Humans must care for their bodies to stay healthy. People of different races, cultures and genders have developed technologies that improve human health and quality of life. Animals can survive only in environments in which their needs can be met. Living things that can better adapt to changes in their environment have a greater chance of survival. Species of animals that are not able to adapt to changes in their environments can become endangered or extinct.
Light travels through some materials better than others.
Light travels through air in straight paths. Shadows are created when objects interrupt the path of light. Different factors affect the size, shape and sharpness of shadows. A shadow's length is determined by the angle of an object in relation to its light source. Shaded areas have cooler temperatures.