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Diving into the world of water that isn't salty and the life it supports.
Did you know that only about of all the water on Earth is freshwater, and most of that is locked away in ice? Imagine if you had to find all the water you need for drinking and bathing from just a tiny fraction of the world's supply!
Freshwater ecosystems are divided into two main groups based on how the water moves. Rivers and streams are lotic ecosystems, meaning the water is constantly moving. Gravity pulls water from high places, like mountains, down to lower areas. Because the water moves fast, it often has more oxygen, which helps certain fish breathe. Lakes and ponds are lentic ecosystems. This means the water is mostly still, filling up a basin or a hole in the ground. Because the water doesn't race away, plants can easily take root at the bottom or float on the surface without being washed downstream.
Quick Check
If you are standing next to a body of water that is flowing quickly toward the ocean, are you at a river or a lake?
Answer
You are at a river.
Wetlands are amazing places where the land is covered by shallow water for at least part of the year. You might know them as swamps, marshes, or bogs. Wetlands are like the 'kidneys' of the Earth. They act as natural filters, trapping pollutants and sediment before they can reach the open ocean. They also act like giant sponges. During heavy rain, wetlands soak up extra water, which prevents flooding in nearby towns. Without wetlands, our drinking water would be much dirtier and our homes would be at higher risk of floods!
Imagine you have a bucket of muddy water and a sponge. 1. If you pour the water onto a flat sidewalk, the mud spreads everywhere. 2. If you pour the water onto a thick sponge, the sponge traps the dirt and lets clearer water drip out the bottom. This is exactly how a wetland cleans the environment!
Quick Check
What are two important jobs that wetlands do for the environment?
Answer
They filter pollutants out of the water and soak up extra water to prevent flooding.
Life in freshwater has to adapt to its surroundings. In fast-moving rivers, you will find the trout. These fish have streamlined bodies that allow them to swim against strong currents. In the still waters of lakes and wetlands, you'll find water lilies. These plants have wide, flat leaves that float on the surface to catch sunlight. You will also find frogs, which are amphibians. They need the calm, shallow water of wetlands to lay their eggs safely. Each of these species plays a role in the food chain, keeping the ecosystem balanced.
Consider the relationship between a frog and a lily pad: 1. The lily pad provides a resting place for the frog to stay out of the water. 2. The frog eats insects that might harm the plant. 3. If the water starts moving too fast (like a river), the lily pad would be torn away, and the frog would lose its home.
Imagine a town decides to pave over a wetland to build a shopping mall. 1. Calculate the impact: If the wetland used to soak up gallons of rain, that water now has nowhere to go. 2. Predict the result: The nearby river will rise faster, potentially causing a flood. 3. Pollution: The oil from the mall's parking lot will wash directly into the river instead of being filtered by the wetland plants.
Which term describes a 'moving' water ecosystem like a stream?
Why would a water lily struggle to survive in the middle of a fast-moving river?
Wetlands help prevent floods by soaking up excess rainwater.
Review Tomorrow
In 24 hours, try to explain to a friend why a wetland is like a 'natural kidney' for the Earth.
Practice Activity
Draw a picture of a river flowing into a lake. Label one animal that lives in the fast water and one plant that lives in the still water.