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Context for this case:
Prerequisites:
Cognitive Apprenticeship Features:
Supporting References:
Relevant CA Content Standards |
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FINDING TECHNICAL TERMS:
A good description uses (and introduces its readers to) appropriate
technical terms for its topic (as noted in "Specifics" under the Content
section of the description
guidelines).
This bone-fracture description uses many such terms, which you can point
out as you go through it with students.
Some are explained (implicitly defined) within the text:
cortical bone lines 11-12
trabecular bone lines 13-15
five named bones lines 17-27
vertebra
femur
tibia
humerus
iliac crest
resorption lines 35-36
turnover lines 33-36
osteoporosis lines 42-43
buckling lines 67, 76-79
Other technical terms are used here but never explained:
lattice line 14
collagen line 15
trabecula(e) line 29
tomography line 51
You can explain these terms, have students look up their meanings, or
discuss for which audiences including a definition of each within
the description text would be a good use of space.
FINDING COMPARISONS:
Comparisons (and negative comparisons or contrasts;
see "contrast classes" at (4) in the teacher notes on
Exercise 0)
are a very practical
way to introduce new information by connecting it (positively or negatively)
to other, more familiar, things.
You and your students can find (and discuss the explanatory
contributions of) quite a few useful comparisons throughout the
bone-fracture description. Examples include:
Positive comparisons--
"fracture more easily" line 2
sponges lines 29-30
dented can lines 76-82
Negative contrasts--
solid/lattice structure lines 9-15
balanced/unbalanced
turnover lines 40-41
short struts/long columns lines 54-58
young/old bone stress lines 60-64
FINDING OTHER USABILITY FEATURES:
The guidelines recommend several other text
usability
features that
also appear in this description.
Among those for which students can search and whose role you can review
are these:
ADDING HEADINGS:
The writer of every useful long description needs to organize the text
carefully and reveal to the reader what that organization is (first
section of the good-description
guidelines).
The first two sentences in this case reveal that this process description
has a problem/solution structure, a common pattern in science text.
The first sentence poses the problem and the second announces the solution
that the rest of the description provides.
(A) Placing Headings. Normally section headings would reveal (visually outline) the organization of a description as long as this one. All have been omitted here to create an activity opportunity for students. You can offer the class a set of (good) candidate headings (perhaps printed on large sheets of paper and distributed randomly) and invite students (or groups) to propose a "best location" for each candidate. For example, here is a list of helpful headings for this description and their likely insertion points:
Overview line 1
Bone Structure line 8
Bone Turnover line 32
Loss of Density line 39
Trabecular Shape Change line 50
Trabecular Pitting line 70
Adding such headings is an authentic, valuable part of text revision
that requires students to understand the overall gist of the description,
not just its isolated sentences.
(Scrambling the candidate headings eliminates trivial guessing.)
(B) Evaluating Headings. Distinguishing between appropriate headings (those that show readers the actual text structure) and inappropriate ones (too broad, too narrow, just decorative) is a related, more demanding, revision skill. Students can practice that skill too if you offer a few bad headings, either after placing the good set or mixed among them for a more challenging exercise. Here are some sample inappropriate headings for this bone-fracture description (all are topics mentioned in the text, often in many places, but none clarifies the text's problem/solution structure no matter where they are put):
Tomography
Bone Resorption
Trabeculae
Building Blocks of the Spine
Comparing the signalling roles, the help provided to readers, of the good
and bad candidate headings reveals to students that headings should do
more than visually break up long stretches of text.
They should also add useful intellectual content on their own.
ADDING FIGURES:
Text and figures (pictures) often complement each other in technical
publications. Earlier exercises showed students how relevant, well-placed
figures can enrich and clarify a description. For example,
This exercise approaches text-figure integration from the other direction.
The bone-fracture draft description contains no figures, but it could
benefit from some.
Hence, revising it provides a chance for students to practice two
important skills:
(1) selecting and placing figures to supplement the words available, and
(2) distinguishing appropriate, helpful figures from inappropriate,
unhelpful candidates when self-editing
(for background, see Edward Tufte's website).
As with illustrated
instructions,
I always point out to students that
the same basic usability principles (summarized in the guidelines)
that yield good descriptive text also yield good descriptive graphics
(although implementation is visual rather than purely verbal).
(A) Unhelpful Possible Figures. Many pictures vaguely related to this description but not really helpful for improving it are available in textbooks and online. Two that I have used effectively in class are (linked but not reproduced here for copyright reasons):
(B) Helpful Possible Figures. In contrast to the poor choices above, here are two alternative figures that easily enrich the bone-fracture description (from Ann Parker's article):
Students should always be on the lookout for (guideline-inspired) ways to make even good text better, and the same applies to good graphics. Useful as they already are, the trabecular-bone and young/old-vertebrae figures could still be improved in these ways (which you can prompt students to suggest or explore):
The four figures offered here are by no means the only ones that you could discuss when revising the bone-fracture draft description. These examples nicely demonstrate the skill-building potential of this activity, however.
1 2 Old bones fracture more easily than 3 young ones, even under small amounts 4 of stress. 5 This is partly because old bones lose 6 density, but partly because they also 7 change their structure. 8 9 Many human bones contain two different 10 internal structures. 11 Some central tissue is quite solid 12 (cortical bone). 13 Other tissue, however, contains a 14 cellular foam or open-celled lattice 15 of collagen (trabecular bone). 16 Trabecular bone occurs in 17 * individual parts of the spine 18 (vertebrae), 19 * the femur (the long bone that joins 20 the knee to the hip), 21 * the tibia (the larger of the two 22 bones connecting the knee to the 23 ankle), 24 * the humerus (the long bone linking 25 the shoulder to the elbow), and 26 * the iliac crest (the widest part of 27 the hip bone). 28 29 Trabeculae are like sponges. 30 They absorb loads from the joints just as 31 Styrofoam absorbs impacts in packages. 32 33 All bone renews itself regularly. 34 The human body continuously removes 35 old bone (resorption) and replaces it 36 with new bone (formation). 37 The average bone turnover rate is 38 about 6 years. 39 40 In menopausal women, however, this 41 turnover process becomes unbalanced. 42 More bone is resorbed that is formed, 43 so bone density decreases (osteoporosis). 44 Medical treatments for osteoporosis 45 usually focus on stopping resorption 46 of old bone while still allowing new 47 bone to fill in. 48 Reducing turnover in this way leaves 49 bone more massive yet also more brittle. 50 51 Three-dimensional computed-tomography 52 images reveal a structural change in 53 human trabecular bone with age. 54 In young bone, the trabeculae form a web 55 of short, stubby struts. 56 In older bone, on the other hand, these 57 trabeculae are mostly long, slender 58 columns. 59 60 Fracture (failure) in younger bones 61 usually happens when stress overcomes 62 the strength of the bone tissue. 63 Fracture in older bones happens at 64 much lower stress levels. 65 The long, thin trabeculae in old bones 66 are unstable. 67 Hence, when compressed, they buckle at 68 far lower stresses than bone tissue 69 normally withstands. 70 71 Bone resorption forms small pits on the 72 surface of the trabeculae. 73 As bone turnover increases, the number 74 of pits increases too. 75 76 An empty aluminum can requires much 77 stress to crush it axially. 78 But with a small dent in its side wall 79 the can buckles easily. 80 In the same way, trabecular pits are 81 themselves enough to destabilize 82 bone lattice. 83 In old human bone, 60% of trabeculae 84 are vulnerable to buckling just because 85 of their pits.
This exercise most closely supports the following California
English-Language Arts content standard(s).
Grades 9 and 10:
Reading:
"Critique the logic of functional documents by examining the sequence of
information and procedures in anticipation of possible reader
misunderstandings." (2.7)
Writing:
"Use precise language, action verbs, sensory details, appropriate
modifiers, and the active rather than passive voice." (1.2)
"Revise writing to improve the logic and coherence of the organization and
controlling perspective, the precision of word choice, and the tone
by taking into consideration the audience, purpose, and formality of
the text." (1.9)
"Include visual aids...anticipate and address readers' potential
misunderstandings, biases, and expectations." (2.3e)
"Use technical terms and notations accurately." (2.3f)