Chapter 7 — Structural Organisation in Animals

Chapter 7 of the Class 11 Biology NCERT textbook, "Structural Organisation in Animals", covers this topic. It explains the structural organisation of animals through tissues, organs, and organ systems, with detailed anatomy and morphology of the frog as a representative vertebrate example.

• Hierarchy enables division of labour — The chapter builds the idea that complex animals are organized in levels—cells to tissues to organs to organ systems—so that different structures can specialize and share the work of keeping the body alive.
• Four basic tissue types — It teaches that all complex animals are built from just four tissue types—epithelial, connective, muscular, and neural—which combine in different proportions to form every organ.
• The frog as a model vertebrate — Using Rana tigrina, the chapter shows how a real amphibian integrates digestive, circulatory, respiratory, nervous, excretory, and reproductive systems, and how traits like cold-bloodedness and camouflage fit its life.

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