For a standard graded algebra $R$, we consider embeddings of the the poset of
Hilbert functions of quotients of $R$ into the poset of ideals of $R$, as a way
of classification of Hilbert functions. There are examples of rings for which
such embeddings do not exist. We describe how the embedding can be lifted to
certain ring extensions, which is then used in the case of polarization and
distraction. A version of a theorem of Clements--Lindstr\"om is proved.
We study the dependence of graded Betti numbers of monomial ideals on the
characteristic of the base field. The examples we describe include bipartite
ideals, Stanley--Reisner ideals of vertex-decomposable complexes and ideals
with componentwise linear resolutions. We give a description of bipartite
graphs and, using discrete Morse theory, provide a way of looking at the
homology of arbitrary simplicial complexes through bipartite ideals.