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.
Pre-emergent herbicides kill weeds as they germinate from their seeds. To be effective, pre-emergent herbicides are applied directly to the soil and spread with a light application of water. The herbicide makes a barrier of poison that reduces the chance of weed germination, says the University of Illinois.erbicides that require contact are sprayed onto the plant and absorbed through the waxy layer of the leaf. Contact herbicides will kill only the area they touch and do not kill the weed roots, meaning the weed may grow back, says the University of Illinois Extension.