Vertical spaces between paragraphs in beamer.tex

\documentclass{beamer}
\usepackage{lipsum}

% Paragraph spacing
\setlength{\parskip}{1ex}
\makeatletter
\def\@listi{\leftmargin\leftmargini
            \topsep 0pt       % Space before/after list
            \parsep 0pt       % Space between paragraphs within an item
            \itemsep 0pt}     % Space between separate items
\let\@listI\@listi
\makeatother

\begin{document}
\begin{frame}{Vertical spaces between paragraphs}
  \lipsum[1][1-2]

  \begin{itemize}
    \item \lipsum[1][3]
    \item lipsum
    \item \lipsum[1][4-5]
  \end{itemize}

  \lipsum[2][1-3]

  \lipsum[2][4]
\end{frame}
\end{document}