Homeostasis is one of the fundamental characteristics of
living things. It is the maintenance of the internal
environment within tolerable limits.
With regard to any parameter, an organism may be a conformer
or a regulator. Regulators try to maintain the parameter at
a constant level, regardless of what is happening in its
environment. Conformers allow the environment to determine
the parameter. For instance, endothermic animals maintain a
constant body temperature, while ectothermic animals exhibit
wide variation in body temperature.
This is not to say that conformers may not have behavioral
adaptations that allow them to exert some control over the
parameter in question. For instance, reptiles often sit on
sun-heated rocks in the morning to raise their body
temperatures.
An advantage of homeostatic regulation is that it allows the
organism to function more effectively. For instance,
ectotherms tend to become sluggish at low temperatures,
whereas endotherms are as active as always. On the other
hand, regulation reqires energy. One reason why snakes can
eat only once a week is that they use much less energy for
maintaining homeostasis.
Homeostasis in the human body
All sorts of factors affect the suitability of the human
body fluids to sustain life; these include properties
like temperature, salinity, acidity (carbon dioxide), and
the concentrations of nutrients and wastes (urea,
glucose, various ion, oxygen). Since these properties
affect the chemical reactions that keep bodies alive,
there are built-in physiological mechanisms to maintain
them at desirable levels.
This control is achieved with various organs in the body.
For example:
Thermal regulation:
The skeletal muscles can shiver to produce heat if the body
temperature is too low. Non-shivering thermogenesis involves
the decomposition of fat to produce heat. Sweating cools the
body with the use of evaporation.
Chemical regulation
The pancreas produces insulin and glucagon to control blood-
sugar concentration. The lungs take in oxygen and give off
carbon dioxide.
The kidneys remove urea, and adjust the concentrations of
water and a wide variety of ions.
Most of these organs are controlled by hormones secreted
from the pituitary gland, which in turn is directed by the
hypothalamus.
Homeostatic systems show several properties they are
ultrastable; their whole organisation, internal,
structural, and functional, contributes to the maintenance
of equilibrium they are unpredictable (the resulting effect
of a precise action often has the oppposite effect to what
was expected)
A frequent paradox for those responsible for the maintenance
and evolution of a complex system (be it a body, an
ecosystem, a state, or a planet) is how can a stable
organization whose goal is to maintain itself and endure, be
able to change and evolve?
Wikipedia
I read something in a 1979 edition of World Book
Encyclopedia which I found interesting. I have no idea if it
is true but was intriqued by the premise. According to
Gordon Farrell "Scientists believe that homeostasis
indicates the degree of evolution (gradual development) of a
species. The steadier an organism's internal systems, the
more independent it is of the external environment. In turn,
the more independent it is of its external environment, the
more highly developed it is.
By this token [censored] Sapiens may not have that steady of an
internal system. External factors impinging on the organism
include changes in temperature, the presence or absence of
sunlight, the presence or absence of specific chemicals, the
availability of nutrients and water, and the presence of
potentially infectious organisms and parasites.
The regulation of salt and water balance is another example
of homeostasis. The kidneys play an important role in
maintaining the correct water content of the body and the
correct salt composition of extracellular fluids. External
changes which lead to excessive fluid loss initiate feedback
mechanisms which act to maintain the body's fluid content
and the kidneys act to limit water loss via excretion.
The advantage of homeostasis is that the organism can adjust
to changes, for example in temperature and water
availability, without its component cells being adversely
affected since they are having all their needs met by the
controlled internal environment. Warm blooded animals are
capable of living in a range of different habitats from cold
polar regions to hot tropical regions because of the
effectiveness of their mechanisms for temperature control.
On the other hand, cold-blooded animals are more restricted
in the range of habitats in which they can flourish due to
their lack of homeostatic control.
A constant internal environment makes it possible for cells
to become more specialised and efficient at a particular
task. Thus some cells can become organised into tissues
specialised to maintain the ionic composition of the
internal environment (eg: the kidneys), and others maintain
optimum levels of O2 and CO2 (eg: the lungs).
A possible disadvantage of homeostasis is that it requires
the organism to invest effort into maintaining internal
stability. For example, additional energy will be required
to maintain a warm body temperature in a cooler external
environment. This could be a problem if food is scarce.
Also, on occasion the complex web of homeostatic
regulations and controls may break down, giving rise to
illness. If systems, organs, tissues, and cells that are
normally concerned in maintaining internal balances become
damaged or diseased, the survival of the whole organism can
be put at risk.
One observation is that [censored] Sapiens increasingly live in a
more artificially controlled environments although such
changes may take quite awhile to effect homeostatic
controls. So when Mr. Farrell states, "The steadier an
organism's internal systems, the more independent it is of
the external environment" I'm thinking of "external
environment" as that which the organism doesn't control.
Therefore the more independent it is of its external
environment (that which it doesn't control), the more highly
developed it is. A highly controlled and regulated
artificial environment may become over time a part of the
organism's internal systems.
Admittedly [censored] Sapiens are still far from this point but
maybe someday they won't be. Of course, I'm very interested
in the role homeostasis plays in aggression. Earlier it was
stated a frequent paradox for those responsible for the
maintenance and evolution of a complex system is how can a
stable organization whose goal is to maintain itself and
endure, be able to change and evolve? I think the answer to
that is homeostasis can change and evolve but extremely
slowly in terms of Darwinian evolution. Many of the
homeostatic controls we have we share with other animals.
It has been stated with regard to any parameter, an organism
may be a conformer or a regulator. Regulators try to
maintain the parameter at a constant level, regardless of
what is happening in its environment. Conformers allow the
environment to determine the parameter. For instance,
endothermic animals maintain a constant body temperature,
while ectothermic animals exhibit wide variation in body
temperature.
In terms of aggression probably both conformer and regulator
roles are at play. Conformers allowed the environment to
determine the parameter due to Darwinian evolution
imprinting aggression on our DNA.
Michael