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Biology Topic Index | 2026 O-Level to 2027 SEC G3 Pure and Combined Science

Biology Topic Index for Pure and Combined Science is eduKateSingapore’s canonical syllabus map for students moving from 2026 O-Level Biology language into the 2027 G3 SEC Science system. Students searching O-Level Biology topics, Pure Biology syllabus, Combined Science Biology, 6093 Biology, K325 Biology, K327 or K328 need a route that separates the full Pure Biology content from the Combined Science Biology component without treating them as interchangeable.

From 2027, G3 Pure Biology uses K325, with 6093 shown by SEAB as the 2026-and-earlier reference code. G3 Combined Science routes containing Biology use K327 Physics/Biology or K328 Chemistry/Biology, replacing reference codes 5087 and 5088. The Combined Biology section shares the same broad biological architecture but contains fewer named topics than Pure Biology.

This page belongs to the Secondary Science Shelf. It is a syllabus-facing index. Mechanism depth routes into Science World and the broader How Secondary Science Works owner.

2027 G3 Pure Biology: K325

SEAB organises K325 into four major themes and 14 topics.

I. Cells and the Chemistry of Life

  • 1. Cell Structure and Organisation
  • 2. Movement of Substances
  • 3. Biological Molecules

II. The Human Body — Maintaining Life

  • 4. Nutrition in Humans
  • 5. Transport in Humans
  • 6. Respiration in Humans
  • 7. Excretion in Humans
  • 8. Homeostasis, Co-ordination and Response in Humans
  • 9. Infectious Diseases in Humans

III. Living Together — Plants, Animals and Ecosystems

  • 10. Nutrition and Transport in Flowering Plants
  • 11. Organisms and their Environment

IV. Continuity of Life

  • 12. Molecular Genetics
  • 13. Reproduction
  • 14. Inheritance

2027 G3 Combined Science Biology component

The Combined Science Biology section is organised into 12 named topics.

  • Cell Structure and Organisation
  • Movement of Substances
  • Biological Molecules
  • Nutrition in Humans
  • Transport in Humans
  • Respiration in Humans
  • Infectious Diseases in Humans
  • Nutrition and Transport in Flowering Plants
  • Organisms and their Environment
  • Molecular Genetics
  • Reproduction in Humans
  • Inheritance

Compared with Pure Biology, the named Pure topics Excretion in Humans and Homeostasis, Co-ordination and Response in Humans do not appear as separate named Combined Biology topics in the 2027 content structure. Students should still follow the exact learning outcomes in their own syllabus rather than infer scope only from headings.

The Biology dependency map

  • Cell structure → specialised cells → tissues/organs.
  • Membranes and movement of substances → absorption, exchange and transport.
  • Biological molecules → nutrition and metabolism.
  • Nutrition → respiration → energy for life processes.
  • Transport in humans → gas exchange, tissues and homeostasis in Pure Biology.
  • Plant nutrition → transport → ecosystems.
  • DNA/molecular genetics → reproduction → inheritance.

Cells are a gateway topic

Cell structure is not merely a diagram-label chapter. Later topics depend on membrane function, organelles, specialised structures and levels of organisation.

A student who memorises labels without linking structure to function will carry that weakness into transport, respiration, genetics and plant biology.

Movement of substances

Diffusion, osmosis and movement across membranes should be learned as particle and concentration-gradient mechanisms, not as vocabulary definitions only.

Questions often change the surface context while preserving the same movement principle.

Biological molecules

Proteins, carbohydrates and lipids connect nutrition, enzymes, energy storage and cell structure. Tests and practical observations should be linked to what the molecule is and why it matters.

Human nutrition

The digestive system is a system problem: mechanical breakdown, chemical digestion, enzymes, absorption and transport work together.

Naming organs is only the first layer.

Transport in humans

Blood, heart and vessels should be understood through transport purpose, pressure, structure and exchange.

Atlas will add a dedicated Transport in Humans owner later in Estate E.

Respiration

Respiration is a cellular energy-releasing process; breathing is ventilation. Strong answers keep those processes distinct.

This distinction is a common diagnostic point.

Infectious disease

Students should connect pathogen transmission, host response, prevention and evidence rather than reduce the topic to lists of diseases.

Mechanism and public-health reasoning matter.

Flowering plants

Plant nutrition and transport link photosynthesis, roots, xylem, phloem and environmental exchange.

Treat the plant as a functioning system rather than separate labelled diagrams.

Ecosystems

Ecology questions require relationships: energy transfer, nutrient movement, populations, interdependence and environmental change.

A good answer follows the causal chain from changed condition to organism/population/ecosystem effect.

Molecular genetics

DNA and genes connect molecular information to proteins, traits and inheritance. Students should distinguish gene, allele, chromosome and DNA clearly.

Vocabulary precision is part of conceptual precision.

Reproduction and inheritance

Reproduction describes biological continuity; inheritance describes how genetic information is transmitted and expressed across generations.

Diagrams and probability-like genetic reasoning should remain connected to the underlying biology.

Pure-only depth to watch

Pure Biology explicitly names Excretion and Homeostasis/Co-ordination/Response as separate topics. Those systems deepen the theme of maintaining stable internal conditions and responding to environmental change.

Students moving from Combined to Pure should not assume that familiar shared chapters represent the whole additional depth.

Practices of Biology

  • microscopy and biological drawings
  • experimental variables and controls
  • food tests and observations
  • tables and graphs
  • rates and percentage change
  • biological interpretation of unfamiliar data
  • evaluation of methods
  • evidence-based explanations

The Biology explanation chain

Structure → function → process → consequence.

Example: thin alveolar wall → short diffusion distance → faster gas exchange → supports oxygen uptake.

This structure is stronger than a memorised sentence because it can transfer to new organs and contexts.

Common Biology failure modes

  • labels memorised without structure-function reasoning
  • diffusion/osmosis mixed up
  • breathing confused with respiration
  • observations given without biological mechanism
  • cause and effect reversed
  • genetics terminology imprecise
  • graph trend described but not explained
  • practical variables not controlled

How to use the index

  1. Confirm K325, K327 or K328.
  2. Mark shared and Pure-only topics.
  3. Diagnose weak concepts by mechanism, not chapter score alone.
  4. Route deeper ‘why’ questions into Science World.
  5. Return to data, practical and unfamiliar-context questions.
  6. Retest with changed examples.

Next Atlas owners

Use the canonical Enzymes and Transport in Humans owners for syllabus-facing learning; both route onward into the deeper Living World and human-biology mechanisms already present in Science World.

Frequently asked questions

What replaces O-Level Pure Biology in 2027?

G3 Biology K325; 6093 is the 2026-and-earlier reference code.

Which Combined Science codes contain Biology?

K327 Physics/Biology and K328 Chemistry/Biology.

How many named topics are in 2027 Pure Biology?

Four themes containing 14 named topics.

How many named Biology topics are in the 2027 G3 Combined Science structure?

12 named topics.

Are Pure and Combined Biology identical?

No. They overlap substantially but differ in named scope and expected depth.

Where does this sit in Atlas?

This is the canonical Biology syllabus index under the Secondary Science Shelf.

The final Biology rule

Biology becomes manageable when structure, function and process remain connected. Confirm the syllabus route, use the index to find the topic, then follow the mechanism until the biological consequence can be explained from first principles.

Opening Biology concept owners

Explore the connected learning guides

Choose the question that brought you here. Open one useful guide, try a small task, and stop when you have what you need.

Take one question further

The same learning habit can travel across subjects, while each subject keeps its own methods. These routes help you notice a difficulty, understand one part of it, and return to something you can do.

A word is familiar, but using it is difficult.

Move from recognising a word to retrieving it in a new context. Understand vocabulary plateaus.

Try it without the guide: Choose one word you already know. Close the guide and use it in a new sentence. Explain why it fits; try another context tomorrow.

A piece of writing has ideas, but the reader loses the thread.

Make the order of events and the links between sentences clear. Explore composition writing.

Try it without the guide: Choose one short paragraph. Read the relevant explanation, close it, and revise the paragraph. Ask someone to tell you what happened and why.

The Mathematics seems familiar, but marks still disappear.

Find the first point where the working stops being reliable. Find Secondary 4 A-Math mark leakage.

Try it without the guide: For a Secondary 4 A-Math question you have attempted, locate the first uncertain line. Repair that step, then try a comparable question without the worked answer.

A Science fact is remembered, but the explanation is incomplete.

Connect the evidence to a scientific idea and the resulting change. Follow the Primary Science learning route.

Try it without the guide: Choose a familiar Primary Science example. Explain the evidence, the idea and the result without notes. Then change one condition and explain your prediction.

Two accounts of the world seem to disagree.

Check the question, source, date and evidence before combining claims. Explore the World Knowledge research library.

Try it without the guide: Take one claim. Find the source best placed to support it, note its date, and state what remains uncertain. Return to your original question.

There is plenty of help, but independence is hard to see.

Check what the learner can understand and do after support is removed. Understand how education works.

Try it without the guide: Choose one small task the child has practised. Agree on a calm, brief attempt without prompts. Use what happens to choose one next step, then stop.

For the structure behind these connections, read the eduKateSingapore runtime manifest and the eduKate ecosystem boot contract. The reader map describes public navigation; those manifests preserve the wider ownership and return rules.