Final answer:
Organisms such as archaea and cyanobacteria can thrive in the extreme conditions of Yellowstone's hot springs, with some surviving near boiling temperatures by utilizing chemical energy, while others form colorful mats through photosynthesis in slightly cooler areas.
Step-by-step explanation:
The organisms that can grow in the hot springs of Yellowstone National Park are particularly robust and unique. Among these, a group of organisms identified in the 1970s, called archaea, can thrive in extreme conditions, such as temperatures near and even at the boiling point of water (around 100°C). In addition, hyperthermophilic organisms like those from the archaeal genus Sulfolobus inhabit the Morning Glory pool, living comfortably at temperatures between 60°C-80°C and a pH of 3.
Another fascinating aspect of these hot springs is the presence of cyanobacteria, which form vibrant colored mats due to their photosynthetic activity. In areas such as the Grand Prismatic Spring, with temperatures near 92°C, these bacteria use the chemical energy supplied by various substances in their hostile environment, since the temperatures are too high for photosynthesis. The color gradients in these springs, such as green, yellow, and orange, are caused by the photosynthetic bacteria capturing some wavelengths of sunlight for energy and reflecting others, which contributes to the distinct coloration.
Furthermore, the varying temperatures within the springs encourage different densities and types of microbial life. As observed in Figure 22.4, as water flows away from the heat source and cools, the cell density of cyanobacteria increases, which is visually apparent by the greener edges compared to the center of the streams.