Junior high school biology essay sample 1: Why are tree trunks round? During the process of observing nature, I accidentally discovered that the shape of tree trunks is approximately round - hollow cone-shaped. Why are tree trunks conical? What are the benefits of conical trunks? In order to explore these issues, I conducted more in-depth observations and analysis. With the help of my tutor, I looked up relevant information and learned that the stems of plants play a role in supporting the plant body and transporting water and other nutrients. The stems of trees are mainly composed of vascular bundles. The supporting role of the stem is mainly borne by xylem wood fibers. Although the stems of woody plants will become thicker year by year, within a certain time range, the number of wood fibers in the stems is constant, that is, the cross-sectional area of ??the tree stems is constant. Next, we designed experiments around a certain cross-sectional area of ??the tree trunk, assuming that the cross-section of the tree trunk grew into different shapes, to explore the reasons and advantages of the conical shape of the tree trunk. After experiments, we found that: (1) When the cross-sectional area and length are constant, the triangular prism-shaped object has the largest longitudinal support force and the smallest lateral bearing force; the longitudinal support force of the cylindrical object is not as good as that of the triangular prism-shaped object, but the lateral bearing force is the largest; ( 2) Among trunks of equal mass and different shapes, short cone-shaped trunks can bear the greatest wind force; (3) Wind is a natural phenomenon that affects the shape of the cross-section of trees and the height of tree growth. The nearly conical trunk has a low center of gravity, and the huge root system is connected to the earth, making the center of gravity lower and more stable; (4) The trunk has a round cross-section, which can reduce damage and has stronger mechanical strength. , can withstand the attack of wind. At the same time, due to the influence of wind, the bending degree of the tree trunk is similar everywhere. No matter which direction the wind comes from, the resistance of the tree trunk is similar, and the tree trunk is not easily damaged. The above experiments reflect the laws of nature and the inspiration given by nature: (1) A columnar object with a triangular cross-section has the maximum longitudinal support, and its shape can be used in construction, such as angle steel, etc.; (2) The cross-section is circular Round objects have the greatest lateral bearing capacity. Building materials of similar shapes can be found everywhere, such as TV towers, telephone poles, etc. In the process of my observation, experiment and analysis, I gradually explained and revealed the mystery of the conical shape of the tree trunk, increased my knowledge, and applied the learned knowledge with practice, which not only consolidated the learned knowledge, but also improved the learning ability. interest, and also initially learned scientific observation and analysis methods. Sample Essay 2: What is the effect of vinegar on flowers? Vinegar is a commonly used condiment in life, and flowers can purify the ecological environment and beautify our lives. Have you ever thought about the relationship between vinegar and flowers? We started exploring this topic out of curiosity. People with rich experience in growing flowers tell us that applying some vinegar solution to potted flowers can improve the growth of potted flowers, increase the number of flowers, and make the flowers colorful and luxuriant. This was quickly confirmed in our experiments. Do vinegar solutions with different concentrations have different effects on flowers? This is the second phase of our experiment. We selected four pots each of Gypsophila, Primula, and Moonflower with the same growth, and divided them into four groups. Each group (three pots) has three types of flowers, which are numbered and labeled respectively. At the same time, we took edible white vinegar and prepared it into three solutions with different concentrations: 1% (pH value 2~3), 0.01% (pH value ≈ 4), and 0.0001% (pH value ≈ 6), and gave them separately every day. Three groups of potted flowers are sprayed with a vinegar solution, and the fourth group of potted flowers are sprayed with clean water without vinegar. Observe and record the growth of the flowers every five days. The results of this experiment are: Spraying low-concentration vinegar (pH value ≈ 6) has no obvious effect on these types of flowers; flowers sprayed with medium-concentration vinegar (pH value ≈ 4) grow significantly better than the other groups, and the flower buds More, the flowering period is advanced, the flowers are more colorful, and the flowering period is also extended; spraying high-concentration vinegar with a pH value of 2-3 will cause the flowers to wither prematurely. Through this experiment, we can tell you: Spraying some vinegar appropriately when planting flowers can make the flowers grow better. However, you must control the concentration of the vinegar solution. If the acetic acid is too concentrated, it will damage the flowers.

Smoking, smoking is harmful to health, but everyone knows it, but there are still so many people smoking? Some people smoke because they feel a bit handsome, and some people smoke to relieve their worries. They look intoxicated when they see others smoking. Ah! I have been in a bad mood recently! I also smoke! It seems that smoking can eliminate my sadness and make me less melancholy. But I find that I am even more sad! Not only does it not eliminate my sadness, it actually makes it worse! Friends, for the sake of your own health and the people who care about you, please don’t smoke! Smoking has many harmful effects. It not only devours the health and life of the person who smokes it, but also pollutes the air and harms others. 1. Lung disease: When cigarettes are burned, they release 38 toxic chemicals, among which the harmful ingredients mainly include tar, carbon monoxide, nicotine, dioxins and irritating smoke. Tar can cause damage to the mouth, throat, trachea, and lungs. The tar in tobacco smoke is deposited on the villi of the lungs, destroying the function of the villi, increasing phlegm, and causing chronic pathological changes in the bronchi, such as tracheitis, emphysema, cor pulmonale, and lung cancer. According to statistics, 74% of people who inhale smoke suffer from lung diseases after the age of 60, while the proportion of non-smokers who suffer from lung diseases after the age of 60 is only 4%. This is a shocking number. 2. Cardiovascular disease: The carbon monoxide in cigarettes reduces the oxygen content in the blood, causing related diseases such as high blood pressure. Smoking constricts coronary arteries, reducing or blocking their supply, causing myocardial infarction.

Smoking can increase adrenaline, cause the heartbeat to accelerate, increase the load on the heart, affect blood circulation, and lead to more than 20 diseases such as cardiovascular and cerebrovascular diseases, diabetes, sudden death syndrome, decreased respiratory function, and stroke. 3. Smoking causes cancer: research It has been found that smoking is the fastest and most abundant way to generate free radicals. Each puff of cigarette will produce at least 100,000 free radicals, which can lead to cancer and many chronic diseases. Recently, a 50-year study of 35,000 smokers conducted by Tidcliffe Hospital in Oxford, UK, concluded that lung cancer, stomach cancer, pancreatic cancer, bladder cancer, liver cancer, oral cancer, and sinus cancer wait until 11 Types of cancer "significantly associated" with smoking. Why smokers are prone to colds is because the body's lymphocyte activity is reduced, leading to cancer. In view of the three major factors that cause smoking and cancer, the sooner you quit smoking, the better. 4. Smoking can also lead to osteoporosis and early menopause. Smoking can cause men to lose sexual and reproductive functions. Smoking by pregnant women can lead to premature delivery and underweight fetuses, and increase the chance of miscarriage. Smoking causes teeth to turn yellow and causes bad breath. Smoking harms everyone. People who smoke passively are five times more harmful than smokers. For the health of you and your family, you should quit smoking as soon as possible to prevent yourself from becoming a slave to smoking. 5. The harm of smoking to intelligence. Smoking can affect people's concentration. Some people think that smoking can refresh your mind, eliminate fatigue, and trigger inspiration. This has no scientific reason. Experiments have shown that smoking seriously affects people's intelligence and memory, thereby reducing the efficiency of work and study. Smoking has hundreds of harms but no benefits. 53% of children in China are passively smoked, which is more harmful and prone to pneumonia, bronchitis, severe asthma and other diseases. If the current smoking situation continues, children's intellectual development, smoking families, and individuals will pay a huge price.

Campus Energy Saving and Environmental Protection Essay: Energy Saving and Environmental Protection Essay (Tip: 100 words is just enough to write an argument!) What do the earth’s environmental changes remind us of? Earth Day is a day of repentance to Mother Earth. Let us think about the disasters that humans have caused to the earth through excessive consumption of resources and pollution of the environment; let us think about the unshirkable responsibility that each of us has in such disasters. When the fragile ecology becomes difficult to maintain, how will human consumption continue? When the earth is suffering from a terminal disease, how long can humans survive? Earth Day is also the day of salvation for mankind itself. Human beings are both the creators and victims of environmental disasters, and they are also the managers of environmental disasters. Each of us can participate in environmental protection by choosing a green lifestyle: saving resources and reducing pollution; green consumption and environmentally friendly purchases; reuse and multiple uses; garbage classification and recycling; saving species and protecting nature. Green life is the message of the new century, which guides the business community to develop green technology and clean production; green life is the requirement of the new century, which encourages politicians to assume the responsibility for sustainable human development; green life is the fashion of the new century, It embodies a person's civilization and literacy, and also marks the quality and strength of a nation. China, with the most fragile ecosystem in history, is experiencing the largest population and the greatest development pressure in history. Patriots, let us first cherish the foundation on which this nation depends for survival, and let us start with every environmental protection behavior.