All forms of farming have major impacts on biodiversity, especially when new land is brought into cultivation. Habitats are destroyed and new ecological niches created which allow typical farmland species of birds, insects, mammals and weeds to establish themselves.
Herbaceous stem grow thicker as a result of cell division in the vascular cambium of the stem.
I believe you're looking for "chemical digestion".
Chemical digestions is where food that we ate is digested into simpler and soluble molecules that can be absorbed by our body. Enzymes are used as a catalyst to speed up the reaction.
One example is the digestion of lipids. Enzyme named lipase is used to speed up the digestion of lipids into 3 fatty acid molecules and 1 glycerol. This way, our body can absorb these simple molecules, and use them in order to make our body function.
On the other hand, physical digestion does not include enzymes, such as chewing in our mouth, therefore, don't mix them up!