📚 Year 9 SQA Biology: Quick Reference Handbook of Formulas & Theorems | 九年级 SQA 生物：公式定理速查手册
This handy revision guide gathers every essential formula, equation and quantitative relationship you need for Year 9 SQA Biology. Use it to check microscope calculations, respiration and photosynthesis word equations, genetic probability, sampling methods and energy transfer ideas. Each section gives the core statement in bold, followed by a short worked insight in English and Chinese, so you can quickly refresh your memory before tests.
这本速查手册汇集了九年级 SQA 生物课程必须掌握的公式、方程式和数量关系。涵盖显微镜计算、呼吸与光合作用文字方程式、遗传概率、采样方法以及能量传递等要点。每一节都用粗体标出核心定理，并配以英中双语简析，方便考前快速回顾。
1. Magnification Formula | 放大倍数公式
The total magnification of a light microscope is found by multiplying the power of the eyepiece lens by the power of the objective lens being used. This works because each lens magnifies the image in turn.
光学显微镜的总放大倍数等于目镜放大倍数乘以当前所用物镜的放大倍数，这是因为每个透镜依次把图像放大。
Total Magnification = Eyepiece Magnification × Objective Magnification
If the eyepiece is 10× and you move to the high‑ the field of view and the depth of focus, so you need to adjust the fine focus carefully.
如果目镜为 10×，转到高倍物镜 (40×)，总放大倍数为 400×。注意放大倍数越大，视野和景深越小，需要细致调节细准焦螺旋。
2. Photosynthesis Word Equation | 光合作用文字方程式
Photosynthesis is the process plants use to convert light energy into chemical energy stored in glucose. The summary word equation shows the raw materials and the products.
光合作用是植物将光能转变为储存在葡萄糖中的化学能的过程，文字方程式概括了反应物和产物。
Carbon dioxide + Water → Glucose + Oxygen
(in the presence of light and chlorophyll)
Light energy, absorbed by chlorophyll in chloroplasts, drives the reaction. The glucose can be used immediately for respiration or converted into starch for storage. Oxygen is released as a by‑product, which is why plants are so important for maintaining atmospheric oxygen levels.
叶绿体中的叶绿素吸收光能驱动反应。生成的葡萄糖既可立即用于呼吸，也可转变为淀粉储存。氧气作为副产品释放，这也是植物维持大气氧气含量的重要原因。
3. Aerobic Respiration Word Equation | 有氧呼吸文字方程式
Aerobic respiration releases energy for cells by breaking down glucose using oxygen. It occurs continuously in the mitochondria of most living cells.
有氧呼吸通过氧气分解葡萄糖为细胞提供能量，在大多数活细胞的线粒体中持续发生。
Glucose + Oxygen → Carbon dioxide + Water (+ energy released as ATP)
The energy is used for muscle contraction, building new molecules, cell division and maintaining body temperature in mammals. Carbon dioxide and water are waste products that are removed from the body via the lungs, skin and kidneys.
释放的能量用于肌肉收缩、合成新分子、细胞分裂以及哺乳动物维持体温。二氧化碳和水是废物，通过肺、皮肤和肾脏排出体外。
4. Anaerobic Respiration Equations | 无氧呼吸方程式
When oxygen is in short supply, cells can still release a small amount of energy through anaerobic respiration. The pathway differs between animal cells and yeast.
当氧气不足时，细胞仍可通过无氧呼吸释放少量能量。动物细胞与酵母的代谢途径不同。
In animal muscle: Glucose → Lactic acid (+ a little energy)
Lactic acid builds up in muscles during vigorous exercise, causing fatigue and cramps. It is later oxidised back when oxygen becomes available — this is called the oxygen debt.
剧烈运动时乳酸在肌肉中积累，引起疲劳和痉挛。当氧气恢复后乳酸被氧化，此过程称为氧债。
In yeast: Glucose → Ethanol + Carbon dioxide (+ a little energy)
This type of anaerobic respiration is called fermentation. It is used commercially to make bread rise, produce alcoholic drinks and manufacture biofuels. The carbon dioxide bubbles create the air pockets in bread dough.
酵母的这种无氧呼吸称为发酵，用于面包蓬松、酿酒和生物燃料生产。二氧化碳气泡在面团中形成气孔。
5. Osmosis Principle | 渗透原理
Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water potential to a region of lower water potential. No energy is required — it is a passive process.
渗透是水分子通过部分透膜从水势较高区域向水势较低区域的净移动，无需能量，属于被动过程。
The water potential is affected by the concentration of solutes: a dilute solution has a high water potential, while a concentrated solution has a low water potential. In plant cells, osmosis makes the cell membrane push against the cell wall, keeping the cell turgid and supporting the plant. In animal cells, too much water intake can cause the cell to burst (lysis), so body fluids are regulated carefully.
水势受溶质浓度影响：稀溶液水势高，浓溶液水势低。植物细胞中，渗透使细胞膜紧贴细胞壁，维持细胞膨压以支撑植物。动物细胞若吸水过多会胀破（溶血），因此体液受到严格调控。
6. Diffusion Principle | 扩散原理
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration, resulting in even distribution. Like osmosis, it is a passive process and does not require cellular energy.
扩散是粒子从较高浓度区域向较低浓度区域的净移动，最终均匀分布。与渗透一样，这也属于被动过程，无需细胞能量。
The rate of diffusion is influenced by concentration gradient, temperature, surface area and particle size. A steeper gradient and a larger surface area speed up diffusion. In the lungs, oxygen diffuses from the alveoli into the blood, while carbon dioxide diffuses in the opposite direction, both following their concentration gradients.
扩散速率受浓度梯度、温度、表面积和颗粒大小影响。梯度越大、表面积越大，扩散越快。在肺部，氧气从肺泡扩散入血，二氧化碳反向扩散，均沿浓度梯度进行。
7. Enzyme Activity & Rate of Reaction | 酶活性与反应速率
Enzymes are biological catalysts that speed up chemical reactions without being used up. Each enzyme has an active site that fits a specific substrate — often described by the 'lock and key' model. The rate of an enzyme‑controlled reaction can be measured and is affected strongly by temperature and pH.
酶是生物催化剂，能加速化学反应而自身不消耗。每种酶的活性位点与特定底物匹配，常被比作“锁钥模型”。酶促反应速率可以测量，并且显著受温度和 pH 影响。
To calculate the rate of reaction from a practical, you can use the reciprocal of the time taken for a change to occur or the amount of product formed per unit time:
可通过实验测得的反应速率公式为：用变化所需时间的倒数或单位时间内产物的生成量计算。
Rate = 1 / Time (s⁻¹) or Rate = Quantity of product / Time
Enzymes work fastest at an optimum temperature (for most human enzymes about 37 °C) and an optimum pH. Beyond these points, the enzyme's active site changes shape irreversibly — the enzyme becomes denatured and the reaction rate drops sharply. This principle explains why high fever or extreme pH can be harmful to the body.
酶在最适温度（人体酶约 37 °C）和最适 pH 下活性最高。超出范围后，活性位点发生不可逆变形，酶变性失活，反应速率急剧下降。这解释了为什么高烧或极端 pH 对身体有害。
8. Punnett Square and Genetic Probability | 庞纳特方格与遗传概率
A Punnett square is a grid used to predict the genotypes of offspring from a genetic cross. The alleles from each parent are placed along the top and side, and the possible combinations are filled in the boxes.
庞纳特方格是一种预测杂交后代基因型的表格。将亲本等位基因分别列在顶部和侧边，框内填入可能的组合。
f a specific genotype = (Number of squares with that genotype) / (Total number of squares)
tio is typically 1 BB : 2 Bb : 1 bb. The probability of a dominant phenotype is 3/4 (or 75%), while the probability of the recessive phenotype is 1/4 (25%). These probabilities apply to each offspring independently.
两个杂合子杂交（如 Bb × Bb）时，基因型比例一般为 1 BB : 2 Bb : 1 bb。显性性状出现的概率为 3/4 (75%)，隐性性状为 1/4 (25%)。每个后代的概率彼此独立。
9. Population Density Calculation | 种群密度计算
To study an ecosystem, ecologists often need to estimate how many organisms of a species live in a given area. The simplest method uses quadrat sampling to find the mean number per unit area.
研究生态系统时，生态学家常需估算某物种在给定区域内的个体数。最简单的方法是利用样方调查求单位面积平均数量。
ensity = Total number of individuals counted / (Number of quadrats × Area of each quadrat)
For plants or slow‑moving animals, you place a quadrat of known area randomly, count the individuals inside and repeat several times. The average is multiplied across the whole habitat area to give an estimate of the total population. Random placement and enough replicates are key to reliable data.
对于植物或缓慢移动的动物，将已知面积的样方随机投放，计数框内个体并多次重复。将平均值乘以栖息地总面积即可估算种群总量。随机布设和充足重复是获得可靠数据的关键。
10. Capture–Mark–Recapture (Lincoln Index) | 捕捉–标记–重捕法（林肯指数）
For mobile animals, ecologists use the capture–mark–recapture method. Animals are caught, marked in a harmless way and released. Later, a second sample is captured, and the proportion of marked individuals is noted.
对于活动能力强的动物，生态学家采用捕捉–标记–重捕法。先捕获一批动物，无害标记后释放；随后二次捕捉，记录其中已标记个体的比例。
Estimated population size (N) = (M × C) / R
uals recaptured in the second sample. This formula assumes that marked animals mix randomly with the rest, that no births, deaths or migration occur between samples, and that marks are not lost.
其中 M 为第一次标记数，C 为第二次捕获总数，R 为第二次捕获中带标记的数目。该公式假设标记动物随机混入群体，两次采样期间无出生、死亡或迁移，且标记不会脱落。
11. Biomass in Food Chains | 食物链中的生物量
Biomass is the total mass of living material (usually dry mass) at a particular trophic level. In a food chain, biomass is often represented as a pyramid of biomass, with the producers at the base having the greatest biomass and top carnivores the least.
生物量指某一营养层次活体物质的总质量（通常以干重计）。在食物链中，通常用生物量金字塔表示，生产者位于塔底、生物量最大，顶级消费者生物量最小。
When drawing a pyramid of biomass, each bar is drawn to scale and labelled with the organism's name. The width of the bar is proportional to the biomass at that level. Only a fraction of the biomass eaten by a consumer is turned into new body tissue; the rest is lost through respiration, egestion and excretion.
绘制生物量金字塔时，每个横条按比例绘制并标注生物名称。条的宽度代表该层次的生物量。消费者摄入的生物量只有一小部分转化为新的身体组织，其余因呼吸、排遗和排泄而散失。
12. Energy Transfer Efficiency | 能量传递效率
Energy is transferred along a food chain, but a large proportion is lost at each stage, mainly as heat from respiration. The efficiency of transfer from one trophic level to the next can be calculated with a simple formula.
能量沿食物链传递，但每一级都会有大量能量损失，主要因呼吸作用以热的形式散失。从一个营养级到下一营养级的传递效率可用简单公式计算。
Efficiency (%) = (Energy in next trophic level / Energy in previous trophic level) × 100
Typically, only about 10% of the energy is passed on, which explains why food chains rarely have more than four or five trophic levels. The same formula can be applied to biomass transfer. Understanding this efficiency helps explain why eating plants is more energy‑efficient than eating meat.
通常只有约 10% 的能量被传递下去，因此食物链很少超过四到五个营养级。同样的公式也适用于生物量传递效率。理解这一点有助于解释为什么食用植物比食用肉类更节能。
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