Let high school students appreciate the beauty of life science

It is a pity that Morgan's Law of chain exchange is not explained in the current textbooks. First, the content of the third law is not complicated and easy for students to understand. Second, it shattered a nearly perfect theoretical system. Fortunately, almost all biology teachers will not ignore the third Law, the harmonious theoretical system has an irresistible charm! Even a small cell is a unified living system, with a modest karyotoplasmic ratio, exquisite coordination of various organelles (such as the formation of secreted proteins), ways of expanding the area of biochemical reactions (such as the cristae of mitochondria and the grana of chloroplasts)... The high degree of harmony they achieve in the movement of contradictions is amazing!

When learning "ecological engineering", the course standard requires students to grasp the knowledge goal is to understand the basic principles of ecological engineering. If students are allowed to swallow these principles all at once, it will inevitably cause "indigestion", and the examples given in the textbooks are not only far from the SAR students' geographical location, but also far from their cognition. Therefore, I took the opportunity of comprehensive practical activities carried out by the school to lead the students to Guangming Farm, which is a national agricultural high-tech park, and let the students personally investigate the original and time-honored mulberry based fish pond in the Pearl River Delta region, so as to deeply explore the efficient and harmonious artificial ecosystem of mulberry planting, mulberry leaf rearing, cocoon reeling, silkworm sand, silkworm pupa, fish breeding with silk reeling wastewater and fish manure mulberry. Feel the brilliance and creativity of our working people. In the mulberry field to collect mulberry weeding, in the fish pond spread feed, before leaving, also brought back some of the farm ant silkworm to learn silkworm rearing. The enthusiasm and activity of the students was beyond my expectation!

3. Explain the relevance of biological thinking

Thinking is the most concentrated manifestation of wisdom.

Throughout the history of life science development, new views and theories, new ideas and methods, new discoveries and creations, almost every major breakthrough is accompanied by new thinking. Peas and fruit flies were well suited for genetic experiments, Engelman explored the use of a brilliant combination of water and aerobic bacteria in photosynthesis, echoes of the classic ideas of Avery, Hershey and Chase, evolution, the theory of the cell, the discovery of enzymes, and the nature of hormones. The mobile Mosaic model of cell membrane and the bold creation of the double helix structure model of DNA molecules, these epoch-making great achievements, all show the great power of perfect thinking! On the contrary, Waltheimer's ingenuity in exploring the source of pancreatin and Helmont's experiment in exploring the source of willow weight gain failed, and it was not because of wrong thinking! It can be seen that the appropriateness of biological thinking plays a decisive role.

Teaching "The structure of DNA" is after teaching the classic experiment that proves "DNA is the main genetic material of living things", I ask the students to think about such a question: from the analysis of DNA structure, why did nature choose DNA as the genetic material? What is the suitability of DNA as genetic material?

I guided the students to analyze the characteristics of the molecular structure of DNA: Although the chemical composition of DNA is only four deoxynucleotides, due to the huge size of the molecule, there are various ways of arrangement and combination, storing a large amount of genetic information, reflecting the diversity of genetic material; A particular DNA has its specific deoxynucleotide sequence, indicating the specificity of genetic material; In the DNA molecule, the "stair handrail" frame of alternating phosphate and deoxyribose is very stable, and the hydrogen bond accumulation of the "stair step" between A and T, C and G is also very strong, which is not easy to open, showing the stability of genetic material. The double helix structure can replicate itself precisely, so that genetic continuity can be maintained between parents and offspring. DNA controls metabolic processes and character development through gene expression; Mutations can occur under certain conditions, and after mutations can continue to replicate, producing heritable variations. In contrast, RNA and protein, the former has small molecular weight, little genetic information, most of them are single strand, the structure is unstable; The latter is not self-replicating, is not molecularly stable, and cannot be passed on to future generations. Therefore, neither is suitable as genetic material. Such biological thinking that increases one percent and decreases one percent is too short makes people fall in love.

Harvard University students once said that biology is the most difficult to learn, because although there are certain laws of life activities, their laws are not as obvious and fixed as the laws of mathematics, physics and chemistry, which requires students to have a very flexible thinking when learning this course, and they must be able to see the overall situation. With the view of system, the view of universal connection, the view of movement development, the view of unity of opposites and so on to view and analyze the various forms of life.