Question

Go to nearby pound observe organisms living in the pounds and biodegradable substances mixing and water how they affect on those organisms write your observation

Answer 1

I usually use this activity to introduce the unit on water pollution and to teach serial dilution
technique. It can be used either as an introduction or as a reinforcing activity, but it should be
linked to an in-depth discussion of water pollution by common forms of biodegradable waste
such as sewage. Oxygen sag curves, eutrophication, and BOD (Biological Oxygen Demand)
should be included in the discussion.
• Milk works very well as a biodegradable material. You can also use cream, 10 percent sugar
sucrose solution, clear juices like apple or white grape, etc. It's important that the color of the
biodegradable solution does not obscure the methylene blue color change. It's important to
point out that these materials, while biodegradable, are usually not the culprits in water pollu-
tion. Sewage, agricultural runoff, and industrial effluent are usually the problem, but they are
not easily handled safely in a classroom situation. The students need to keep in mind that this
activity works better as an analogy rather than as a re-creation of a common real-life situation.
• You can purchase methylene blue from any science products supplier. Methylene blue is clear
in the absence of oxygen and blue in the presence of oxygen. The time for color change will
vary depending on the concentration of biodegradable material, but I always tell students to
watch the tubes -- it may be quick if you use a concentrated solution.
• You can purchase any commercial yeast packets from a supermarket. Don't hydrate the yeast
until just before the lab. I usually use a 1:10 dilution -- 1 ml of dry yeast to 10 ml of tap water. You'll need to adjust the volume required depending on the number of lab groups. Again,
remind students that yeast are usually not the principal decomposers of biodegradable waste
but are easily handled safely in a classroom setting.
• It's important to use test tube racks that allow you to see the contents of the test tubes so that
you don't have to disturb the tubes to observe the color change. Any movement of the tubes
will affect the dissolved oxygen levels as air is mixed into the solution.
• It's easiest to have the methylene blue in dropper bottles.
• I usually have the students produce a formal lab report as an assessment