Levels of Organisation
From a single cell → to a complete living organism. The Biological Russian Nesting Dolls.
🧠 The Factory Analogy
🔭 Explore Each Level
Cell
Zoom: 100×📖 Syllabus Definition
The basic unit of life. The smallest unit that can carry out all the functions of a living organism.
🧍 Human Example
A single Muscle Cell
🌿 Plant Example
A single Palisade Cell
🏗️ Build a Living Thing
⚠️ The Leaf Trap — Examiner's Most Common Trick
Leaf
ORGAN ✅
Contains:
• Palisade tissue
• Spongy mesophyll tissue
• Xylem tissue
• Phloem tissue
• Epidermis tissue
Stem
ORGAN ✅
Contains:
• Xylem tissue
• Phloem tissue
• Cortex tissue
• Epidermis tissue
Root
ORGAN ✅
Contains:
• Root hair tissue
• Xylem tissue
• Phloem tissue
• Cortex tissue
WHY? An organ is defined as a structure containing multiple different types of tissue. A Leaf contains palisade tissue AND spongy tissue AND xylem AND phloem. That makes it an organ, NOT just a tissue.
📝 Definition Builder — Fill the Gap
Write the complete syllabus definition for Tissue:
🔑 Keyword Summary — Paper 4 Essentials
Cell
Basic unit of life
Tissue
Similar cells → shared function
Organ
Group of tissues → specific functions
Organ System
Group of organs → body functions
Organism
Complete living being
⚠️ Leaf/Stem/Root
= ORGANS (not tissues!)
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