species currently identified (Nelson, 2002). Their occupation of
many diverse niches, attributed to their ability to adapt to radically changing ecological conditions, sets the platform for their
evolutionary story. Tardigrades are readily available in moss and
lichens and can be cultured for students to observe and take care
of in terrariums (Nelson, 2002).
The workbook “Tardigrada: Trundlers in Time” was created to
engage students in a slightly fanciful narrative that highlights tardigrade evolution, along with amusing activities and relaxing lessons
with coloring-book elements. The workbook has not been published
but is available for download on the Time Tree website (http://www.
timetree.org/public/data/pdf/Joe Tardigrada.pdf). A few of the images
are presented in this article, but the full effect of the workbook is
intended to move students through many of the common terms of
evolutionary thinking. We propose evolutionary thinking as the
“master narrative” to help students casually synthesize a dynamic,
comprehensive, panoramic view of evolutionary process. We also
present tardigrade evolution within a broad ecological framework.
“One innovative notion,” writes Catley (2006), “is that classification
is best understood in an ecological context, such that the sets of
interrelationships are presented as manifestations of natural selection over very long periods of time.” We achieve this geological timescale in our narrative through the character “Joe Tardigrada” and his
travels around the globe.
Thus, the workbook takes an evolutionary/ecological view in
story format, encourages naturalist-style observation, and includes
classical drawing exercises, while promoting phylogenetic thinking.
It should be printed and used to color in, draw in, and make notes
in. It can be given as homework or structured as an in-class assignment. We suggest that the workbook be used in conjunction with
a wet lab or as part of a larger lesson plan on evolution, at the discretion of the instructor. It takes about one hour to finish but is
intended as a contemplative prelude to more rigorous study, so students can take up to a week to complete it. Many comprehensive,
visually well-presented articles have been published on tardigrade
metabolism, anatomy, ecology, and evolution, and labs are available
online for culturing or maintaining living specimens (see Further
Resources below). Our purpose is not to rewrite this already accessible knowledge, but rather to provide a “point of entry,” an alternative
to the standard PowerPoint presentation on tardigrades. The workbook introduces evolution, phylogeny, and computer databases to
start building an evolutionary mental construct and more intuitive
thinking in interpreting phylogenetic trees.
Visual metaphor is used in the workbook as a powerful way to
imagine processes we cannot see (Pramling, 2009) and enhance comprehension of ideas. An example of this can be seen in Figure 2, which
depicts Joe Tardigrada carrying his genome with him as he travels
through time and around the earth – a simple cartoon conveying
the concept of a genome, represented as a vagabond’s belongings.
When we speak of genomes, students typically conceive of them only
as abstracted sequence data and may forget that genomes are a nested
network of complementary, replicating molecules in the cells of an
organism. The takeaway message from Figure 2 is that where an
organism travels, so does its genome.
The workbook uses the phylum Tardigrada to channel the complexities students may encounter in evolutionary theory in a way that
can be applied to any organism. The entertaining, artistic narrative
is designed to help students retain useful genetic and evolutionary
Table 1. Tardigrada workbook features.
Concept Activities Outcome
Characters Using morphological characters to draw a
Students familiarize themselves with species’ anatomy
through drawing to understand visible phenotypic
changes and the metabolisms of Tardigrada as part of
phenotypic expression (cryptobiosis, oxybiosis).
Divergence Text, cartoons, and story line Students connect concepts of divergence and
speciation through cartoon metaphors.
Adaptive radiation Exploring a variety of ecosystems with
tardigrades and morphing a “prototype”
tardigrade through drawing
Students learn the importance of variation, natural
selection, and the concept of transitional processes as
they make their drawings “morph” in new
Phylogenetic tree Exploring unresolved relationships in
invertebrate metazoans through drawing
Students understand morphological physical traits as
being coded by genes. They see variations in forms
and explore how DNA, which codes for the proteins
expressed, produces this variation. Size, shape, colors,
patterns, and presence or absence of characteristics are
highlighted by the workbook activities.
Time Tree database
Comparing a wide range of species with
Tardigrada, including vertebrate mammals
Students play with the database and familiarize
themselves with the potential of Time Tree, with more
structured and specific applications to follow.