To explore a learn node to study and report on something for biology, why not the common nematode. The “What are Nematodes?” webpage at the University of Nebraska-Lincoln begins:

Nematodes are the most numerous multicellular animals on earth. A handful of soil will contain thousands of the microscopic worms, many of them parasites of insects, plants or animals. Free-living species are abundant, including nematodes that feed on bacteria, fungi, and other nematodes, yet the vast majority of species encountered are poorly understood biologically.

You can click from this explanatory page to something of an illustrated parts list for nematodes called: Interactive Diagnostic Key to Plant Parasitic, Freeliving and Predaceous Nematodes. Shown here is one of the head appendages. Bananas are a fruitful place to observe nematodes in action; excellent materials for that topic can be found on IITA Research to Nourish Africa’s Banana Nematology pages. Described there is nematode damage and symptoms caused not by “a single nematode species attacking bananas, but a complex of several species.” Nematodes can also play role in insect control. A University of Florida article explains how biological control nematodes work. The Nematode.net Genome Sequencing Center at Washington University in St. Louis is an detailed repository of nematode facts and images, the picture of the Meloidogyne hapla at the top of this post.

More learn nodes at: learnodes.com

More learn nodes at: learnodes.com

A look at an example of the arsenic problem in drinking water is provided by the American Museum of Natural History’s 2007-08 special exhibit on Water, which describes a situation where arsenic foiled attempts to get good water by drilling below bacterial contamination:

In Bangladesh, millions of deep wells were drilled to end use of bacteria-laced surface water. It worked: for instance, infant mortality dropped sharply. But many of the wells turned out to contain high levels of naturally occurring arsenic—an extremely toxic chemical element with serious health effects. Today, experts are working to develop inexpensive methods of removing arsenic from the water.

So how would you get arsenic out of water? Three pages from a Stiochiometry tutorial at Carnegie Mellon University’s openlearning initiative describes a method developed by Prof. Fakhrul Islam, a chemist at Bangladesh’s Rajshahi University. The tutorial is Arsenic remediation: Using powder to absorb arsenic from water.