The planet upon which we live is composed of inanimate (nonliving) materials
such as minerals and water.
One can distinguish living from nonliving material by the fact that living
material carries on a series of functions known as the life processes.
These life processes include:
• responsiveness to stimuli
Variations among human organisms
The human organism is known scientifically as Homo sapiens, meaning the
intelligent human being. There is a more or less common form for human beings,
but no two individuals are exactly alike in detail.
This even includes identical twins. (One tends to be left-oriented and the other
As a result, there is a tremendous variation among humans which has been further
complicated by selection and propagation of specific traits by humans themselves.
Given the variations among human organisms, various methods of categorization
have been established to achieve some common order. The method we will use is
referred to as somatotyping.
Somatotyping categorises human beings into three different groups:
• Ectomorphs, who tend to be thin-bodied individuals.
• Endomorphs, who tend to be broad-bodied individuals.
• Mesomorphs, who have a body form between the other two.
There are significant differences among human beings within these categories.
These differences exist not only in body form but also in internal anatomy of structures
and susceptibility to diseases.
General Body Functions
The living human being performs many functions as a part of daily life:
• Motion and locomotion
The body takes in materials for energy, growth, and repair. Since the body cannot produce its
own energy, it must continually take in foods to supply that energy to carry on the life processes.
This food also provides materials for growth and repair of the cells and tissues.
Motion and Locomotion
Being an erect, standing organism, the body requires special supporting structures. At the same
time, it needs a mechanical arrangement to allow the parts to move (motion) and to move from
place to place (locomotion).
For the species to continue, there must be reproduction - the formation of new human
beings belonging to subsequent generations.
All biological activity is controlled by three major systems of the human body:
• the nervous system
Hormones provide a chemical control system.
The nervous system works much like circuitry in a computer.
In the final analysis, however, all of the structures and functions of the body are
determined by special units called genes, the study of which is genetics and the
transmission of which is heredity. Heredity determines the potential range of an
organism's characteristics. The environment determines which potential characteristics
are developed and to what degree.
As we have previously mentioned, energy is required to carry on the life
processes of each individual human being.
One of the laws of nature is conservation of energy. This means that energy
cannot be created or destroyed but only transformed. For example, electricity can be
transformed into heat.
The human body cannot produce energy on its own and must,
therefore, continuously take in a fresh supply of energy.
Except for a few special situations, all of the energy for living matter on Earth
is received from the Sun through solar radiation.
Green plants trap and bind this solar energy in molecules of glucose by the process of
Humans take this glucose into their bodies directly by eating green plants or
indirectly by eating the flesh of plant-eating animals. The human body releases the
trapped energy from glucose by a process known as metabolic oxidation.
Energy released by metabolic oxidation is used to form the compound adenosine triphosphate (ATP)
from adenosine diphosphate (ADP). ATP is like a charged battery; the"discharged battery" is called ADP. Molecules of ATP are present in all of the living cells of the body.
Within each cell, molecules of ATP are "discharged" to release a large quantity of energy to drive the various life processes.
Through further metabolic oxidation, the resulting ADP molecules are "recharged" to form ATP molecules once again.
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