2. Watersheds This is an area where rain joins together to flow into streams, rivers, lakes, or wetlands. This is the drainage basin. The watershed boundary is the highest elevation between two watersheds. What happens on the land of a watershed affects the quality of water in the aquatic environments and organisms that live there. There can be saltwater and freshwater ecosystems.

3. Freshwater Ecosystems Can be divided into two groups: Lotic- relatively fast moving water ecosystems Lentic- relatively slow moving (seems to stand still) water ecosystems

4. Lentic Bodies of Water Includes: Lakes Ponds Wetlands

5. Lotic Ecosystems of Water Includes: Rivers Streams Smaller feeder streams and rivers that empty into a larger stream or river are called tributaries Brooks Creeks And human-made channels

6. Stream Sizes Streams are classified by size: First-order- smallest Second-order-when two first-order streams meet Third-order- formed when two second-order streams meet This process continues until the stream or river empties into a lake or the ocean.

7. Reaches River systems are divided into 3 different region: Upper Reaches- Includes the regions of the stream with the greatest slope (includes headwaters and riparian zone); rapids, riffles and waterfalls are abundant here with boulders and cobbles that are too heavy to be swept away; organisms that live here must be good swimmers, find small pools created by rocky projections, or hold on by attaching themselves to surfaces; contains fewer species of plants and animals than other regions of the river, and the populations that are present are smaller.

8. Reaches Middle Reaches- Includes third and fourth-order streams; slope is moderate and U-shaped channel is wider; bottom is covered with boulders, cobble and gravel; riparian zone widens to form a floodplain and the path of the streams has more curves and meanders; trees and rooted plants grow along the edge providing food and shelter for some species; has the greatest variety of habitats with a combination of shallow areas and deeper pools; fewer rapids and less erosion occurs here; most organisms are found in the pools and shallow areas at the water’s edge; number of species and population densities are higher than in upper reaches.

9. Reaches Lower Reaches- includes sections with a gentle, steady flow; slope has a low slant and the river meanders across a wide valley; U-shaped channel is deeper and wider than middle and upper reaches; eroded materials from middle and upper reaches is deposited here; bottom covered with gravel, sand, and silt; no rapids, riffle, or waterfalls; riparian zone is a floodplain several miles wide; seasonal flooding deposits sand and soil on the land creating marshes and swamps; turbidity prevents sunlight from reaching the bottom limiting photosynthesis; community of plants and animals in lower reaches is similar to a pond.

10. Habitats There are a variety of habitats or places where organisms can live in an aquatic ecosystem and depend on the volume of flowing water and slope of the channel. Could include: Surface film- where water meets air; air-breathing insects that may walk on or hang from the surface of the water. Open water- area where the rooted plants do not reach the surface; may find large fish, turtles and birds, and microscopic organisms called plankton.

11. Habitats Bottom- area of rocks, sand, or mud that is the habitat of small organisms like bacteria, snails, worms, sponges, crayfish, and some larvae of aquatic insects; fish create nests in streams to deposit eggs. Water’s edge- where water meets land; home to the greatest number of species of plants and animals; many small organisms can be found on leaves and stems of plants; plants provide hiding places for small fish and other organisms find some protection or a place to breed. Human-made channels- straight box-like ditches that have been dug to move water more efficiently.