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.