Phase d.indd

Lessons: Presenting Scientifi c Findings
In the fourth and fi nal section of the unit students must present their own “scientifi c story” of what happened on the island: Why did the fi nches die and how were the survivors able to live? Students make posters that show key fi ndings of their investigations, and they summarize their conclusions in an oral presentation. They may use journal entries to generate their story and cite data collected from the computer software as evidence that supports their story. During the presentations, classmates ask questions and evaluate each others’ stories. In this process they develop skills for constructing scientifi c arguments and communicating scientifi c results. An important part of this process is to help students see that there are a number of ways to interpret the data and construct a coherent argument that can be backed up with the data.
To put closure on the unit, once the student presentations conclude, students watch the rest of the New Explorers video to learn about and compare their own answers with the answers developed by the Galapagos scientists. Important ideas to discuss during the presentations and in the concluding discussions include these key components of natural selection: • Variation — do students recognize that there was variation in different fi nch traits? Ask students
what the source of this variation is, whether the advantageous and less advantageous beak existed in the
fi nch population before the drought.
Changing distribution of traits — discuss the distribution of beak sizes in the population before
and after the drought. It is important to understand how this change in the average has occurred. Have
individual birds changed in their beak length? (No.) Then why is the average length different?
Generalization — ask students to speculate about what might occur in the fi nch population under
another pressure, asking them to talk about advantages of traits and distribution of traits, or ask them
to speculate about other organisms.
In preparation for an oral presentation, students will create a poster presentation which will include a written story describing their fi ndings, backed up with evidence that they have gathered from their computer investigations.
CPS SG 3 A1, 2, 3, 4,
CPS SG 5 A1, 2, 3, 4,
CPS SG 10 A2; B1,
CPS SG 3 A1, 2, 3, 5
• Student journals and printouts from computer CPS SG 5 A1, 6, 9
CPS SG 10 A2; B1,
• Tell the students that their fi nal report for the unit will be • Using evidence from the computer investigation and pre- viously written journal entries, they will need to choose the most important pieces of evidence which support • Students should write their own “scientifi c story” of what happened on the island: Why did the fi nches die and why did the survivors live? They may use journal entries and data from the computer to generate the story.
• Graphs included in the poster must be explicitly cited in the written story. For example “We found that rainfall DID matter in the death and survival of the fi nches (Graph 1).” • Encourage students to use their artistic abilities to orga- nize the poster. Important components to include are: Title, Names, Story, Evidence. Everything they want to include must fi t on the poster itself.
Teacher Notes
In 1977 something happened to the finches in the island of Daphne Major. Something caused 40% of the finches to die, yet 60% of the finches managed to survive. Why did the finches die? How did some In 1977, the finches died because of the lack of food that usually grows during the wet and dry seasons. In 1977 the amount of rainfall was very little compared to others, there was only 20 cm of the wet season and none in the dry seasons. The foods the finches ate are seeds from the Tribulus, Cactus, Portulaca and Chamae plants. In our research we found out that the most common food that grows alot out of all of them is the Tribulus plant. But the seeds of this plant are hard and all of the others are soft and medium. This makes it very hard for the finches to open unless they have very strong beaks. Your can see this happening in the finch profiles #5 - dry season of 77. This Tribulus plant grows in the dry season as well as wet seasons, all of the others don’t grow as much as the Tribulas plant in the dry seasons. So if there’s not much food in the dry seasons and the trubulus seeds is hard to open . How will the finches survive? The finches could only eat the seed if they had strong beaks to open the shell of the seed. So in conclusion our resources showed that most of the adults were the ones who really survived and the babies didn’t survive as much as the adults. The babies don’t have strong beaks and therefore wouldn’t be able to open the seeds. The adults have strong beaks and could open them easier than the babies. So who ever could open the seeds lived and the ones who couldn’t get it open starved to death.
Example Finch story from the poster of two seventh grade girls at Inter-American Overview:
Each team of students uses their poster to explain their fi ndings from their investi gation to the rest of the class. Other students in the class ask questions and can make suggestions about their interpretation.
CPS SG 4 A1, 2, 6;
CPS SG 4 A1, 2, 5;
Explanation Comment sheets (enough for each student to sentation skills and critical listening skills.
Teacher Notes
• The use of peer comment
• Present the guidelines about the presentation. Say: “Your presentation should be about 5 minutes. Don’t just read your story. Present the important ideas. Remember that you are a team of scientists. You should each have a role in your presentation; it will be up to your team to decide how to divide up the contributions.” • Give each group a chance to give their presentation. Some teachers like to ask for volunteers; others pick the order and call upon each group in turn.
• At the end of each presentation, encourage other stu- dents in the class to ask questions and make suggestions. Encourage students to focus on the important criteria for evaluating explanations: “Does the explanation fi t the data they presented? Are there any important steps that are left out? Is each claim backed up by evidence? Have they demonstrated that they have ruled out alternative explanations?” • Have students fi ll out the Explanation Comment sheet Teacher Notes
• If students have practiced
A: Neat poster. Clear explanation. Evidence is cited and shown and is clearly written. Some possibilities have been leave the division of labor up to them. If you feel your B: Neat poster. Clear explanation but some evidence may not be cited or shown. Not sure of any other possibilities.
lines, some alternatives are to divide up the presentation C: Fair poster. Fair explanation. Vaguely written explanation. chance to talk, or the group can pick a spokesperson to give the main story, with D: Poster present. Vague explanation. Not enough evidence. the other members point-ing to and commenting on each part of the data when relevant.
A sample grading scheme for evaluating the student presentation and I enjoy students’ thoughtfulness, their novel ideas, their thoughtful and never-ending questions. I definitely do not look for the right answer. I look for:1. A thoughtful approach – do they have a strategy, a plan. Did they sort their data in a logical way? 2. Do they have a hypothesis and were they willing to 3. Are their explanations built piece by piece based on 4. Do they have several pieces of data to support each claim or did they find one thing and leave it at that? 5. I look for passion – do they really believe what they have concluded? Can they cite more evidence that supports their claim? — Linda Patton, Von Steuben Metropolitan Science Center Things you liked about the presentation and
Questions and suggestions
Students learn about the results of the Galapagos scientists’ investigations and can compare the type of explanations their class developed with the current best scientifi c explanation. A general discussion pulls together the core ideas of the unit.
CPS SG 12 B1, 2, 3
CPS SG 11 A4; C1
CPS SG 12 A3; B1,
What Darwin Never Saw videotape Objective
• Have a full-class discussion to pull together the main ideas that arose in the presentations. Are all their stories very similar? Is there one most popular theory? Are there a number of different • Tell the students that you will be showing them a videotape in which Peter and Rosemary Grant, the Galapagos scientists who studied Daphne Major, talk about their understanding of what happened during the drought of 1977.
• Discuss: “How is the work that we did like what the scientists did?” Points you may want to highlight include: “You have Teacher Notes
gotten a taste of what science is like. Science is about coming up with hypotheses, recording your ideas, testing your ideas, and revising them. What you did is like what scientists do, only on a smaller scale (less data, etc.)” • Discuss: “Do you think they came to the same conclusion that you did? Why do you think their answers might be different?” Points you may want to bring out: (1) The scientists looked at lots of data; your students have only had a small sample of the data the scientists collected. (2) The scientists worked and worked on this question for months and months, looking at data, testing ideas, and arguing about them. (3) Scientists have lots of practice and training in looking at graphs, collecting data, and they are specialists in fi nches, which allows them to pick out patterns in data.
Procedure cont.
Teacher Notes
• Explain the goal in doing this. “This assignment is not to see ‘who got it right and who did not.’ It took the scientists a long time, and a process of looking at lots of data, and arguing about it for months, in order to come up with their conclusions. You have only had a small sample of the data the scientists had to work with. As the scientists looked at more and more data, their ideas developed and changed. At many points in their process, they had several different hypotheses and were not sure which was a better fi t with the data. So your work is like the work the scientist did in their initial stages. I am show- ing you the videotape so you can see the type of explanations that scientists develop when they work on problems like you • Show the videotape segment in which the Grants discuss the drought (approximately 36 min. 50 sec. on the tape).
• Have students discuss what aspects of their explanations were • An additional topic for a closing discussion is to connect what happened to the fi nches to what occurs in natural selection. An extreme drought is a selection pressure, something that causes problems for a population of organisms, in this case, the fi nches. There is variation in the population; some fi nches are heavier, some have bigger wing spans, bigger beaks, and so on. One of these features on which the fi nches vary seems to be related to better survival. According to the Grants, the fi nches with larger beaks could crack open the tribulus seeds that remained during the drought. Because of this, the surviv-ing birds tended to have longer beaks. Since many of the shorter-beaked birds died off during the drought, the average beak length has increased. When the remaining birds give birth to new birds, they will be likely to have longer beaks like their parents. Thus, we are seeing a gradual shift in the length of the beaks in the population because of the selective pressure. This is evolution by natural selection – a stress causes a change in the population on some feature.



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