The difficulty of this lesson is to make and observe the temporary packaging of onion skin.
(A) students in the actual operation problems:
1, microscope stage tilted
2. "Jing" calligraphy and painting is too large, and the torn inner epidermis is too large to be made easily.
3, will not cover the cover glass, there will be a lot of bubbles.
4. The dropper is inverted after absorbing the reagent, which pollutes the rubber head.
(B) the classroom process records
On Thursday afternoon, the lab was in poor contact with the projector, so it was impossible to play the temporary video and the projector could not be used normally.
1, demonstration experiment: the teacher demonstrates the operation process of the experiment. (once)
(1) Quantitatively emphasize the size of "well" (0.5cm*0.5cm).
(2) Demonstrate the use of the cover glass: after touching the water drops, cover it slowly (the students can't see clearly, and the effect is not good), and emphasize the use of the dropper.
(3) Without adding iodine solution, observe that the inner epidermis is replaced by the outer epidermis (there are large purple vacuoles, and no dyeing is needed).
Student experiment: (The students are very interested and excited about this experiment. They emphasized whispering and were not allowed to leave their seats without permission. )
(1) patrol to guide students' experiments. Basically, every group knows the experimental process and can basically achieve standardized operation. But there are two problems in tearing the outer skin: a: torn outer belt pulp.
B: The torn skin can't be flattened in clean water, resulting in the cells being multilayer under the microscope.
(2) A group experiment was very successful and wanted to share it with all the students, so interested students were asked to go to the corresponding group to watch it, and the scene soon became chaotic. Therefore, make adjustments and observe in turn in each group. (Please ask the assistant supervisor to leave in private)
(3) Emphasis on recording observation results: however, the inspection has not been implemented and needs to be improved.
(3) classroom gains:
1, according to the learning situation and teaching conditions, the teacher personally demonstrated the experiment, which made the students feel more substituted and the learning effect was better.
2. The students' practical ability is very strong, and the experimental results are higher than expected.
(Class 6.5 is not as proficient in the use of microscope as Class 6.2, so students stop to review the use of microscope when they find this problem in the experiment, and the time for making and assembling films in the later stage is also tight. Most groups only completed the assembly once together, but the effect was not bad. )
(4) Thinking opinions
Teacher Wu Chuanrong comments:
As can be seen from the record of reflection, Kiki is willing to use her brains, meticulous and concerned about students. There are several suggestions for your reference:
First, reflect on the problems in teaching.
You should record your thoughts on how to attend the next class. It can be a specific way. For example: how to prepare dyes? How to avoid similar situations in the future after the video is not finished? How to solve all kinds of difficulties when students make films? How to share movies among groups in an orderly way? ..... Of course, you can also write down your doubts about how to solve the problem.
Second, pay attention to the accuracy of expression.
For example, it is mentioned in the article that the problem that students easily encounter in operation is "tilt of microscope stage", which I don't quite understand.
Teacher Cao Yang's comments:
Personally, I think iodine solution also has a "sense of ceremony" effect on dyeing and packaging. Actually, there is a place to buy iodine solution. You can report to the school leaders and buy in advance.
In three microscope classes, I choose to read robert hooke's written materials, know the names of various parts of the microscope, access and store the microscope, and practice dimming for one class; The second lesson, continue to practice dimming, learn to adjust the focal length to observe the ready-made film, and preview the onion skin film for video; The third lesson, review the video, make slices of onion skin, observe the slices by yourself, and the teacher takes pictures to leave traces.
Thinking and discussion:
Thank you for your comments and suggestions. Now my thoughts are as follows, please criticize and correct me.
(1) Because I took this course temporarily and had no experience in the early stage, I didn't confirm whether the students brought iodine solution or iodophor, and I didn't prepare dyes myself, so I need to improve and pay attention to it in future classes;
(2) Before class, we didn't carefully watch the video playback of the courseware, which also caused some students who did the demonstration experiment in this class to be unclear. In future courses, we should check all the materials and equipment needed for class in advance to ensure the orderly development of the class;
(3) According to the students' cognitive level, it is best to describe all the operations "quantitatively" intuitively. For example, the size of the word "well" requires students to mark "0.5cm*0.5cm".
(4) With regard to outstanding works and works that need improvement, comments can be made in the class projection, feedback can be given to students in time, and class record albums can be created and uploaded to QQ group albums in time.
(5) Regarding the tilt of the microscope stage, it is clearly mentioned in the microscope operation of biology textbooks for junior and senior high schools that the stage needs to be placed horizontally for temporary loading observation to avoid the lens being polluted by dye solution.
(6) After thinking and consulting information, the onion skins in primary and junior high schools are temporarily packed with inner skins. Perhaps the purpose of textbook design is to let students master the basic skills of dyeing.
(The picture below shows "Tilt of microscope stage")