Reading and answers the question: There are many theories of aging, but virtually all fall into the
category of being hypotheses with a minimum of supporting evidence.
One viewpoint is that aging occurs as the body's organ systems become
less efficient. Thus failures in the immune system, hormonal system,
5 and nervous system could all produce characteristics that we associate
with aging. Following a different vein, many current researchers
are looking for evidence at the cellular and sub cellular level.
It has been shown that cells such as human fibroblasts (generalized
tissue cells) grown in culture divide only a limited number of times
10 and then die. (Only cancer cells seem immortal in this respect.)
Fibroblast cells from an embryo divide more times than those taken
from an adult. Thus some researchers believe that aging occurs at
the cellular level and is part of the cell's genetic makeup. Any
event that disturbs the cell's genetic machinery such as mutation,
15 damaging chemicals in the cell's environment, or loss of genetic
material, could cause cells to lose their ability to divide and thus
bring on aging. Other theories of aging look at different processes.
Chronological aging refers to the passage of time since birth and
20 is usually measured in years. While chronological age can be useful
in estimating the average status of a large group of people, it is
a poor indicator of an individual person's status because there is
a tremendous amount of variation from one individual to the next
in regard to the rate at which biological age changes occur. For
25 example, on the average, aging results in people losing much of their
ability to perform strenuous activities, yet some elderly individuals
are excellent marathon runners.
Another type of aging is cosmetic aging, which consists of changes
30 in outward appearance with advancing age. This includes changes in
the body and changes in other aspects of a person's appearance, such
as the style of hair and clothing, the type of eyeglasses, and the
use of a hearing aid. Like chronological aging, it is frequently
used to estimate the degree to which other types of aging have occurred.
35 However, it is an inaccurate indicator for either purpose because
of variation among individuals and because a person's appearance
is affected by many factors that are not part of aging, including
illness, poor nutrition, and exposure to sunlight.1. The author believes the theories of aging are
2. In line 7, the word "evidence" refers to
3. The word "vein" in line 6 is closest in meaning to
4. The author of the article points out that cancer cells
5. The word "culture" in line 9 is closest in meaning to
6. It can be inferred from the passage that fibroblast cells
7. As explained in this passage, the theory of aging which examines the cellular level would NOT assign which of the following as a cause of aging?
8. According to the passage, chronological aging is not a good indicator of an individual's status regarding aging because
9. The author implies all of the following about cosmetic aging EXCEPT