activity 25 The Big Change BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN Grade K Quarter 3 Activity 25 SC.F.1.1.3 The student describes how organisms change as they grow and mature. SC.H.1.1.1 The student knows that in order to learn, it is important to observe the same things often and compare them. ACTIVITY ASSESSMENT OPPORTUNITIES The following suggestions are intended to help identify major concepts covered in the activity that may need extra reinforcement. The goal is to provide opportunities to assess student progress without creating the need for a separate, formal assessment session (or activity) for each of the 40 hands-on activities at your grade. 1. Tell students that, like them, scientists work in groups to compare observations. Ask students to discuss within their groups some ways that the pupa stage helps a butterfly. Then, ask each group to share one of its ideas. (The pupa stays still to avoid attracting predators. If touched, the chrysalis may shake to scare away predators. The pupa blends in with its space. The pupa uses stored energy to change form instead of using it to move around.) 2. Use the Activity Sheet(s) to assess student understanding of the major concepts in the activity. In addition to the above assessment suggestions, the questions in bold and tasks that students perform throughout the activity provide opportunities to identify areas that may require additional review before proceeding further with the activity. broward county hands-on science Quarter 3 243
244 activity 25 The Big Change
activity 25 The Big Change OBJECTIVES Students observe the butterfly larvae enter the pupal stage. The students discuss the pupal stage in butterfly development observe and draw the butterflies chrysalises SCHEDULE About 40 minutes, when the butterfly larvae start to pupate (7 10 days after they arrive in the classroom). VOCABULARY chrysalis pupa pupae MATERIALS For each student 1 Activity Sheet 25 1 magnifier For each team of two 1 container, 1-oz, with butterfly larva (from Activity 23) For the class 1 butterfly tower 16 paper clips 1 ruler, metric* *provided by the teacher PREPARATION 1 2 3 Schedule this activity when most of the butterfly larvae have begun to hang from the lids of their containers, and at least a few have formed into pupae. Make a copy of Activity Sheet 25 for each student. Set up the butterfly tower in your classroom. To do this, withdraw the assembled tower from its package and locate the top of the tower with three support strings attached. Each string terminates in a loop. Insert one of the three loops in the plastic ring, then slip the loop over the rings so it is firmly attached to the ring. Repeat this process with the other string loops to make a single, secure, and nontangling connecting loop. Lift this loop to extend the butterfly tower to its full length. Hang the butterfly tower where it can be easily observed by the students. Note: Do not place the tower in direct sunlight or close to excessive heat. If you are unable to hang the butterfly tower from the ceiling, you may suspend it from a meter stick placed on top of a cabinet or bookshelf. To do this, lay the stick on top of the cabinet or other flat surface at least 1.5 m (5 ft) from the floor. Next, place the stick so at least 40 cm (16 in.) of the stick extends from the cabinet or shelf. Place a few heavy objects, such as books, on top of the end of the stick that rests on the cabinet or shelf. This will counterbalance the weight of the butterfly tower. Before hanging the tower, rotate it so the side access door is facing you, to allow easy access to the tower. broward county hands-on science Quarter 3 245
BACKGROUND INFORMATION As insects grow and develop, they go through distinct life stages, a process known as metamorphosis. Meta means change, and morpho means shape. Metamorphosis refers to the dramatic changes in shape or form that these insects experience. Both butterflies and moths begin life as eggs, hatch into larvae, become pupae, and emerge as adults. The pupal stage is sometimes called the resting stage because, in this stage, insects usually do not move around. In reality, it is not a time of rest, but a time of great transformation. While the insect is in the pupal stage, many complex physical and chemical changes take place and its entire body structure is rearranged. The larvae do not, for example, just grow wings. Rather, their entire body dissolves inside the pupal case and is rearranged, molecule by molecule, into the new adult form. Exactly how this occurs is still not entirely understood by scientists. Butterflies form pupae that are smoothskinned and have a very specific shape and color, depending upon the species. Another term for a butterfly pupa is a chrysalis. The chrysalises usually hang from threads attached to twigs or leaves (see Figure 25-1) and often have spots of iridescent gold. The Painted Lady pupae are brown with small black and gold spots. 246 activity 25 The Big Change The first sign butterfly larvae give that they are about to enter the pupal stage is to climb to the top of their container and hang from the lid in a J (see Figure 25-2). About 24 hours after this occurs, they molt one last time, and the pupa emerges. The molted exoskeleton looks like a small (0.5 cm or 0.2 in.) furry tuft, and often remains attached to the pupal case. The Painted Lady butterflies will spend 7 10 days in their chrysalises before emerging as adults. In the first few days after they form, the chrysalises will swing back and forth vigorously if disturbed. This behavior is probably an attempt to scare away predators. Figure 25-1. The Painted Lady pupa, or chrysalis. Figure 25-2. A Painted Lady larva hanging before it forms its pupa.
Activity Sheet 25 The Big Change 1. Draw a butterfly larva getting ready to change into a pupa. Drawings will vary. 2. Draw the chrysalis of the butterfly. Drawings will vary. 1 Guiding the Activity Distribute a copy of Activity Sheet 25 and a magnifier to each student. Handling them very gently, distribute the containers with butterfly larvae to each team of two. 3. Date the larva formed a chrysalis: Dates will vary. 4. Length of a chrysalis: Lengths will vary. cm Additional Information Have students use the magnifiers to observe larvae hanging from the lids and draw them on their activity sheets. Since moving the containers may disturb the larvae at this stage, you may want to arrange to have the students take turns observing the larvae without moving the containers from the regular place in the classroom. If you need to move them, do so very slowly and carefully to avoid knocking the larvae off. Place the containers on the students desks and tell them they should not touch them during this time. If some of the larvae have already formed into pupae, have students observe these also, and draw them on their activity sheets. broward county hands-on science Quarter 3 247
2 3 Guiding the Activity Focus on those containers that have pupae. Tell students that this completely new form they are seeing is called a pupa (plural, pupae). Write pupa and pupae on the board. Explain that a pupa is a phase that the larva changes into as it becomes an adult. It has a different appearance than either the larva or the adult. Write chrysalis on the board. Explain that the pupa of a butterfly is also called a chrysalis. Have them note the date that the butterfly larvae formed chrysalises, and enter this information on the activity sheet. Also, measure an average chrysalis and help students enter this data on their activity sheets. Ask, How are the chrysalises of the butterflies different from the larvae? Ask, Do the chrysalises move around? Ask, Do you think the chrysalises will grow bigger over time? After the pupae have formed, carefully remove the lids from the containers and place them in the butterfly tower. Wash out the 1-oz containers and return them to the kit along with the magnifiers. 248 activity 25 The Big Change Additional Information Many other kinds of insects also form pupae as they develop into adults. The pupa of a moth is called a cocoon. The chrysalises are not hairy or bristly. They have no legs or head that can be seen. They are lighter brown in color and have two rows of short spikes with shiny gold dots. No, although students may notice that for the first day or so after they form, Painted Lady chrysalises will swing vigorously if they are disturbed. This behavior is probably helpful in frightening away predators. Students answers will probably vary. Since the larvae grew so dramatically, they may think this kind of growth will continue. The lids with chrysalises attached can be laid on the floor of the tower, chrysalis side up, or hung, chrysalis side down, from the sides of the tower by hooking paper clips through the plastic of the lids and through the net of the tower (see Figure 25-3). If any of the chrysalises become detached from the lids, lay them carefully on the floor of the tower.
Guiding the Activity Additional Information R EINFORCEMENT Have student look at pictures of other kinds of chrysalises and cocoons in the Butterflies and Moths book and in other resource books. Make a bulletin board display explaining the difference between chrysalises and cocoons. Figure 25-3. Transferring a butterfly chrysalis to the butterfly tower. Assessment Opportunity This Reinforcement also may be used as an ongoing assessment of students understanding of science concepts and skills. SCIENCE JOURNALS Have students place their completed activity sheets in their science journals. C LEANUP Collect the magnifiers and return them to the kit. SCIENCE AT HOME Have students explore outdoor areas near their homes for examples of chrysalises and cocoons. broward county hands-on science Quarter 3 249
Connections Science Challenge Show students pictures of grasshopper or cricket nymphs and ask them what they see. (Students may think they are looking at adult insects.) Tell students that these insects develop differently from the way butterflies do. They do not go through larval or pupal stages. Instead, the young insects look like smaller adults, with some differences. Encourage students to collect pictures or make drawings of these insects in their nymph and adult stages. Science Extension Ask students if they have ever turned over a log or stone to expose an ant nest, or if they have ever seen a wasp nest hanging from a tree or building. Explain that wasps and ants live in groups and that each insect has a job that helps the group survive. Suggest that students look through books and magazines to find pictures of social insects, such as ants, wasps, termites, or honeybees. Prompt students to pay particular attention to the differences among the insects within a colony, for example, queens are larger and winged. Help students to understand the different jobs of the insects. (For example, worker honeybees clean the hive and feed the larvae; soldiers protect the hive; drones are males that mate with the queen; the queen lays eggs.) Tell students that like the insects, they have jobs to do. Ask them to share what these jobs might be. (keep my room clean, pick up my toys, come to school to learn) Science and Math Tell students that a scientist once figured out that a particular type of caterpillar increased its weight more than 4,000 times during its 56-day larval stage. As a class, calculate how much a 7-pound newborn baby would weigh after 56 days if it gained weight at that rate. (28,000 pounds) Use the equation 1 lb = 0.45 kg to convert this weight to kilograms. (12,600 kg) That s more than an adult elephant weighs! 250 activity 25 The Big Change Science and Careers Tell students that entomology, the study of insects, is just one branch of the larger field of biology. Invite a biologist or, alternatively, a science teacher, to visit the class and discuss his or her career. Ask the visitor to talk about the various specialties within biology. Before the visit, have students brainstorm lists of questions they would like to ask the visitor. Afterward, remind students to write a thankyou note to their visitor. Science and Language Arts On the board, write 1 pupa, 2 pupae, and explain that pupa is another word of Latin origin that ends in a and forms the plural by adding e. Write pupa and pupae in the appropriate columns of the chart the class began in the Science and Language Arts in Activity 21. Science, Technology, and Society Show students a scrap of silk fabric, and ask them if they know where silk comes from. (The larva of the silk moth spins the cocoon when it becomes a pupa.) Thousands of years ago, the Chinese discovered that the cocoon of the silk moth could be used to make this beautiful fabric. Tell students that to get silk, the cocoons are first boiled to soften them. Then, workers find and separate the end of the silky thread that forms each cocoon. They twist together five to seven threads and unwind them from the cocoons. To help students visualize the process, demonstrate this step using several small balls of yarn. Tell students that each cocoon, which is only about an inch in size, is made from one thread that is one-half to threequarters of a mile long! Help them understand how far that is by using an example, such as the distance between two familiar points. About 2,000 to 3,000 cocoons are needed to make 1 pound of silk.