Animal Kingdom

Introduction

• Over a million species of animals described.
• Classification helps in systematic positioning of species.

4.1 Basis of Classification

• Fundamental features used in classification:
  • Arrangement of cells
  • Body symmetry
  • Nature of coelom
  • Patterns of digestive, circulatory, and reproductive systems.

4.1.1 Levels of Organisation

• Cellular Level: e.g., Sponges with loose cell aggregates.
• Tissue Level: e.g., Coelenterates where cells form tissues.
• Organ Level: e.g., Platyhelminthes with tissues forming organs.
• Organ System Level: e.g., Annelids, Arthropods with systems for specific functions.

4.1.2 Symmetry

• Asymmetrical: e.g., Sponges.
• Radial Symmetry: e.g., Coelenterates, Ctenophores.
• Bilateral Symmetry: e.g., Annelids, Arthropods.

4.1.3 Diploblastic and Triploblastic Organisation

• Diploblastic: Two germ layers (ectoderm and endoderm) e.g., Coelenterates.
• Triploblastic: Three germ layers (additional mesoderm) e.g., Platyhelminthes.

4.1.4 Coelom

• Coelomates: Body cavity lined by mesoderm.
• Pseudocoelomates: Body cavity not completely lined by mesoderm.
• Acoelomates: No body cavity.

4.1.5 Segmentation

• Serial repetition of segments (e.g., earthworm).

4.1.6 Notochord

• Chordates have notochord; non-chordates do not (e.g., Porifera to Echinoderms).

4.2 Classification of Animals

• Broad classification based on fundamental features.

4.2.1 Phylum Porifera

• Known as sponges; marine and asymmetrical.
• Cellular level organization with water transport system.
• Reproduction: Sexual (internal fertilization) and asexual (fragmentation).

4.2.2 Phylum Coelenterata (Cnidaria)

• Aquatic, radially symmetrical.
• Tissue level organization with cnidocytes for defense and prey capture.

4.2.3 Phylum Ctenophora

• Marine, radially symmetrical with comb plates for locomotion.

4.2.4 Phylum Platyhelminthes

• Flatworms; bilaterally symmetrical, triploblastic and acoelomate.

4.2.5 Phylum Aschelminthes

• Roundworms; pseudocoelomate, bilaterally symmetrical.

4.2.6 Phylum Annelida

• Segmented worms with closed circulatory system.

4.2.7 Phylum Arthropoda

• Largest phylum with jointed appendages.

4.2.8 Phylum Mollusca

• Soft-bodied with calcareous shell.

4.2.9 Phylum Echinodermata

• Spiny-skinned marine animals with radial symmetry and water vascular system.

4.2.10 Phylum Hemichordata

• Worm-like with proboscis, collar, and trunk.

4.2.11 Phylum Chordata

• Possess notochord, dorsal nerve cord, and gill slits.
• Subphyla: Urochordata, Cephalochordata, Vertebrata.

Subphylum Vertebrata

• Further divided into classes: Cyclostomata, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, Mammalia.

Classes Overview

• Cyclostomata: Jawless vertebrates like lampreys.
• Chondrichthyes: Cartilaginous fishes e.g., sharks.
• Osteichthyes: Bony fishes e.g., Rohu.
• Amphibia: Dual life, e.g., frogs.
• Reptilia: Scaly skin, e.g., crocodiles.
• Aves: Birds with feathers and beaks.
• Mammalia: Warm-blooded with mammary glands.

Summary

• Classification is based on fundamental features like symmetry, coelom, and notochord.
• Each phylum has distinctive characteristics.
• Chordates are distinguished by the presence of a notochord.

Exercises

• Questions on classification challenges, coelom importance, digestion types, and phylum-specific features.