Response to Changes in the Environment (Edexcel IGCSE Biology (Modular)): 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