Weeds are plants which grow were they are not wanted. A plant which competes withs humans for soil possession and space. Weed is also a plant that originated from the natural environment. Benefits of weeds, they serve as food to some animals , vegetables to humans , decompose to form manure ,some Weds are used in the making of mat and are used as fire wood the also possess medical values, weeds like sunflower their seeds are used in the production of oil. They are also used in fancing and some used to control soil erosion and also food for wildlife. Interspecific is competition between two different species of plant while intraspecific is competition between the same specie of plant . Weed biology,the study growth , extablishment ,reproduction and life cycle of weeds. Weed ecology.the study of weed and how it interacts with it's environment and some living organisms. Not all weed seed germinate the next farming season because weed seeds have a dormancy machanism where all seeds produce dont germinate the following year . Weed seed dissemination . The are two ways in which seeds can be disseminated that is artificial and natural method . Weeds have no way of movement and must depend on other forces for dissemination. Natural method :wind , some weed seeds have special adaptation that aid the spread by wind e.g small and light seeds feathery and pappus and winged appendages. Water: movement of weed seeds on the surface of water ,streams and irrigation canals and also floods .some have adaptations like cucumbers, air filled bladders which can flod on water. Animals: animals carry seeds which cling on their furs and cloths and ingested spread ,the seeds have adaptations like hooks ,bristle Barb's catch in animals , resistant in digestion and excreted in animals feces