Chapter 7 — Structural Organisation in Animals

Class 11 Biology Chapter 7 covers the structural organisation of animals through tissues, organs, and organ systems, with detailed anatomy and morphology of the frog as a representative vertebrate example.

Structural organisation in animals involves the hierarchical arrangement of cells into tissues, organs, and organ systems that enable division of labour and body function. All complex animals consist of four basic tissue types organised into organs like the stomach, heart, and kidney. When organs work together, they form systems such as the digestive and respiratory systems. The chapter uses the frog (Rana tigrina), a common Indian amphibian belonging to class Amphibia, as a model organism to study vertebrate structure. Frogs exhibit cold-blooded characteristics, colour-changing ability for camouflage, and dormancy during extreme seasons. Their well-developed anatomical systems include digestive, circulatory, respiratory, nervous, excretory, and reproductive systems, each specialised for specific functions.

1. 01Animals are organised hierarchically: cells form tissues, tissues form organs, organs form organ systems that work together for survival
2. 02All complex animals contain four basic tissue types: epithelial, connective, muscular, and neural tissue
3. 03Frogs are cold-blooded (poikilothermic) amphibians with moist skin enabling both cutaneous and pulmonary respiration
4. 04Frog digestive system is short because they are carnivores; food is captured by a bilobed tongue and processed through the mouth, oesophagus, stomach, intestine, and cloaca
5. 05Frog circulatory system has a three-chambered heart (two atria, one ventricle) with portal systems connecting liver-intestine and kidney-body
6. 06Frog reproductive system is external with females laying 2500-3000 ova that develop through a tadpole larval stage before metamorphosis into adults