Problem 8 - Biology: The Dynamic Science

Question

The major source of nutrients in the headwaters of a small stream is from: a. dead leaves and other organic matter from adjacent land. b. photosynthesis by phytoplankton. c. photosynthesis by floating aquatic plants. d. the activity of chemoautotrophic bacteria. e. minerals from the underlying bedrock.

Step-by-Step Solution

Answer

The major source of nutrients in the headwaters of a small stream is from dead leaves and other organic matter from adjacent land.

Step 1: Understand how nutrients enter the stream

It's important to remember that headwaters of small streams are frequently surrounded by terrestrial, or land-based, ecosystems. Additionally, these waters are located at higher altitudes where the sunlight needed for photosynthesis may be limited. Therefore, these factors may help to rule out options which mention photosynthesis as a primary nutrient source.

Step 2: Consider terrestrial nutrient sources

Knowing that headwaters are often situated near land ecosystems and considering the lack of sunlight at higher altitudes, the first option now seems more credible. The decomposition of organic matter like dead leaves as they fall in the water from surrounding land provides essential nutrients to the ecosystem key to its survival and prosperity.

Step 3: Evaluate other options

Although other options may contribute to a lesser extent, the primary source, especially in headwaters of small streams, is organic matter from adjacent land. Chemoautotrophic bacteria, although able to produce nutrients without the need for sunlight, are generally not the major source in headwaters, while minerals from the underlying bedrock can contribute but are unlikely to be the primary source. Therefore, the primary source is more likely to be organic matter from the surrounding land.