1 Mechanical digestion is evident, where one can see the breaking down of large food particles into smaller ones after being ground by the teeth. 2  While the chemical changes that take place happen within the body and are not visible.
Using a pre-emergent herbicide around your property could stop these territorial plants from overtaking your home's most valued green space. Pre-emergent herbicide is a type of weed killer that prevents weed seeds from sprouting. Unlike normal herbicide, it is meant to stop weeds from growing in the first place by spraying or spreading a chemical onto the soil so that weeds have difficulty placing down their roots.
preÂ·curÂ·sor. That which precedes another or from which another is derived, applied especially to a physiologically inactive substance that is converted to an active enzyme, vitamin, hormone, etc., or to a chemical substance that is built into a larger structure in the course of synthesizing the latter.preÂ·curÂ·sor/ (preÂ´kur-ser) something that precedes. In biological processes, a substance from which another, usually more active or mature, substance is formed. In clinical medicine, a sign or symptom that heralds another.precurÂ´sory.