The regulation of internal environment by animals: homoeostasis
All living organisms have ideal environmental conditions for survival and reproduction. Animals have an internal environment as well as the external environment they are living in. If their internal environment deviates too much from the ideal they may experience reduced function or even die. Homoeostasis is the adapted ability of an organism to regulate its internal environment to deal with changes in the external environment. (Raven 1999) Animals are grouped into two separate categories in respect to homeostasis: conformers and regulators. Conformers, or ectotherms, are not capable of maintaining their internal environment when faced with unfavorable external conditions. Therefore, they are forced to constantly seek out favorable environments and exert behaviors designed to counteract the environmental challenge. An example of a conformer is a lizard, which will bask in the sun to increase its internal temperature or seek shade to decrease it. Regulators, or endotherms, use physiological mechanisms to counteract changes in their external environment and maintain ideal conditions internally. (Campbell 2005) An example of a regulator is a human. We are able to regulate our body temperature even in very diverse conditions by shivering, sweating, and several other physiological mechanisms. The process of regulation is a five-step process (as shown in figure 1). First, the external environment effects a change in the internal environment (i.e. a rise in temperature). Second, the change is identified by a receptor (i.e. a nerve cell). Third, the receptor sends the information to the control center of the animal (i.e. the brain). Fourth, the control center sends the information to an effector (i.e. the pituitary gland). Fifth, the effector makes a change in the body to restore homeostasis (i.e. sweating to reduce temperature).
There are several environmental variables that animals must...
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