activities 22&23 Body Parts and Products (Sessions I and II) BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN Grade K Quarter 3 Activities 22 & 23 SC.F.1.1.1 The student knows the basic needs of all living things. 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. SC.H.1.1.3 The student knows that in doing science, it is often helpful to work with a team and to share findings with others. 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. Session I Activity 22: Remind students that humans have body parts that help them sense the environment where they live. Ask, How does a body part like our nose help us? (Our nose helps us smell food, which we need to eat to stay alive.) Ask, What body parts can you see on the larva that help it sense things? (They have eyes but no ears or nose. They have a mouth, but we do not know if they can taste things. They have legs and bristles that help them feel their surroundings.) 2. Session II Activity 23: Tell the students that scientists use tools to help them learn. Ask, As you worked like scientists to study your larva, what tools did you use to help you learn? (We used a ruler to measure length, and a magnifier to see the body parts more clearly.) Then ask, What are some things you noticed using these tools that changed as the larvae grew? (The larvae got longer. They produced waste material that collected in the containers. They molted their exoskeletons.) 3. Use the Activity Sheet(s) to assess student understanding of the major concepts in the activity. broward county hands-on science Quarter 3 223
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. 224 activities 22 & 23 Body Parts and Products
activities 22&23 Body Parts and Products OBJECTIVES Students learn some of the body parts of the larvae. By making detailed observations over time, they learn how larvae grow and develop. MATERIALS For each student 1 Activity Sheet 22 1 magnifier The students learn the names of the body parts of the larvae observe these body parts on the living specimens observe the growing larvae every 2 days for approximately 7 15 days SCHEDULE Session I Activity 22 About 40 minutes, with continuing observation sessions every 1 or 2 days for 4 days. Session II Activity 23 3 or 4 days after Session I, with continuing observation sessions for about a week, or until the larvae pupate. VOCABULARY exoskeleton frass mandibles molt segments sucker feet true legs For each team of two 1 container, 1-oz, with butterfly larva (from Activity 21) For the class 1 overhead projector* 1 ruler, metric* 1 transparency, Looking at Larvae *provided by the teacher PREPARATION Session I Activity 22 1 2 Arrange to have the use of an overhead projector. Make a copy of Activity Sheet 22 for each student. broward county hands-on science Quarter 3 225
BACKGROUND INFORMATION The butterfly larvae in the kit are a species commonly known as Painted Ladies. There is great variety among the larvae of different butterfly species. However, despite their variations, all larvae have some basic structures in common. All of them have mandibles, or biting mouth parts (although they cannot bite us), and segmented bodies, and most have six true legs. In addition, butterfly larvae usually have four to ten sucker feet, or false legs. If students have previously learned that all insects have six legs, they may find the many legs on the caterpillars confusing. Upon closer examination, however, it can be seen that the front three pairs of legs on the larvae differ from the rest. These true legs are pointed and are segmented like all insect legs, while the remaining legs are stumpy and are known as sucker feet or false legs (see Figures 22-1 and 22-2). Butterfly larvae have five pairs of sucker feet in addition to their three pairs of true legs. Some species of larvae, such as inchworms, have only two sets of sucker feet. The sucker feet help the larvae to move around effectively; these feet disappear in the adult stage. Larvae spend most of their time eating, using the clipping mouth parts or mandibles on the bottom of their heads. These are difficult to see when the larvae are small, but are more easily seen as the larvae grow. Insects have a stiff outer cuticle, or exoskeleton, that gives their body shape and provides structural support. (This is true even of the soft-looking butterfly larvae.) In order to be flexible enough to move and crawl, insects are divided into segments, or sections. The indentations and lines that mark off the segments become more visible on the butterfly larvae as they grow. 226 activities 22 & 23 Body Parts and Products As insects outgrow their stiff exoskeletons, they molt, or shed their old skins and expand their bodies. Shortly afterwards the outer layer of their new, expanded body hardens again into a larger exoskeleton. This usually happens many times as an insect grows to maturity. The molted exoskeletons of some insects keep the form of the insect and are easily recognizable. In other species, like the butterfly larvae in this kit, the molted exoskeletons shrivel up and look like tufts of fur. As the students observe the larvae, they are likely to notice small green balls forming in the butterfly larvae containers. These are the waste products of the insects, called frass. Students will also see silken webs being formed. All larvae produce silk from glands near their mouth. They use the silken webs to help them move around or to spin about themselves as a protection, depending upon their species.
Activity Sheet 22 Body Parts and Products Session I Activity 22 Write the names of the parts on this drawing of the larva. 1. Can you find all these parts on your live larva? head the butterfly larva segments bristles 1 Guiding the Activity Session I Activity 22 Tell students that today they will learn more about their larvae. Distribute a copy of Activity Sheet 22 to each student. Project the Looking at Larvae transparency on the overhead, and point out the heads of the larvae. Additional Information Ask, What do you think larvae might have on their heads? Tell students that larvae have very small eyes on their heads; apparently, the eyes are only strong enough to tell dark and light apart. Larvae do not have ears or noses like humans, but they do have mouths. The mouth is a very important part of their heads, since larvae spend a huge amount of their time eating. mandibles true legs sucker feet 2. How long is a butterfly larva today? cm The transparency shows both butterfly and moth larvae. Explain that moths, like butterflies, go through a larval stage. See Figures 22-1 and 22-2. Students are likely to say that the larvae have mouths and eyes on their heads. They may wonder if they have noses or ears like humans. It could be said that the larvae s purpose in life is to eat! broward county hands-on science Quarter 3 227
Guiding the Activity Additional Information head segments bristles head segments 2 3 mandibles true legs sucker feet Figure 22-1. The body parts of the butterfly larva. Point out the term mandibles on the overhead and say that mandibles are the mouth parts of the larvae with which they snip and clip their food. Ask, Does anyone know how many legs an insect is supposed to have? Ask, How many legs does this picture of the butterfly larva have? Write true legs and sucker feet on the board. Tell the students that butterfly larvae often seem to have more than six legs, but actually have two different kinds of legs. They have six true legs near the front of their bodies and four to ten false legs, known as sucker feet. The sucker feet help them to move around more easily. Point out the true legs and the sucker feet on the overhead. Write segments on the board. Explain that insects bodies are divided into segments or sections. Tell students that these segments allow the insect to bend; without segments it would not be flexible enough to move easily. 228 activities 22 & 23 Body Parts and Products mandibles true legs The mandibles on the live larvae will probably be too small for the students to see at this point. Insects have six legs. sucker feet Figure 22-2. The body parts of the moth larva. The picture shows eight legs. Explain that each of these is one of a pair, so the larva seems to have 16 legs. The true legs are pointed and have joints, like all true insect legs, while the sucker feet are short and stumpy and end in suction cups. On the Painted Lady butterfly larvae, the true legs are darker in color than the sucker feet.
4 Guiding the Activity Have students label the body parts on the larvae illustrations on their activity sheets. Distribute the butterfly larvae in their containers and two magnifiers to each team of two. Additional Information Keep the overhead projection in place to help them with this. Review how to use the magnifiers if necessary. 5 6 7 Allow time for students to observe the larvae and look for the body parts discussed. Use a ruler to measure the length of one of the butterfly larvae, and help students write the result on their activity sheets. Replace the Looking at Larvae transparency in the kit. Collect the magnifiers and containers with larvae. Replace the magnifiers in the kit, and return the containers with butterfly larvae to their place in the classroom. Every 1 or 2 days, distribute a magnifier and their containers with butterfly larvae to each team of two. Session II Activity 23 Distribute magnifiers and containers with butterfly larvae to each team of two and have students observe larvae as in step 4. When students have had time to observe their larvae, ask, How have the larvae changed? Ask, What else do you notice in the butterfly larvae s containers? Tell them that the small green balls are actually the waste products of the larvae. Write frass on the board, and tell them that frass is the word used for the waste product of an insect. Students should not open the butterfly larvae containers, as this is likely to introduce bacteria into them, which will grow readily on the larvae food. They will need to make their observations through the sides of the containers. It is best not to remove the butterfly larvae from their containers, to avoid contaminating the containers with bacteria. Allow time for students to observe the larvae. The larvae are growing rapidly. Students are likely to notice small balls of green material, many thin webs, and bits of black material that look like tufts of fur or pieces of the larvae s skin. The students may even see the larvae producing the frass. As time goes on, they will see more and more frass as each larva eats more of the food and passes it through its body. broward county hands-on science Quarter 3 229
Guiding the Activity Additional Information Tell the students that the larvae spin webs of silk from special organs near their mouths. Most moth larvae do this, as do many kinds of butterfly larvae. Explain that the larvae use the silken webs to help them move around, or to spin about themselves as protection. 8 You may also want to point out that silk fabric comes from silkworms, moth larvae bred and raised by people for their silk. Write exoskeleton on the board. Tell students that the larvae have a stiff outer layer to their bodies, which gives them their shape and provides structural support. This layer is called an exoskeleton. Ask, If our skeletons were on the outside of our bodies, what would happen when we grew? Write molt on the board and explain that insects molt, or shed, their exoskeletons when they have grown too big for them. Tell students that what look like tufts of fur or bits of the larvae s skin in the containers are actually the molted skins of the butterfly larvae. Every 2 days, have students examine the butterfly larvae with the magnifier. Continue this as the larvae become pupae and until they emerge as adults. 230 activities 22 & 23 Body Parts and Products Students should understand that this would make it difficult to grow. The old exoskeleton splits down the back and the insect climbs out of it.
R EINFORCEMENT Have students look at pictures of butterfly and moth larvae in the reference book included in the kit and in library books, and pick out these other larvae s true legs, sucker feet, and segments. 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 to the kit. Return the containers with butterfly larvae to their places in the classroom. Have students wash their hands. broward county hands-on science Quarter 3 231
Connections Science Challenge Ask students whether they know of any other animals besides insects that have exoskeletons. Students may mention lobsters or other crustaceans. Provide books and magazines for students to find pictures of other types of animals that have exoskeletons. exo means out or outside, so an exoskeleton is a skeleton that is outside the body. Ask students where we find our own skeletons. (inside our bodies) Then, write the word endoskeleton on the board. Challenge students to identify the word part that means inside. (endo) Science Extension Tell students that insects do not have ears and cannot hear sounds as we do. However, they do have a sense organ, the tympanum, that can detect vibrations. As a class, do the following activity to observe the vibrations caused by sound waves: Stretch a piece of plastic wrap over one end of a cardboard tube. Make a megaphone by rolling a piece of paper into a cone, taping the edge, and inserting the small end into the uncovered end of the tube. Tape a piece of posterboard to the wall. Shine a flashlight on the plastic wrap so that a reflection of the wrap appears on the posterboard. When a student speaks or sings loudly into the megaphone, the plastic wrap will vibrate, as shown by the jiggling reflection. Science and Math As a class, measure and record the lengths of five butterfly larvae. Calculate their average length each day until the larvae pupate. Plot these averages on a line graph with the horizontal axis labeled Time (days) and the vertical axis labeled Length (mm). Ask students why the line goes up from left to right. (The larvae get bigger as time passes.) Help students visualize this change by sketching increasingly bigger larvae on the graph to represent data points. Science and Language Arts On the board, write the term exoskeleton, and underline the combining form exo. Explain that 232 activities 22 & 23 Body Parts and Products Science and Social Studies Tell students that in the 1800s, a French scientist named Jean Henri Fabre did experiments with a kind of caterpillar that lives in groups and makes silken tents in trees. Fabre noticed that when the caterpillars left the tent to find food, they always walked in single file, with each caterpillar following a thin strand of silk laid down by the caterpillar in front of it. Ask students what game is similar to the caterpillars behavior. (follow the leader) Instead of using silk strands, what kinds of cues do students use in follow the leader? (spoken commands, hand and facial gestures) Science, Technology, and Society Provide students with life science and biology textbooks and library books and have them find photographs showing magnified views of insects heads, mouth parts, legs, eyes, antennae, tympanums, and other structures. Explain that the less-highly magnified views were photographed through an ordinary microscope that uses light beams, similar to the light beams that shine through windows on a sunny day. The more-highly magnified views were produced by a microscope that uses beams of electrons to make a picture. Electrons are tiny particles that you cannot see and that have an electrical charge, much like the static electricity you feel when you touch a doorknob after walking across a carpet.