G3 Biology becomes easier when unfamiliar terms are connected to what living structures actually do. A student who knows that diffusion, osmosis and active transport describe different processes can explain the movement of substances accurately. Someone who distinguishes gene, allele and chromosome is less likely to guess in genetics questions. Here are 200 Biology terms and meanings organised into 20 practical sets for students taking SEC 2027 G3 Biology (SEAB code K325).

Singapore’s 2027 G3 Biology K325 builds across cells and biological molecules, maintaining life in the human body, plants and ecosystems, and continuity of life. SEAB gives older code 6093 for reference; combined G3 Science uses different subject codes. This list is an original eduKate revision aid, not an official 200-word vocabulary syllabus. Study words together with diagrams, mechanisms, experiments and the precise learning outcomes in the examination-year syllabus.

Quick information for parents and students:

• Start with the ten words linked to your child’s most frequent errors.
• Draw each structure, then label its function in one sentence.
• Explain biological processes as starting conditions → mechanism → outcome.
• Use evidence when interpreting biological data, graphs and practical observations.
• Confirm the actual course through SEAB’s 2027 G3 subject listing before choosing revision materials.

1–10: Cells and basic structures

1. cell — Smallest structural and functional unit of living organisms.
2. cell membrane — Selectively permeable boundary controlling movement into and out of a cell.
3. cell wall — Rigid outer structure supporting a plant or bacterial cell.
4. cytoplasm — Material within a cell where many chemical processes take place.
5. nucleus — Organelle containing most of a eukaryotic cell’s DNA.
6. mitochondrion — Organelle where much aerobic respiration occurs.
7. chloroplast — Plant organelle where photosynthesis takes place.
8. vacuole — Membrane-bound compartment containing stored fluid and materials.
9. ribosome — Small cell structure making proteins.
10. organelle — Specialised structure performing a function inside a cell.

Transfer question: Where in a living organism could you observe this structure or process?

11–20: Organisation and specialised cells

11. tissue — Group of similar cells performing related functions.
12. organ — Body structure containing different tissues working together.
13. organ system — Several organs cooperating in a major function.
14. organism — An individual living thing.
15. cell differentiation — Process in which cells develop specialised structures and functions.
16. root hair cell — Plant cell adapted to absorb water and mineral ions.
17. red blood cell — Blood cell adapted to carry oxygen using haemoglobin.
18. nerve cell — Specialised cell transmitting electrical impulses.
19. muscle cell — Cell able to contract and produce movement.
20. palisade mesophyll cell — Leaf cell with many chloroplasts for light absorption.

Transfer question: Which term is often confused with one in this group, and what is the difference?

21–30: Movement across membranes

21. diffusion — Net movement of particles down their concentration gradient.
22. osmosis — Net movement of water through a partially permeable membrane from higher to lower water potential.
23. active transport — Energy-requiring movement across a membrane against a concentration gradient.
24. concentration gradient — Difference in concentration between two regions.
25. partially permeable membrane — Barrier allowing some molecules through more readily than others.
26. water potential — Measure used to predict the direction of water movement.
27. turgid — Firm state of plant cell when filled with water.
28. flaccid — Limp state of plant cell with reduced turgor.
29. plasmolysis — Separation of plant cell membrane from wall after water loss.
30. surface-area-to-volume ratio — Comparison influencing how effectively substances enter and leave cells.

Transfer question: Explain one cause-and-effect relationship using two terms from this set.

31–40: Biological molecules

31. carbohydrate — Organic compound used for energy and some structural roles.
32. glucose — Simple sugar used in cellular respiration.
33. starch — Plant storage polysaccharide made from glucose.
34. glycogen — Storage carbohydrate in animals and fungi.
35. cellulose — Structural carbohydrate forming plant cell walls.
36. lipid — Water-insoluble biological molecule including fats and oils.
37. fatty acid — Component of many fats and oils.
38. glycerol — Three-carbon alcohol forming part of triglycerides.
39. protein — Biological polymer built from amino acids.
40. amino acid — Small molecule that serves as a protein building block.

Transfer question: What observation or diagram could support this explanation?

41–50: Enzymes and food tests

41. enzyme — Biological catalyst speeding reactions without being consumed overall.
42. substrate — Reactant on which an enzyme acts.
43. active site — Region of an enzyme binding the substrate.
44. enzyme-substrate complex — Temporary combination formed during enzyme action.
45. denaturation — Loss of functional protein shape after unsuitable conditions.
46. optimum temperature — Temperature giving highest activity under specified conditions.
47. optimum pH — pH giving highest enzyme activity under specified conditions.
48. Benedict’s test — Heated chemical test for reducing sugars.
49. Biuret test — Test detecting peptide bonds in proteins.
50. iodine test — Test in which iodine solution turns blue-black with starch.

Transfer question: Where in a living organism could you observe this structure or process?

51–60: Human digestion: body parts

51. alimentary canal — Continuous digestive passage from mouth to anus.
52. oesophagus — Tube carrying swallowed food to the stomach.
53. stomach — Muscular organ mixing food with acidic digestive juice.
54. duodenum — First part of the small intestine receiving bile and pancreatic juice.
55. ileum — Part of small intestine specialised for nutrient absorption.
56. colon — Large-intestine section absorbing water and forming faeces.
57. pancreas — Gland producing digestive enzymes and important hormones.
58. liver — Organ involved in metabolism, detoxification and bile production.
59. gall bladder — Organ storing and concentrating bile.
60. salivary gland — Gland secreting saliva to moisten food and begin starch digestion.

Transfer question: Which term is often confused with one in this group, and what is the difference?

61–70: Digestive processes and absorption

61. ingestion — Taking food into the mouth.
62. mechanical digestion — Physical breakdown of food into smaller pieces.
63. chemical digestion — Breaking large food molecules into smaller ones by chemical reactions.
64. peristalsis — Rhythmic muscle contractions moving food through the gut.
65. absorption — Movement of digested nutrients across the intestinal wall.
66. assimilation — Use of absorbed nutrients by body cells.
67. egestion — Removal of undigested material as faeces.
68. villus — Fingerlike structure increasing intestinal absorbing surface.
69. lacteal — Lymph vessel in a villus absorbing many dietary fat products.
70. bile — Liver-made fluid helping emulsify fats in digestion.

Transfer question: Explain one cause-and-effect relationship using two terms from this set.

71–80: Blood components and roles

71. plasma — Fluid part of blood carrying dissolved substances and cells.
72. haemoglobin — Iron-containing protein carrying oxygen in red blood cells.
73. platelet — Cell fragment helping blood clot.
74. white blood cell — Blood cell involved in defence against disease.
75. phagocyte — White blood cell that engulfs pathogens or debris.
76. lymphocyte — White blood cell involved in targeted immune responses.
77. antibody — Protein binding specifically to an antigen.
78. antigen — Molecule or feature recognised by the immune system.
79. blood clot — Mass of cells and fibres helping stop bleeding.
80. fibrin — Insoluble protein strands stabilising a blood clot.

Transfer question: What observation or diagram could support this explanation?

81–90: Heart, vessels and circulation

81. artery — Blood vessel carrying blood away from the heart.
82. vein — Blood vessel carrying blood towards the heart.
83. capillary — Very narrow blood vessel allowing exchange with tissues.
84. atrium — Upper chamber of the heart receiving blood.
85. ventricle — Lower heart chamber pumping blood out.
86. valve — Structure preventing backward flow in a vessel or heart.
87. systole — Phase when the heart chamber contracts.
88. diastole — Phase when a heart chamber relaxes and fills.
89. coronary artery — Vessel supplying the heart muscle with oxygenated blood.
90. tissue fluid — Fluid surrounding body cells and mediating exchange with capillaries.

Transfer question: Where in a living organism could you observe this structure or process?

91–100: Breathing and cellular respiration

91. trachea — Windpipe that carries air towards the lungs.
92. bronchus — Major airway branching from the trachea into a lung.
93. bronchiole — Smaller branch of the lung airways.
94. alveolus — Tiny air sac providing a surface for gas exchange.
95. diaphragm — Muscle beneath the lungs helping change chest volume.
96. inhalation — Movement of air into the lungs.
97. exhalation — Movement of air out of the lungs.
98. aerobic respiration — Energy-releasing breakdown of nutrients using oxygen.
99. anaerobic respiration — Energy release without oxygen, with less energy from glucose in human cells.
100. oxygen debt — Extra oxygen needed after exercise to support recovery from anaerobic activity.

Transfer question: Which term is often confused with one in this group, and what is the difference?

101–110: Excretion and the kidney

101. excretion — Removal of waste products of metabolism and excess substances.
102. kidney — Organ filtering blood and regulating water and solute balance.
103. ureter — Tube carrying urine from kidney to bladder.
104. urinary bladder — Organ temporarily storing urine.
105. urethra — Tube carrying urine from bladder out of the body.
106. nephron — Functional filtering and processing unit of a kidney.
107. glomerulus — Capillary knot where filtration begins.
108. ultrafiltration — Pressure-driven filtering of small molecules from blood.
109. selective reabsorption — Recovery of useful substances from filtrate into blood.
110. dialysis — Method removing wastes and adjusting fluids when kidneys cannot do so adequately.

Transfer question: Explain one cause-and-effect relationship using two terms from this set.

111–120: Homeostasis and hormonal control

111. homeostasis — Maintenance of a relatively stable internal environment.
112. negative feedback — Regulatory process counteracting a change from a set range.
113. stimulus — Change detected by a receptor.
114. receptor — Cell or structure detecting a stimulus.
115. effector — Muscle or gland producing a response.
116. hormone — Chemical messenger made by a gland and carried to target cells.
117. insulin — Pancreatic hormone helping lower raised blood glucose.
118. glucagon — Pancreatic hormone helping increase low blood glucose.
119. osmoregulation — Regulation of water and dissolved substance balance.
120. antidiuretic hormone — Hormone increasing water reabsorption by the kidneys.

Transfer question: What observation or diagram could support this explanation?

121–130: Nervous control and sense organs

121. central nervous system — Brain and spinal cord together.
122. sensory neurone — Cell carrying impulses from receptors towards the central nervous system.
123. relay neurone — Cell linking neurones within the central nervous system.
124. motor neurone — Cell carrying impulses towards an effector.
125. synapse — Junction transmitting signals between neurones or to effectors.
126. reflex action — Rapid automatic response to a stimulus.
127. reflex arc — Pathway through which a reflex signal travels.
128. retina — Light-sensitive layer at the back of the eye.
129. iris — Coloured eye tissue controlling pupil diameter.
130. pupil reflex — Automatic adjustment of pupil size to light intensity.

Transfer question: Where in a living organism could you observe this structure or process?

131–140: Infections and prevention

131. pathogen — Microorganism or agent that can cause infectious disease.
132. virus — Infectious agent reproducing only inside suitable host cells.
133. bacterium — Single-celled organism lacking a membrane-bound nucleus.
134. infectious disease — Disease caused by a pathogen and capable of transmission.
135. transmission — Passing a pathogen between hosts or through a route.
136. vaccination — Administration of vaccine to stimulate protective immune response.
137. vaccine — Preparation designed to help the immune system recognise a pathogen.
138. antibiotic — Medicine that targets bacterial infections but not viruses.
139. antibiotic resistance — Ability of bacteria to survive an antibiotic that once affected them.
140. immunity — Body’s ability to resist a particular infectious agent.

Transfer question: Which term is often confused with one in this group, and what is the difference?

141–150: Photosynthesis and leaf structure

141. photosynthesis — Process converting light energy into chemical energy stored in organic molecules.
142. chlorophyll — Pigment absorbing light for photosynthesis.
143. stoma — Pore in a leaf through which gases and water vapour pass.
144. guard cell — Cell controlling the size of a stoma.
145. spongy mesophyll — Leaf tissue with spaces allowing gas movement.
146. cuticle — Waxy leaf covering that limits water loss.
147. vascular bundle — Group of conducting tissues within a plant.
148. carbon dioxide — Gas used as a raw material in photosynthesis.
149. light intensity — Amount of incident light power per unit area.
150. limiting factor — Condition restricting the maximum rate of a process.

Transfer question: Explain one cause-and-effect relationship using two terms from this set.

151–160: Water, sugars and plant transport

151. xylem — Plant tissue carrying water and dissolved mineral ions.
152. phloem — Plant tissue transporting sugars and other organic solutes.
153. transpiration — Loss of water vapour from a plant, especially through stomata.
154. translocation — Movement of organic nutrients in phloem.
155. root pressure — Pressure arising from water entering roots and their xylem.
156. water uptake — Absorption of water into roots and other plant tissues.
157. mineral ion — Dissolved charged nutrient taken up by plant roots.
158. sieve tube element — Phloem cell forming part of a transport tube.
159. companion cell — Cell supporting a neighbouring phloem sieve tube element.
160. transpiration stream — Flow of water from roots through xylem to leaves.

Transfer question: What observation or diagram could support this explanation?

161–170: Ecosystems and feeding

161. habitat — Place where an organism lives.
162. ecosystem — Interacting organisms and their physical surroundings.
163. population — Individuals of one species living in a defined area.
164. community — Populations of different species in an area.
165. producer — Organism making organic food from simple raw materials.
166. consumer — Organism obtaining energy by feeding on other organisms.
167. decomposer — Organism breaking down dead material and waste.
168. food chain — Sequence showing energy transfer through feeding.
169. food web — Interconnected food chains in an ecosystem.
170. trophic level — An organism’s feeding position in a chain or web.

Transfer question: Where in a living organism could you observe this structure or process?

171–180: Ecology, change and conservation

171. competition — Organisms seeking the same limited resources.
172. predation — Interaction in which one animal kills and eats another.
173. interdependence — Species relying on one another for some needs.
174. bioaccumulation — Build-up of a substance within an organism over time.
175. biomagnification — Increase in concentration of some substances along food chains.
176. biodiversity — Variety of living organisms in an environment.
177. conservation — Protection and careful management of organisms and habitats.
178. deforestation — Removal of forest cover from land.
179. global warming — Long-term rise in Earth’s average surface temperature.
180. sustainability — Meeting needs without undermining future ecological and social capacity.

Transfer question: Which term is often confused with one in this group, and what is the difference?

181–190: DNA, genes and chromosomes

181. DNA — Molecule storing much of an organism’s hereditary information.
182. gene — DNA sequence influencing a functional product or inherited trait.
183. chromosome — Long DNA-containing structure carrying many genes.
184. allele — Alternative version of a gene.
185. genotype — Genetic makeup at one or more relevant genes.
186. phenotype — Observable characteristics resulting from genes and environment.
187. dominant allele — Allele whose effect is expressed in a heterozygote in simple inheritance.
188. recessive allele — Allele expressed in a simple trait when no dominant allele is present.
189. homozygous — Having two identical alleles at a given gene.
190. heterozygous — Having two different alleles at a given gene.

Transfer question: Explain one cause-and-effect relationship using two terms from this set.

191–200: Reproduction and inheritance

191. mitosis — Cell division producing genetically similar daughter cells under ordinary conditions.
192. meiosis — Division reducing chromosome number to form reproductive cells.
193. gamete — Haploid reproductive cell such as sperm or egg.
194. fertilisation — Fusion of gamete nuclei to form a zygote.
195. zygote — First cell formed after fertilisation.
196. embryo — Early developing organism.
197. ovulation — Release of an egg from an ovary.
198. menstruation — Periodic shedding of the uterine lining.
199. inheritance — Passing genetic information from parents to offspring.
200. natural selection — Process favouring inherited variants associated with greater reproductive success.

Transfer question: What observation or diagram could support this explanation?

Why Biology needs precise words instead of memorised paragraphs

Example 1: Diffusion is not active transport

Diffusion is the net movement of particles down a concentration gradient due to random motion. Active transport moves substances across a membrane against a concentration gradient using energy, typically from respiration. The two processes may transport the same substance in different circumstances, but the direction and energy requirement are not interchangeable. In an unseen root-hair question, decide whether the movement is with or against the relevant gradient before selecting the process.

Example 2: Why a villus is effective

A villus has a large surface area, a thin epithelial lining, a rich blood capillary network and a lacteal. These are not just names: they explain how digested substances cross the intestinal wall and are transported away. Absorption concerns entry from the gut into body transport systems; assimilation concerns how cells subsequently use the absorbed nutrients. Writing only “it helps digestion” does not explain the structure-function relationship.

Example 3: Aerobic respiration and breathing are not synonyms

Breathing moves air into and out of the lungs. Gas exchange occurs mainly between alveoli and surrounding blood. Cellular respiration releases usable energy from food molecules within cells. These connected processes happen at different levels of organisation. A useful answer identifies which level the question asks about: organ system, tissue or cell.

Example 4: Insulin and glucagon illustrate negative feedback

Following a meal, blood glucose may rise, prompting the pancreas to release insulin. When blood glucose is lower, glucagon may promote the release of glucose from stored glycogen. The regulatory aim is to keep concentrations within a suitable range, not permanently force glucose to zero. Homeostasis and negative feedback help explain why the response changes with the initial condition.

Example 5: The meaning of alleles in a genetic cross

In a simple one-gene example, two heterozygous parents represented as Aa × Aa can produce AA, Aa, Aa and aa genotypes, with probabilities 1/4, 1/2 and 1/4. Under complete dominance, these genotypes correspond to a 3:1 dominant-to-recessive phenotype expectation. That is a probability model for offspring, not a guarantee about the next four children. Students must understand allele, genotype and phenotype to interpret the ratio.

Example 6: Food chains need arrows showing energy transfer

Grass → grasshopper → bird is a feeding sequence. The arrows indicate energy transfer from food to consumer. Removing grasshoppers could affect the population of birds, but the outcome depends on other food sources, predation and environmental conditions. An evidence-led response should explain the likely relationship and avoid claiming that every species change has one inevitable effect.

How to answer a Biology practical or data question

1. Identify what was measured: distinguish observed data from an inferred explanation.
2. Check the biological level: molecule, cell, organ, system, organism or ecosystem.
3. Name the mechanism: diffusion, enzyme reaction, circulation, hormone feedback, reproduction or inheritance.
4. Trace the direction: for substances, energy and signals, say what moves from where to where.
5. Evaluate evidence: look for controls, alternative explanations, repeat measurements and missing information.

Example: when a plant tissue changes mass in sugar solution, do not claim the sugar simply “enters” or “leaves” without identifying the conditions. Determine the water-potential relationship and consider osmosis; the observed mass change must support the direction proposed.

Four weeks: learn Biology as a connected system

1. Week 1 — Cell foundations: sets 1–5. Practise plant and animal cell diagrams, transport processes, food tests and the function of enzymes.
2. Week 2 — Human body: sets 6–14. Trace food, blood, oxygen, nitrogenous waste, reflex pathways and infection prevention through appropriate systems.
3. Week 3 — Plants and ecology: sets 15–18. Explain photosynthesis, movement of water and sugars, food webs and environmental change.
4. Week 4 — Continuity of life: sets 19–20, then mixed practice. Work through genetic crosses, reproduction sequences and unfamiliar question data; revisit every word that caused a wrong inference.

Ten new terms can be a reasonable short session, but learners should spend at least as much time retrieving and applying old vocabulary as copying new terms. If the child already knows 150 terms confidently, target the remaining uncertainty instead of resetting the whole glossary.

Common Biology explanation errors

• Calling excretion the removal of undigested food; that is egestion, whereas excretion removes metabolic waste.
• Claiming a large enzyme molecule is “used up”; enzymes are catalysts and are not consumed overall.
• Confusing blood’s plasma with the cell’s cytoplasm.
• Writing that plants receive all food from soil rather than making organic food through photosynthesis.
• Assuming natural selection deliberately creates useful traits because an organism needs them.
• Confusing inherited genetic variation with changes in appearance caused only by the environment.

Frequently asked questions

Is this the official K325 word list?

No. SEAB publishes a syllabus of content and learning outcomes, not this 200-term eduKate glossary. Use the official 2027 K325 syllabus to verify coverage.

Is G3 Biology the same as combined Science Biology?

No. K325 is a separate Biology subject; combinations such as K327 and K328 include Biology with another science and have different requirements.

Do students need to know the exact wording of every definition?

Key ideas must be scientifically accurate, but memorising only a sentence without understanding its mechanism is fragile. Explain definitions in fresh examples.

Should Biology revision use diagrams?

Yes. Labelled diagrams help connect structures and functions, but they should also be interpreted in unseen contexts.

Are health examples an invitation to diagnose oneself?

No. Biology classroom examples explain biological mechanisms; personal medical concerns require appropriately qualified healthcare advice.

How can we practise without adding stress?

Use a five- to ten-minute retrieval quiz, one labelled diagram and one “why” question, then stop or switch to a different task. Return to the same concept several days later.

Official sources and next reading

SEAB’s 2027 G3 syllabus index lists Biology K325 with older reference 6093. The K325 PDF covers cell processes, human systems, plant biology, ecology, molecular genetics, reproduction and inheritance. For assessment context read What Happens in G3 Biology K325: practical, genetics and structured answers and Pure Science or Combined Science for Secondary 3?. Choose Biology support after identifying whether the difficulty is vocabulary, understanding, diagram interpretation or applying concepts.

eduKate Punggol study guide, November 2026. An independently written glossary, not a replacement for SEAB examination instructions or school science-laboratory guidance.