Summary The Need for Communication

The Need For Communication:


 Homeostasis is the maintenance of the internal environment in
a constant state despite external changes.
 A stimulus is any change in the environment that causes a
response.
 A response is a change in behaviour as a result of a change in
the environment.


 All chemical reactions in the body are controlled by enzymes –
if the enzymes don’t work, the organism dies.
 To keep enzymes working efficiently, cells need to maintain
conditions at (or close to) the optimum of those enzymes.
 Conditions include temperature, pH, an aqueous environment
that keeps substrates & products in solution, & freedom from
toxins & excess inhibitors.
 Organisms have to cope with changing external conditions
which can place stress on an organism.
 If an organism is to survive, changes in the external
environment must be monitored & the organism must be able
to respond to reduce or eliminate the stress.
 The response can be behavioural, physiological or both.


 Responding to internal stimuli:
o Most cells in a multicellular organism don’t come into
contact with the external environment.
o The internal environment of an organism is altered
through the metabolic processes of its cells – these
alterations may disrupt the cells’ processes.