Suppose you are teaching a general science course in a middle school and the first unit of the year is ecosystems. Suppose further that your college professor introduced you to a method called concept mapping, and you decide to use it to identify the concepts that students might need to understand a unit on ecosystems. Figure 7.20 shows the subconcepts and their relationship to the general concept of ecosystem.
Concept Map for a Teaching Unit on Ecosystems
What is the best way to teach students concepts as depicted on this concept map? Recent research (see Chapter 2) has suggested that students construct their own ideas about their world---including concepts---and any attempt to teach "new" concepts to students must take this into consideration. Researchers who have supported this view have been labeled "constructivists" because of their belief that students construct their own knowledge structures---concepts, beliefs, theories. More often than not, the concept-base that students bring to your class is naive and full of misconceptions. To understand science from the constructivist view means that students will have to change their concept--hence the term conceptual-change.
The Learning Cycle Model
A number of constructivist models have emerged over the last thirty years that suggest that teachers should sequence instruction into a series of teaching/learning phases. The sequences have been described as learning cycles. For example, the earliest example of a learning cycle was suggested by Chester Lawson in which he described scientific invention as "Belief - Expectation - Test." But the first direct application of a learning cycle to science teaching was proposed by Robert Karplus, Director of the Science Curriculum Improvement Study (SCIS) in 1970. He proposed a three phase cycle consisting of preliminary exploration, invention, and discovery. In essence, Karplus believed that students need to first explore the concept to be learned using concrete materials. The initial introduction of the concept was called invention. In this phase the teacher assumed an active role in helping the students use their exploration experiences to invent the concept. To Karplus, the discovery phase provided the student with the opportunity to verify, apply or further extend knowledge of the "invented" concept.
Recent work by Charles R. Barman (1990), and the team of Lawson, Abraham and Renner (1989) have proposed a learning cycle based on the work of Karplus, but have changed the terminology. We shall use their terminology in this book when we refer to the learning cycle model.
The learning cycle has three phases that form the foundation for sequencing science lessons. Normally a sequence would take at least three sessions---see the sample lessons that follow. Exploration, concept introduction and concept application phases are described below.
Exploration Phase. During this phase the students explore a new concept or phenomenon with "minimal guidance." Students might make observations of and classify objects. They might be involved in "messing about" with batteries, bulbs and wires to find out how the light bulb works. Students might also perform experiments to gather data to test an hypothesis. In short, the exploration phase allows the students to examine "new ideas" and test them against their own ideas. Students are actively engaged in interacting with ideas, as well as their peers during the exploration phase. During this phase the teacher should facilitate the work of the students by establishing a reasons for exploring new ideas. The use of discrepant events, followed by interesting science activities is a way to get into the exploration phase. The teacher plays a facilitative role during this phase.
Concept Introduction Phase (Also called the Term Introduction Phase). During this phase the teacher assumes a more direct, active role and uses the students' exploratory activities as a means of introducing the scientists view of the concept or theory that was investigated in the exploratory phase. During this phase students express their ideas about the concepts and ideas, and the teacher presents in very succinct ways, the meaning of the concepts and ideas from a scientific point of view. The teacher assumes the direct/interactive mode during this phase planning lessons along the guidelines presented in the direct/interactive section. The concept introduction phase is an intermediary step, and the teacher should move quickly to the next phase.
Concept Application Phase. The concept application phase is a student centered phase in which small teams of students engage in activities designed to apply and extend their knowledge of science concepts. The teacher should design activities that challenge the students to debate and defend their ideas. Activities in the concept application phase should be problem-oriented. The teacher resumes the facilitative role in the concept application phase.
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What can be learned from skulls? Overview: Students observe a variety of vertebrate skulls and attempt to identify the animal and what it eats. Concepts such as herbivore, omnivore, carnivore, nocturnal, diurnal and niche are introduced. Exploration Phase. Skulls are placed at ten numbered stations. Students work in small teams and "visit" each numbered station, or the skulls are passed to each team. The teacher explains that the teams should be challenged to make inferences, like paleontologists do, about the lifestyle and habitat of vertebrates by observing their skulls. The teacher provides each group with one copy of the following questions: • What type of food does this animal eat, and what is the evidence for your inference? • Is this animal active during the day, night, or both? What is the evidence? • Is the animal a predator or a prey? Why? Concept Introduction. After the student teams have gathered data on each skull, conduct a session in which you ask different teams to describe each skull. Conduct a discussion focusing on the differences among the skulls. Students will focus on teeth. Write their words on the board they use to describe them. Use the teeth to suggest function. Introduce the terms herbivore, carnivore and omnivore. Ask the students to explain what these terms mean. You can clarify student concepts and misconceptions by explaining carefully, for example: "This animal has sharp teeth for tearing and no flat teeth for grinding. This implies that it eats only animals. An animal that eats other animals is called a carnivore." Concept Application. Provide opportunities for students to investigate a variety of bones in addition to skulls. What inferences can they make from the structure about their function? |
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What Caused the Water to Rise? Overview. Students invert a cylinder over a candle burning in a pan of water. They notice that the flame soon goes out and water rises into the cylinder. They engage in discussions to explain their observations. They then test their explanations which leads to new explanations and understanding of combustion, air pressure and scientific inquiry. Materials. aluminum pie tins, birthday candles, matches, modeling clay, cylinders (open at one end), jars (of various shapes and sizes), syringes, rubber tubing. Exploration. Begin the lesson by giving each team a student hand out describing the inquiry procedure, as well as the materials listed above. Students should then be given the opportunity to explore the phenomenon by the following these procedures: 1. Pour some water into the pan. Stand a candle in the pan using the clay for support. After 30 minutes of experimenting stop the students for a discussion of their results. Focus the students on the questions Why did the flame go out? and Why did the water rise? The most likely explanation (misconception) to the second question is that since the oxygen was "burned up" the water rose to replace the oxygen which was lost. Lead the students to realize that is hypothesis predicts that varying the number of burning candles will not effect the level of water rise. Four candles, for instance, would burn up the available oxygen faster and go out sooner than one candle, but they would not burn up more oxygen hence the water should rise to the same level. Have students do the experiment. The results will show that the water level is affected by the number of candles (the more candles, the higher the water level). Their ideas has been contradicted. Explain that an "alternative explanation" is needed and ask the students to propose one. As students propose alternative ideas do not tell them if they are correct. For example, the "correct" explanation (the heated air escaped out the bottom) should not be revealed even if students suggest it. Ask students to think of ways to test their hypotheses. If they propose the heated air hypothesis, this should lead to the prediction that bubbles should be seen escaping from the bottom of the cylinder. As alternative hypotheses are suggested, have the students test the hypotheses and look for evidence to support predictions. If students do not suggest the "correct" explanation, suggest it yourself. You might say, "What do you think about this idea? The heat from the flame heats the air and forces it out the the bottom of the cylinder." Encourage students to test your explanation rather than accepting as is. Concept Introduction. After students have collected data testing various hypotheses, you should introduce the "correct" explanation again and introduce the term air pressure and a molecular model of gases which assumes air to be composed of moving particles that have weight and can bounce into objects (such as water) and push them out of the way. Concept Application. Provide a number of problem solving situations in which students must apply air pressure and the molecular model of matter. • Application Problem #1: Give students a rubber tubing, a syringe, a beaker and a pan of water. Tell them to invert the beaker of water in the pan of water. Challenge them to find a way to fill the beaker with water in that position. (The students will try forcing water in, before discovering they must extract air from the beaker. • Application Problem #2: Challenge the students to find a way to insert a peeled, hard boiled egg into a bottle with an opening that is smaller in diameter than the egg. They can not touch the egg after it is placed on the mouth of the jar. (After a small amount of water in the bottle has been heated, it is only necessary to place the smaller end of the egg over the opening of the bottle to form a seal. The egg will be forced into the bottle by the greater air pressure outside as the air cools inside. • Application Problem #3: Pour a small amount of very hot water into a large (2 L) plastic soda bottle. Then screw the cap on tightly to form a seal. Place the bottle on a desk so that students can view it. The plastic bottle will begin to be crushed. Challenge the students to explain the result using the molecular model of gases and air pressure. |