Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
B I O L O G Y ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Arthropod Genetics by Sharon Zumwalde T hink about invertebrates for a minute. Do arthropods come to mind? The phylum Arthropoda is the most diverse of the invertebrates, spanning from horseshoe crabs to lobsters to insects. These organisms have in common their exoskeletons, segmented bodies, and jointed limbs. I take advantage of the phylum’s diversity to spark students’ creativity and problem-solving skills, during a review and application activity in which students build their own arthropods and predict the traits of their imaginary offspring. I use this activity after teaching back-to-back units on arthropods and genetics in my seventh grade life science class. In the multi-step review, students 1. Construct imaginary arthropods. 2. Select dominant and recessive traits along with genotypes and phenotypes for their imaginary arthropods. 3. Construct Punnett squares showing possible gene combinations from the cross of two imaginary arthropods. 4. Determine traits of the offspring and construct sample specimens. 20 science scope February 2000 To do this activity, students must first have a solid grounding in arthropod classification, basic genetics vocabulary, and problem-solving with Punnett squares. Students must understand dominant and recessive genes, genotypes and phenotypes, and purebred and hybrid (homozygous and heterozygous) traits. This activity spotlights the ability to apply and work with given genetic information. It combines creativity and hands-on construction with the concepts of classification and genetics. Setting up Figure 1 shows a list of suggested materials for building arthropods, but you can use whatever is available as long as specific materials are designated for dominant and recessive forms of each trait. For example, I assign toilet paper rolls as a dominant body trait, and paper cups as a recessive body trait. Likewise, wax paper represents a dominant wing form, while foil is a recessive form. I keep materials for each body Sharon Zumwalde is a seventh grade life science teacher at Milford Junior High in Milford, Ohio. ○ ○ ○ ○ ○ ○ ○ ○ B ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ part in separate boxes, and have students pick what materials they will use from the boxes. Spiders and beetles and crabs, oh my! To start off, I provide students with the worksheet on page 23. Students can work individually or in pairs to create their animals. I use slips of paper to randomly assign students to specific divisions of Arthropoda, to ensure variety in the resulting menagerie. I also tell students to keep their assignments secret throughout the building stage, so that later other students can practice classifying their classmates’ animals. Construction usually takes at least one science class period. Once students’ creative ideas have come to fruition, it’s time to do some analysis. I reveal which materials represent dominant traits and which are recessive, and then students record the genotypes and phenotypes of their animals’ traits. In the case of dominant traits, I allow students to choose whether they want them to be purebred or hybrid. Once the genotype and phenotype is ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ I O L O ○ identified and recorded for each trait, students can “mate” their creations with the other creatures. To prepare for the event, students first identify and record the genotypes and phenotypes of the potential mate, and then construct Punnett squares showing the offsprings’ possible gene combinations for each trait (see page 23). Students also need to identify the phenotype of each genotype within the Punnett square and determine if each trait is purebred or hybrid. From this information students can compile a list of possible genotypes and phenotypes for offspring of the pairing and apply their creativity once again to construct sample offspring. For assessment, I assign 10 points to each phase of the project: Arthropod Construction, Mapping the Family Genes, Punnett Squares, and the Offspring, for a total of 40 possible points. I check that students construct their arthropods correctly (see Figure 2), and I also assess students’ ability to correctly identify the genotype, phenotype, hybrid, and purebred nature of their creations. PHOTO COURTESY OF THE AUTHOR ○ Some of the many arthropods created by students. February 2000 science scope 21 G Y B I O L O G Y ○ ○ ○ ○ ○ ○ ○ ○ ○ FIGURE 1 Body Legs Eyes Antennae Wings FIGURE 2 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Dominant toilet paper rolls (AA, Aa) plastic cups (BB, Bb) Styrofoam egg cartons (CC, Cc) popsicle sticks (DD, Dd) colored straws (EE, ee) colored pipe cleaners (FF, Ff) white buttons (GG, Gg) colored Styrofoam peanuts (HH, Hh) blue pom-poms (II, Ii) white twist ties (JJ, Jj) Q-tips (KK, Kk) paper clips (LL, Ll) coffee filters (MM, Mm) waxed paper (NN, Nn) Construction checklist Ten points awarded if all body parts are present and correct, 8 points if one is missing or incorrectly placed, 5 points if more than one is missing or incorrect. science scope ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Materials list: genotypes and phenotypes Chilopoda (centipedes) ____ 1 pair of legs per body segment ____ poisonous jaws (student’s choice of materials) ____ 1 pair of antennae Diplopoda (millipedes) ____ 2 pairs of legs per body segment ____ 1 pair of antennae Crustacea (shrimp, lobsters, crabs) ____ 5 pairs of legs ____ attached to fused head/thorax ____ 2 pairs of antennae Arachnida (spiders, scorpions) ____ 2 body parts (head and thorax) ____ 4 pairs of legs Insecta (ants, beetles, dragonflies) ____ 3 body parts (head, thorax, abdomen) ____ 3 pairs of legs ____ attached to thorax ____ one pair of antennae ____ wings (optional) 22 ○ February 2000 Recessive Styrofoam balls (aa) paper cups (bb) cardboard egg cartons (cc) coffee stirrers (dd) white or striped straws (ee) white pipe cleaners (ff) colored buttons (gg) white Styrofoam peanuts (hh) colored pom-poms (ii) colored twist ties (jj) toothpicks (kk) short pipe cleaners (ll) cellophane paper (mm) foil (nn) Extensions This activity easily lends itself to cross-curricular teaching. In language arts class, students can 1. Name their animals and write a descriptive paragraph on their habitat, food, predators, and structural adaptations. 2. Identify and describe possible characteristics for a third generation of arthropods, based on the second-generation offspring. 3. Propose changes in their animals’ environment and describe how their animals might adapt to those changes. For instance, • a drought may occur, • a foreign species that shares the same food source as the animal may be introduced into the habitat, • a predator may be introduced into the habitat, or • the habitat may be destroyed by pollution or human development. In any case, students will learn that thinking creatively and critically go hand in hand. You and your students will enjoy making the connections between bugs and genes. Acknowledgements This activity is adapted from a workshop presented by Beryl Stoddard at the 1997 NSTA Convention in New Orleans: “The Genetics and Adaptations of Artful Arthropoda.” ○ ○ ○ ○ ○ ○ ○ ○ B ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ I O L O ○ Building arthropods Arthropod construction Build an arthropod by selecting one material for each characteristic: body segments, legs, eyes, and antennae. Do not mix white and colored materials. Give your creature the characteristics of your assigned arthropod, but be creative too! Materials Body: egg cartons, toilet paper rolls, Styrofoam balls, paper and plastic cups Legs: straws, popsicle sticks, coffee stirrers, pipe cleaners, plastic straws Eyes: buttons, Styrofoam peanuts, chenille pom-poms Antennae: twist ties, Q-tips, toothpicks, paper clips, short pipe cleaners Wings: waxed paper, coffee filters, foil, cellophane paper Mapping the family genes Your arthropod Phenotype Genotype Another arthropod Phenotype Genotype Body Legs Eyes Antennae Wings Punnett squares Make a Punnett square for each of the characteristics above to show the cross between two parent arthropods. Be sure to indicate both the genotype and phenotype of all traits. Also identify the traits as either purebred or hybrid. Body Legs Eyes Antennae Wings The offspring Using the information from your Punnett squares, select traits to include in a sample offspring. Record the phenotypes and genotypes of your offspring’s traits in the chart below. Build your sample offspring using the materials provided. Phenotype Genotype Body Legs Eyes Antennae Wings February 2000 science scope 23 G Y