In terms of organisms, photosynthesis occurs in autotrophes that contain the green pigment chlorophyll. This would include the entire plant kingdom, half of the Protista (the algae), & half the Moneran Kingdom (the blue-green algae).
A standard twin mattress is 39 by 75 inches. A king is 76 by 80 inches. This means that a headboard for a king bed is going to be about 76 inches or wider, plenty wide enough to go along the length of a twin bed. Headboards are often slightly wider than the bed for which they are made.
Yes, the mattress industry uses 2 Twin E.L. (Extra Long) boxsprings which each measures 38 x 80 and are then placed under a 76 x 80 king mattress. What makes this whole thing confusing is when you place 2 twin mattresses side by side they are the exact same width as a standard king size bed.