The Characteristics of Life
The following is a typical introduction to
a first-level course in Human Biology or Human Anatomy and Physiology.
Biology is the study of living beings - including both plants and
animals.
Many courses in biology and related subjects start by
defining living things by listing the
"Characteristics
of Life" and examples of each of
these characteristics for plants, animals, humans, or
whatever categories apply to the main subject and level
of the course.
Courses in Human Anatomy
and Physiology concentrate on the human species so the table
below includes comments on each of the characteristics as applied
to humans:
Characteristics of Life:
|
Comments in case of humans:
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|
|
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Eating |
 |
|
Movement |
Examples include movement
of limbs, facial
tissues, materials
through the digestive system,
and so on. |
|
Reproduction
|
This is the means by which the species as a whole continues
beyond the life-span of any single individual. The human
reproduction process involves the exchange of genetic information
and material. |
|
Breathing
|
Breathing involves the intake of air from outside the
body, absorption of oxygen gas (O2) for use within
the body, and the release of the waste product carbon dioxide gas (CO2) from
the body.
The action of breathing is described on the pages about the
respiratory system. |
|
Growing
|
The term "growing" refers to the increase in size of a
person during his/her childhood, typically until the age
of about 18 years. It can be affected by a lifestyle
factors - such as a well-balanced diet, by genetic factors
- e.g.
coming from a relatively "short" or "tall" family, and also
by certain hormonal conditions that affect growth/development. |
|
Waste (excretion)
|
This term refers to removal from the body of waste products
that may have been formed by metabolic processes. Examples
include:
- Breathing out (of the body) carbon dioxide (C2O)
and water (H2O),
the waste products from aerobic
respiration.
- Sweating, removal of waste products from the body via
the skin.
- Urinating. (Urea is nitrogenous waste, i.e. it is from
proteins.)
- Defecating. Strictly, materials that leave the body by
the process of defecation are undigestable food materials
- rather than waste products formed by the metabolic processes
that occur in the body. (Their colour is due to the undigestable
food itself, and to the effects of any excess bile.)
|
|
Secretion
|
Examples of substances secreted from the human body
include:
- Hormones (somtimes described simply as "chemical messengers")
- Sebum (from sebaceous glands), e.g. ear wax.
|
|
Circulation
|
In human there are two circulation systems:
Primary Circulation = Blood
Circulation,
and
Secondary Circulation = The Lymphatic System.
|
Note that the "characteristics of life" headings in the list above
are layman's terms rather than medical terms and are listed in
no particular order. Comparable lists in textbooks vary. If this
topic forms part of your syllabus check the characteristics and
terminology specified for your particular course.
... End of Page ...
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