\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{arrows}
\begin{document}
\begin{tikzpicture}[xscale=6]
\draw[-latex] (-.2,0) -- (1.2,0) ;
\draw[shift={(0,0)},color=black] (0pt,3pt) -- (0pt,-3pt) node[below] {$ 0 $};
\foreach \x in {1,2,3,4}{
\draw[shift={({1/\x},0)},color=black] (0pt,3pt) -- (0pt,-3pt) node[below] {$ \dfrac{1}{\x} $};
\draw[o-*] (0,.5*\x) --node[]{$ I_{\x} $} ({1/\x},.5*\x);
}
\end{tikzpicture}
\end{document}