Edexcel A Level (IAL) Biology -3.2 Levels of Organisation of Cells- Study Notes- New Syllabus
Edexcel A Level (IAL) Biology -3.2 Levels of Organisation of Cells- Study Notes- New syllabus
Edexcel A Level (IAL) Biology -3.2 Levels of Organisation of Cells- Study Notes -Edexcel A level Biology – per latest Syllabus.
Key Concepts:
- 3.2 understand how the cells of multicellular organisms are organised into tissues, tissues into organs, and organs into organ systems
Cell Organisation in Multicellular Organisms
🌱 Introduction
Multicellular organisms have many specialized cells.
To perform life functions efficiently, cells work together in a hierarchical organisation:
Cell → Tissue → Organ → Organ System → Organism
🔹 Cells
- Definition: The basic unit of structure and function in living organisms.
- Specialization: Cells are specialized to perform specific functions.
- Example: Red blood cells carry oxygen, nerve cells transmit impulses.
🔹 Tissues
Definition: A group of similar cells performing a common function.
| Organism Type | Tissue | Function |
|---|---|---|
| Plants | Xylem | Transport water |
| Plants | Phloem | Transport food |
| Animals | Muscle tissue | Movement |
| Animals | Epithelial tissue | Covers and protects body surfaces |
| Animals | Connective tissue | Supports and binds other tissues |
🔹 Organs
Definition: A structure made of different types of tissues working together to perform a specific function.
| Organ | Tissues Involved | Function |
|---|---|---|
| Heart | Muscle tissue, connective tissue, epithelial tissue | Pumps blood |
| Leaf | Epidermis, mesophyll, vascular tissue | Photosynthesis and gas exchange |
| Lungs | Epithelial tissue, connective tissue, smooth muscle | Gas exchange (O₂ in, CO₂ out) |
🔹 Organ Systems
Definition: A group of organs working together to perform a major life function.
| System | Organs | Function |
|---|---|---|
| Circulatory system | Heart, blood vessels, blood | Transport of oxygen, nutrients, and wastes |
| Digestive system | Stomach, intestines, liver | Breakdown and absorption of food |
| Respiratory system | Lungs, trachea, bronchi | Gas exchange |
| Nervous system | Brain, spinal cord, nerves | Coordination of body activities |
🌿 Hierarchy Diagram
Cell → Tissue → Organ → Organ System → Organism
Each level increases in complexity and specialization.
💡 Key Points
- Cells specialize to perform a function.
- Similar cells → tissues, tissues → organs, organs → organ systems.
- Organisation allows efficiency and division of labour in multicellular organisms.
🧠 Quick Recap
Cell → Basic unit of life → Red blood cell, muscle cell
Tissue → Group of similar cells → Muscle tissue, xylem
Organ → Different tissues working together → Heart, leaf
Organ system → Organs working together → Circulatory system, respiratory system
Organism → Whole living being → Human, plant