Phytoplankton include all unicellular photosynthetic organisms and may live in the ocean or freshwater. Phytoplankton are the food source for zooplankton, tiny, floating animals and thus are the base of the food chain. In addition, pigments give plants and algae their colors by absorbing some wavelengths and reflecting others. The most common plant pigment is chlorophyll which absorbs red and blue light and reflects green, hence plants look green. 2 O, the same compounds used to produce glucose during photosynthesis.
All organisms carry on respiration.
The two processes work together to cycle carbon through the earth s plants and animals. RubisCO may have formed about 3 billion years ago when life forms first began to emit oxygen. This suggests that changing CO 2 and O 2 levels in the atmosphere may have lead to the enzyme becoming more efficient in its use of CO 2 over geologic time. The outside wall is composed of silica impregnated with pectin.