The goal of every animal is to survive. All animals strive to maintain an ideal internal environment, where their cells operate at peak efficiency, for example humans aim to keep their body temperature at 32 C°.
- Any higher and there is a risk of damaging cells and harming the body.
- Too low, and the cells cannot function properly.
However maintaining a constant temperature
comes at a cost. A large amount of energy is
used to increase the internal temperature.
This is why animals such as bears and squirrels
hibernate during winter.
The maintenance of the internal environment in a relatively stable state in the face of changes in either the external or internal environment
Vertebrates have complex feedback systems in place to monitor and maintain their bodily functions. Blood Co2, glucose and water levels are only a few of the things the body regulates through feedback systems.
All organisms undergo some form or homeostasis, some are just more complex than others. For example Protozoan Volvox will use their flagella and actively seek out light, in order to increase their rate of photosynthesis.
Feedback systems, work via signal transduction. Signal transduction is a method of cellular communication. One cell produces a signalling molecule which activates a specific receptor located on or in another cell. This produces a change in the target cell.
Just because the goal of every organism is to maintain a relatively stable internal environment dose not mean that they need to expend energy.
For example
The Hyas araneus or decorator crab (seen to the right) is an osmoconformer. This means that the solute concentration of the external environment is roughly the same as its internal environment.
A positive of this is that the crab doesn't spend much energy maintaining it’s internal environment. However a negative, is that the crab is at the mercy of the environment.
On the other hand Carcinus maenas or the common shore crab (shown to the left) is an osmoregulator. This means that the solute concentration in its body is relatively constant regardless of the external environment.
A positive of this is that they can move around and enter different environments. However they must expend a large amount of energy to keep their internal environment stable if they are in an extreme external environment.
Signalling between cells can be accomplished through chemicals. The endocrine and nervous systems are two of the body's prime signalling methods. They release hormones and neurotransmitters, respectively, which bind to specific receptors on target cells.
