Most of the grade one classes study the rain forest when they study an ecosystem. This year, when I asked this class, what they knew about the rain forest, they said they were studying the desert.
I did a quick change up to this lesson. We pulled up images of the desert to look at.
Students used oil pastels for cactus to make it appear waxy and slightly shiny. They used chalk pastels for the background to give it a dusty dry feeling. They could add an animal if they chose to in whatever medium they chose.