The Characteristics of Life

The following is a typical introduction to a first-level course in Biology (incl. Human Biology) and Human Anatomy and Physiology.

Biology is the study of living beings including plants, animals and fungi.

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.

As courses in Human Anatomy and Physiology concentrate on the human species, the following table includes comments on each of the characteristics as applied to humans:

Characteristics of Life:

The comments below apply to the example of a human (biological organism).



Examples include movement of limbs, facial tissues, materials through the digestive system,
and so on.


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 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.


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 lifestyle factors - such as a 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.


Examples of substances secreted from the human body include:

  • Hormones (somtimes described simply as "chemical messengers")
  • Sebum (from sebaceous glands), e.g. ear wax.


In human there are two circulation systems:

  • Primary Circulation = Blood Circulation,
  • Secondary Circulation = The Lymphatic System.

Some biology courses and textbooks list a specific number of basic characteristics of life, e.g. 6 characteristics of life or 7 characteristics of life. The comments included above includes examples of the basic characteristics of life for the case of humans as opposed to e.g. apes (which are similar in many respects), plants or even bacteria.

See also characteristics of fungi.

Compare humans with gorillas

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