chapter 3...

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1 Physical Development Chapter 3 Part 2 “I stand in awe of my body.” -Henry David Thoreau Longevity How long do we live? Life span the maximum life span of a species Average life expectancy age an average individual can expect to live Greater proportion of older adults
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3 Why do we age? If we didn’t age and die, why reproduce at all? Human body is not a machine Cellular Clock Theory Cell division Hayflick limit cells can only divide and reproduce a certain number of times What tells a cell when it’s time to die? Telomeres ends of DNA molecules Shorten with each cell division When it gets too short, cell division stops and cell experiences aging How do we know how long the telomeres are to begin with? Inherited length
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4 Free Radical Theory Free radicals unstable molecules produced from environmental exposure Interact with other tissues and damage
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Chapter%203%20part%202 - Physical Development Chapter 3...

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