Year 8 Cambridge Biology Mock Test Analysis | Year 8 剑桥生物单元测试模拟卷解析

📚 Year 8 Cambridge Biology Mock Test Analysis | Year 8 剑桥生物单元测试模拟卷解析

This article provides a detailed analysis of a mock unit test for Year 8 Cambridge Biology. Each question is broken down to clarify key concepts, common misconceptions, and correct reasoning, helping you revise effectively.

本文对一份 Year 8 剑桥生物单元模拟测试卷进行详细解析。通过对每道题目的拆解，帮助你理清核心概念、纠正常见误区、掌握正确解题思路，为复习提供清晰的引导。

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1. Cell Structure and Organelles | 细胞结构与细胞器

Question: Which of the following structures is found in a plant cell but NOT in an animal cell? A) Nucleus B) Cell membrane C) Chloroplast D) Mitochondria

问题：下列哪个结构存在于植物细胞中，但不存在于动物细胞中？A) 细胞核 B) 细胞膜 C) 叶绿体 D) 线粒体

Answer: C) Chloroplast

答案：C) 叶绿体

Chloroplasts are the organelles where photosynthesis takes place. They contain the green pigment chlorophyll, which uses light energy to convert carbon dioxide and water into glucose and oxygen. Animal cells never possess chloroplasts.

叶绿体是进行光合作用的细胞器。它含有绿色色素叶绿素，可利用光能将二氧化碳和水转化为葡萄糖和氧气。动物细胞中绝不含叶绿体。

Incorrect options: Both plant and animal cells have a nucleus (controls activities and stores DNA), a cell membrane (controls entry and exit of substances), and mitochondria (site of aerobic respiration). Therefore, these structures do not distinguish plant cells from animal cells.

错误选项解析：植物与动物细胞都具有细胞核（控制生命活动并储存遗传物质）、细胞膜（控制物质进出）和线粒体（有氧呼吸的场所），因此这些结构不能作为植物细胞独有的特征。

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2. Transport in Plants: Xylem and Phloem | 植物运输：木质部与韧皮部

Question: Which plant tissue transports water and dissolved minerals upwards from the roots? A) Phloem B) Xylem C) Epidermis D) Mesophyll

问题：哪一种植物组织负责将水和溶解的矿物质从根部向上运输？A) 韧皮部 B) 木质部 C) 表皮 D) 叶肉

Answer: B) Xylem

答案：B) 木质部

Xylem vessels are thick-walled tubes formed from dead cells. They carry water and mineral ions from the roots to the stems and leaves in one direction. This movement is driven by transpiration pull from the leaves.

木质部导管是由死细胞构成的厚壁管状结构，能将水和矿质离子从根部单向运送到茎和叶。这一运输过程依靠叶片的蒸腾拉力驱动。

Phloem, on the other hand, transports sugars and amino acids made in the leaves to other parts of the plant in both upward and downward directions. This process is called translocation. Epidermis is a protective outer layer, and mesophyll is the site of photosynthesis in the leaf.

韧皮部则负责将叶片制造的糖类和氨基酸以双向运输的方式输送到植物各个部位，这一过程称为转运。表皮是起保护作用的外层组织，叶肉是叶片中进行光合作用的部位。

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

Question: Which feature of the alveoli in the lungs allows efficient gas exchange? A) Thick, muscular walls B) Small surface area C) One-cell-thick walls D) Lack of blood supply

问题：肺部肺泡的哪一特征有利于高效的气体交换？A) 厚实的肌肉壁 B) 表面积小 C) 单细胞厚度的薄壁 D) 缺乏血液供应

Answer: C) One-cell-thick walls

答案：C) 单细胞厚度的薄壁

Alveoli have walls that are only one cell thick, which minimises the diffusion distance for oxygen and carbon dioxide. They also provide a very large total surface area, a moist inner surface, and are surrounded by dense networks of capillaries. All these features speed up gas exchange.

肺泡壁仅有一个细胞的厚度，这使得氧气和二氧化碳的扩散距离极短。此外，肺泡还能提供巨大的总表面积、湿润的内壁，并且被密集的毛细血管网包裹。这些特征共同加速了气体交换。

Thick walls would slow diffusion; a small surface area would reduce the amount of gases exchanged; rich blood supply is essential and is present, not absent. Therefore, options A, B and D are incorrect.

肺泡壁增厚会减慢扩散速度；小的表面积会使气体交换量减少；而肺泡周围的确有丰富的血液供应，并非缺乏。因此选项 A、B 和 D 都是错误的。

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4. Flower Structure and Pollination | 花的结构与传粉

Question: In a flower, which part produces pollen grains? A) Stigma B) Ovary C) Anther D) Petal

问题：在花的结构中，哪个部位产生花粉粒？A) 柱头 B) 子房 C) 花药 D) 花瓣

Answer: C) Anther

答案：C) 花药

The anther is the male part of the flower, located at the tip of the stamen. It contains pollen sacs that produce and release pollen grains. Pollen carries the male gametes necessary for fertilisation.

花药是花的雄性部分，位于雄蕊的顶端，内含花粉囊，用于产生和释放花粉粒。花粉携带授精所需的雄配子。

The stigma is the sticky surface that receives pollen; the ovary contains ovules and develops into the fruit; petals attract pollinators with their colour and scent. None of these structures produce pollen.

柱头是接受花粉的黏性表面；子房含有胚珠，将来发育成果实；花瓣借助颜色和气味吸引传粉者。这些结构均不产生花粉。

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5. Food Chains and Predator-Prey Relationships | 食物链与捕食关系

what is the most likely immediate effect on the rabbit population if all foxes are removed? decreases C) The rabbit population increases D) The rabbit population dies out immediately

问题：在食物链 草 → 兔 → 狐 中，如果所有狐狸都被移走，最直接的后果是什么？A) 兔子的数量保持不变 B) 兔子的数量减少 C) 兔子的数量增加 D) 兔子立即灭绝

Answer: C) The rabbit population increases

答案：C) 兔子的数量增加

Removing the foxes removes the only predator of the rabbits, so fewer rabbits will be eaten. As a result, the rabbit population will rise rapidly, at least in the short term.

移走狐狸意味着移除了兔子唯一的天敌，因此被吃掉的兔子数量减少，短期内兔子的数量会迅速增加。

However, the increase in rabbits may lead to overgrazing of grass, causing a food shortage later. This could eventually bring the rabbit population down again. The choice 'dies out immediately' is unrealistic, and 'stays the same' ignores the predator-prey dynamic.

然而，兔子数量的激增可能导致过度啃食青草，进而引发食物短缺，最终使兔子数量再度下降。选项“立即灭绝”不符合实际，而“保持不变”则忽略了捕食者与猎物的动态关系。

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6. Digestion and Enzymes | 消化与酶

Question: Which type of nutrient is mainly required for growth and repair of body tissues? A) Carbohydrate B) Protein C) Lipids (fats) D) Vitamin C

问题：哪种营养物质主要用于身体组织的生长和修复？A) 碳水化合物 B) 蛋白质 C) 脂类（脂肪）D) 维生素 C

Answer: B) Protein

答案：B) 蛋白质

Proteins are made up of amino acids and are essential for building new cells, repairing damaged tissues, and making enzymes and hormones. Growing children and teenagers have particularly high protein requirements.

蛋白质由氨基酸构成，对于构建新细胞、修复受损组织以及制造酶和激素至关重要。处于生长发育期的儿童和青少年对蛋白质的需求尤其高。

Carbohydrates provide the body's main source of energy; lipids provide insulation and energy storage; vitamin C helps maintain healthy skin and gums and prevents scurvy, but it is not primarily used for growth and repair.

碳水化合物是人体的主要能量来源；脂类用于保温与能量储存；维生素 C 有助于维持皮肤和牙龈的健康并预防坏血病，但它并不是生长与修复的主要原料。

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7. Photosynthesis Experiment: Testing a Leaf for Starch | 光合作用实验：检测叶片淀粉

Question: In the starch test, why is a leaf boiled in ethanol? A) To kill the leaf cells B) To remove chlorophyll (the green colour) C) To make the leaf soft D) To stop photosynthesis

问题：在淀粉检测实验中，为什么要用乙醇煮沸叶片？A) 杀死叶细胞 B) 去除叶绿素（绿色） C) 使叶片变软 D) 停止光合作用

Answer: B) To remove chlorophyll

答案：B) 去除叶绿素

Boiling the leaf in ethanol dissolves the chlorophyll, turning the leaf white or pale. This decolourisation is essential so that the blue-black colour of the iodine-starch complex can be seen clearly without the green pigment masking it.

用乙醇煮沸叶片可以溶解叶绿素，使叶片变为白色或浅色。这一脱色步骤非常关键，以便后续用碘液测试时，能够清晰观察到淀粉与碘形成的蓝黑色，而不被绿色色素掩盖。

The leaf is first boiled in water to soften it and break down cell membranes; ethanol is then used in a water bath (never directly over a flame) to extract chlorophyll. The step of killing cells is partly done by boiling in water, but the main purpose of ethanol is decolourisation.

实验步骤中，叶片先经水煮使其软化并破坏细胞膜，随后在热水浴中利用乙醇提取叶绿素（切勿直接在火焰上加热乙醇）。杀死细胞的作用主要由水煮完成，而使用乙醇的主要目的是脱色。

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8. Microorganisms and Disease | 微生物与疾病

Question: The common cold and influenza are caused by which type of pathogen? A) Bacterium B) Virus C) Fungus D) Protist

问题：普通感冒和流感是由哪一类病原体引起的？A) 细菌 B) 病毒 C) 真菌 D) 原生生物

Answer: B) Virus

答案：B) 病毒

Viruses are extremely small infectious agents that can only reproduce inside living host cells. They cause many common illnesses, including the cold, influenza, and chickenpox. Antibiotics are ineffective against viruses.

病毒是极其微小的感染性颗粒，只能在活的宿主细胞内繁殖。它们会引发多种常见疾病，包括感冒、流感和水痘。抗生素对病毒无效。

Bacteria are single-celled organisms that can cause diseases such as cholera and tuberculosis, but they are not responsible for the common cold. Fungi can cause conditions like athlete's foot, and protists include organisms such as Plasmodium that cause malaria.

细菌是单细胞生物，会引起霍乱、肺结核等疾病，但与普通感冒无关。真菌可导致足癣等感染，而原生生物中包括引起疟疾的疟原虫。

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