📚 351. Characteristics of Living Organisms | 351. 生物的特征
All living things, from the tiniest bacterium to a giant blue whale, share a set of essential life processes. In IGCSE Edexcel Biology, we group these into the memorable acronym MRS GREN – Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition – often with an extra 'C' for Control (homeostasis). Mastering these characteristics helps us decide whether something is truly alive, and it forms the foundation for every topic that follows.
从最小的细菌到巨大的蓝鲸，所有生物都共享一套基本的生命活动。在爱德思 IGCSE 生物课程中，我们通常用缩写词 MRS GREN 来记忆这些特征——运动、呼吸、感应、生长、生殖、排泄和营养，有时还会加上一个“C”代表控制（稳态）。掌握这些特征有助于我们判断某物是否真的具有生命，而这也是后续所有知识的基础。
1. What Is Life? An Overview | 什么是生命？概述
Biologists define a living organism as something that can carry out all of the life processes independently. If an object shows all the characteristics of MRS GREN at some stage in its life cycle, it is considered alive. Non-living things, such as rocks or water, might show one or two features (e.g. water can move), but they do not exhibit all of them simultaneously.
生物学家将生物定义为能够独立执行所有生命活动的个体。如果某个物体在其生命周期的某个阶段表现出 MRS GREN 的全部特征，它就被视为有生命。非生物，如岩石或水，可能表现出其中一两个特征（例如水可以流动），但它们并不同时展现所有特征。
2. Movement | 运动
All living organisms can move, even if very slowly. Animals move their whole bodies to find food, escape predators or seek a mate. Plants move more subtly: shoots grow towards light (phototropism) and roots grow towards gravity (geotropism). Inside cells, cytoplasm streams to transport substances – this is intracellular movement.
所有生物都能运动，哪怕非常缓慢。动物通过整体移动来寻找食物、躲避捕食者或寻找配偶。植物的运动更为微妙：茎尖向光生长（向光性），根向重力方向生长（向地性）。在细胞内部，细胞质流动以运输物质——这是胞内运动。
3. Respiration | 呼吸
Respiration is the chemical reaction that releases energy from food molecules. It happens in every living cell and is not the same as breathing (ventilation). The energy released, in the form of ATP, fuels processes like muscle contraction, active transport and keeping warm. The summary equation for aerobic respiration is:
呼吸是从食物分子中释放能量的化学反应。它发生在每个活细胞中，与呼吸（换气）不是一回事。释放的能量以 ATP 形式存在，为肌肉收缩、主动运输和保暖等过程提供动力。有氧呼吸的总方程式为：
Glucose + Oxygen → Carbon dioxide + Water (+ energy)
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ energy as ATP)
Anaerobic respiration in animal cells produces lactic acid, while in yeast it produces ethanol and carbon dioxide. IGCSE students need to recall the key differences and word equations for both.
动物细胞中的无氧呼吸产生乳酸，而酵母的无氧呼吸则产生乙醇和二氧化碳。IGCSE 考生需牢记两者的关键区别及文字方程式。
4. Sensitivity | 感应
Living organisms detect and respond to changes in their internal or external environment – a stimulus. A response helps survival. Examples include pupils constricting in bright light, plants bending towards a window, or bacteria swimming away from toxic chemicals. Plants use hormones such as auxin to coordinate responses.
生物能察觉并响应其内、外部环境的变化——即刺激。这种响应有助于生存。例如，瞳孔在强光下缩小、植物向窗口弯曲，或细菌游离有毒化学物质。植物利用生长素等激素来协调响应。
5. Growth | 生长
Growth is a permanent increase in size and dry mass, achieved by cell division and cell enlargement. Animals tend to grow all over their bodies and eventually stop, while plants often grow from meristems at root and shoot tips and can continue growing throughout life. Measuring dry mass (biomass) is the most accurate way to track growth because it excludes water content changes.
生长是体积和干重的永久性增加，通过细胞分裂和细胞增大实现。动物通常全身生长并最终停止，而植物往往通过根尖和茎尖的分生组织生长，并可终生持续。测量干重（生物量）是追踪生长最准确的方法，因为它排除了水分含量的变化。
6. Reproduction | 生殖
All organisms produce offspring, ensuring the survival of their species. Reproduction can be asexual (one parent, genetically identical clones, e.g. binary fission in bacteria, runners in strawberries) or sexual (two parents, genetically varied offspring, e.g. humans, flowering plants). IGCSE candidates must be able to compare advantages: sexual reproduction creates variation, which aids adaptation; asexual reproduction is rapid and requires no mate.
所有生物都能产生后代，确保物种的延续。生殖方式可能为无性（一个亲本，遗传上相同的克隆，如细菌的二分裂、草莓的匍匐茎）或有性（两个亲本，遗传变异的子代，如人类、开花植物）。IGCSE 考生需要比较两者的优点：有性生殖产生变异，有助于适应环境；无性生殖速度快且无需配偶。
7. Excretion | 排泄
Excretion is the removal of toxic waste products of metabolism from the body. It is distinct from egestion (removal of undigested food). Key excretory products include carbon dioxide from respiration (excreted via the lungs), urea from the breakdown of excess amino acids (excreted by the kidneys) and excess water and salts (skin and kidneys). The liver plays a central role in producing urea through deamination.
排泄是将代谢产生的有毒废物排出体外。它与排遗（排出未消化的食物）不同。主要的排泄物包括呼吸产生的二氧化碳（通过肺排出）、过量氨基酸分解产生的尿素（由肾脏排出）以及多余的水和盐（皮肤和肾脏）。肝脏通过脱氨基作用在尿素生成中起核心作用。
8. Nutrition | 营养
Nutrition is the intake of materials for energy, growth and repair. Organisms can be autotrophs (make their own food using light or chemical energy, e.g. green plants through photosynthesis) or heterotrophs (obtain ready-made organic food by feeding on other organisms, e.g. animals, fungi). A balanced diet in humans must include all seven nutrient groups: carbohydrates, proteins, lipids, vitamins, minerals, water and dietary fibre.
营养是为获取能量、生长和修复而摄取物质的过程。生物可以是自养型（利用光能或化学能制造自身食物，如绿色植物通过光合作用）或异养型（通过摄食其他生物获取现成的有机食物，如动物、真菌）。人体均衡饮食必须包含全部七类营养素：碳水化合物、蛋白质、脂类、维生素、矿物质、水和膳食纤维。
9. Homeostasis – The Extra 'C' | 稳态——“C”的补充
Modern biology often includes Control or Homeostasis as an essential characteristic. Homeostasis is the maintenance of a constant internal environment, such as body temperature, blood glucose concentration and water balance. In humans, the nervous and endocrine systems work together to detect deviations and trigger corrective mechanisms (negative feedback). For IGCSE, understanding skin responses to temperature change and the role of insulin and glucagon is crucial.
现代生物学常将控制或稳态列为一个重要特征。稳态指维持稳定的内部环境，如体温、血糖浓度和水分平衡。人体通过神经和内分泌系统协同作用，检测偏差并启动纠正机制（负反馈）。对 IGCSE 而言，理解皮肤对温度变化的反应以及胰岛素和胰高血糖素的作用至关重要。
10. Applying the Characteristics: Is It Alive? | 应用特征：它是有生命的吗？
Viruses, such as the influenza virus or bacteriophage, are a fascinating borderline case. They show no movement, respiration, sensitivity, growth or excretion outside a host cell. They also do not feed. They can only reproduce by hijacking a host cell's machinery. Therefore, they are not considered living organisms. Similarly, a car engine 'respires' by burning fuel, but it does not grow or reproduce; it fails the MRS GREN test.
病毒，如流感病毒或噬菌体，是一个有趣的临界面。它们在宿主细胞外不表现运动、呼吸、感应、生长或排泄，也不进食。它们只能通过劫持宿主细胞进行复制。因此，它们不被视为生物。同样，汽车引擎通过燃烧燃料进行“呼吸”，但它不会生长或繁殖，通不过 MRS GREN 检测。
11. Key Exam Tips for IGCSE Edexcel | IGCSE 爱德思考试关键技巧
Edexcel IGCSE exam questions often ask you to list the characteristics of living organisms and give a clear example of each. Use the acronym MRS GREN to recall all seven. Whenever possible, link the characteristic to a specific named organism and a precise cellular process. For instance, 'yeast respires anaerobically to produce ethanol' is a strong, mark-winning statement. Beware of mixing up respiration with breathing, and excretion with egestion – these distinctions frequently appear in multiple-choice and short-answer questions.
爱德思 IGCSE 考试常要求列出生物的特征并为每个特征举出明确的例子。用缩写词 MRS GREN 来回忆全部七点。尽量将特征与特定命名生物及精确的细胞过程联系在一起。例如，“酵母进行无氧呼吸产生乙醇”就是一个很有力、能得分的好答案。注意不要混淆呼吸和换气，以及排泄与排遗——这些区别经常出现在选择题和简答题中。
Published by TutorHao | Biology Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图