This paper considers pattern forming nonlinear models arising in the study of
thermal convection and continuous media. A primary method for the derivation of symmetries and conservation
laws is Noether’s theorem. However, in the absence of a Lagrangian for the equations investigated, we propose
the use of partial Lagrangians within the framework of calculating conservation laws. Additionally, a nonlinear
Kuramoto-Sivashinsky equation is recast into an equation possessing a perturbation term. To achieve this,
the knowledge of approximate transformations on the admissible coefficient parameters is required. A perturbation
parameter is suitably chosen to allow for the construction of nontrivial approximate symmetries. It is demonstrated
that this selection provides approximate solutions.