Chapter 3, Problem 17STP

Summary Introduction

To determine:

The difference between the freshwater ecosystem in the starting of the river and the end of the river.

Introduction:

The rivers are the water bodies that originate from the mountains having snow caps (not necessarily) and flow through the plains. In the end they drain into the oceans, where the meeting point of the river and the ocean forms an estuary.

Explanation of Solution

Point X: In the upper course of the river (headstream), that is the starting point, the flow of water is high, the river is shallow and more turbulence is there. In this case, the anchorage of the planktons and the plants is not possible. Hence, a smaller number of planktons are observed. The fishes living in this water feed on flowing microbes and have a streamlined body that assist in swimming. The oxygen concentration is high here, which helps in proper respiration of the fast-moving species.

Point Y: In the lower course of the river, which is near the mouth, the water is deep and moves slowly. The oxygen concentration is also not uniform through the water body. The organisms in this ecosystem represent stratification and layered. The organism living in the deep regions are adapted to less oxygen concentration. The amount of aquatic plants in this region is high and there are many bottom dwelling species.