2. Organisation of the Organism (Cambridge IGCSE Biology 0610 for exams in 2023,2024 and 2025)

Overview of Topic 2 in the Cambridge IGCSE syllabus.
Emphasis on cells as the basic unit of life, analogous to building blocks for organisms.

Nucleus: Control center containing genetic material; stores DNA and coordinates cellular activities.
Mitochondria: Powerhouse of the cell; site of aerobic respiration for energy production.
Cell Membrane: Selectively permeable barrier; controls entry and exit of substances, protecting the cell.
Cytoplasm: Jelly-like substance housing organelles; site of numerous chemical reactions.
Ribosomes: Sites of protein synthesis; crucial for making various proteins needed by the cell.

Structures commonly found in both animal and plant cells:
- Nucleus
- Mitochondria
- Cell Membrane
- Cytoplasm
- Ribosomes
Cell Wall: Made of cellulose; provides structural support and protection.
Chloroplasts: Contain chlorophyll; site of photosynthesis, converting sunlight into usable energy.
Vacuole: Contains cell sap; used for storage and maintaining cell shape.

Nucleus: Coordinates cellular functions and stores genetic material.
Mitochondria: Vital for energy production through aerobic respiration.
Cytoplasm: Medium for chemical reactions; supports organelles.
Ribosomes: Essential for producing proteins necessary for various cellular functions.
Cell Membrane: Protects the cell and regulates substance movement.
Cell Wall (Plant Cells): Offers support and protection.
Chloroplasts: Enable photosynthesis, essential for plant nutrition.
Vacuole: Storage and structural integrity of plant cells.

Similarities and differences compared to animal cells:
- Contains circular DNA and plasmids, enabling genetic material exchange.

Cells are produced by the division of existing cells.
Levels of biological organization:
- Cells → Tissues (groups of similar cells)
- Tissues → Organs (groups of different tissues)
- Organs → Organ Systems (groups of organs)
- Organ Systems → Multicellular Organism

Ciliated Cells: Move mucus in airways; have hair-like structures (cilia).
Root Hair Cells: Absorb minerals and water; located in plant roots.
Palisade Mesophyll Cells: Contain chloroplasts for photosynthesis; located in leaves.
Neurons: Transmit electrical impulses; nerve cells.
Red Blood Cells: Transport oxygen; contain hemoglobin.
Gametes (Sperm and Egg Cells): Responsible for reproduction; nuclei fuse to form an embryo.

Understanding magnification:
- Magnification = Image Size / Actual Size.
Both sizes must be in millimeters.
Example Problem: If a leaf image is 30mm and its actual thickness is 2mm, magnification = 30 / 2 = 15 (no units).