  For a map $f:I \rightarrow I$, a point $x \in I$ is periodic with period $p
\in \mathbb{N}$ if $f^p(x)=x$ and $f^j(x)\not=x$ for all $0<j<p$. When $f$ is
continuous and $I$ is an interval, a theorem due to Sharkovskii (\cite{BC})
states that there is an order in $\mathbb{N}$, say $\lhd$, such that, if $f$
has a periodic point of period $p$ and $p \lhd q$, then $f$ also has a periodic
point of period $q$. In this work, we will see how an extension of this order
$\lhd$ to an ultrapower of the integer numbers yields a Sharkovskii-type result
for non-wandering points of $f$.

Dynamical Systems