A one-dimensional electromagnetic particle-in-cell simulation is performed to study wave excitation due to an isotropic electron beam in a plasma system. The waves excited by the electron beam are analysed with the fast Fourier transformation and the wavelet transformation. The results show that the isotropic beam electrons can excite the whistler and the Langmuir instabilities. Also, the strong damping of whistler modes due to the emergence of electrostatic waves together with the appearance of temperature anisotropy in the electron beam can be found. Furthermore, the velocity distributions indicate that beam electrons are heated in the direction parallel to the ambient magnetic field. The background electrons still exhibit an isotropic velocity distribution, which is different from that of the beam electrons.