1. 1 preparing lessons

Teachers should pay full attention to this concept, and take lectures and evaluation as a "lesson". First of all, we should make clear the requirements of Discipline Guidance Opinion, Curriculum Standards and Examination Instructions in those years, make clear the rules and trends of the questions in recent years, and determine the purpose of evaluation; Secondly, it is necessary to determine which topics to talk about briefly, which topics to focus on and what methods to talk about; In what way and to what extent; Finally, it is necessary to clarify students' mistakes and reasons, and how to prescribe the right medicine.

1.2 tag

Carefully review the examination paper, pay attention to the students' answers, especially the subjective questions, what types of questions are answered well, what types of questions are answered poorly, and what are the reasons for the mistakes, so as to be aware of them. Point out the causes of typical mistakes on paper, write positive comments on creative solutions and take notes.

1.3 data statistics

Count the students' scores and losses one by one, and calculate the score rate of each question. Generally speaking, the comprehensive questions with the highest error rate, involving the intersection of multiple knowledge points and wide ideas for solving problems should be taken as the focus of evaluation, while the questions with low error rate and enlightening should also be taken seriously, so that other students can learn from them in time and nip in the bud.

Classification analysis of 1.4

Classification: classify according to the knowledge points, problem-solving methods and error types involved in the test paper. According to the knowledge points, the questions related to the same or similar knowledge points in the test paper are grouped together; According to the problem-solving method, the questions in the test paper that use the same problem-solving method or involve the same biological knowledge are grouped together; According to the types of mistakes, such as "unclear concept", "knowledge loophole", "poor knowledge application ability" and "carelessness", it can not only improve classroom efficiency, but also help students clear their minds and leave a deep impression on the causes of mistakes. Analysis: According to the problems reflected by the test paper data and error types, teachers should first find the reasons from themselves, whether the knowledge points are thorough and comprehensive, whether the process and methods are infiltrated, and whether the teaching methods are appropriate; Then the reason for finding students is that students' subjective efforts are not enough, or students' learning methods, thinking methods, problem-solving skills, answering norms or psychological factors.

1.5 reflective solution

Students may have some problems when solving problems, and sometimes they may have some whimsy, which the teacher may not notice in advance. Teachers should grasp these points in time and ask themselves some questions: ① Is there a solution that is closer to the actual thinking of students? ② Is there a better solution? ③ Is there a simpler solution? ④ Whether it is an acceptable method for students; ⑤ Do you think less about special circumstances?

1.6 formulation of evaluation method

Generally speaking, there are several ways to comment on test papers: ① Classified comment: it is suitable for difficult questions. To sum up, we can strengthen a certain knowledge point, solve ideas and methods, easily concentrate students' attention and help them understand and master; (2) Key comments: it is suitable for questions with moderate difficulty, certain comprehensiveness and flexibility, mainly highlighting the mastery of knowledge and skills; (3) Student comments: It is suitable for questions with less overall difficulty. The teacher focuses on a few mistakes, and the students mainly correct, discuss and correct them according to the answers, and the teacher gives timely guidance.

2 classroom comments

A successful lecture and evaluation class can help students improve their knowledge structure, promote their understanding of knowledge, master skills and improve their thinking ability. To achieve this goal, teachers should pay attention to the timeliness, pertinence and compensation of evaluation, and pay attention to evaluation strategies.

2.1* * Concerns

A clever doctor can give a good prescription to a patient, and the key is to diagnose the cause of the patient. For most students' sexual problems, teachers should seriously diagnose students' answers, or ask some students to describe their own problem-solving ideas, find out the reasons for the mistakes, and take targeted measures to correct and make up for them in time. For example, unclear concepts are a common cause of errors. In teaching practice, many students study hard, but their grades are not ideal. The direct reason is often that their understanding of concepts is not thorough enough and their application and transformation are not flexible enough. When commenting, teachers should grasp typical topics, guide students to break through existing knowledge, eliminate interference and draw conclusions.

Case 1: The physiological process that can occur in the human environment is ()

Synthesis of antibody a oxidative decomposition of pyruvate b

C neurotransmitter diffuses from presynaptic membrane to postsynaptic membrane, and D starch is digested into glucose.

Analysis: The test point of this question is the concept of internal environment. Internal environment is the liquid environment in which cells in the body live, and it is extracellular fluid, including tissue fluid, plasma and lymph. The formation of antibodies and the decomposition of pyruvate are completed in cells, and intracellular fluid does not belong to the internal environment (extracellular fluid); Starch digestion occurs in the digestive tract and belongs to the external environment. Neurotransmitters diffuse from presynaptic membrane to postsynaptic membrane through synaptic cleft, and the interstitial fluid in synaptic cleft belongs to internal environment.

Through this topic, teachers can summarize the differences between intracellular fluid, extracellular fluid (internal environment) and external environment for students, thus consolidating students' understanding of the concept of internal environment. This enables students to analyze a problem and understand a concept; Correcting a wrong question can solve a large class of problems.

2.2 Variants of Key and Difficult Issues

The key knowledge and skills that students are required to master in Examination Instructions can be changed by changing questions, such as "multiple solutions to one question": examining and analyzing the same question from different perspectives and different directions, breaking the limitations of students' understanding, cultivating the diversity of thinking, mobilizing students' enthusiasm for learning, allowing students at different levels to have their own benefits and allowing students to choose appropriate and operable methods; "One question is changeable": dig deep into the typical questions with high discrimination and appropriate difficulty, change the questioning methods and types of questions, expand the knowledge content and application scope of questions, make them become typical examples in the classroom, and strengthen students' mastery of some difficult questions from multiple angles, aspects and levels.

Case 2: A series of problems arising from the phototropism principle of plants.

Principle of plant phototropism: One-sided illumination makes auxin at the tip of plant seedlings transfer from phototropism to phototropism and transport downwards, resulting in uneven distribution of auxin below the tip of seedlings, with more distribution on the phototropism side and less distribution on the phototropism side. Results The seedlings grew fast on the backlight side, but slowly on the phototropic side, and grew towards the light source.

Basic question: Comparing the auxin content of two agar blocks in figure 1, the best experimental design scheme and result is ().

Analysis: According to the phototropism principle, from the point of view of minimizing the experimental error caused by individual differences, the answer is D.

Elongation: Any condition that can make the auxin unevenly distributed on both sides of the seedling growth site can generally make the seedling grow curved.

Variant 1: Judge the growth direction of the seedlings in Figure 2 (mica sheets are inserted in the seedlings).

Answer: a bends to the left and grows; B bends to the left and grows; Vertical growth; D bends to the right and grows; E does not grow; F bends to the left and grows.

Analysis: This topic mainly inspires students from the phototropism principle, and learns to analyze the specific situation of uneven distribution of auxin caused by external or internal factors and the direction of plant bending growth.

Variant 2: When plants are stimulated by the environment, the distribution and growth of auxin shown in Figure 3 are correct (black dots represent the distribution of auxin) ().

Analysis: There are two test sites in this question: (1) The uneven distribution of auxin is the internal cause of plant bending growth; (2) The sensitivity of stem and root to auxin is different, and the sensitivity of root is higher. Therefore, in 1234⑤, according to the direction of plant bending, it can be judged that the auxin distribution on the fast-growing side is more. But ⑧ On the contrary, the slow growth side is because high concentration inhibits growth. So the answer is a.

2.3 Comprehensive problem development

When commenting, teachers should make use of the topic, give full play to the knowledge radiation function of commenting, take the topic as a bridge, consciously connect the knowledge points that students may forget, which are related to the topic but not related to the topic, strengthen the vertical and horizontal connection and integration of knowledge, and build a knowledge network.

Case 3: If the number of chromosomes in animal sperm is n, then the cycle of chromosomes in animal somatic cells containing 4N is ().

Mitotic metaphase

C, late stage of the second meiosis, D, late stage of mitosis.

In this paper, the quantitative changes of chromosomes and DNA during mitosis and meiosis are summarized in table 1.

Special reminder: secondary mother cells are in the late stage of meiosis. Because of the separation of chromatids, chromosomes have a temporary doubling process. At this time, the chromosome number is 2n, but the DNA content remains unchanged.

Analysis: According to the table 1 and the special reminder, the answer is D.

Consolidation design: The chromosome number of an animal somatic cell in the late mitosis stage is 24, and the DNA molecular number and chromosome number of a cell in the late meiosis stage of the animal are () respectively.

A 12、 12 B 24、48 C 24、24 D 12、24

Analysis: Before chromosome replication (G 1 period) or after chromatid separation (late mitosis and late meiosis), each chromosome contains one DNA molecule, and after replication, each chromosome contains two DNA molecules. According to the above table and tips, if the number of chromosomes is 4n=24 and the number of DNA molecules is 4c=24, then the number of chromosomes in the cell at the second meiosis stage is 2n= 12. The number of DNA molecules is 2c= 12, and the answer is a.

3 Supplement and improve after class

According to the individual problems recorded in the marking process and statistical classification analysis, teachers should give individual counseling after class. Because classroom evaluation is mainly aimed at the problems of most students, teachers often have no time to pay attention to the special problems of individual students in solving problems. By taking measures such as spot-checking papers after marking and redoing wrong questions, students are urged to classify, take notes and reflect on wrong questions, weak questions and questions with correct answers but wrong thinking methods, and design supporting variant exercises to consolidate them. Moreover, in future exams, the transformation method reproduces the problem that students are generally wrong. Through targeted consolidation exercises, teachers let students understand concepts in comparison, experience methods in change and solve weaknesses.

4. Talk about the role of classroom evaluation

In addition, some problems can only be exposed in the specific operation process. Listening to lectures and evaluating classes is to find out the deficiencies in teaching through solving problems, correcting and reflecting. The purpose is to find and fill in the blank, pursue the optimization of problem-solving methods and maximize the teaching effect, and promote the effectiveness of teaching.