Year 7 CAIE Biology: Essential Core Concepts Review | Year 7 CAIE 生物：核心知识点梳理

📚 Year 7 CAIE Biology: Essential Core Concepts Review | Year 7 CAIE 生物：核心知识点梳理

Welcome to the Year 7 CAIE Biology revision guide. This article summarises the essential core concepts you need to master, from the characteristics of life to human body systems, classification, ecology and health. Each section presents key facts with clear explanations to support your learning and exam preparation.

欢迎阅读 Year 7 CAIE 生物复习指南。本文梳理了必须掌握的核心知识点，从生命特征到人体系统、分类、生态与健康，每部分都提供清晰解释，助力你的学习与备考。

1. Characteristics of Living Things | 生物的特征

All living organisms share seven life processes, often remembered by the acronym MRS GREN. These processes define what it means to be alive and apply to both plants and animals.

所有生物都共有七种生命过程，常用首字母缩写 MRS GREN 来记忆。这些过程定义了生物体的本质，适用于植物和动物。

Movement: All living things move. Animals move their entire bodies to find food or escape danger. Plants move more slowly, for example, turning leaves towards sunlight or roots towards water.

运动：所有生物都会运动。动物移动整个身体以寻找食物或躲避危险。植物移动较慢，例如叶子转向阳光或根部向水生长。

Respiration: This is the chemical process that releases energy from food inside cells. Every living cell carries out respiration, usually using oxygen and glucose, to produce energy for all life activities.

呼吸作用：这是细胞内从食物释放能量的化学过程。每个活细胞都进行呼吸作用，通常利用氧气和葡萄糖，为一切生命活动提供能量。

Sensitivity: Living organisms can detect and respond to changes in their surroundings. A rabbit runs when it senses danger; a plant shoot bends towards light. These reactions are called responses.

感应：生物能探测并回应环境变化。兔子察觉到危险就跑；植物嫩芽向光弯曲。这些反应称为响应。

Growth: All organisms increase in size and mass by adding new cells or enlarging existing ones. Growth is permanent and continues through much of an organism’s life.

生长：所有生物通过增加新细胞或使现有细胞变大，永久地增大体积和质量。生长几乎贯穿生物的整个生命过程。

Reproduction: Living things produce offspring, ensuring the continuation of their species. Reproduction may be sexual, involving two parents, or asexual, requiring only one parent.

繁殖：生物产生后代，确保物种延续。繁殖可以是有性的，涉及两个亲本，也可以是无性的，只需一个亲本。

Excretion: Organisms must remove toxic waste products generated by their own metabolism. In humans, the kidneys filter blood and produce urine; plants excrete oxygen and water vapour.

排泄：生物必须排除自身代谢产生的有毒废物。人体中，肾脏过滤血液并形成尿液；植物则排出氧气和水蒸气。

Nutrition: All living things need nutrients to supply energy and raw materials for growth. Animals obtain food by eating other organisms, while plants make their own food by photosynthesis.

营养：所有生物都需要营养物质来提供能量和生长原料。动物通过摄食其他生物获取食物，植物则通过光合作用制造食物。

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2. Cells – The Basic Units of Life | 细胞——生命的基本单位

Cells are the smallest units that can carry out all seven life processes. Some organisms exist as single cells, such as bacteria and amoebae, while most visible organisms are multicellular, built from many specialised cells working together.

细胞是能完成全部七种生命过程的最小单位。一些生物以单细胞形式存在，如细菌和变形虫，而大多数可见生物是多细胞的，由许多特化的细胞协同构成。

An animal cell typically contains a cell membrane, a nucleus, cytoplasm and mitochondria. The cell membrane acts as a selective barrier, controlling which substances enter and exit. The nucleus houses the organism’s genetic material (DNA) and directs all cellular activities. Cytoplasm is a jelly-like fluid where most chemical reactions occur. Rod-shaped mitochondria are the ‘powerhouses’ that release energy via respiration.

动物细胞通常含有细胞膜、细胞核、细胞质和线粒体。细胞膜作为选择透过性屏障，控制物质进出。细胞核包含遗传物质 (DNA)，指导所有细胞活动。细胞质是胶状液体，大多数化学反应在此发生。杆状的线粒体是通过呼吸作用释放能量的“动力工厂”。

A plant cell possesses all the structures found in animal cells, plus three additional components: a rigid cell wall made of cellulose for support, chloroplasts containing chlorophyll to capture light energy for photosynthesis, and a large permanent vacuole filled with cell sap that helps maintain turgor pressure.

植物细胞除了拥有动物细胞的所有结构外，还有三个额外的组分：由纤维素构成的坚硬细胞壁起支撑作用；含有叶绿素的叶绿体捕获光能进行光合作用；以及充满细胞液的大液泡，帮助维持膨压。

Below is a quick comparison of the two cell types:

以下是两种细胞类型的快速对比：

Feature	Animal cell	Plant cell
Cell membrane	Present	Present
Nucleus	Present	Present
Cytoplasm	Present	Present
Mitochondria	Present	Present
Cell wall	Absent	Present (cellulose)
Chloroplasts	Absent	Present (in many cells)
Large permanent vacuole	Absent	Present

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3. Specialised Cells | 特殊细胞

In multicellular organisms, cells become adapted to perform specific functions. This is called cell specialisation, and the specialised cell’s shape, structure and contents match its job.

在多细胞生物中，细胞会适应并执行特定功能，这称为细胞特化。特化细胞的形状、结构和内含物均与其功能相匹配。

Red blood cells carry oxygen throughout the body. They are biconcave discs with no nucleus, which provides more space for haemoglobin – the red pigment that binds oxygen. Their shape also increases surface area for faster oxygen diffusion.

红细胞负责在全身运送氧气。它们是双凹圆盘状，无细胞核，这为血红蛋白提供了更大空间——血红蛋白是结合氧气的红色色素，其形状亦增大了表面积以加快氧气扩散。

Root hair cells are found in the tips of plant roots. Each cell has a long, thin extension that greatly increases the surface area for absorbing water and dissolved minerals from the soil by osmosis and active transport.

根毛细胞位于植物根尖。每个细胞都有细长的突起，极大地增加了表面积，便于通过渗透和主动运输从土壤中吸收水分和溶解的矿物质。

Sperm cells are the male gametes. They have a streamlined head containing the nucleus (with half the genetic material) and a long tail (flagellum) that propels the sperm towards the egg. The middle section is packed with mitochondria to supply the energy needed to swim.

精子细胞是雄性配子。它们具有流线型的头部，内含细胞核（带有半数遗传物质），并有一条长尾（鞭毛）推动精子向卵子游动。中段充满线粒体，以提供游泳所需的能量。

Nerve cells, or neurons, are specialised to transmit electrical impulses quickly. They have a cell body with branching dendrites to receive signals and a long axon covered in a fatty myelin sheath that speeds up signal conduction.

神经细胞（神经元）特化为快速传递电信号。它们有胞体和分支状的树突用于接收信号，以及一条被脂质髓鞘包裹的长轴突，能加速信号传导。

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4. Levels of Organisation: From Cells to Systems | 组织的层次：从细胞到系统

In large organisms, cells are organised into increasingly complex levels: cells → tissues → organs → organ systems → organism. Each level builds on the one before it, enabling the body to carry out complex functions.

在大型生物中，细胞组织成越来越复杂的层次：细胞 → 组织 → 器官 → 器官系统 → 生物体。每一层次都建立在前一层次之上，使身体能执行复杂的功能。

A tissue is a group of similar cells working together to perform a specific function. For example, muscle tissue consists of many muscle cells that contract to cause movement. Animal tissues also include epithelial tissue, connective tissue and nervous tissue.

组织是一群相似的细胞协同执行特定功能。例如，肌肉组织由许多肌肉细胞组成，通过收缩引起运动。动物组织还包括上皮组织、结缔组织和神经组织。

An organ is a structure made of different tissues that collaborate to carry out a major job. The stomach, for instance, contains muscular tissue to churn food, glandular tissue to release enzymes, and epithelial tissue to line and protect its inner surface.

器官是由不同组织构成的、协同执行重要功能的结构。例如，胃含有肌肉组织搅拌食物，腺体组织释放酶，上皮组织衬里并保护其内壁。

Organs work together in organ systems. The digestive system includes the mouth, oesophagus, stomach, intestines and liver, all cooperating to break down food and absorb nutrients. Other systems include the circulatory, respiratory and skeletal systems.

器官在器官系统中共同工作。消化系统包括口腔、食道、胃、肠和肝脏，它们协同分解食物并吸收营养。其他系统还包括循环系统、呼吸系统和骨骼系统。

Plants also show levels of organisation. Palisade mesophyll cells (photosynthetic cells) form leaf tissue, which combines with other tissues to make a leaf – an organ. Leaves, stems and roots are organs that build up the shoot system and root system of a whole plant.

植物也表现出层次。栅栏叶肉细胞（光合细胞）构成叶组织，与其他组织共同形成叶这一器官。叶、茎和根等器官构成整株植物的地上系统和根系。

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5. Classification of Living Organisms | 生物分类

Scientists classify organisms into groups based on shared features. This helps us identify species, understand evolutionary relationships and communicate clearly about biodiversity. The largest groupings are called kingdoms.

科学家根据共同特征将生物分门别类，这有助于鉴定物种、理解进化关系，并清楚地交流生物多样性信息。最大的分类群称为界。

The five-kingdom system commonly taught includes: Animals (multicellular, heterotrophic, no cell walls), Plants (multicellular, autotrophic, cell walls of cellulose), Fungi (mostly multicellular, heterotrophic, cell walls of chitin), Protists (mostly unicellular eukaryotes like amoeba), and Prokaryotes (unicellular organisms without a nucleus, such as bacteria).

通常讲授的五界系统包括：动物界（多细胞、异养、无细胞壁），植物界（多细胞、自养、纤维素细胞壁），真菌界（多数多细胞、异养、几丁质细胞壁），原生生物界（多为单细胞真核生物，如变形虫），原核生物界（无细胞核的单细胞生物，如细菌）。

The animal kingdom is divided into vertebrates and invertebrates. Vertebrates have a backbone and are further grouped into five classes: mammals (fur/hair, produce milk, warm-blooded), birds (feathers, lay hard-shelled eggs, warm-blooded), reptiles (dry scaly skin, lay soft-shelled eggs, cold-blooded), amphibians (moist skin, lay eggs in water, cold-blooded) and fish (scales, gills, fins, cold-blooded).

动物界分为脊椎动物和无脊椎动物。脊椎动物有脊柱，可进一步分为五个纲：哺乳类（体被毛/毛发、产母乳、温血），鸟类（有羽毛、产硬壳卵、温血），爬行类（干燥鳞片皮肤、产软壳卵、冷血），两栖类（潮湿皮肤、水中产卵、冷血）和鱼类（有鳞片、鳃和鳍、冷血）。

Classification keys, especially dichotomous keys, are tools used to identify organisms. They present a series of two-choice questions about observable characteristics. By following the correct choices, you can narrow down and determine a species’ identity.

分类检索表，尤其是二分键，是用来鉴定生物的工具。它们提出一系列关于可观察特征的两个选择问题。通过选择正确选项，你可以逐步缩小范围并确定物种身份。

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6. Plants: Structure, Transport and Reproduction | 植物：结构、运输与繁殖

Flowering plants are the most familiar group in the plant kingdom. Their body is divided into three main organs: roots anchor the plant and absorb water and minerals; stems support the plant and transport substances; leaves are the main sites of photosynthesis.

开花植物是植物界中最常见的类群。它们的身体分为三个主要器官：根固定植物并吸收水分和矿物质；茎支撑植物并运输物质；叶是光合作用的主要场所。

Plants have transport systems called xylem and phloem. Xylem vessels carry water and dissolved minerals from the roots up to the leaves. Phloem tubes transport glucose and other nutrients made in the leaves to all other parts of the plant for growth or storage.

植物具有被称为木质部和韧皮部的运输系统。木质部导管将水和溶解的矿物质从根向上输送到叶。韧皮部管道将叶中制造的葡萄糖和其他营养物质输送到植物的所有其他部位，用于生长或储存。

The flower is the reproductive organ. Its main parts include brightly coloured petals to attract pollinators, the male stamens (anther and filament) that produce pollen, and the female carpel (stigma, style and ovary) that contains ovules. Pollination is the transfer of pollen from anther to stigma.

花是繁殖器官。其主要结构包括色彩鲜艳的花瓣以吸引传粉者，产生花粉的雄性雄蕊（花药和花丝），以及含有胚珠的雌性雌蕊（柱头、花柱和子房）。传粉即花粉从花药传到柱头的过程。

After pollination, a pollen tube grows down to the ovary and delivers male nuclei to the ovule. Fertilisation occurs when a male nucleus fuses with an egg cell to form a zygote. The ovary develops into a fruit, protecting the seeds, which can be dispersed by wind, animals, water or explosive mechanisms.

传粉后，花粉管向下长到子房，将雄性细胞核送至胚珠。当雄核与卵细胞融合形成合子时，受精便发生了。子房发育成果实，保护种子。种子可通过风、动物、水或弹射机制传播。

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7. Breathing and Gas Exchange in Humans | 人类的呼吸与气体交换

Breathing is the physical process of moving air into and out of the lungs, while gas exchange refers to the diffusion of oxygen into the blood and carbon dioxide out of the blood. You do not need to confuse breathing with cellular respiration – they are linked but different.

呼吸运动是将空气吸入和排出肺部的物理过程，而气体交换则指氧气扩散进血液和二氧化碳从血液中扩散出来。切勿将呼吸运动与细胞呼吸混淆——它们相互关联但并不相同。

Air enters through the nose and mouth, passes the pharynx, larynx and trachea. The trachea splits into two bronchi, which branch into narrower bronchioles, ending in tiny air sacs called alveoli. The walls of the alveoli are only one cell thick and surrounded by capillaries.

空气通过口鼻进入，经咽、喉和气管。气管分支为两条支气管，再分为更细的细支气管，末端为微小的气室——肺泡。肺泡壁仅一个细胞厚，并被毛细血管包围。

In the alveoli, oxygen diffuses from the air into the blood, while carbon dioxide diffuses from the blood into the alveolar air to be exhaled. This exchange occurs because of concentration gradients – there is more oxygen in the inhaled air and more carbon dioxide in the arriving blood.

在肺泡中，氧气从空气扩散进血液，而二氧化碳从血液扩散到肺泡气体中被呼出。这种交换依赖于浓度梯度——吸入气体中氧气浓度较高，而到来的

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