High School Biology: Summary of experimental knowledge, application of principles and attention are all explained one by one!
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The 19 experiments in the textbook stipulated in the high school syllabus can be divided into:
(1) Microscopic observation experiments: one, three, four, six, ten, twelve;
(2) Inquiry-based experiments: seven, nine, thirteen, fifteen, seventeen, nineteen;
(3) Confirmatory experiments: two, eight;
(4) Simulation experiments: five, eleven, sixteen;
(5) Investigation experiments: fourteen, eighteen.
Experiment 1: Observing the Distribution of DNA and RNA in Cells (Compulsory P26)
1. Principle, steps, conclusion
2. Precautions for experimentation
(1) Material selection: oral epithelial cells or onion inner epidermal cells (colorless) [purple onion epidermal cells or mesophyll cells can not be used to prevent color interference]
(2) Slow water flow rinsing purpose: to prevent the cells on the slide from being washed away.
(3) The role of several reagents in experiments
(1) 0.9% NaCl solution (normal saline): Maintain the normal morphology of oral epithelial cells.
(2) 8% hydrochloric acid: a. change the permeability of the cell membrane and accelerate the entry of stains into the cell; b. separate the DNA and protein in the chromosome, which is conducive to staining.
(3) Methyl green pyrrol red dyeing solution: mixed and need to be used now.
Experiment 2 Detection of reduced sugars, fats and proteins in biological tissues (compulsory 1 P18)
1. Experimental principle and steps
(1) Reducing sugar identification experimental material requirements: it must be white or light color, and the reducing sugar content is high.
[Do not use green leaves, watermelon, blood and other materials to prevent color interference; potatoes (containing starch), sugar cane, sugar beet (containing sugar) can not be used.] 】
(2) The only need for heating: reducing sugar identification, and must be heated in a water bath, can not be directly heated with alcohol lamp. If not heated, no brick red sediment appears.
(3) Non-reducing sugar (such as sucrose) + Ferrin reagent (water bath heating), the phenomenon is not colorless but light blue [the color of Cu(OH)2].
(4) The only thing that needs a microscope - fat identification, experiment with the action of 50% alcohol - wash away the floating color.
(5) Fei Lin reagent: need to be mixed and added, and now used; biurea reagent: need to be added separately (first add A solution, then add B solution).
Experiment 3 Observe a variety of cells with a microscope (compulsory one P7)
1. Use of microscope
2. Precautions for the use of microscopes
First low and then high: first low magnification and then high magnification.
Magnification: Refers to the magnification of the "length".
The relationship between the lens and the magnification: the shorter the eyepiece, the longer the objective, and the closer the objective is to the slide, the greater the magnification.
3. Comparison of high magnification and low magnification
Experiment 4 Observation of mitochondria and chloroplasts (compulsory one P47)
1. Experimental principle
(1) Chloroplasts are green, do not need to be stained, and are directly observed after filming.
(2) The mitochondria need to be dyed blue-green with Kenna green (a living cell dye of the obligatory mitochondria) and filmed for observation.
2. Experimental materials
(1) Observe chloroplasts with moss or spinach leaves;
(2) Observe the mitochondria with human oral epithelial cells.
3. Pay attention to the problem
(1) The temporary loading of the film during the experiment should always be kept in a water state.
(2) Select fresh and black algae leaves: because the leaves are thin and small, the chloroplast is clear, and the leaflets can be taken to directly produce films;
Experiment 5 Exploring the permeability of membrane through simulation experiments (compulsory one P60)
1． Composition of the permeation system (pictured) and conditions
(1) Semi-permeable membrane: it can be a biofilm with an optional permeability membrane, or it can be a physical filter membrane.
(2) The difference in the concentration of the solution on both sides of the membrane: refers to the quantitative concentration of the substance, not the mass concentration.
2. Precautions
(1) The direction of movement of water molecules: it can move in both directions, but the water molecules as a whole are from low concentration → high concentration.
(2) After the osmotic equilibrium is reached, as long as there is a liquid level difference Δh, the concentration of the S1 solution is still greater than the concentration of the S2 solution.
(3) If S1 is a 10% sucrose solution and S2 is a 10% glucose solution (if neither can penetrate the semi-permeable membrane), the water molecules enter the beaker from the funnel to the funnel level to decrease.
Experiment 6 Observation of plasma wall separation and restoration of plant cells (compulsory one P61)
1. Principle: Mature plant cells constitute an osmotic system
2. Process
3. Conditions for the separation of the mass wall
Live plant cells, large vacuoles, poor concentration
4. Analysis of the causes of mass wall separation
External causes: external solution concentration> cell fluid concentration;
Internal causes: the protoplasmic layer is equivalent to a semi-permeable membrane, and the elasticity of the cell wall is less than that of the protoplasmic layer;
Manifestations: Vacuoles change from large to small, the color of cell fluid changes from light to dark, and the protoplasmic layer and cell wall are gradually separated.
5. Special reminder
(1) Plant cells with large vacuoles and color must be selected for easy observation under a microscope.
(2) If the experiment is done with 50% sucrose solution, the plasma wall separation can occur but cannot be restored, because the cells die due to excessive dehydration.
(3) If you use urea, KNO3 and other solutions, there will be automatic recovery.
Experiment 7 Exploring the Factors Affecting Enzyme Activity (Compulsory One P78)
1. High efficiency of enzymes - comparing the decomposition of hydrogen peroxide under different conditions
(1) Experimental process analysis
(2) Precautions for experimentation
Fresh liver must be used as experimental material during the experiment, and organic matter such as catalase in fresh cells may be inactivated by the bacteria.
2. The specificity of enzymes
The independent variables in this experiment can be different reactants or different enzyme types; the dependent variable is whether the reactants are decomposed.
3. Explore the effect of temperature on enzyme activity
(1) Since catalase decomposes when heated, hydrogen peroxide cannot be used as a substrate.
(2) Since the Ferrin reagent needs to be heated when it is used, the iodine solution should be used to detect the dependent variable.
4. Explore the effect of pH on enzyme activity
Think: Why can't you use amylase as a substrate to explore pH experiments?
A: Because starch breaks down under acidic conditions, this is important for judging amylase
Whether the hydrolysis of starch can be interfered with. Therefore, it cannot be used.
Experiment 8 Extraction and Isolation of Chloroplast Pigment (Compulsory One P97)
1. The principle of extracting pigments
Pigments can be dissolved in organic solvents such as absolute ethanol.
2. Separation of pigment principle
Each pigment diffuses differently with the chromatograph on the filter paper, thereby separating the pigment.
[The solubility is large and the diffusion rate is fast; the solubility is small and the diffusion rate is slow.] 】
3. The role of each substance
Absolute ethanol: dissolve and extract pigments;
Chromatography: separation of pigments;
Silica: sufficient grinding;
Calcium carbonate: Neutralizes organic acids released when the vacuole breaks, preventing the destruction of pigment molecules.
4. Separation results
The filter strips are "Hu Huang ab" from top to bottom. 【The width and narrowness of the pigment band are related to the pigment content】
Experiment 9 Exploring the Breathing Mode of Yeast (Compulsory One P91)
1. Principle
Aerobic conditions: C6H12O6+6O2+6H2O6 →CO2+12H2O+energy
Anaerobic conditions: C6H12O6 → 2C2H5OH + 2CO2 + small amount of energy
2. Detection
(1) Detect the production of CO2: make the clarified lime water turbid, or make the bromine thymol blue aqueous solution from blue to green and then yellow.
(2) Detection of alcohol production: orange potassium dichromate solution, under acidic conditions, reacts with alcohol and becomes gray-green.
Experiment 10 Observation of mitosis of cells (compulsory one P115)
1. Materials
Onion root tip (or onion, garlic)
2. Steps
(1) Cultivation of onion root tips
(2) The production process of loading the tablets: dissociation (dissociation solution) → rinsing (washing with water for 3min) → dyeing (gentian violet or magenta acetate) → production
3. Observation
(1) First find the cells in the root tip meristem under the low magnification: the cells are square, tightly arranged, and some cells are dividing.
(2) Observation under high magnification: the number of cells in the inter division period is the largest.
4. Pay attention to the problem
(1) Why can only the root tip be used for each root? When is the best time to take the root tip? why? A: Because cells in the apical meristem can undergo mitosis; from 10 a.m. to 2 p.m.; because cells are active at this time.
(2) What is the purpose of dissociation and tablet pressing? Why add another slide when pressing the tablet?
A: The purpose of dissociation and tablet pressing is to separate the cells from each other; adding another slide is to prevent the coverslip from being crushed.
(3) What is the role of hydrochloric acid during dissociation?
A: Decomposes and dissolves the cell stromal.
(4) Why rinse?
A: Wash off hydrochloric acid for easy dyeing.
(5) Why look for a segregation area? What are the characteristics of the segregation zone?
A: Because only cells in the meristem area at the root tip are able to undergo cell division;
The meristem zone is characterized by a square shape of cells and a tight arrangement.
(5) Can the observed cells change from mid-stage to late stage?
A: No, because the cells are dead at the time of observation and only stay for a certain period of time.
(6) Can observing onion epidermal cells see chromosomes? Why?
A: No, because onion epidermal cells can no longer divide.
(8) If the chromosomes cannot be seen during observation, what are the possible causes?
A: No meristem cell was found; no cells in the division phase were found; the staining solution was too thin; the staining time was too short.
Experiment 11 The Relationship between Cell Size and Material Transport (Compulsory One P110)
[Simulation explores the relationship between cell surface area and volume]
Cells are simulated with agar blocks, which contain phenolphthaleins, meet NaOH, are purple-red in color, showing the rate of diffusion of the substance (NaOH) in the agar block.
2. Conclusion
The ratio of the surface area to volume of the agar block decreases with the increase of the agar block;
The ratio of the volume of NaOH diffusion to the volume of the entire agar block decreases as the agar block increases.
Experiment 12 Observation of meiosis of cells (compulsory 2 P21)
1. Method steps
Low magnification observation → high magnification observation → drawing
2. Discussion
(1) How to determine whether a cell in the field of view is in the first division of the meiosis or the second division of the meiosis?
Answer: The first division of the meiolar will occur homologous chromosome association, tetragram formation, homologous chromosomes arranged in pairs at the equatorial plate position, homologous chromosome separation, and chromosomes moving to the poles of the cell are composed of two chromatids, respectively; in the middle of the second division of the meioditary, the non-homologous chromosomes are arranged in a single position at the equatorial plate position of the cell, and the chromosomes that move to the two poles of the cell do not contain chromatids.
(2) What are the differences in chromosomes in metaphase cells compared to the second division of meiodes? What about the end?
Answer: In the middle of the first division of the meiolar, the two homologous chromosomes are arranged on both sides of the equatorial plate of the cell, and the chromosomes at the poles of the cell at the end of the cell are composed of a complete set of non-homologous chromosomes of the cell, the number of which is half of the number of somatic cell chromosomes, and each chromosome is composed of two chromatids; in the middle of the second division of the subtraction, the centromere points of all chromosomes are arranged at the position of the equatorial plate of the cell. The chromosomes of the terminal cell poles do not contain chromatids.
Experiment 13 Low temperature induced chromosome doubling (compulsory 2 P88)
Low temperatures inhibit the formation of spindles, preventing cells from dividing into two daughter cells, doubling the number of chromosomes in the cell.
2. Method steps
(1) When the onion grows about 1 cm of adventitious roots, put it in the low temperature chamber of the refrigerator (4 °C) and induce incubation for 36 h.
(2) Take the root tip of about 0.5-1 cm, soak it in Carnot's solution for 0.5-1 h, fix the morphology of the cells, and rinse it twice with 95% alcohol.
(3) Production and loading: dissociation → rinsing→ dyeing → filmmaking
(4) Observation and comparison: There are both normal diploid cells and cells with changed number of chromosomes in the field of view.
3. Discussion
Colchicine and low temperature can induce the doubling of the number of chromosomes, what are the similarities in principle between the two methods?
Answer: Colchicine and low temperature can induce the doubling of the number of chromosomes, the principle is to inhibit the formation of spindles, so that the chromosomes can not move to the poles of the cell, and cause the number of chromosomes in the cell to double.
Experiment 14 Investigation of Common Human Genetic Diseases (Compulsory 2 P91)
1. Requirements
The population surveyed was large enough; single-gene genetic diseases with higher incidence in the population were selected. 【Such as red-green blindness, albinism, high myopia, etc.】
2. Calculation formula
Experiment 15 Exploring the Effect of Plant Growth Regulators on The Rooting of Cuttings (Compulsory Three P51)
1. Commonly used auxin analogues
α-Naphthaleneacetic acid (NAA), 2,4-D,phenylacetic acid (IPA), indolebutyric acid (IBA)
2. Method
Immersion method: The concentration of the solution is required to be low, and it is best to treat it in a place with shade and high air humidity.
Dipping method: The base of the cuttings can be dipped in a higher concentration of liquid (about 5s) and about 1.5cm deep.
3. Pre-experiment
First design a set of experiments with a large concentration gradient for exploration, and design meticulous experiments on this basis.
4. Control irrelevant variables
For example, the length of treatment should be consistent, and the plant material used should be the same as possible.
Experiment 16 Simulated detection of urine glucose
1. Sampling
Urine of normal people and urine of diabetic patients
2. Detection method
Ferrin reagent (water bath heating)
3. Results
The brick red precipitate that occurs in the test tube is the urine of diabetic patients, and the urine of normal people that does not appear brick red precipitate.
Experiment 17 Exploring the Dynamic Change of Yeast Number in Culture Medium (Compulsory 3 P68)
(1) Yeast can be cultured with liquid medium, and its growth is related to factors such as composition, space, pH, and temperature in the culture medium.
(2) Count directly under the microscope using a blood cell counting plate.
[Because it is impossible to distinguish between live and dead bacteria, it will lead to high statistical results]
(1) How to count yeast?
The sampling method is used: first place the coverslip on the counting chamber, use a pipette to aspirate the culture solution, drop on the edge of the coverslip, let the culture liquid penetrate by itself, the excess culture solution is sucked out with filter paper, and the yeast cells are all settled to the bottom of the counting chamber, count the number of yeasts in a small square, and then use this as a basis to estimate the total number of yeasts in the test tube.
(2) The test tube should be gently shaken several times before aspirating the culture medium for counting, with the purpose of evenly distributing the yeast in the culture medium and reducing the error;
(3) If there are too many yeasts in a small square and it is difficult to count, what measures should be taken? A: Increase the dilution multiple
Experiment 18 Study on the Richness of Animal Taxa in Soil (Compulsory Three P75)
1. Method
Sampler sampling method.
2. Collect with a trap
It takes advantage of the characteristics of soil small animals that darken, humidify and avoid high temperatures.
3. There are two statistical methods of richness
The first is the name calculation method; the second is the visual estimation method.
Experiment 19 Exploring the Succession of Communities in Aquariums (or Fish Tanks) (Compulsory 3 P68)
1. Purpose of the experiment
Explore the succession of biomes.
2. Experimental requirements
(1) The aquarium must be sealed and transparent, placed in a well-ventilated and well-lit place indoors, but avoid direct sunlight.
(2) Composition: non-biological components, producers, consumers and decomposers
(3) The number of biological components should not be too much, so as not to damage the food chain
Master of Biology