Desert and desert-scrub biomes are characterized by specific types of plant and animal life. Creosote bushes are found throughout areas such as the Mojave Desert. They are used by roadrunners for nesting, and also provide a home for desert tortoises. Bushes growing low to the ground in sand. Photo by Samulili What type of plant is the creosote bush?

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.