The state of maintaining a stable internal environment regardless of changing external conditions is called
.

The first line of defence (or outside defence system) includes physical and chemical barriers that are always ready and prepared to defend the body from infection. These include your skin, tears, mucus, cilia, stomach acid, urine flow, 'friendly' bacteria and white blood cells called neutrophils.
<span>Physical weathering is a term used in science that refers to the geological process of rocks breaking apart without changing their chemical composition. Over time, movements of the Earth and environment can break apart rock formations, causing physical weathering.</span>