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Project Grade 8 Art & Music

Stippled Microbe ID Cards for the Wendlow Reclamation Lab

A grade 8 scientific illustration project: students stipple ink ID cards of activated-sludge organisms for operators at a fictional plant, then test and revise them.

Objectives

  1. Students will explain how bacteria, protozoa, and rotifers in an aeration tank clean wastewater and why operators examine them under a microscope.
  2. Students will draw four organisms from reference images with observational accuracy, using stippling density to build value in black ink only.
  3. Students will design a consistent card layout with labels, leader lines, and a correctly scaled scale bar.
  4. Students will write concise informative text for each card and revise one card based on evidence from a match test.

Vocabulary

Activated sludge
Activated sludge is a living brown mixture of helpful bacteria and other microbes that wastewater plants grow on purpose. The microbes clean the water by eating the waste in it.

Also: aeration tank, protozoa, cilia, rotifer, stippling, scale bar, leader line

Teacher overview

Most municipal wastewater treatment plants rely on living organisms to do the main work of cleaning. In an activated-sludge aeration tank, air bubbled through the wastewater lets bacteria consume dissolved organic waste, and protozoa and rotifers graze on the bacteria. Operators at many plants place a drop of this mixture under a microscope, because the kinds of organisms that dominate tell them whether the biological process is young, recovering, or stable. In this project students produce a set of four stippled ink identification cards for new operators at the fictional Wendlow Water Reclamation Facility, test whether a classmate can use the cards to identify unlabeled images, and revise the cards before presenting them to the lab supervisor, a role the teacher plays.

The science misconception to address first is that wastewater is cleaned mainly by chemicals and filters, and that bacteria in a treatment plant are germs to be killed. Secondary treatment is biological: the plant grows and manages a community of microorganisms so that they eat the waste. Open Session 1 by asking where students think the "cleaning" happens, then show the aeration tank and the food chain inside it.

Several art misconceptions are also common. Students who have seen cartoon germs draw what they expect, with faces, smooth outlines, and bright symmetry, rather than what the reference image shows. They also tend to stipple with an even scatter of dots across the whole shape, which produces a flat gray. In scientific illustration, value comes from dot density: dots packed closely read as dark and widely spaced dots read as light, and translucent organisms such as ciliates are drawn with a light outline and sparse interior stippling so that internal structures remain visible. Finally, students often assume that a larger drawing means a larger organism, which is why every card carries a scale bar scaled with the drawing.

Choose reference micrographs that include a scale bar. Pond water and hay infusions contain many of the same kinds of protozoa and rotifers, so a class with microscopes can add live observation, but the project works entirely from printed images.

Stippled Microbe ID Cards for the Wendlow Reclamation Lab — Grade 8 Art & Music
Name: ____________________________ Date: ______________

Project Brief

Driving question: How can four ink drawings help a new operator recognize the tiny living things that clean wastewater?

The client. The town of Prestow and its Wendlow Water Reclamation Facility are fictional. Each day, wastewater from homes and schools flows into the plant. In large aeration tanks, air is bubbled through the water. Bacteria use the oxygen to eat the waste that is dissolved in the water. Tiny single-celled creatures called protozoa, and tiny animals called rotifers, eat the bacteria. This living mix is called activated sludge. Operators check a drop of it under a microscope. The kinds of creatures they see tell them how well the process is working. The lab supervisor at Wendlow wants a set of four ID cards for new operators to keep beside the microscope.

The four organisms:

  • Amoeba. A single cell with no fixed shape. It moves slowly by pushing out blob-like arms. When amoebas are the most common creature, the sludge is usually young, as when the process is starting up or recovering from a problem.
  • Free-swimming ciliate. An oval or slipper-shaped cell covered with tiny hairs called cilia, which it beats to swim quickly. When these are most common, the process is usually improving but not yet fully settled.
  • Stalked ciliate. A bell-shaped cell on a thin stalk. A ring of cilia around the rim of the bell sweeps food inside. The stalk can coil up quickly like a spring. When these are most common, the process is usually healthy and stable, and the water leaving the plant is clean.
  • Rotifer. A tiny animal made of many cells. Its head has two crowns of cilia that look like spinning wheels, and its body ends in a forked foot. When rotifers are common, the sludge is usually older and stable.

Operators never judge the process from one creature alone. They look at which kinds are most common and compare that with their other tests.

Card rules:

  • Make four cards, one for each organism, on 4-by-6-inch card stock held upright.
  • Use black ink only. The lab will photocopy the cards, so do not use color or pencil shading.
  • Show light and dark with stippling (dots), plus a few hatched lines if needed. Dots placed close together look dark. Dots spread apart look light.
  • Draw what you see in the reference image. Do not add faces or cartoon features.
  • Put the drawing in the top part of the card. Label at least three features, such as cilia, stalk, or foot, using leader lines that do not cross.
  • Add a scale bar that matches your drawing. For example, suppose your reference image has a scale bar 2 centimeters long labeled 50 micrometers, and your drawing is twice as large as the image. Then your scale bar should be 4 centimeters long and still say 50 micrometers.
  • Put a text block at the bottom. Write the organism's name in large letters. Then write no more than 40 words on what it looks like, how it moves, and what it means when it is the most common creature.
  • All four cards must share one layout, with the name, labels, and scale bar in the same places.

The match test. A tester from another team gets your four cards and four unlabeled reference images. The tester has two minutes to match each image to a card. You record which matches were right and which card slowed the tester down.

What you turn in: You will turn in the four finished cards, your match-test record, and one revised card with a short note explaining what you changed and why. You will also present your set to the lab supervisor.

Milestones

  1. Session 1, learn the process and observe (50 minutes): Learn what happens inside an aeration tank and why operators use microscopes. Study the four reference images. Make a pencil contour drawing of each organism, drawing only its edges and main parts. Label three features on each drawing. Output: four contour studies, each with three labeled features.

  2. Session 2, practice stippling and ink two cards (50 minutes): Make a stipple value strip of five boxes that runs from very light to very dark. Then lay out your card template so that the drawing, labels, scale bar, and text block each have a set place. Lightly draw the amoeba and the free-swimming ciliate on two cards, and ink them with stippling. Output: a five-step value strip and two inked drawings.

  3. Session 3, finish the drawings and write the text (50 minutes): Draw and ink the stalked ciliate and the rotifer. Add leader lines, labels, and a scale bar to all four cards. Write each text block in 40 words or fewer. Output: four complete cards.

  4. Session 4, test, revise, and present (50 minutes): Run the match test with a tester from another team, and record the results. Choose the card that caused a wrong match or slowed the tester most. Revise it on a fresh card, and write a note explaining the change. Present your set to the lab supervisor, and explain one choice you made to help a new operator. Output: a match-test record, a revised card with a note, and a short presentation.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Rubric
Criterion Emerging Developing Proficient Advanced
Observation from reference The drawings look like cartoon germs or leave out the main parts of the organism. The overall shapes are close, but key features such as the stalk, the cilia, or the forked foot are missing or wrong. Each drawing matches its reference image in shape, proportion, and main features. Each drawing matches its reference closely, including smaller features that help tell similar organisms apart.
Stippling and value Dots are scattered evenly, so the drawing looks flat, or pencil shading is used. Dot density changes in places, but the value strip and drawings show only two or three clear values. Dot density builds a clear range from light to dark, and translucent cells stay light enough to show inner parts. Value is controlled so precisely that form and transparency read clearly, and the cards photocopy cleanly.
Layout, labels, and scale bar Labels are missing or cross, or there is no scale bar. Labels and scale bars are present, but the layout changes from card to card, or a scale bar is not scaled to its drawing. All four cards share one layout, labels use leader lines that do not cross, and each scale bar is scaled correctly. The layout guides the eye from name to drawing to text, and the labels are placed so they never cover important features.
Text block The text is missing, over the word limit, or incorrect about what the organism means. The text describes the organism but leaves out what its abundance tells the operator. In 40 words or fewer, each text block describes the organism's look and movement and correctly states what it means when it is most common. Each text block is precise and consistent in structure across all four cards, using terms such as cilia and stalk correctly.
Test and revision No match test was run, or no card was revised. A card was revised, but the change is not connected to the test results. The revised card fixes a problem found in the match test, and the note explains the change. The revision fixes the problem, and the note uses the tester's results to explain why the new version should work better.

Differentiation

Support

Provide a card template with the drawing box, label lines, scale-bar position, and text box already printed, so students focus on observation and stippling. Offer a traced light outline of each organism for students who struggle with proportion, and have them add the stippling and labels themselves. Give a text-block frame: "Looks like ___. Moves by ___. When it is most common, ___."

Extension

Ask students to research one more activated-sludge organism, such as filamentous bacteria, which can form long threads that keep the sludge from settling, and to design a fifth card that matches the set. They then write two or three sentences explaining which features of their layout made the new card easy to add without redesigning the others.

ELL supports

Pre-teach "cell," "cilia," "stalk," "foot," "dot," and "scale bar" by pointing to each feature on a projected reference image. Provide a picture glossary of the four organisms with their names in English and, where possible, in students' home languages. Allow text blocks to use short phrases rather than full sentences, and let students give their presentation by pointing to features on their cards while naming them.

Extensions

If microscopes are available, students can collect a small sample of pond water under adult supervision, staying on the bank rather than wading in, look for protozoa and rotifers, and make a quick field sketch of any organism that resembles one of their cards. Students wash their hands after handling the sample. They compare the live organism with the card and note one feature that looked different when the organism was moving.