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.
A standard twin bed, or single bed, is designed for one person. They are 39 inches (100 cm) wide and 75 inches (190 cm) long. These types of beds are popular for kids, and are often found in day beds and trundle beds as well. Bedding is easy to find for a standard twin bed. An extra long twin bed is very common in college dorm rooms.