ingridscience

Before the lesson, find some good habitats for decomposers e.g.under logs and dead leaves, then take the students to these sites.

Students hunt for anything living in the soil. As they look more closely they will notice smaller and smaller animals. e.g. worms, wood bugs, slugs, snails. Also fungi and bacteria.

Discuss with the students what these animals eat, and that many of them have an important role as decomposers - living things that eat dead plant and animal matter. They break down living things into simple molecules that can be then used by plants (carbon compounds to CO2; nitrogen cpds to nitrite, nitrate and N2; phosphorus cpds to phosphate).
Decomposers often prefer it moist, dark and damp, where the rotting process is fastest.

Optional: study the animals more closely with magnifiers on site.
Optional: collect a few animals in soil to take back to the classroom, study more closely and make a food web.
Optional: collect worms or wood bugs to keep in a habitat in the classroom. Or release worms or wood bugs that have been in the classroom for a while.

Return any animals that do not have a habitat in the classroom to their collection site.

This is the last activity of the Honey Mystery.

Students compare the "fingerprints" of the left paw of each cat (as the investigators determined that someone picked up the honey jar with their left hand). See the worksheet.
Identify whether each print is an arch, loop or whorl.

Then look at the prints found on the honey jar (this can be given as a separate piece of paper to stick onto the worksheet).
identify which cat made the prints on the jar.

For our case, it was the black cat that stole the honey.

Please note that in a class of students it is likely that one of them is at least partially colourblind (1 in 12 males are colourblind). As this is an activity distinguishing colours, these students will not be able to tell some colours apart and perceive some colours differently, although the activity will be no less interesting for them. The common red/green colour blindness means reds and greens (or colours containing reds and greens such as browns) look similar. More information at colourblindawareness.org and colorblindguide.com/post/the-advantage-of-being-colorblind.

Before the lesson, write the note using one of the black pens. Example of what it can read: "What you seek is buried under the old cedar at the back of the house". Something more applicable to the classroom or school building would be better.

In the lesson, read the note to the students, and show them the black pens that might have written the note, and that they will use chromatography to figure out which one. Demonstrate the steps below, before allowing them to proceed.

Prepare chromatography strips for the black pens:
Cut out filter paper, using the template to make the correct size. Draw a pencil line across the paper, where indicated on the template (see 1st photo).
With each black pen make a line across the strip of the filter paper, over the pencil line.

Prepare chromatography strip for the ink on the note:
Cut off a small piece of the note with a word on it, lay it word-side down on a filter paper strip, at the same level as the line on the template, and use a paperclip to attach them together. (2nd photo.)

Run the chromatograms:
Clip the top of the filter paper strips with the small binder clips (for all the black candidate pens, and for the note). Then thread the coffee stir stick through the binder clip arms and lay the sticks across the top of the tub. The filter paper should dip into the water, but the black lines and the piece of note are above the water line. Allow the chromatograms of the three candidate pens to run (3rd photo). Wait three our four minutes until the colours have separated up the filter paper to within 1cm from the binder clip.
Although the chromatogram with the note is not as distinct as the chromatograms from the black lines, the colours should still be distinguishable, so that the pen that wrote the note can be identified (see 4th photo comparing the chromatogram from a line and from a note).

Many black pens have a different chromatography pattern (see 5th image). Note that marker brands change their ink composition now and again (e.g. crayola now has more ink colours in some of their black markers).

How does chromatography work?
The coloured dye molecules in the ink of the pen are attracted to both the water that it is in, but also the surface of the filter paper. Each different colour is attracted to the water or the filter paper to different extents. As the water moves up, the dye molecules that are most attracted to the water will move along fast with it. If the dye molecules are mostly attracted to the paper, they will get stuck to the paper and not move along with the water at all. Most colours are attracted to both the water and the paper, so will travel with the water for a while, then stick to the paper for a while. Depending on the relative attraction of a dye to the water and the paper, a colour will travel at its own rate. The differing rates of travel separate out the colours.

Students view human and animal hairs with magnifiers and ideally a microscope. They can tape them to a worksheet, piece of paper or microscope slide to make viewing easier. They should notice different colours and widths. Under the transmission microscope the pattern of scales on the surface of the hair will also vary.

For a lesson on animal hair function:
Look at the different thicknesses of hair and discuss their purpose. Dense, fine underfur (for warmth) and the long, coarse guard hairs (for protection against the weather and dirt, to raise when confronting other animals.

For a lesson on forensics:
Discuss how hairs are quite different from each other. They can often be used to determine the race of the person they came from, and also whether the hair was dyed. Hair also contains chemicals that have been ingested, so can be tested for drugs or other chemicals.
Students can have an array of hairs in little baggies, and guess their source e.g. cat hair may have identifiable colours distinct from human hair.

Optional: Give students other kinds of "trace evidence" each in their own baggie, for students to try and identify, to mimic a crime scene investigation e.g. paint flakes, wood splinter, carpet hairs.

Forensic scientists may find hair with a root attached - you can pull out a hair from your head forcibly to see the root (a tiny white blob). The root contains hair cells, which can be used to extract DNA and identify a person involved in a crime.

(Background: There has been a crime among the stuffed animals. Pooh's honey was stolen while he was sleeping. The empty jar was found near him. The investigators collected hair samples from the honey jar and put them in baggies.)

Each student is given a worksheet, and asked to record the hair colours of each stuffed animal that was found in the vicinity of the crime scene. See attached worksheet and image.

Each student is given two baggies, containing hair samples 1 and 2 respectively from the crime scene.
Students hold the samples against white paper and black paper and use a magnifier to determine the colour of each hair. They will need to look closely as there was not much hair recovered from the crime scene.
They tape the baggie next to the recorded hair colour.

By matching the hair samples from the crime scene with the hair colours of each stuffie, students figure out which of the stuffies are still suspects. (The black and brown bear, and also both cats as the brown hair could have been Poohs.)