Earth Science

Life on Earth

Freshwater Ecosystems

Study Tip
Studying diagrams for this topic will help you visualize the different types of freshwater ecosystems.

Freshwater Ecosystems

Freshwater ecosystems contain bodies of water that have almost no salt content. These include lakes and ponds, rivers and streams, reservoirs, wetlands, and groundwater.

Study Tip
Studying diagrams for this topic will help you visualize the different types of freshwater ecosystems.

Lakes

Lakes are divided into three zones:

Zone
Description
Animals
Surface (littoral)
Sloped area closest to the edge of the water
Snails, insects, smaller fish
Open-water (photic/limnetic)
Shallow area of water, receives abundant sunlight
Larger fish such as bass or trout
Deep-water (aphotic/profundal)
Deeper area of water, receives little to no sunlight
Scavengers such as crabs and catfish. Decomposers such as fungi and bacteria
Factors that affect ecosystems in lakes:

Factors that affect ecosystems in lakes:

  • Light
  • Pressure
  • Temperature
  • Vegetation  

Wetlands

Certain specialized plants are able to grow in regions of land that holds a great deal of water.

Type
Description
Animals
Marshes
Shallow wetlands that are around lakes, streams, or the ocean. Grasses and reeds are common, but trees are rare.
Frogs, shrimps, turtles
Swamps
A wetland with lush trees and vines, found in low-lying areas beside slow-moving rivers.
Crayfish, alligators, newts
Marshes
Marsh
Swamps
Swamp

Earth Science

Rivers and Streams

Streams are bodies of water that have a current. Streams are classified based on size, depth, speed, and location. In streams, water always flows downhill. The path a stream takes, and its speed, varies with rock type, topography, and many other factors.  

Stream terminology:

Term
Description
Confluence
Point where two streams come together
Mouth
Point in which steam comes into a large body of water
Estuary
Point where stream meets the ocean
Concept Check
  • What similarities do the different types of freshwater ecosystems have?
  • What are the different zones in a lake?
  • Describe two types of wetlands.