Animal Biology Key Concepts Review | IB WJEC 科学：动物 考点精讲

📚 Animal Biology Key Concepts Review | IB WJEC 科学：动物 考点精讲

Animals are multicellular, eukaryotic organisms that form a major component of the biosphere. This revision guide covers essential topics from the IB and WJEC specifications, including animal diversity, physiology, reproduction, and ecology. Understanding these concepts will help you master exam-style questions and build a strong foundation in biological sciences.

动物是多细胞真核生物，是生物圈的重要组成部分。本考点精讲涵盖 IB 和 WJEC 课程大纲中的核心主题，包括动物多样性、生理学、生殖和生态学。理解这些概念将帮助你掌握考试题型，为生物科学打下坚实基础。

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1. Characteristics of Animals | 动物的基本特征

All animals share several key characteristics: they are multicellular, heterotrophic, and eukaryotic. Most animals reproduce sexually, possess specialized tissues such as nervous and muscle tissue, and exhibit a life cycle that includes a blastula stage during embryonic development. They lack rigid cell walls, which allows for greater mobility.

所有动物都有几个关键特征：它们是多细胞、异养的真核生物。大多数动物进行有性生殖，拥有神经组织和肌肉组织等特化组织，并在胚胎发育过程中经历囊胚阶段。它们缺乏坚硬的细胞壁，这使得它们具有更大的运动能力。

Animals obtain nutrients by ingestion, unlike fungi which absorb nutrients externally. They store carbohydrates as glycogen. The evolutionary trend in animals shows increasing complexity, with the development of tissues, organs, and organ systems such as digestive, circulatory, and respiratory systems.

动物通过摄食获取营养，与真菌通过外部吸收不同。它们以糖原形式储存碳水化合物。动物的进化趋势表现为复杂性逐渐增加，出现了组织、器官和系统，如消化系统、循环系统和呼吸系统。

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2. Animal Classification and Phylogeny | 动物分类与系统发育

Animal classification is based on morphological, molecular, and developmental data. The animal kingdom is divided into major phyla, including Porifera (sponges), Cnidaria (jellyfish, corals), Platyhelminthes (flatworms), Annelida (segmented worms), Mollusca (snails, clams, octopuses), Arthropoda (insects, crustaceans), Echinodermata (starfish), and Chordata (vertebrates).

动物分类基于形态学、分子和发育数据。动物界分为主要门类，包括多孔动物门（海绵）、刺胞动物门（水母、珊瑚）、扁形动物门（扁虫）、环节动物门（分节蠕虫）、软体动物门（蜗牛、蛤蜊、章鱼）、节肢动物门（昆虫、甲壳动物）、棘皮动物门（海星）和脊索动物门（脊椎动物）。

Phylogenetic trees constructed using DNA sequencing help clarify evolutionary relationships. Key features used in classification include body symmetry (radial vs. bilateral), presence of coelom (acoelomate, pseudocoelomate, coelomate), embryological development (protostome vs. deuterostome), and segmentation.

利用 DNA 测序构建的系统发育树有助于阐明进化关系。分类所用的关键特征包括体对称性（辐射对称与两侧对称）、体腔的有无（无体腔、假体腔、真体腔）、胚胎发育方式（原口动物与后口动物）以及是否分节。

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3. Animal Tissues and Organ Systems | 动物组织与器官系统

Animal bodies are organised into four main tissue types: epithelial, connective, muscle, and nervous. Epithelial tissue covers body surfaces and lines cavities; connective tissue supports and binds other tissues; muscle tissue enables movement through contraction; nervous tissue transmits electrical impulses for coordination.

动物身体由四种基本组织构成：上皮组织、结缔组织、肌肉组织和神经组织。上皮组织覆盖体表并衬于体腔；结缔组织支持和连接其他组织；肌肉组织通过收缩实现运动；神经组织传递电冲动以协调机体活动。

Organ systems work together to maintain homeostasis. The digestive system breaks down food and absorbs nutrients. The circulatory system transports oxygen, nutrients, and waste products. In mammals, a four-chambered heart separates oxygenated and deoxygenated blood, increasing metabolic efficiency.

器官系统协同工作以维持内稳态。消化系统分解食物并吸收营养。循环系统运输氧气、营养和废物。在哺乳动物中，四腔心脏将含氧血和缺氧血分开，提高了代谢效率。

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4. Nutrition and Digestion | 营养与消化

Animals are heterotrophs and can be classified by diet: herbivores, carnivores, and omnivores. Digestion involves both mechanical and chemical breakdown of food. In humans and many vertebrates, the alimentary canal includes the mouth, oesophagus, stomach, small intestine, large intestine, and associated glands like the liver and pancreas.

动物是异养生物，可按食性分为植食动物、肉食动物和杂食动物。消化包括食物的机械性和化学性分解。在人类和许多脊椎动物中，消化道包括口腔、食道、胃、小肠、大肠以及肝、胰等附属腺体。

Enzymatic hydrolysis is central to digestion. For example, amylase in saliva breaks down starch into maltose; pepsin in the stomach acts on proteins; and lipase with bile salts emulsifies fats in the small intestine. Villi and microvilli in the small intestine dramatically increase the surface area for absorption.

酶促水解是消化的核心。例如，唾液中的淀粉酶将淀粉分解为麦芽糖；胃中的胃蛋白酶作用于蛋白质；脂肪酶在胆汁盐的帮助下乳化脂肪。小肠中的绒毛和微绒毛极大地增加了吸收表面积。

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

Gas exchange is the process by which oxygen is taken in and carbon dioxide is released. Animals use various respiratory surfaces: gills in fish, tracheae in insects, lungs in mammals and birds, and moist skin in amphibians. These surfaces are thin, moist, and highly vascularised to facilitate diffusion.

气体交换是摄入氧气和排出二氧化碳的过程。动物利用不同的呼吸表面：鱼类的鳃、昆虫的气管、哺乳动物和鸟类的肺以及两栖动物湿润的皮肤。这些表面薄、湿润且血管丰富，有利于扩散。

The human respiratory system consists of the trachea, bronchi, bronchioles, and alveoli. Inhaled air passes through these structures to reach the alveoli, where oxygen diffuses into blood capillaries. Haemoglobin in red blood cells binds oxygen for transport. Ventilation is driven by the diaphragm and intercostal muscles.

人体呼吸系统由气管、支气管、细支气管和肺泡组成。吸入的空气经过这些结构到达肺泡，氧气在此扩散进毛细血管。红细胞中的血红蛋白结合氧气进行运输。通气由膈肌和肋间肌驱动。

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6. Circulatory Systems | 循环系统

Circulatory systems can be open or closed. Insects and some molluscs have an open circulatory system, where blood (haemolymph) bathes organs directly. Vertebrates and annelids have a closed circulatory system, with blood confined to vessels, allowing higher pressure and more efficient nutrient delivery.

循环系统可以是开放式或封闭式。昆虫和某些软体动物具有开放式循环系统，血液（血淋巴）直接浸润器官。脊椎动物和环节动物具有封闭式循环系统，血液局限于血管内，可产生较高压力，输送营养更高效。

The mammalian heart consists of two atria and two ventricles. The right side pumps deoxygenated blood to the lungs (pulmonary circuit), while the left side pumps oxygenated blood to the body (systemic circuit). Valves prevent backflow, and the cardiac cycle is initiated by the sinoatrial node, the natural pacemaker.

哺乳动物心脏由两个心房和两个心室组成。右侧将缺氧血泵入肺部（肺循环），左侧将含氧血泵至全身（体循环）。瓣膜防止回流，心动周期由窦房结（天然起搏器）启动。

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7. Reproduction and Development | 生殖与发育

Animals exhibit both sexual and asexual reproduction. Sexual reproduction involves the fusion of gametes (sperm and egg) to form a zygote, which undergoes mitosis and differentiation. It promotes genetic variation. Asexual methods such as budding (hydra) and fragmentation (planaria) produce genetically identical offspring.

动物可进行有性生殖和无性生殖。有性生殖涉及配子（精子和卵子）融合形成受精卵，受精卵经历有丝分裂和分化。它促进了遗传变异。出芽生殖（水螅）和断裂生殖（涡虫）等无性方式产生遗传上相同的后代。

In mammals, internal fertilisation is followed by gestation. The placenta facilitates nutrient and gas exchange between mother and foetus. The human reproductive system is regulated by hormones such as testosterone, oestrogen, and progesterone, which control gamete production and the menstrual cycle.

在哺乳动物中，体内受精后进行妊娠。胎盘促进母体与胎儿之间的营养和气体交换。人类生殖系统由睾酮、雌激素和孕酮等激素调控，这些激素控制配子的产生和月经周期。

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8. Nervous and Endocrine Control | 神经与内分泌调控

The nervous system provides rapid, short-term responses to stimuli. Neurons transmit impulses via action potentials. A synapse is the junction between two neurons, where neurotransmitters like acetylcholine propagate the signal. The central nervous system (brain and spinal cord) integrates information and coordinates responses.

神经系统对刺激做出快速、短期的反应。神经元通过动作电位传递冲动。突触是两神经元之间的连接点，乙酰胆碱等神经递质在此传播信号。中枢神经系统（脑和脊髓）整合信息并协调反应。

The endocrine system uses hormones for slower, longer-lasting regulation. Key endocrine glands include the pituitary, thyroid, adrenal, and pancreas. Insulin and glucagon from the pancreas regulate blood glucose through negative feedback. Together, the nervous and endocrine systems maintain homeostasis.

内分泌系统利用激素进行较慢、持久的调节。主要内分泌腺包括垂体、甲状腺、肾上腺和胰腺。胰腺分泌的胰岛素和胰高血糖素通过负反馈调节血糖。神经系统和内分泌系统共同维持内稳态。

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9. Animal Behaviour and Ecology | 动物行为与生态学

Animal behaviour can be innate (genetically programmed) or learned. Innate behaviours include reflexes, taxes (directional movement towards a stimulus), and fixed action patterns. Learned behaviours, such as habituation, imprinting, and classical conditioning, allow animals to adapt to their environment.

动物行为可以是先天的（由基因决定）或后天习得的。先天行为包括反射、趋性（朝向刺激的定向运动）和固定动作模式。习得行为，如习惯化、印记和经典条件反射，使动物能够适应环境。

Ecology studies interactions between animals and their environment. Population size is affected by birth rate, death rate, immigration, and emigration. Energy flows through trophic levels: producers → primary consumers → secondary consumers. Only about 10% of energy is transferred between levels, limiting food chain length.

生态学研究动物与其环境之间的相互作用。种群大小受出生率、死亡率、迁入和迁出的影响。能量流经营养级：生产者→初级消费者→次级消费者。各营养级之间只有约10%的能量传递，这限制了食物链的长度。

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10. Evolution and Adaptation | 进化与适应

Natural selection is the primary mechanism of evolution. Individuals with advantageous traits are more likely to survive and reproduce, passing those traits to the next generation. Over time, this leads to adaptation—the change in a population to become better suited to its environment.

自然选择是进化的主要机制。具有有利性状的个体更可能生存和繁殖，并将这些性状传递给下一代。随着时间的推移，这导致了适应——种群变得更适合其环境的变化。

Examples of animal adaptations include camouflage in stick insects, the long neck of a giraffe for reaching high foliage, and antifreeze proteins in Antarctic fish. Speciation occurs when populations become reproductively isolated, often due to geographical barriers (allopatric speciation) or genetic differences within the same area (sympatric speciation).

动物适应的例子包括竹节虫的伪装、长颈鹿的长颈以够到高处树叶，以及南极鱼类的抗冻蛋白。当种群发生生殖隔离时，物种形成即发生，这通常由地理障碍（异域物种形成）或同一区域内遗传差异（同域物种形成）引起。

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