IGCSE Edexcel Science: Animal Biology Key Notes | IGCSE Edexcel 科学：动物考点精讲

📚 IGCSE Edexcel Science: Animal Biology Key Notes | IGCSE Edexcel 科学：动物考点精讲

This revision guide distils the core principles of animal biology covered in the IGCSE Edexcel Science specification. From cellular architecture to organ systems, nutrition, gas exchange, coordination, excretion and reproduction, each section highlights the essential facts and processes you must master for the examination. Use these paired English-Chinese paragraphs to reinforce your understanding and bilingual recall.

本复习指南凝练了IGCSE Edexcel科学考试大纲中动物生物学的核心原理。从细胞结构到器官系统、营养、气体交换、协调控制、排泄和生殖，每一节都突出你必须掌握的重要事实和过程。利用这些中英文对照段落来强化理解和双语记忆。

1. Animal Characteristics and Cell Structure | 动物特征与细胞结构

Animals are multicellular eukaryotes that carry out seven life processes: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition (MRS GREN). They are heterotrophic, obtaining organic food by ingestion.

动物是多细胞真核生物，执行七个生命过程：运动、呼吸、感应、生长、繁殖、排泄和营养（MRS GREN）。它们属于异养生物，通过摄食获取有机食物。

Animal cells lack a rigid cell wall and chloroplasts. Each cell is bounded by a partially permeable cell membrane, encloses cytoplasm and contains a nucleus that stores genetic material, mitochondria for aerobic respiration, and ribosomes for protein synthesis.

动物细胞没有坚硬的细胞壁和叶绿体。每个细胞由一层部分通透的细胞膜包裹，内部含有细胞质、储存遗传物质的细胞核、用于有氧呼吸的线粒体以及负责蛋白质合成的核糖体。

Under a light microscope, animal cells often appear irregular in shape. When stained with methylene blue, the nucleus becomes clearly visible. Mitochondria are too small to be seen without an electron microscope.

在光学显微镜下，动物细胞通常形状不规则。用亚甲蓝染色后，细胞核清晰可见。线粒体太小，须用电子显微镜才能观察到。

2. Levels of Organisation and Tissues | 组织层次与动物组织

Animal bodies are hierarchically organised: similar cells group together to form tissues, tissues work together to form organs, and organs form organ systems that carry out major body functions.

动物身体具有等级结构：相似的细胞组合成组织，组织共同工作构成器官，器官再构成执行主要生理功能的器官系统。

Four main types of animal tissue are recognised. Epithelial tissue covers body surfaces and lines cavities; connective tissue such as bone, cartilage and blood supports and binds other tissues; muscle tissue contracts to produce movement; nervous tissue transmits electrical impulses.

动物组织主要有四种类型。上皮组织覆盖体表并衬在腔体内表面；结缔组织如骨骼、软骨和血液起支撑和连接作用；肌肉组织收缩产生运动；神经组织传递电冲动。

An example of an organ is the stomach, which contains epithelial tissue for secretion, muscular tissue for churning, and nervous tissue to coordinate contractions. A system such as the digestive system includes the stomach, intestines and associated glands.

胃是一个器官的实例，它包含用于分泌的上皮组织、用于搅拌的肌肉组织以及协调收缩的神经组织。消化系统这样的器官系统则包括胃、肠和相关腺体。

3. Nutrition and the Digestive System | 营养与消化系统

Animals require carbohydrates, proteins, lipids, vitamins, minerals, water and dietary fibre. Large insoluble molecules must be broken down by mechanical and chemical digestion into small, soluble substances that can be absorbed.

动物需要碳水化合物、蛋白质、脂类、维生素、矿物质、水和膳食纤维。大分子不溶性物质必须通过物理性和化学性消化分解成可吸收的小分子可溶性物质。

The human digestive system consists of the mouth, oesophagus, stomach, small intestine, large intestine, rectum and anus, along with glands such as the salivary glands, liver and pancreas. Peristalsis pushes food along the gut.

人体消化系统包括口腔、食道、胃、小肠、大肠、直肠和肛门，以及唾液腺、肝脏和胰腺等腺体。蠕动推动食糜沿消化道前进。

Key digestive enzymes: amylase breaks down starch into maltose in the mouth and small intestine; protease (pepsin in stomach, trypsin from pancreas) digests proteins into amino acids; lipase hydrolyses lipids into fatty acids and glycerol. Bile emulsifies fats, enhancing lipase action.

关键消化酶：淀粉酶在口腔和小肠将淀粉分解为麦芽糖；蛋白酶（胃蛋白酶在胃中，胰蛋白酶来自胰腺）将蛋白质消化为氨基酸；脂肪酶将脂类水解为脂肪酸和甘油。胆汁乳化脂肪，增强脂肪酶的作用。

Absorption takes place mainly in the ileum of the small intestine. The ileum is lined with villi and microvilli, providing a large surface area. Each villus contains a lacteal for lipid absorption and a network of capillaries for glucose and amino acids.

吸收主要在小肠的回肠段进行。回肠内壁布满绒毛和微绒毛，提供了巨大的表面积。每根绒毛内部含有吸收脂类的乳糜管以及吸收葡萄糖和氨基酸的毛细血管网。

4. Circulatory System and Blood | 循环系统与血液

Mammals have a closed, double circulatory system consisting of the heart, blood vessels and blood. The double circuit separates oxygenated blood pumped from the left ventricle to the body (systemic) from deoxygenated blood pumped from the right ventricle to the lungs (pulmonary).

哺乳动物拥有封闭的双循环系统，由心脏、血管和血液组成。双循环将左心室泵出的含氧血（体循环）与右心室泵出的去氧血（肺循环）分开。

The heart is a four-chambered muscular pump. The right atrium receives deoxygenated blood; the right ventricle sends it to the lungs. The left atrium receives oxygenated blood from the lungs; the thicker-walled left ventricle propels it around the whole body. Valves prevent backflow.

心脏是一个四腔肌肉泵。右心房接收去氧血，右心室将其送往肺部。左心房接收来自肺部的含氧血，壁更厚的左心室将其泵送至全身。瓣膜防止血液倒流。

Table comparing blood vessels:

Feature 特征	Artery 动脉	Vein 静脉	Capillary 毛细血管
Wall thickness 壁厚	Thick, muscular, elastic 厚、肌性、弹性	Thinner, less elastic 较薄，弹性小	One cell thick 单细胞厚度
Lumen 管腔	Narrow 窄	Wide, often with valves 宽，常有静脉瓣	Very narrow 极窄
Blood flow 血流	Away from heart, high pressure 离开心脏，高压	Towards heart, low pressure 回流心脏，低压	Links arteries and veins, allows exchange 连接动静脉，物质交换

Blood consists of plasma, red blood cells, white blood cells and platelets. Red blood cells contain haemoglobin, which binds oxygen for transport. White blood cells defend against pathogens. Platelets are involved in clotting.

血液由血浆、红细胞、白细胞和血小板组成。红细胞含有血红蛋白，能结合氧气进行运输。白细胞防御病原体。血小板参与凝血过程。

5. Gas Exchange and Respiration | 气体交换与呼吸

The thoracic cavity contains the lungs, protected by the ribcage. Air enters through the trachea, which branches into bronchi and then bronchioles, ending in clusters of alveoli. Alveoli provide a huge surface area for gas exchange.

胸腔内容纳着肺，受到肋骨保护。空气经气管进入，气管分支为支气管，再分支为细支气管，最终止于成簇的肺泡。肺泡为气体交换提供了巨大的表面积。

Features of alveoli: thin walls (one cell thick), moist surface, dense capillary network, and a steep concentration gradient maintained by ventilation and blood flow. Oxygen diffuses from alveoli into blood; carbon dioxide diffuses in the opposite direction.

肺泡的特征：壁极薄（单细胞厚度）、湿润的表面、密集的毛细血管网，以及由通气和血流维持的陡峭浓度梯度。氧气从肺泡扩散入血，二氧化碳朝相反方向扩散。

Ventilation involves the diaphragm and intercostal muscles. During inhalation, the diaphragm contracts and flattens, the external intercostal muscles contract, raising the ribcage. Thoracic volume increases, pressure decreases, and air is drawn in. Exhalation is largely passive but can be forced.

肺通气依赖膈肌和肋间肌。吸气时，膈肌收缩并变平，外肋间肌收缩抬起肋骨。胸腔容积增大，压力降低，空气被吸入。呼气主要靠被动回弹，但也可由用力呼出加强。

Aerobic respiration releases energy from glucose using oxygen. The balanced symbol equation is:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ energy)

有氧呼吸利用氧气从葡萄糖中释放能量。配平后的符号方程式为：

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O（+ 能量）

Anaerobic respiration in animals produces lactic acid and much less energy: Glucose → Lactic acid. An oxygen debt builds up, which is repaid by continued deep breathing after exercise.

动物体内的无氧呼吸产生乳酸和少得多的能量：葡萄糖 → 乳酸。同时形成氧债，运动后通过持续深呼吸来偿还。

6. Nervous System and Reflexes | 神经系统与反射

The nervous system consists of the central nervous system (brain and spinal cord) and peripheral nerves. It enables rapid, short-lived responses. Receptors detect stimuli; effectors (muscles or glands) bring about responses.

神经系统由中枢神经系统（脑和脊髓）以及周围神经组成。它能够引起快速而短暂的反应。感受器探测刺激，效应器（肌肉或腺体）产生响应。

A neurone is specialised to carry electrical impulses. Sensory neurones carry impulses from receptors to the CNS; motor neurones carry impulses from the CNS to effectors. Relay neurones in the CNS connect the two.

神经细胞（神经元）特化以传导电冲动。感觉神经元将冲动从感受器传至中枢神经系统；运动神经元将冲动从中枢神经系统传至效应器。中枢内的联络神经元将二者连接起来。

At a synapse, a neurotransmitter chemical diffuses across the gap, triggering an impulse in the next neurone. Synapses ensure impulses travel in one direction only.

在突触处，神经递质化学物质跨过间隙扩散，在下一个神经元中触发冲动。突触确保了冲动只能沿单一方向传递。

A reflex arc is a rapid, automatic, protective pathway that bypasses conscious thought. Example: touching a hot object leads to immediate withdrawal. The pathway: receptor → sensory neurone → relay neurone in spinal cord → motor neurone → effector muscle.

反射弧是一条快速、自动、保护性的通路，不经有意识思考。例如：触碰烫的物体会立即缩手。其通路为：感受器 → 感觉神经元 → 脊髓中的联络神经元 → 运动神经元 → 效应肌肉。

7. Hormonal Coordination and Homeostasis | 激素协调与稳态

Hormones are chemical messengers secreted by endocrine glands into the bloodstream. They travel to target organs and produce slower but longer-lasting effects than nerve impulses. Two key examples are insulin and adrenaline.

激素是由内分泌腺分泌入血液的化学信使。它们随血流运送到靶器官，产生比神经冲动更慢但更持久的效果。两个关键例子是胰岛素和肾上腺素。

Insulin, released by the pancreas when blood glucose rises, stimulates the liver and muscles to convert glucose into glycogen, lowering blood glucose. Glucagon, also from the pancreas, has the opposite effect. This negative feedback maintains homeostasis.

当血糖升高时，胰腺释放胰岛素，刺激肝脏和肌肉将葡萄糖转化为糖原，从而降低血糖浓度。同样来自胰腺的胰高血糖素则起到相反作用。这种负反馈机制维持了体内稳态。

Adrenaline is secreted during ‘fight or flight’ situations. It increases heart rate, dilates pupils, raises blood glucose levels, and diverts blood to muscles, preparing the body for action.

肾上腺素在“战斗或逃跑”情境中分泌。它加快心率、扩大瞳孔、升高血糖水平并将血液指向肌肉，使身体做好行动准备。

Homeostasis also includes thermoregulation. The skin controls heat loss through sweating, vasodilation and vasoconstriction. A rise in core temperature is detected by the hypothalamus, which triggers cooling mechanisms.

稳态还包括体温调节。皮肤通过出汗、血管舒张和血管收缩来控制散热。核心温度升高时，下丘脑感知到变化并启动降温机制。

8. Excretion and Kidney Function | 排泄与肾功能

Excretion is the removal of metabolic waste products, primarily carbon dioxide from respiration and urea produced in the liver from excess amino acids. The kidneys filter the blood and produce urine.

排泄是指代谢废物的排出，主要是呼吸产生的二氧化碳以及肝脏从多余氨基酸产生的尿素。肾脏过滤血液并生成尿液。

Each kidney contains about one million nephrons. Blood enters through the renal artery and is filtered under pressure in the glomerulus and Bowman’s capsule. This ultrafiltration forces out water, glucose, salts and urea, but leaves blood cells and large proteins behind.

每个肾脏包含约一百万个肾单位。血液经肾动脉流入，在肾小球和鲍曼氏囊中受压滤过。超滤作用迫使水、葡萄糖、盐和尿素滤出，但血细胞和大分子蛋白质被留在血液中。

Selective reabsorption occurs in the proximal convoluted tubule, where all glucose, some ions and most water are reabsorbed back into the blood. The remaining fluid passes through the loop of Henle and collecting duct, where water balance is finely adjusted by ADH. Urine contains urea, excess salts and water.

选择性重吸收发生在近曲小管，全部的葡萄糖、部分离子和大部分水被重新吸收回血液。剩下的液体流经亨利氏袢和集合管，在抗利尿激素（ADH）的精细调节下水盐平衡得以维持。尿液中含尿素、多余的盐和水。

9. Reproduction in Animals | 动物的生殖

Reproduction can be asexual (one parent, genetically identical offspring) or sexual (fusion of male and female gametes, producing genetic variation). Most animals reproduce sexually.

生殖可以是无性的（单一亲本，后代基因相同）或有性的（雄配子与雌配子融合，产生遗传变异）。大多数动物进行有性生殖。

The male reproductive system produces sperm in the testes, which are transported through the sperm ducts. The female reproductive system produces eggs in the ovaries; fertilisation typically occurs in the oviduct (fallopian tube).

男性生殖系统在睾丸中产生精子，精子经输精管输送。女性生殖系统在卵巢中产生卵子；受精通常发生在输卵管中。

The menstrual cycle is controlled by hormones: FSH stimulates egg maturation, LH triggers ovulation, oestrogen repairs the uterine lining, and progesterone maintains it. If no fertilisation occurs, progesterone levels drop, causing menstruation.

月经周期受激素调控：促卵泡激素（FSH）促进卵子成熟，黄体生成素（LH）触发排卵，雌激素修复子宫内膜，孕酮维持内膜。若未受精，孕酮水平下降，引起月经来潮。

After fertilisation, the zygote divides and implants into the uterine wall. The placenta allows exchange of nutrients, oxygen and waste between mother and foetus without mixing blood. Amniotic fluid protects the developing embryo.

受精后，合子分裂并植入子宫内膜。胎盘允许母体和胎儿之间交换营养、氧气和废物，但血液不相混。羊水保护发育中的胚胎。

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IGCSE Edexcel Science: Animal Biology Key Notes | IGCSE Edexcel 科学：动物 考点精讲