Animal IGCSE OCR Science: Key Points Review | IGCSE OCR 科学：动物 考点精讲

📚 Animal IGCSE OCR Science: Key Points Review | IGCSE OCR 科学：动物 考点精讲

Animals are a central topic in OCR GCSE Combined Science biology. A thorough understanding of their cell structure, organ systems, and classification is essential for answering exam questions accurately. This revision guide summarises the key 'Animal' points, covering everything from organelles to natural selection.

动物是 OCR GCSE 综合科学生物学的核心主题。透彻理解它们的细胞结构、器官系统和分类对于准确回答考试题目至关重要。本复习指南总结了关键的“动物”考点，涵盖从细胞器到自然选择的全部内容。

1. Animal Cell Structure | 动物细胞结构

• Animal cells are eukaryotic and contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. 动物细胞是真核细胞，含有细胞核、细胞质、细胞膜、线粒体和核糖体。
• The nucleus controls cell activities and stores genetic information on chromosomes. 细胞核控制细胞活动，并在染色体上储存遗传信息。
• Mitochondria are the sites of aerobic respiration, releasing energy in the form of ATP. 线粒体是有氧呼吸的场所，以 ATP 的形式释放能量。
• Ribosomes carry out protein synthesis using the code from DNA. 核糖体利用 DNA 上的密码进行蛋白质合成。
• Unlike plant cells, animal cells lack a cellulose cell wall, chloroplasts and a large permanent vacuole. 与植物细胞不同，动物细胞没有纤维素细胞壁、叶绿体和大液泡。
• Animal cells sometimes contain small temporary vacuoles and may store glycogen granules. 动物细胞有时含有小的临时液泡，并可能储存糖原颗粒。

2. Cell Division and Stem Cells | 细胞分裂与干细胞

• Mitosis produces two genetically identical daughter cells, used for growth, repair and asexual reproduction in animals. 有丝分裂产生两个遗传上相同的子细胞，用于动物的生长、修复和无性生殖。
• Stem cells are unspecialised cells that can divide and differentiate. In animals, embryonic stem cells can become any cell type, while adult stem cells can only differentiate into a limited range of cells. 干细胞是未分化的细胞，可以分裂和分化。在动物中，胚胎干细胞可以变成任何细胞类型，而成体干细胞只能分化成有限类型的细胞。
• Stem cells are used in medicine to treat conditions such as paralysis and diabetes, but the use of embryonic stem cells raises ethical issues. 干细胞在医学上用于治疗瘫痪、糖尿病等疾病，但使用胚胎干细胞引发了伦理问题。
• Meristems are plant stem cells; animals rely on adult and embryonic stem cells for cell renewal. 分生组织是植物的干细胞；动物依赖成体和胚胎干细胞进行细胞更新。

3. Digestive System and Enzymes | 消化系统与酶

The digestive system breaks down large insoluble molecules into small soluble ones that can be absorbed into the blood. 消化系统将大的不溶性分子分解为可溶于水的小分子，以便吸收进入血液。

• Bile is produced by the liver, stored in the gall bladder and emulsifies fats, increasing the surface area for lipase action. 胆汁由肝脏产生，储存在胆囊，能乳化脂肪，增大脂肪酶作用的表面积。
• Enzyme activity is affected by temperature and pH: high temperatures denature the enzyme, and pH changes the shape of the active site. 酶活性受温度和 pH 影响：高温会使酶变性，pH 改变会改变活性部位的形状。
• The small intestine is adapted for absorption with millions of villi that provide a large surface area, a thin epithelium and a rich blood capillary network. 小肠通过数百万绒毛增加吸收面积，绒毛上皮薄且有丰富的毛细血管网。

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4. Circulatory System: Heart and Blood Vessels | 循环系统：心脏与血管

• Mammals have a double circulatory system: the pulmonary circulation carries blood to the lungs, and the systemic circulation carries blood to the rest of the body. 哺乳动物具有双循环系统：肺循环将血液输送到肺部，体循环将血液输送到身体其他部位。
• The heart has four chambers: right atrium, right ventricle, left atrium and left ventricle. Valves prevent backflow of blood. 心脏有四个腔室：右心房、右心室、左心房和左心室。瓣膜防止血液倒流。
• The left ventricle has a thicker muscular wall because it pumps blood at higher pressure around the whole body. 左心室肌肉壁更厚，因为它以更高的压力将血液泵送到全身。

• Deoxygenated blood enters the right atrium from the vena cava, moves to the right ventricle and is pumped to the lungs via the pulmonary artery. Oxygenated blood returns to the left atrium via the pulmonary vein and is pumped out through the aorta. 缺氧血从腔静脉进入右心房，经右心室通过肺动脉泵向肺部。富氧血通过肺静脉返回左心房，再经主动脉泵出。

5. Components of Blood and Their Functions | 血液成分与功能

• Red blood cells are biconcave discs with no nucleus, packed with haemoglobin that binds oxygen in the lungs and releases it in tissues. 红细胞是双凹圆盘状、无核，充满血红蛋白，能在肺部结合氧气，在组织中释放氧气。
• White blood cells defend the body against pathogens. Phagocytes engulf microorganisms, and lymphocytes produce antibodies. 白细胞保护身体免受病原体侵害。吞噬细胞吞噬微生物，淋巴细胞产生抗体。
• Platelets are small cell fragments that help blood clot, preventing excessive bleeding and entry of pathogens. 血小板是小的细胞碎片，有助于血液凝固，防止过度出血和病原体进入。
• Plasma is a pale yellow liquid that transports red and white cells, platelets, dissolved nutrients (glucose, amino acids), carbon dioxide, urea, hormones and heat. 血浆是淡黄色液体，运输红细胞、白细胞、血小板、溶解的营养物质（葡萄糖、氨基酸）、二氧化碳、尿素、激素和热量。

6. Respiratory System and Gas Exchange | 呼吸系统与气体交换

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