How do unicellular organisms drink

The condition of a body of water

Waters such as streams, rivers, lakes and ponds represent a habitat for many living beings. Humans depend on this community to be preserved. Humans catch fish and they get their drinking water from the lakes or from the groundwater in the ground. The quality of the groundwater also depends on how clean the water is. The Water pollution takes place through fertilizers from agriculture or through wastewater from industry or households. It is therefore important that these entries are kept as small as possible. You can use sewage treatment plants or you can make sure that no harmful substances get into the sewage in the household.
One exists in the waters Food cycle: Fish or beetles eat smaller animals, smaller animals such as crabs or insect larvae eat algae and plants. Microscopic creatures like the eyelash animals also like to eat bacteria. The bacteria have the task of breaking down dead organisms. But there is also a Oxygen balance: Animals and small aquatic organisms such as protozoa need oxygen to breathe, which is dissolved in the water. The colder the water, the more oxygen is dissolved in the water. Fast currents, waterfalls or swells favor the dissolving of oxygen from the air in the water. Small, dormant ponds with lots of plant material and algae contain less oxygen. The most important source of oxygen in water, however, are plants and algae. They make the gas. But why is there less oxygen in the small ponds?
There are many more decaying creatures in small, plant-rich bodies of water. Then the bacteria come into play: They decompose the dead organisms. In doing so, however, they consume oxygen. If nutrients from fertilizers also get into the water, the plants and algae temporarily receive more food. They start to multiply. As a result, the unicellular organisms and animals also receive more food temporarily. They also multiply. But now there are also more dead organisms and thus considerably more bacteria. At this moment it can suddenly happen that the oxygen content decreases dangerously and the animals suffocate in the water. When all animals die, the water “tips over”. The functioning of the community is then permanently disturbed.

Depending on the water quality, the waters are divided into Water quality classes a. Grade I water contains a lot of oxygen. The load with organic material from remains of living beings is low. This water is suitable as drinking water. Living things like stonefly larvae need this water quality. Quality class II water is slightly contaminated, the oxygen content is somewhat lower. Mayfly larvae, small crabs or snails feel at home in such water. For each quality level there are typical living beings, they are called Pointer organisms. The water quality class can be determined by determining the aquatic organisms in a body of water.

Text: Aquatic community with work tasks (pdf)


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