Evolution: GCSE WJEC Science Revision | 进化考点精讲

📚 Evolution: GCSE WJEC Science Revision | 进化考点精讲

Welcome to this focused revision guide on evolution, designed specifically for GCSE WJEC Science. Evolution explains the vast diversity of life on Earth and how species change over time. This article breaks down key concepts such as natural selection, evidence for evolution, speciation, and the development of resistance in organisms, all aligned with the WJEC specification. Use this resource to reinforce your understanding and prepare effectively for your exams.

欢迎阅读这篇专为 GCSE WJEC 科学设计的进化复习指南。进化可以解释地球生物的巨大多样性以及物种如何随时间发生变化。本文梳理了自然选择、进化证据、物种形成以及生物抗药性发展等核心概念，内容完全贴合 WJEC 考试大纲。利用这份材料巩固理解，为你的考试做好充分准备。

1. What is Evolution? | 什么是进化？

Evolution is the change in the inherited characteristics of biological populations over successive generations. These changes are driven by processes such as natural selection, where organisms with advantageous traits are more likely to survive and reproduce. Over long periods, evolution can lead to the formation of new species, explaining the diversity of life we see today.

进化是指生物种群逐代累积的遗传特征变化。这些变化由自然选择等过程驱动，拥有有利性状的生物更有可能存活和繁殖。经过漫长的时间，进化可以导致新物种的形成，这解释了我们今天看到的生物多样性。

It is important to remember that individuals do not evolve during their lifetime. Evolution acts on populations, not single organisms. The raw material for evolution is genetic variation within a population, which arises from mutations and sexual reproduction.

务必牢记，个体在其一生中并不会发生进化。进化作用于种群层面，而非单一生物体。进化的原始材料是种群内的遗传变异，这些变异来源于基因突变和有性繁殖。

2. Darwin’s Theory of Natural Selection | 达尔文的自然选择理论

Charles Darwin proposed the theory of evolution by natural selection after observing wildlife on his voyage on HMS Beagle. He noticed that species were well-adapted to their environments and that variation existed within every population. His theory, published in ‘On the Origin of Species’, became the foundation of modern evolutionary biology.

查尔斯·达尔文在乘贝格尔号军舰航行并观察野生生物后，提出了自然选择进化论。他注意到每个物种都很好地适应了自身环境，且每个种群内都存在变异。他的著作《物种起源》奠定了现代进化生物学的基石。

Darwin’s key observations included overproduction of offspring, variation among individuals, and a constant struggle for survival. From these he deduced that individuals with characteristics better suited to the environment are more likely to survive, reproduce, and pass on those favourable traits to their offspring. Over many generations, this leads to gradual changes in the population.

达尔文的关键观察包括：后代过度繁殖、个体之间存在变异以及持续的生存斗争。他由此推断，性状更适应环境的个体更可能生存下来、繁衍后代，并将那些有利性状遗传给下一代。经过许多世代，就会导致种群的逐渐变化。

3. The Process of Natural Selection | 自然选择的过程

Natural selection can be broken down into a series of logical steps that explain how populations adapt to their surroundings. These steps must be understood clearly for GCSE WJEC exams.

自然选择可分解为一系列逻辑步骤，用以解释种群如何适应其环境。GCSE WJEC 考试要求清晰理解这些步骤。

Variation: Individuals in a population show a wide range of characteristics due to genetic differences.
Variation (变异): 由于遗传差异，种群内的个体表现出广泛的性状差异。
Competition: Organisms produce more offspring than can survive, leading to competition for limited resources such as food, water, and space.
Competition (竞争): 生物繁殖的后代数量超过环境所能承载的限度，这导致对有限资源（如食物、水和空间）的竞争。
Survival of the fittest: Individuals with characteristics that give them an advantage in the struggle for survival are more likely to live long enough to reproduce.
Survival of the fittest (适者生存): 性状在生存斗争中占据优势的个体，更有可能存活到繁殖年龄。
Inheritance: These successful individuals pass on their advantageous alleles to the next generation. The frequency of these favourable traits increases over time.
Inheritance (遗传): 这些成功存活的个体将优势等位基因传递给下一代。随着时间推移，这些有利性状的出现频率就会上升。

This process is not random; it is directed by the environment selecting particular variations. Consequently, a population becomes better adapted to its habitat.

该过程并非随机；环境会定向筛选特定的变异。因此，种群会越来越适应其栖息地。

4. Variation and Its Importance | 变异及其重要性

Genetic variation is the difference in DNA sequences between individuals within a population. Without variation, natural selection would not be possible because all organisms would be equally suited or unsuited to environmental changes. Variation ensures that some individuals have a better chance of surviving when conditions change.

遗传变异是指种群内个体之间 DNA 序列的差异。没有变异，自然选择便无从发生，因为所有生物对环境变化的适应能力将完全相同。变异保证了一部分个体在环境条件发生变化时拥有更大的生存机会。

Sources of variation include mutations, which are random changes to DNA, and sexual reproduction, which shuffles alleles through meiosis and random fertilisation. In GCSE WJEC Science, you should be able to explain why a wide range of variation is advantageous for the long-term survival of a species.

变异的来源包括基因突变（DNA 的随机变化）以及有性繁殖（通过减数分裂和随机受精对等位基因进行重组）。在 GCSE WJEC 科学考试中，你需要能够解释广泛的变异为什么对一个物种的长期生存是有利的。

5. Examples of Natural Selection: Antibiotic Resistance | 自然选择的例子：抗生素耐药性

Antibiotic resistance in bacteria is a clear and medically relevant example of natural selection that frequently appears on WJEC exam papers. When a population of bacteria is exposed to an antibiotic, most are killed. However, some bacteria may carry a mutation that gives them resistance to that antibiotic.

细菌的抗生素耐药性是自然选择的一个清晰且与医学相关的例子，经常出现在 WJEC 试卷中。当细菌种群接触某种抗生素时，大多数细菌会被杀死。然而，可能有些细菌携带着使其对该抗生素产生抗性的突变。

These resistant bacteria survive and reproduce rapidly because their competition has been removed. The whole new population inherits the resistance gene, making the antibiotic ineffective. This is why it is essential to complete prescribed antibiotic courses and avoid overuse of antibiotics.

这些具有耐药性的细菌存活下来并迅速繁殖，因为它们的竞争者已被清除。整个新种群都继承了耐药基因，致使抗生素失效。这就是为什么必须完成抗生素处方疗程并避免滥用抗生素。

MRSA (Methicillin-resistant Staphylococcus aureus) is often cited as an example of a superbug that has evolved resistance to multiple antibiotics, illustrating how natural selection happens rapidly in organisms with short generation times.

MRSA（耐甲氧西林金黄色葡萄球菌）常被引用为进化出多重耐药性的超级细菌实例，可以说明世代周期短的生物中自然选择如何快速发生。

6. Examples of Natural Selection: Peppered Moth | 自然选择的例子：桦尺蛾

The peppered moth (Biston betularia) is a historic example of evolution in action. In pre-industrial England, the light-coloured form of the moth was well camouflaged against lichen-covered tree bark, making it less visible to predators. The dark form existed but was rare because it was easily spotted and eaten by birds.

桦尺蛾（Biston betularia）是验证进化的一个历史事例。在工业革命前的英格兰，浅色型桦尺蛾在长满地衣的树皮上伪装良好，不易被天敌发现。深色型虽然存在但十分罕见，因为容易被鸟类发现并捕食。

During the Industrial Revolution, soot killed lichens and darkened tree trunks. The dark moths now had better camouflage, while the light moths became more visible. Consequently, the dark allele increased in frequency within the population. Clean air legislation later reversed this trend, demonstrating natural selection driven by environmental change.

工业革命期间，煤烟杀死了地衣并将树干染黑。深色型蛾获得了更好的伪装，而浅色型更易被发现。因此，深色等位基因在种群中的频率上升。后来的空气净化法令又使这一趋势发生逆转，这也证明了环境变化驱动的自然选择。

7. Evidence for Evolution: Fossils | 进化证据：化石

Fossils provide the preserved remains or traces of organisms from the distant past, found in rocks. The fossil record shows how species have changed gradually over millions of years, offering strong direct evidence for evolution.

化石是保存在岩石中的远古生物的遗骸或痕迹。化石记录显示了物种在数百万年间如何逐渐变化，为进化提供了强有力的直接证据。

By arranging fossils in chronological order, scientists can trace the development of modern species from simpler ancestors. Transitional fossils, such as Archaeopteryx (with both reptilian and bird-like features), illustrate the links between major groups of organisms.

通过将化石按时间顺序排列，科学家可以追溯现代物种从更简单的祖先演变的过程。过渡型化石（例如兼具爬行动物和鸟类特征的始祖鸟）揭示出主要生物类群之间的关联。

However, the fossil record is incomplete because most organisms do not fossilise, and geological processes can destroy fossils. Despite these gaps, the evidence overwhelmingly supports a branching tree of life.

然而，化石记录并不完整，因为大多数生物不会形成化石，且地质作用可能破坏化石。尽管存在这些缺失，证据仍然压倒性地支持生命之树不断分支的观点。

8. Evidence for Evolution: Comparative Anatomy | 进化证据：比较解剖学

Comparing the structures of different organisms provides further compelling evidence for common ancestry. Homologous structures are body parts that share a similar underlying anatomy but have different functions in different species, indicating they evolved from a common ancestor.

比较不同生物的结构，为共同祖先理论提供了另一类强有力的证据。同源结构是指基本解剖构造相似但功能不同的人体部位，表明它们是从一个共同祖先进化而来。

A classic example is the pentadactyl limb — the five-fingered limb structure found in mammals, birds, reptiles, and amphibians. The forelimb of a human, a bat’s wing, and a whale’s flipper all contain similar bone arrangements (humerus, radius, ulna, carpals), adapted for different purposes.

典型例子是五指肢结构 — 在哺乳动物、鸟类、爬行动物和两栖动物中都能找到的五指型附肢。人的手臂、蝙蝠的翅膀和鲸鱼的鳍状肢都包含着相似的骨骼排列（肱骨、桡骨、尺骨、腕骨），适应于不同用途。

In contrast, analogous structures (like insect and bird wings) perform similar functions but have different underlying anatomy; they do not indicate close evolutionary relationships but rather convergent evolution.

与之相对，同功结构（例如昆虫和鸟类的翅膀）功能相似但解剖结构不同，并不表示亲密的进化关系，而是趋同进化的结果。

9. Evidence for Evolution: Molecular Biology | 进化证据：分子生物学

Advances in DNA and protein sequencing have added powerful molecular evidence for evolution. All living organisms share the same genetic code and many fundamental biochemical pathways, strongly supporting the idea that life shares a common origin.

DNA 和蛋白质测序技术的发展，为进化提供了强有力的分子证据。所有生物共享相同的遗传密码以及许多基础生化过程，这有力地支持了生命拥有共同起源的观点。

By comparing DNA sequences or the amino acid sequences of common proteins like cytochrome c, scientists can estimate how closely related different species are. Species that diverged more recently have more similar sequences. For instance, human and chimpanzee DNA are about 98.8% identical, reflecting a close common ancestor.

通过比较 DNA 序列或常见蛋白质（如细胞色素 c）的氨基酸序列，科学家可以估算不同物种之间的亲缘关系远近。分化时间越近，序列相似度越高。例如，人类与黑猩猩的 DNA 约有 98.8% 相同，反映了有较近的共同祖先。

Molecular clocks, based on the constant rate of some mutations, can even be used to estimate when two species split from a common ancestor. This evidence independently confirms the evolutionary timelines inferred from fossils.

基于某些突变恒定速率的分子钟，甚至可以用来估算两个物种从共同祖先分化而来的时间。这类证据独立地验证了从化石推断的进化时间线。

10. Speciation: How New Species Form | 物种形成：新物种如何形成

Speciation is the evolutionary process by which new biological species arise. The most common mechanism covered in WJEC GCSE Science is geographical isolation, leading to allopatric speciation.

物种形成是新生物种产生的进化过程。WJEC GCSE 科学中涉及的最常见机制是地理隔离导致的异域物种形成。

A population of the same species becomes physically separated by a geographical barrier such as a mountain range, river, or ocean. The two groups experience different environmental conditions and selection pressures. Over many generations, they accumulate different genetic changes so that they can no longer interbreed to produce fertile offspring even if the barrier is removed. At this point, they are considered separate species.

同一个物种的种群因山脉、河流或海洋等地理屏障而物理隔开。两个群体面临不同的环境条件和选择压力。经过许多世代，它们各自积累不同的遗传变化，以至于即便屏障消失也无法再交配产生可育后代。此时，它们便被认为是不同的物种。

Darwin’s finches on the Galápagos Islands are a classic example, where isolated populations of finches on different islands evolved distinct beak shapes suited to available food sources.

加拉帕戈斯群岛上的达尔文雀便是一个经典例子，不同岛屿上隔离的雀鸟种群进化出各自独特的喙形，以适应可获得的食物来源。

11. Comparing Darwin and Lamarck | 比较达尔文与拉马克

Before Darwin, Jean-Baptiste Lamarck proposed an alternative theory of evolution based on the idea that organisms could acquire characteristics during their lifetime and pass them on to offspring — the ‘law of use and disuse’. The WJEC specification expects you to contrast his ideas with Darwin’s theory.

在达尔文之前，让-巴蒂斯特·拉马克提出了另一种进化理论，认为生物一生中获得的特征可遗传给后代 — 即“用进废退”法则。WJEC 考试大纲要求对比拉马克的观点与达尔文学说。

Aspect (方面)	Darwin’s Theory (达尔文理论)	Lamarck’s Theory (拉马克理论)
Mechanism (机制)	Natural selection acts on existing variation	Organisms change by use/disuse of organs
Inheritance (遗传)	Only genetic changes in gametes are passed on	Changes acquired during life are inherited
Example (例子)	Giraffes with longer necks survive to pass on genes	Giraffes stretch their necks to reach leaves, offspring inherit stretched necks

Lamarck’s theory has been disproved because we know that acquired characteristics do not change DNA in sex cells. Darwin’s mechanism, supported by genetics, forms the modern synthesis of evolutionary biology.

拉马克的理论已被证伪，因为我们知道获得性状不会改变生殖细胞的 DNA。达尔文学说得到了遗传学的支持，构成了现代综合进化论的基石。

12. Extinction and Its Causes | 灭绝及其原因

Extinction occurs when no individuals of a species remain. It is a natural part of evolution, with over 99% of all species that ever lived now extinct. Understanding extinction helps scientists recognise threats to modern biodiversity.

当一个物种的再无任何个体存活时，灭绝便发生了。灭绝是进化中的自然组成部分，地球上曾存在过的物种中有超过 99% 现已灭绝。理解灭绝有助于科学家识别现代生物多样性面临的威胁。

Causes of extinction include environmental changes (such as climate change or volcanic eruptions), new predators or diseases, competition with more successful species, and habitat destruction. Human activities, such as deforestation, pollution, and hunting, have dramatically increased the current rate of extinction.

灭绝的原因包括环境变化（如气候变化或火山喷发）、新天敌或新疾病的出现、与更成功物种的竞争以及栖息地破坏。人类活动，如森林砍伐、污染和狩猎，已急剧加快了当前的灭绝速率。

Mass extinctions, like the one that killed the dinosaurs 66 million years ago, allowed surviving groups such as mammals to diversify and dominate. Thus, extinction can also drive new evolutionary radiations.

大规模灭绝事件（如距今 6600 万年前恐龙灭绝）使得幸存者（如哺乳动物）得以多样化并占据主导地位。因此，灭绝也可能推动新进化辐射的发生。

Published by TutorHao | Science Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

Evolution: GCSE WJEC Science Revision | 进化考点精讲