\documentclass{beamer}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\begin{document}
\begin{frame}
\begin{tikzpicture}
\node[draw,rectangle,rounded corners=3pt,fill=blue!10] (a)at(5,4){a};
\node[draw,rectangle,rounded corners=3pt,fill=blue!10] (b)at(4,3){b};
\node[draw,rectangle,rounded corners=3pt,fill=blue!10] (c)at(6,3){c};
\node[draw,circle,rounded corners=3pt,fill=blue!10] (un)at(5,2){1};
\node[draw,rectangle,rounded corners=3pt,fill=blue!10] (deux)at(5,1){2};
\node[draw,rectangle,rounded corners=3pt,fill=blue!10] (trois)at(5,0){3};
\draw[->,draw=blue,fill=blue,line width=0.25mm] (b) -- (a) node[midway,left]{texte1};
\draw[->,draw=blue,fill=blue,line width=0.25mm] (c) -- (a) node[midway,right]{texte2};
\only<2>{
\draw[->,draw=blue,fill=blue,line width=1mm] (un.south) -- (deux.north);
\draw[->,draw=blue,fill=blue,line width=1mm] (deux.south) -- (trois.north);
\draw[->,draw=blue,fill=blue,line width=1mm] (a.south) -- (un.north);
\draw[->,draw=blue,fill=blue,line width=1mm] (b) -- (un);
\draw[->,draw=blue,fill=blue,line width=1mm] (c) -- (un);
}
\end{tikzpicture}
\end{frame}
\end{document}
Ou avec des coordonnées relatives (à ajuster plus facilement que les coordonnées absolues) :
\documentclass{beamer}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}
\begin{frame}
\begin{tikzpicture}[every text node part/.style={align=center}]
\node[draw,rectangle,rounded corners=3pt,fill=blue!10] (trois)at(5,0){Texte vraiment \\ très long};
\node[draw,rectangle,rounded corners=3pt,fill=blue!10] at ($(trois)+(0,1.5)$) (deux) {Texte vraiment très long};
\node[draw,circle,rounded corners=3pt,fill=blue!10] at($(deux)+(0,2.5)$) (un) {Texte vraiment \\ très long};
\node[draw,rectangle,rounded corners=3pt,fill=blue!10] at($(un)+(0,2.5)$) (a) {Texte vraiment très long};
\node[draw,rectangle,rounded corners=3pt,fill=blue!10] at($(un)+(-3,1)$) (b) {Texte vraiment très long};
\node[draw,rectangle,rounded corners=3pt,fill=blue!10] at($(un)+(3,1)$) (c) {Texte vraiment très long};
\draw[->,draw=blue,fill=blue,line width=0.25mm] (b) -- (a) node[midway,left]{bla bla bla};
\draw[->,draw=blue,fill=blue,line width=0.25mm] (c) -- (a) node[midway,right]{bla bla bla};
\only<2>{
\draw[->,draw=blue,fill=blue,line width=1mm] (un.south) -- (deux.north);
\draw[->,draw=blue,fill=blue,line width=1mm] (deux.south) -- (trois.north);
\draw[->,draw=blue,fill=blue,line width=1mm] (a.south) -- (un.north);
\draw[->,draw=blue,fill=blue,line width=1mm] (b) -- (un);
\draw[->,draw=blue,fill=blue,line width=1mm] (c) -- (un);
}
\end{tikzpicture}
\end{frame}
\end{document}
