Is it important to have an experiment in biology in the second year of junior high school, and to ta

Gooseneck flask. Gooseneck flask experiment.

Pasteur devised a new experiment, a very famous one. He poured the broth into two flasks, the first of which was an ordinary flask with the mouth facing up; In the second flask, the neck of the flask is bent into a curved neck flask like a swan's neck. Then bring the broth to a boil and cool.

Instead of plugging the mouth with a stopper, both bottles are left open, allowing outside air to come into unimpeded contact with the surface of the broth. He set the two flasks aside. After three days, microorganisms appeared in the first flask, but not in the second flask.

He put the second bottle down: a month, two months, a year, two years, ......Until four years later, the broth in the flask is still clear and transparent, and has not deteriorated. Why is that?

Pasteur explained that because the first flask was an opening at the top, dust and microorganisms suspended in the air could fall into the neck of the bottle and reach the liquid, where the microorganisms received sufficient nutrients to grow and develop, causing the broth to deteriorate. Although the second bottleneck is also connected to the air, the bottleneck is elongated and curved, and the microorganisms in the air only fall on the curved bottleneck, and will not fall into the broth to grow and multiply and cause spoilage.

It is a gooseneck flask......

The broth was put into a gooseneck flask and did not spoil for a long time, proving that the spoilage was caused by external microorganisms.

The biology test in the second year of junior high school is very important. Because it helps students better understand the basic principles of biology and thus better apply them to real-life situations.

The biology experiment in the second year of junior high school can not only test students' understanding of biological experiments, but also test students' experimental skills and experimental report writing ability. The laboratory rental test is an important part of students' learning biology, which can help students better understand the basic principles of biology, better grasp experimental skills, and can improve students' experimental report writing ability.

In addition, lab exams can also help students better understand the basic principles of biology, better grasp experimental skills, and can improve students' lab report writing skills. Lab exams can help students better understand the basic principles of biology and better master experimental skills. Therefore, students should revise carefully and strive to get good grades.

Precautions for biological experiments in the second year of junior high school:

1. Do not bring flammable and easy-to-use items into the laboratory.

2. Be clear about the items inside the laboratory and be confident about the operation steps.

3. Clarify the experimental items and make test records for the end of the experiment.

4. Pay attention to the toxic substances in the experimental project, many experiments will be exposed to toxic substances, so you should pay special attention to this.

5. The waste generated by Huihui in the process of the experiment cannot be disposed of independently, but should be disposed of according to the teacher's requirements.

6. After the experiment is completed, the experimental equipment should be cleaned up to prevent biochemical pollution.

Summary. It is not mandatory, but students need to be proficient in 12 experiments to lay a solid foundation for subsequent high school biology studies.

It is not mandatory, but students need to be proficient in 12 experiments to lay a solid foundation for subsequent high school biology studies.

Can you add, I don't quite understand it.

According to the "Experimental Operation Specifications for Junior High School Students' Academic Proficiency Examination" promulgated by the Ministry of Education of the People's Republic of China, junior high school biology experiments are one of the compulsory contents of junior high school biology examinations. Its purpose is to enable students to master biological knowledge and experimental skills, improve scientific literacy, and develop scientific thinking through experiments. The 12 experiments involved are "Suntropism", "Variation is Loss", "Preparation of Tissue Reputation Section", "Role of Enzymes", "Respiratory Experiment", "Factors Affecting Photosynthetic Rate", "Cell Quantity Statistics", "Genetic Experiment", "Blood Coagulation Test", "Seed Germination", "Human Organ Location Labeling", and "Pathogenic Bacteria Experiment".

Therefore, the eighth grade students need to master the principles, methods and experimental operation skills of relevant experiments, which will be conducive to their performance in the biology examination, and also has great significance for the improvement of their future learning and scientific research ability.

The student experiments were: practicing the use of a microscope; Observation of plant cells: observation of human oral epithelial cells; Observe the basic tissues of the human body; Observe paramecium; Observe the structure of the seed; Observe the structure of the blade; Green leaves make organic matter in the presence of light; Measure the difference in chest circumference; Permanent smears of human blood are viewed with a microscope; Observe the flow of blood in the tail fin of small fish; knee jerk reflex; 12 experiments such as raising and observing earthworms.

Demonstration experiments include; The seeds underwent an energetic change during germination; The seeds release carbon dioxide during germination; Seeds absorb oxygen during germination; Photosynthesis produces oxygen; the digestive effect of bile on food; the relationship between respiratory movement and diaphragmatic movement; Fermentation phenomenon. A total of 6 demonstration experiments.