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13.71: Adulthood and Aging

Difficulty Level: At Grade Created by: CK-12
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Does getting older have to be a bad thing?

Being older doesn't necessarily mean being unable to do things and not enjoy life. These seniors look as if they thoroughly enjoy life. And some would say that life begins after all the children have moved out of the house.

Adulthood and Aging

Adulthood does not have a definite starting point. A person may be physically mature by age 16 or 17 but not defined as an adult by law until older ages. In the U.S., you can’t join the armed forces or vote until age 18. You can’t buy or use alcohol or take on many legal and financial responsibilities until age 21.

21 Years at http://www.youtube.com/watch?v=d-4i2ZlqLsI is a daily video pictorial of the aging process, from birth to 21 years. Over 7,500 images of the same peson have been condensed in a little over 6 minutes.

Early Adulthood

Early adulthood coincides with the 20s and early 30s. During early adulthood, people generally form intimate relationships, both in friendship and love. Many people become engaged or marry during this time. Often they are completing their education and becoming established in a career. Health problems in young adults tend to be minor. The most common causes of death are homicides, car crashes, and suicides.

Middle Adulthood

Middle adulthood lasts from the mid-30s to the mid-60s. During this stage of life, many people raise a family and strive to attain career goals. They start showing physical signs of aging, such as wrinkles and gray hair. Typically, vision, strength, and reaction time start declining. Diseases such as type 2 diabetes, cardiovascular disease, and cancer are often diagnosed during this stage of life. These diseases are also the chief causes of death in middle adulthood.

Old Age

Old age begins in the mid-60s and lasts until the end of life. Most people over 65 have retired from work, freeing up their time for hobbies, grandchildren, and other interests. Stamina, strength, reflex time, and the senses all decline during old age, and the number of brain cells decreases as well. The immune system becomes less efficient, increasing the risk of serious illnesses such as cancer and pneumonia. Diseases such as Alzheimer’s disease that cause loss of mental function also become more common.

Causes of Aging

Why do we decline in all these ways as we age? Generally, it’s because cells stop dividing and die. There are at least two reasons why cells stop dividing:

  1. Cells are programmed to divide only a set number of times.
  2. Mutations accumulate in DNA, and cells with damaged DNA may not divide.


  • During early adulthood, people form intimate relationships and start careers.
  • Serious health problems start showing up in middle adulthood and old age.
  • Aging occurs as cells lose their ability to divide.


Use this resource to answer the questions that follow.

  1. Do you think longevity has a genetic component? Explain your answer. Include specific examples.


1. When does adulthood begin?

2. Aging is associated with the death of cells. Give two reasons why cells die.

3. Create a timeline of major milestones during adulthood.

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    Period of life after childhood.

    early adulthood

    A period of life that lasts from the 20s to the early 30s.

    middle adulthood

    A period of life that lasts from the mid-30s to the mid-60s.

    old age

    A period of life that begins in the mid-60s and lasts until the end of life.

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    Date Created:
    Feb 24, 2012
    Last Modified:
    Aug 28, 2016
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