Chapter 7 / 7.1 Organ and Organ System

Chapter 7: Structural Organisation in Animals

Let’s break down how animals are built:

🐛 Unicellular organisms (like amoeba) do everything with just one cell – eating, breathing, reproducing.
🐸 Multicellular animals (like frogs or humans) have millions of cells working together in teams.
🔬 Tissues form when similar cells team up for a specific job. There are only 4 basic types in complex animals!
❤️ Organs (like heart/lungs) are made when tissues combine in specific patterns. Example: Your heart contains all 4 tissue types!
🤝 Organ systems (like digestive/respiratory systems) happen when organs work together for big tasks. This teamwork is called “division of labour”.

Meet our amphibian friend! Frogs:

🌊 Belong to class Amphibia (phylum Chordata)
🌡️ Are cold-blooded (poikilotherms) – body temperature changes with the environment
🎨 Can change skin color to hide from enemies (camouflage/mimicry)
😴 Avoid extreme weather by hiding in burrows:
- Summer sleep = Aestivation
- Winter sleep = Hibernation

💦 Skin: Smooth/slippery (thanks to mucus!), always moist, olive green with dark spots on top, pale yellow underneath. Frogs absorb water through skin – they never drink!
🔎 Body parts:
- Divided into head + trunk (no neck or tail!)
- 👃 Pair of nostrils above mouth
- 👀 Bulging eyes covered by a protective nictitating membrane
- 👂 Tympanum (ear membrane) on each side for hearing
- 🦵 Forelimbs + hind limbs for movement

4 Basic Tissues → Form organs → Create organ systems (division of labour!)
Poikilotherms: Animals like frogs whose body temperature depends on the environment
Frog Survival Tactics: Camouflage (mimicry), aestivation (summer sleep), hibernation (winter sleep)
Frog Skin: Moist, water-absorbing, no scales!
Morphology vs Anatomy: External features (morphology) vs internal organs (anatomy)

Keep going! You’re understanding how life organizes itself from cells to whole animals 🙌