NCERT Solutions for Class 11 Biology Chapter 4 – Animal Kingdom
Chapter 4 Animal Kingdom is one of the most detail-intensive chapters in Class 11 Biology, and it is a goldmine of marks in both CBSE board exams and NEET. The chapter systematically classifies the entire animal kingdom into major phyla based on key structural and functional characteristics. From the simplest sponges of Phylum Porifera to the highly evolved Phylum Chordata — including the vertebrates — every phylum has specific features, symmetry types, coelom status, and representative examples that you must know cold. Must check the CBSE resources and NCERT Solutions.
Students who approach this chapter with the right strategy — understand the basis of classification first, then memorise phylum-specific features with examples — find it surprisingly manageable. NCERT Solutions for Chapter 4 Animal Kingdom on Myclass24 are prepared to give you exactly that kind of structured, exam-ready guidance. Whether you are appearing for CBSE boards or NEET from cities like Patna, Nagpur, Coimbatore, Hyderabad, Bhopal, or Kanpur, these solutions will help you answer every question with confidence.
Download PDF – NCERT Solutions for Class 11 Biology Chapter 4 Animal Kingdom
Animals are classified based on several fundamental criteria: level of organisation (cellular, tissue, organ, organ-system), symmetry (radial, bilateral, or asymmetrical), coelom (acoelomate, pseudocoelomate, or coelomate), pattern of digestive system, circulatory system type, and segmentation / notochord presence.
Phylum Porifera (sponges) — the most primitive animals, with a cellular level of organisation. They are predominantly marine, sessile, and have a water canal system. Body has pores called ostia (for water in) and an opening called osculum (for water out). Canal system lined with collar cells (choanocytes) that trap food particles. Skeleton made of spicules (silica or calcium) or spongin fibres. Examples: Sycon (Scypha), Spongilla (freshwater), Euspongia.
Phylum Coelenterata / Cnidaria — first animals with tissue-level organisation. They are diploblastic (two germ layers: ectoderm and endoderm), show radial symmetry, and have a gastrovascular cavity with a single opening. They possess stinging cells called cnidoblasts / nematocysts used for defence and prey capture. They show alternation of generation (metagenesis) between polyp (sessile, asexual) and medusa (free-swimming, sexual) forms. Examples: Hydra (only polyp), Aurelia / jellyfish (only medusa), Obelia (both), Corals (reef-forming). Check out NCERT Solutions for Class 11 Biology and NCERT Solutions for Class 11 for the rest of the chapters.
| Phylum | Symmetry | Coelom | Key Feature | Examples |
| Porifera | Asymmetrical | Absent | Canal system, choanocytes | Sycon, Spongilla |
| Coelenterata | Radial | Absent | Cnidoblasts, nematocysts | Hydra, Aurelia, Coral |
| Platyhelminthes | Bilateral | Acoelomate | Flat body, flame cells | Planaria, Taenia, Fasciola |
| Aschelminthes | Bilateral | Pseudocoelomate | Cuticle, complete gut | Ascaris, Wuchereria |
| Annelida | Bilateral | Coelomate | Metameric segmentation | Earthworm, Leech, Nereis |
| Arthropoda | Bilateral | Coelomate | Jointed appendages, exoskeleton | Cockroach, Butterfly, Crab |
| Mollusca | Bilateral | Coelomate | Mantle, radula | Snail, Octopus, Pila |
| Echinodermata | Radial (adult) | Coelomate | Water vascular system | Starfish, Sea urchin |
| Hemichordata | Bilateral | Coelomate | Proboscis, gill slits | Balanoglossus |
| Chordata | Bilateral | Coelomate | Notochord, dorsal nerve cord | Fish, Frog, Humans |
Phylum Platyhelminthes (flatworms) — first triploblastic (three germ layers), bilaterally symmetrical, acoelomate animals. They have flame cells for osmoregulation and excretion. Most are parasitic — Taenia (tapeworm) causes cysticercosis; Fasciola (liver fluke) causes liver disease in cattle; Schistosoma causes schistosomiasis. Planaria is a free-living flatworm with regenerative ability.
Phylum Annelida — first true coelomates with metameric segmentation (body divided into similar repeating segments). They have a closed circulatory system. Excretion occurs through nephridia. Nereis is marine, dioecious (separate sexes). Earthworm (Pheretima) is hermaphrodite and economically important for soil aeration. Hirudinaria (leech) is an ectoparasite used in medicinal therapy (hirudin anticoagulant).
Phylum Arthropoda is the largest phylum in the animal kingdom — it includes over 80% of all known animal species. They have jointed appendages (the name means 'jointed leg'), a chitinous exoskeleton that is moulted periodically, open circulatory system, and compound eyes. They include insects (Apis/bee, Bombyx/silkworm, Anopheles/mosquito), arachnids (spider, scorpion), crustaceans (crab, prawn), and myriapods (centipede, millipede).
Phylum Chordata is defined by four features present at some stage of life: notochord, dorsal hollow nerve cord, pharyngeal gill slits, and post-anal tail. Non-chordate chordates include Urochordata (sea squirts / tunicates) and Cephalochordata (Amphioxus / Branchiostoma). Vertebrata are the main group — with a vertebral column replacing the notochord. They include Cyclostomata (jawless vertebrates — Petromyzon/lamprey), Chondrichthyes (cartilaginous fish — sharks, rays), Osteichthyes (bony fish — Labeo, Catla), Amphibia (Frog, Salamander), Reptilia (Lizard, Snake, Crocodile), Aves (Birds), and Mammalia (Mammals — including humans). Myclass24 NCERT Solutions for Chapter 4 provide systematic answers and comparison tables for all phyla and vertebrate classes.