SAT2 Biology: Essential Knowledge and Exam Prep Guide | SAT2 生物：必备知识点与备考指南

📚 SAT2 Biology: Essential Knowledge and Exam Prep Guide | SAT2 生物：必备知识点与备考指南

Although the SAT Subject Tests, including SAT2 Biology, were discontinued by the College Board in 2021, the core concepts tested in the Biology E/M exam remain foundational for advanced biology studies such as AP Biology, IB Biology, and university-level life sciences. This guide distills the essential knowledge areas, clarifies common misconceptions, and presents a clear roadmap for self-assessment, covering both the molecular and ecological emphases that used to define the two versions of the test.

尽管美国大学理事会已于 2021 年全面取消包含 SAT2 生物在内的 SAT 学科考试，但该考试 E/M 卷所覆盖的核心知识点仍然是 AP 生物、IB 生物以及大学先修生命科学课程的重要基础。本文将考试要求的核心概念提炼为必备知识点，结合经典易错辨析，帮助读者建立清晰的生物知识框架，无论用于回顾复习还是衔接高阶课程，都具有极高的参考价值。

1. Exam Structure and Content Distribution | 考试结构与内容分布

The SAT2 Biology exam consisted of a common 60-question core section followed by a 20-question specialization in either Ecology (Biology-E) or Molecular Biology (Biology-M). The core accounted for 60% of the total score and covered cellular and molecular biology, genetics, evolution, and organismal biology. Understanding this structure clarifies why certain topics—like photosynthesis and Mendelian genetics—are disproportionately emphasized in preparation.

SAT2 生物考试由 60 道通用核心题和 20 道专项题组成，考生需在生态学（E）或分子生物学（M）中二选一。核心题占总分 60%，覆盖细胞与分子生物学、遗传学、进化和个体生物学。明确这一结构，有助于理解为何光合作用、孟德尔遗传等内容在备考中权重极高，从而合理分配复习时间。

2. Biochemistry and the Cell | 生物化学与细胞

All living organisms rely on four major classes of macromolecules: carbohydrates, lipids, proteins, and nucleic acids. Lipids are nonpolar and insoluble in water, while proteins are polymers of amino acids folded into specific three-dimensional shapes determined by their primary sequence. Enzymes, which are protein catalysts, lower activation energy and exhibit specificity for substrates, often described by the lock-and-key or induced-fit models. The cell is bounded by a phospholipid bilayer with embedded proteins that regulate transport via passive diffusion, facilitated diffusion, and active transport requiring ATP.

生物体依赖四大类有机大分子：糖类、脂类、蛋白质和核酸。脂质非极性强，不溶于水；蛋白质由氨基酸脱水缩合而成，根据一级序列折叠出独特三维结构。酶作为蛋白质催化剂，能降低活化能并对底物具有高度专一性，常用锁钥模型或诱导契合模型解释。细胞由磷脂双分子层包裹，镶嵌其中的蛋白质通过被动扩散、协助扩散和耗 ATP 的主动运输等方式控制物质进出。

Key monosaccharides include glucose, fructose, and galactose (C₆H₁₂O₆); disaccharides include sucrose and lactose; polysaccharides include starch, glycogen, and cellulose.
关键单糖有葡萄糖、果糖、半乳糖，二糖有蔗糖和乳糖，多糖则有淀粉、糖原和纤维素。
The mitochondria and chloroplasts are double-membrane organelles with their own DNA and ribosomes, supporting the endosymbiotic theory.
线粒体和叶绿体均为双膜细胞器，拥有独立的 DNA 与核糖体，这一证据有力地支持了内共生学说。

3. Cellular Energetics: Respiration and Photosynthesis | 细胞能量学：呼吸与光合作用

Cellular respiration converts the energy in glucose to ATP through three main stages: glycolysis in the cytoplasm, the Krebs cycle in the mitochondrial matrix, and the electron transport chain (ETC) on the inner mitochondrial membrane. Glycolysis is anaerobic and yields a net gain of 2 ATP and 2 NADH per glucose. In the presence of oxygen, the link reaction and Krebs cycle produce CO₂ and reduce NAD⁺ and FAD to carriers that donate electrons to the ETC, where oxidative phosphorylation generates up to 34 ATP. The total maximum yield of aerobic respiration is about 36–38 ATP.

细胞呼吸通过三个主要阶段将葡萄糖中的化学能转化为 ATP：细胞质基质中的糖酵解、线粒体基质中的三羧酸循环以及线粒体内膜上的电子传递链。糖酵解为厌氧过程，每分子葡萄糖净产 2 ATP 和 2 NADH。在有氧条件下，连接反应与三羧酸循环释放 CO₂，并将 NAD⁺ 和 FAD 还原为高能载体，其电子经电子传递链传递，结合氧化磷酸化最多可生成约 34 ATP。有氧呼吸理论总产量约为 36–38 ATP。

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ~36–38 ATP

Photosynthesis consists of light-dependent reactions in the thylakoid membrane, where water is split and O₂ is released, producing ATP and NADPH. The Calvin cycle in the stroma uses ATP and NADPH to fix CO₂ into G3P, which can be converted to glucose. C3 plants directly fix CO₂ via RuBisCO, while C4 plants spatially separate initial fixation in mesophyll cells, and CAM plants temporally separate fixation to minimize photorespiration.

光合作用包括类囊体膜上的光反应，水裂解释放 O₂，同时生成 ATP 和 NADPH；叶绿体基质中的卡尔文循环利用这些能量分子固定 CO₂ 合成 G3P，进而转化为葡萄糖。C3 植物通过 RuBisCO 直接固碳，C4 植物在叶肉细胞中将固碳与还原空间分离，CAM 植物则通过昼夜时间分离来减少光呼吸。

6CO₂ + 12H₂O + light → C₆H₁₂O₆ + 6O₂ + 6H₂O

4. Classical Genetics | 经典遗传学

Mendel’s laws include the law of segregation (alleles separate during gamete formation) and the law of independent assortment (genes on different chromosomes assort independently). Test crosses are used to determine the genotype of an individual with a dominant phenotype. Incomplete dominance produces an intermediate phenotype in heterozygotes, while codominance results in both alleles being fully expressed, as seen in ABO blood groups. Sex-linked traits often reside on the X chromosome and show different patterns of inheritance in males and females.

孟德尔定律包括分离定律（等位基因在形成配子时分离）和自由组合定律（非同源染色体上的基因独立分配）。测交用于鉴定显性性状个体的基因型。不完全显性使得杂合子呈现中间表型，共显性则让两个等位基因完全表达，如 ABO 血型。性连锁性状多位于 X 染色体上，在男女中呈现不同的遗传模式。

If a heterozygous red-flowered plant (Rr) is crossed with a white-flowered plant (rr), the expected phenotypic ratio in the offspring is 1 red : 1 white.
若杂合红花 (Rr) 与白花 (rr) 杂交，后代预期表型比例为 1 红 : 1 白。
Color blindness is an X-linked recessive disorder; a carrier mother (XᴺXⁿ) and a normal father (XᴺY) have a 25% chance of producing a color-blind son.
红绿色盲为 X 连锁隐性遗传；携带者母亲 (XᴺXⁿ) 与正常父亲 (XᴺY) 生育男性患儿的概率为 25%。

5. Molecular Genetics and Gene Expression | 分子遗传学与基因表达

DNA replication is semiconservative and involves enzymes such as helicase, which unwinds the double helix, and DNA polymerase, which adds nucleotides complementary to the template strand in the 5’→3′ direction. The leading strand is synthesized continuously, while the lagging strand forms Okazaki fragments. Transcription of a gene yields a primary mRNA transcript that undergoes processing in eukaryotes, including the addition of a 5′ cap, poly-A tail, and the removal of introns by splicing.

DNA 复制为半保留方式，解旋酶解开双链，DNA 聚合酶以模板链为蓝本，沿 5’→3′ 方向添加互补核苷酸。前导链连续合成，后随链则产生冈崎片段。基因转录产生初级 mRNA，在真核细胞中经过 5′ 加帽、3′ 多聚腺苷酸化以及剪接去除内含子等加工，成为成熟 mRNA。

Translation occurs at ribosomes, where tRNA molecules with specific anticodons pair with codons on the mRNA. Each tRNA carries an amino acid; the ribosome catalyzes the formation of peptide bonds. The genetic code is universal and degenerate, with multiple codons specifying the same amino acid. Mutations such as point mutations, frameshifts, and chromosomal rearrangements can alter protein function and lead to genetic disorders.

翻译在核糖体上进行，带有特定反密码子的 tRNA 与 mRNA 上的密码子配对。每个 tRNA 携带相应的氨基酸，核糖体催化形成肽键。遗传密码具有通用性和简并性，多个密码子可编码同一种氨基酸。点突变、移码突变及染色体重排等可改变蛋白质功能，引发遗传性疾病。

6. Evolution and Natural Selection | 进化与自然选择

Natural selection acts on phenotypic variation within a population, increasing the frequency of alleles that confer a reproductive advantage. Genetic drift, including the bottleneck and founder effects, can cause random changes in allele frequencies, especially in small populations. Speciation occurs when populations become reproductively isolated, either through geographic barriers (allopatric speciation) or by mechanisms such as behavioral or temporal isolation (sympatric speciation).

自然选择作用于种群内的表型差异，提高具有繁殖优势的等位基因频率。遗传漂变，包括瓶颈效应和奠基者效应，在小种群中会随机改变基因频率。当种群之间形成生殖隔离时，即可发生物种形成：通过地理屏障隔离的称为异地物种形成，通过行为或时间隔离的则为同地物种形成。

Evidence for evolution includes fossil records, comparative anatomy (homologous and analogous structures), embryology, and molecular biology. For example, the forelimbs of humans, whales, and bats are homologous structures, indicating common ancestry, whereas the wings of birds and insects are analogous, demonstrating convergent evolution.

进化证据包括化石记录、比较解剖学（同源与同功结构）、胚胎学以及分子生物学。例如，人类、鲸和蝙蝠的前肢为同源结构，表明共同祖先；而鸟类和昆虫的翅膀则为同功器官，体现了趋同进化。

7. Ecology and Ecosystems | 生态学与生态系统

Ecology is organized into levels: organism, population, community, ecosystem, and biosphere. Population growth can be exponential under ideal conditions but is usually limited by carrying capacity, described by the logistic growth model. Community interactions include competition, predation, mutualism, commensalism, and parasitism. A niche encompasses not only the habitat but also the role and resource use of a species.

生态学按层次划分：个体、种群、群落、生态系统和生物圈。种群在理想条件下呈指数增长，但通常受环境容纳量限制，符合逻辑斯谛增长模型。群落间相互作用包括竞争、捕食、互利共生、偏利共生和寄生。生态位不仅包含栖息地，还涵盖物种在群落中的功能与资源利用方式。

Energy flows through ecosystems in a one-way direction from producers to consumers, with typically only about 10% of energy transferred between trophic levels. Biogeochemical cycles such as the water, carbon, and nitrogen cycles recirculate essential elements. In the nitrogen cycle, nitrogen-fixing bacteria convert atmospheric N₂ to ammonia, while denitrifying bacteria return N₂ to the atmosphere.

能量沿食物链单向流动，从生产者到各级消费者，营养级间的能量传递效率通常仅为 10%。水、碳、氮等生物地球化学循环使化学元素得以再利用。在氮循环中，固氮菌将大气中的 N₂ 转化为氨，反硝化细菌则将硝酸盐还原为 N₂ 回归大气。

8. Biodiversity and Classification | 生物多样性与分类

Taxonomy classifies life into a hierarchical system: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species. The three-domain system separates Bacteria, Archaea, and Eukarya, reflecting fundamental differences in ribosomal RNA and membrane structure. Within Eukarya, the traditional five-kingdom system includes Protista, Fungi, Plantae, and Animalia, though multiple revisions now emphasize cladistics.

生物分类采用界门纲目科属种的层级框架。三域系统将生物分为细菌域、古菌域和真核生物域，体现了 rRNA 和膜结构的根本差异。在真核生物域内，传统的五界系统包括原生生物界、真菌界、植物界和动物界，而现代分类越来越注重基于进化分支的支序分类学。

Major animal phyla important for SAT2 include Porifera (sponges, no true tissues), Cnidaria (jellyfish, radial symmetry), Platyhelminthes (flatworms, bilateral symmetry), Annelida (segmented worms), Arthropoda (insects, jointed appendages), Chordata (vertebrates, notochord). Key plant divisions include Bryophyta (mosses, no vascular tissue), Filicinophyta (ferns, vascular but seedless), and Spermatophyta (seed plants including gymnosperms and angiosperms).

SAT2 重点动物门包括：多孔动物门（海绵，无真正组织）、刺胞动物门（水母，辐射对称）、扁形动物门（涡虫，两侧对称）、环节动物门（蚯蚓等体节动物）、节肢动物门（昆虫，分节附肢）以及脊索动物门（脊椎动物，具有脊索）。主要植物类群有苔藓植物（藓类，无维管）、蕨类植物（有维管、无种子）和种子植物（包括裸子植物和被子植物）。

9. Plant Physiology | 植物生理学

Plants transport water and minerals from roots to shoots mainly via xylem, driven by transpiration pull, cohesion, and adhesion. Phloem translocates sugars from sources (leaves) to sinks (roots, fruits) through pressure flow. Stomata, controlled by guard cells, regulate gas exchange and water loss. Plant hormones such as auxins promote cell elongation and apical dominance, while ethylene promotes fruit ripening and abscission.

植物主要通过木质部将水分和矿质营养由根向上运输，依靠蒸腾拉力、内聚力和吸附力共同驱动。韧皮部则通过压力流将糖类从源（叶片）运送到库（根、果实）。气孔由保卫细胞调控开闭，平衡气体交换与失水。植物激素中，生长素促进细胞伸长、维持顶端优势，乙烯则加速果实成熟与器官脱落。

Phototropism and gravitropism are growth responses mediated by the asymmetric distribution of auxin. Short-day plants flower when night length exceeds a critical duration, while long-day plants flower under short nights. Phytochrome, a photoreceptor, enables plants to detect photoperiod changes.

向光性和向地性是由生长素不对称分布介导的生长反应。短日植物在夜长超过临界时长时开花，长日植物则在短夜条件下开花。光敏色素作为光受体，使植物能够感知光周期变化。

10. Animal Physiology Overview | 动物生理学概要

The nervous system uses electrochemical signals: neurons communicate via action potentials and synaptic transmission. The endocrine system releases hormones such as insulin, which lowers blood glucose by promoting cellular uptake and glycogen synthesis, and glucagon, which raises blood glucose by stimulating glycogen breakdown. Homeostasis is maintained by negative feedback mechanisms, as seen in thermoregulation and osmoregulation.

神经系统利用电化学信号进行通讯：神经元依靠动作电位和突触传递信息。内分泌系统分泌激素调节生理活动，如胰岛素通过促进细胞摄取葡萄糖和糖原合成降低血糖，而胰高血糖素则通过促进糖原分解升高血糖。稳态通过负反馈机制维持，体温调节和渗透压调节均为典型实例。

The circulatory system of mammals is double and closed, with a four-chambered heart separating oxygenated and deoxygenated blood. The respiratory system relies on the diaphragm and intercostal muscles to change thoracic volume, causing inhalation and exhalation. In the immune system, B cells produce antibodies, while T cells are involved in cell-mediated immunity; vaccination stimulates immunological memory.

哺乳动物为双循环闭管式循环，四腔心脏将含氧血与缺氧血彻底分开。呼吸系统借助膈肌与肋间肌改变胸腔容积，实现吸气和呼气。免疫系统中，B 细胞产生抗体，T 细胞参与细胞免疫；疫苗接种可激发免疫记忆，提供长期保护。

11. Effective Prep Strategies and Common Pitfalls | 高效备考策略与常见误区

Focus on core topics such as energetics, genetics, and ecology, as they form the bulk of the exam. Create visual organizers comparing processes like mitosis vs. meiosis, DNA vs. RNA, and C3 vs. C4 plants. Practice data interpretation and experimental design questions, because the SAT2 Biology heavily tests scientific reasoning. A common mistake is memorizing isolated facts without understanding experimental evidence; instead, ask “What experiment supports this conclusion?” for each concept.

集中精力攻克能量学、遗传学和生态学等核心板块，它们占据大部分题量。利用图表对比有丝分裂与减数分裂、DNA 与 RNA、C3 与 C4 植物等易混概念，强化比较记忆。大量练习数据解读和实验设计题，因为考试高度重视科学推理能力。常见误区是孤立记忆事实而忽略实验证据——建议每学一个概念都追问“什么实验得出了这个结论？”，以此深化理解。

When reviewing, treat specialized topics strategically: if you choose Biology-M, invest extra time in enzyme kinetics and DNA technologies; if Biology-E, master energy flow, population dynamics, and biomes. Additionally, manage your pacing by simulating timed sections, as the original test required answering 80 questions in 60 minutes, demanding both accuracy and speed.

专项复习要有侧重：选考分子生物学的同学应加强酶动力学与 DNA 技术；选考生态学的则必须精通能量流动、种群动态和生物群落。此外，建议严格按照时间模拟练习，原始考试需在 60 分钟内完成 80 题，对准确度与速度的双重要求极高，必须通过限时训练形成答题节奏。

Published by TutorHao | Biology Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

SAT2 Biology: Essential Knowledge and Exam Prep Guide | SAT2 生物：必备知识点与备考指南