<unk> , a kind of taxis, is the phenomenon in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain<unk> micals in their environment. This is important for bacteria to find food (for example, glucose) by swimming towards the highest concentration of food molecules, or to flee from poisons (for example, phenol).  In multicellular organisms,<unk>  is critical to development as well as normal function.  In addition, it has been recognized that mechanisms that allow<unk>  in animals can be subverted during cancer metastasis.<unk>  is called positive if movement is in the direction of a higher concentration of the<unk> mical in question, and negative if the direction is opposite.
Chemotaxis
Excretion
Extraction 
Agglutination
Endocytosis
Resorption
Swelling 
Secretion