Humans depend on photosynthesis because it is responsible for most of Earth's primary productivity and fossil fuels are obtained mostly from remains of prehistoric plants. A typical plant cell contains about 10 to 100 chloroplasts. Several lines of evidence, including DNA evidence, suggest that chloroplasts evolved from an endosymbiotic event, when a eukaryotic cell incorporated photosynthetic cyanobacteria. Chloroplasts contain their own DNA that descended from the cyanobacterial ancestor.
The documents supporting the classroom implementation using this image as an anchoring phenomenon can be found with the Slug Power image here.
Technical details: Different color stains were used to see various structures in the plant cells: nuclei (colored red/cyan/white), cell walls (colored green), and chloroplasts (colored yellow). The stained plants were sectioned and viewed using a confocal microscope.
Credit: Fernan Federici, PhD, Departamento de Genética Molecular y Microbiologia, Universidad Católica de Chile, Chile and Jim Haseloff, PhD, Department of Plant Sciences, University of Cambridge, UK