Biotic refers to anything related to living organisms. It can be used to describe influencing factors or conditions in the environment of a living organism that are caused by another living organism or biological entity. Biotic factors are living things within an ecosystem, such as plants, animals, and bacteria. Examples of biotic materials include wood, straw, humus, manure, bark, crude oil, cotton, spider silk, chitin, fibrin, and bone. The use of biotic materials, and processed biotic materials (bio-based material) as alternative natural materials over synthetics is popular with those who are environmentally conscious because such materials are usually biodegradable, renewable, and the processing is commonly understood and has minimal environmental impact. However, not all biotic materials are used in an environmentally friendly way, such as those that require high levels of processing, are harvested unsustainably, or are used to produce carbon emissions.