b i o l o g y Extreme Arthropods Exploring Evolutionary Adaptations to Polar and Temperate Deserts by Luke Sandro, Juanita M. Constible, and Richard E. Lee, Jr. n this activity, Namib and Antarctic arthropods are used to illustrate several important biological principles. Among these are the key ideas that form follows function and that the environment drives evolution. In addition, students will discover that the climates of the Namib Desert and the Antarctic Peninsula are similar in several ways, and that these arthropods have evolved some analogous adaptations. This investigation is a good introduction to the phylum IArthropoda, the most successful group of animals on Earth, and spotlights the group’s ability to occupy some of the most challenging niches on the planet (National Science Content Standard C; NRC 1996). 24 s c i e n c e s c o p e Summer 2007 b i o l o g y Student Page 1 Part I. Extreme arthropod from scratch your job in this activity is to pick one extreme environment, and then build your own extreme arthropod. it must 1. be an arthropod, with a hard exoskeleton and jointed legs; 5 pts. 2. have at least one adaptation to help it survive each of your environmental conditions; and 10 pts. 3. show your effort, creativity, and understanding of the environment. 10 pts. Extreme arthropod environments 1. The Antarctic Peninsula • Extreme cold in the winter, -20°C (-4°F) and below • Extreme temperature variability—summer temperatures up to 7°C (45°F), with rock and moss surface temperatures of up to 21°C (70°F) • Very short period each year in which small arthropods are able to gather food, due to low temperatures and frozen conditions • High winds on small islands—it’s easy to be blown into the ocean • Extreme dryness—Antarctica’s freshwater is almost all frozen! ice also tends to steal moisture from small arthropods • Exposure to acidity and lack of oxygen, due to immersion in penguin guano (waste) during summer breeding season • Possible immersion in both salt and freshwater due to snowmelt and waves/tides in the summer 2. The dunes of the Namib Desert, Africa • Extreme heat on sand surface during the daytime • Very little food, mostly detritus (dead plants and animals) blown into piles on the dunes by the wind • High winds that blow small animals off dunes and cause water loss from animals • Extreme dryness—the Namib is the driest temperate desert. Fog that occurs an average of 60 days each year is its only reliable water supply • Sand—the sand of the dunes is easily heated by the Sun and blown by the wind, but also provides shelter for animals that can get below its surface On the first day of this lesson, individual students de- in response to the environment. While engaging students sign imaginary arthropods able to survive in either Ant- with the idea of designing the perfectly adapted arthro- arctica or the Namib Desert. On the second day, student pod, the lesson allows them to discover the extraordinary groups use evolutionary “toolboxes” to pick out appropri- designs of real arthropods, which survive in varied and ate adaptations for actual Namib Desert and Antarctic extreme conditions. The activities presented here guide arthropods using a menu of authentic names, adaptations, students to think of arthropods as having a “toolbox” of and photos. This activity involves students in evolution- evolutionary adaptations. This lesson would fit nicely as a ary thought and allows them to collaborate on assembling transition between the end of a biome unit and the begin- adaptations using aspects of technological design to over- ning of an evolution unit. While studying biomes, student come specific environmental problems (Content Stan- groups can choose to investigate either the Namib Desert dards A and E; NRC 1996). or Antarctic Peninsula using library and internet resources prior to this lesson. Because this activity requires little Extreme arthropod lessons prior evolution knowledge, it stimulates student interest In popular auto-racing video games, one can choose special in learning more about the evolutionary mechanisms that tires, shock absorbers, and engine modifications to suit a have caused such amazing adaptations. particular racing environment. The activities presented First, students are asked to create an arthropod from RS here get at the idea that an organism is an accumulation of scratch, inventing adaptations that will help it to survive tho modifications, evolved over thousands or millions of years either Antarctica or the Namib Desert. Second, students Luke Sandro ([email protected]) is a biology teacher at Springboro High School in Springboro, Ohio. Juanita M. Constible is a labora- tory coordinator and science writer and Richard E. Lee, Jr. is a distinguished professor of zoology at Miami University in Oxford, Ohio. Photo by AU Summer 2007 s c i e n c e s c o p e 25 b i o l o g y Student Page 2 Part 2. Build a real extreme arthropod Paste extreme arthropod description here. Paste adaptations in these squares (up to nine for each arthropod)—use “Extreme arthropod toolbox” and the description you pasted above to select adaptations. When your instructor gives you an extreme arthropod photo, attach it to this page. 26 s c i e n c e s c o p e Summer 2007 b i o l o g y construct an arthropod by choosing from a menu of adapta- Day 2: Building a real extreme arthropod tions that will enable the arthropod to survive. 1. In a large group, have students name adaptations they gave to the arthropods that they created on day 1. Note student- Materials generated adaptations that are the same as or similar to real Day 1 adaptations. Ask “If a population evolves a good adaptation • Art supplies, such as colored markers, colored pencils, for its environment, does it stop evolving?” Lead students to or paints the idea that with millions of years of evolution by natural • One per student: Student Page 1 selection, populations of arthropods have been able to accu- mulate a toolbox of enough successful adaptations like this Day 2 to survive conditions that would kill other organisms. • Glue, scissors • One per group: Student Pages 2 and 3 2. Break students into groups of two or three. Distribute one • One per group: Student Pages 4 and 5 copy per group of Student Pages 2 and 3 from the Activity Sheet. Explain that these include adaptations from the ac- tual toolboxes mentioned above, and will be available to Procedures them as they design another extreme arthropod, this time Day 1: Extreme arthropod from scratch trying to come as close to a real-life organism as possible (Student Page 1) by cutting and pasting adaptations. 1. Engage students with a video-game analogy, if possible; 3. Distribute one copy per group of Student Page 4. Assign many students will understand analogies to a car-racing each group one of the four arthropods. Explain that in game, in which players choose the best shock absorb- their groups, they will each be asked to construct the ers, engine modifications, and tires to fit the chosen arthropod, using their toolbox. racetrack. Also, in many role-playing video games of the Dungeons and Dragons-type, players allocate points to 4. Instruct students to complete the questions on Student different character abilities like strength, intelligence, Page 4, and then cut and paste the arthropod description and speed, as well as choosing skills to learn, all to suit and toolbox adaptations appropriate to each arthropod their character to the game environment. directly onto Student Page 2. 2. Explain to students that the Antarctic Peninsula and the Namib Desert present unique challenges to all life forms. 5. Pass out Student Page 5 and ask students to paste the cor- Students will focus on the terrestrial arthropods that in- rect photo onto Student Page 2. Alternative 1: Cover the habit these environments. photo captions and ask students to choose the correct photo 3. Distribute Student Page 1. Ask students to read based on the adaptations they’ve decided their organism through the list of extreme conditions in the Namib has. Alternative 2: Students may draw their version of their Desert and the Antarctic Peninsula. Discuss ways arthropod before seeing the photograph. organisms might survive these conditions. Students will likely be thinking of larger animal adaptations, 6. Assessment: The key below can be used to determine “cor- like those of camels, penguins, and so on. Encour- rectness” of chosen adaptations, but this is not essential as age them to think like a smaller creature that is not long as pasted adaptations are reasonable and follow all rules. endothermic (warm-blooded)—imagining how high Each group can be evaluated on how well they teach the rest winds, sand, and ice might affect them differently as of the class about their particular arthropod; questions pro- small ectotherms (cold-blooded). vided on Student Page 4 can be assessed. 4. In this phase of the activity, students will work individu- ally. Explain that they will design an arthropod that can Key—arthropod genus matched to adaptation card number. survive in one of these two environments, and that it must possess at least one adaptation for each of their Arthropod genus Adaptation card number chosen environment’s extreme conditions. Onymacris 1, 2 or 3, 4, 6, 7, 9, 12, 13, 14 5. Students should creatively draw and present their ar- Lepidochora 3, 5, 6, 7, 9, 12, 13, 14, 15 thropod to the class, explaining how each adaptation ad- Belgica 3, 6, 8, 11, 12 dresses each extreme.