Biology 11th Edition by Cecie Starr ,Ralph Taggart

تمرين 8

Most pigments respond to only part of the rainbow of visible light. If acquiring energy is so vital, then why doesnt each kind of photosynthetic pigment absorb the whole spectrum Why isnt each one black
If early photoautotrophs evolved in the seas, then so did their pigments. Ultraviolet and red wavelengths do not penetrate water as deeply as green and blue wavelengths do. Possibly natural selection favored the evolution of different pigments at different depths. Many relatives of the red alga in Figure 7.16 a live deep in the sea. Some are nearly black. Green algae, such as the one in Figure 7.16 b , live in shallow water. Their chlorophylls absorb red wavelengths, and accessory pigments harvest others. Some accessory pigments also function as shields against ultraviolet radiation.
Speculate on how natural selection may have favored the evolution of different pigments at different depths, starting at hydrothermal vents. You might start at Richard Monasterkys article in Science News (September 7, 1996) on Cindy Lee Dovers work at hydrothermal vents.