Response to Changes in the Environment (Edexcel IGCSE Biology)
Revision Note
Response to Change
Animals and plants need to be able to respond to changes in their internal and external environment (such as changes in temperature or pH) and to coordinate the activities of their different organs
In order to function properly and efficiently, organisms have different control and communication systems that ensure their internal conditions are kept relatively constant
Physiological control systems maintain the internal environment within restricted limits through a process known as homeostasis
Homeostasis is critically important for organisms as it ensures the maintenance of optimal conditions for enzyme action and cell function
Examples of physiological factors that are controlled by homeostasis in mammals include:
core body temperature
metabolic waste (e.g. carbon dioxide and urea)
blood pH
the concentration of glucose in the blood
the water potential of the blood
the concentration of respiratory gases (carbon dioxide and oxygen) in the blood
Homeostatic mechanisms in mammals require information to be transferred between different parts of the body
There are two communication systems in mammals that do this:
the nervous system
the endocrine system
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