Metamorphosis

Metamorphosis
5.10C
Look at a picture of yourself when you were younger. Do you look the same now as you did then? Many things have probably changed. You have gotten taller, your body weighs more, and you are able to do things that you could not when you were younger. In twenty years, you will look and feel different than you do now. Change is part of life as a human. These changes are generally gradual ones. Insects also go through changes in their lifetimes. Their bodies change from the time they are eggs until they are adults. But their bodies change in ways that are different from the change in human bodies. Our bodies keep the same basic structure as we grow. Insects change in more dramatic ways as they develop from eggs to adults. A butterfly changes in size and shape as What are these changes called? it develops from a young insect into an adult. What is metamorphosis? The word metamorphosis comes from Greek words that mean, “changing shape.” Metamorphosis is the process in which a dramatic change in body structure occurs during development. Insects go through metamorphosis as they develop from eggs to adults. As an insect passes through each stage of metamorphosis, it may look very different or it might also look similar to the stage before. Sometimes new body structures appear in one of the stages. For example, caterpillars change from small worm-­‐like insects into butterflies with wings, which is a dramatic change! Not all insects develop from eggs into adults in the same way. There are two types of metamorphosis that insects go through: complete and incomplete. These types of metamorphosis differ in important ways. You will learn more about them as you read through the rest of the lesson. © 2013 Rice University – All Rights Reserved
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Metamorphosis
5.10C
What are the different stages of complete metamorphosis? Many types of insects, such as butterflies and beetles, go through complete metamorphosis. Complete metamorphosis has four stages: organism: a living
thing
• Egg: A female adult insect lays eggs in a safe, protected place. Some time after being laid, the eggs hatch. The organism that comes out of the egg is called a larva. molt: a process in
• Larva: A larva looks nothing like its parent. Have you ever seen which an outer
a caterpillar? It is the larval stage of a butterfly. Though the covering is shed to
caterpillar looks nothing like an adult butterfly, it is the same make room for new
organism! A larva usually has a worm-­‐like body shape. It may growth
grow or molt during this stage, but its basic body shape will stay the same. A larva tries to eat as much as possible to get energy: the ability to
enough energy to enter the next stage of metamorphosis. cause change or do
work
They are usually built to be eating machines! • Pupa: In the pupa stage, an insect wraps itself up in a protective covering for a period of time. While it is in the pupa pupa stage, an insect does not eat and often doesn’t move. New structures grow and the insect’s body shape changes dramatically. adult • Adult: When the pupa stage is complete, an adult insect comes out of the protective covering. The adult form of the insect has all of the body parts and structures that it needs larv
to carry on the rest of its life. This usually involves flying or a dispersing to find mates. egg The pictures below show an insect in two different stages of complete metamorphosis. Which picture shows the larval form of the insect? Which picture shows the adult form? Explain your answers. © 2013 Rice University – All Rights Reserved
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Metamorphosis
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What are the different stages of incomplete metamorphosis? Some types of insects, such as grasshoppers and walking sticks, go through incomplete metamorphosis. This type of metamorphosis has three stages instead of four: • Egg: Similar to complete metamorphosis, an adult female insect lays eggs. When the eggs hatch, a nymph form of the insect comes out. • Nymph: The nymph stage of incomplete metamorphosis is what makes this process different from complete metamorphosis. Unlike a larva, a nymph may look very similar to the adult form of the insect. It is usually smaller and is missing some structures that the adult has (such as full wings). A nymph will grow and molt several times during this stage. As it molts, it develops adult structures and gets larger. For instance, a grasshopper has wing buds, but not true wings yet. A nymph does not enter a pupal stage. • Adult: After growing and molting, a nymph has developed all the structures it needs and is now an adult. This might involve growing full wings such as in an adult grasshopper. Looking to the Future: Butterfly Gardening Butterflies move from flower to flower in a garden. They are feeding on the liquid nectar from the flowers. It’s easy to admire the beautiful shapes and colors of the butterflies. Unfortunately, some butterfly populations are decreasing. Butterflies cannot find food when buildings and roads population: all the
replace gardens and other natural living things that
spaces. The butterflies starve and belong to the same
their populations decrease or even group that live in the
die off. Some people are trying to same area
help the butterflies by making special gardens. Butterfly gardens have flowers and other plants that support all four stages of a butterfly’s life cycle. Some An adult butterfly is drinking nectar plants are a perfect place for an adult butterfly to lay eggs. from this flower. Other plants provide food for caterpillars or space for a pupa. Flowers provide food for the adult butterflies. Some gardeners mark the adult butterflies with tiny tags. These tags help scientists figure out how many butterflies there are in the area. The gardens and the scientists may help to increase butterfly populations. © 2013 Rice University – All Rights Reserved
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Metamorphosis
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Explore the different stages of complete and incomplete metamorphosis. 1. Find some examples of insects in different stages of complete and incomplete metamorphosis. Try to find live examples outside. If this is not possible, find at least four different examples by searching the Internet. Two examples should be of complete metamorphosis, and the other two examples should be of incomplete metamorphosis. 2. If possible, look at each insect under a magnifying glass. Be careful not to touch or disturb the insects. Use your eyes only! A grasshopper is an easy insect to find a. Draw what you see on a piece of paper. and study. This type of insect goes through incomplete metamorphosis. b. Label any parts of the insect that you can identify such as legs, head, antennae, and eyes. 3. Identify whether the insect is going through complete or incomplete metamorphosis. Then, try to identify each stage of metamorphosis. Is it a larva? A nymph? An adult? Use an insect field guide to identify the insects and their stages of metamorphosis. Record what you find out on your piece of paper. What Do You Know? Use what you know about complete and incomplete metamorphosis to fill out the chart below. First, decide if you agree or disagree with the statement on the left side of the chart. Then, explain your decision on the right side of the chart. Agree/Disagree? Explanation Incomplete and complete metamorphosis are exactly the same. ____ Agree ____ Disagree The nymph and the pupa both look very similar to the adult form of an insect. ____ Agree ____ Disagree All insects go through some kind of metamorphosis as they develop. ____Agree ____ Disagree © 2013 Rice University – All Rights Reserved
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Metamorphosis
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Teaching Metamorphosis Work with students to create a tool for teaching younger students about metamorphosis. First, research an insect that goes through complete metamorphosis by finding photos or drawings of what this insect looks like in all four stages of its metamorphosis. Then, research an insect that goes through incomplete metamorphosis. Again, find photos or drawings of what this insect looks like in all three stages of its metamorphosis. Use your research and images to make a teaching tool. It could be: • A short fictional story illustrating the steps involved in complete and incomplete metamorphosis, featuring two types of insects. • A poster illustrating the two different types of metamorphosis, with annotated drawings or photos representing each stage. • Physical models of each stage of metamorphosis, using clay, foam pieces, or other materials. Here are some questions to discuss with your student: • How is complete metamorphosis different than incomplete metamorphosis? • What time of year are you likely to see insects going through metamorphosis? Why do you think this is so? • How long does it take the insects you researched to go through metamorphosis? © 2013 Rice University – All Rights Reserved
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