Classification of Animal Kingdom | SSC CGL Tier 2 - Study Material, Online Tests, Previous Year PDF Download

Animal Kingdom Classification

Chordates and Non-chordates: An Overview

• Non-chordates: Non-chordates lack a notochord and include various worm-like marine species. This phylum encompasses Porifera, Coelenterata, Ctenophora, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, and Hemichordata. General characteristics of non-chordates involve cylindrical, triploblastic, coelomate, or pseudocoelomate structures, diverse respiratory methods, and open circulatory systems.
• Chordates: Chordates, characterized by the presence of a notochord at some stage, extend beyond vertebrates. Invertebrates with a notochord at some point are also classified as chordates. Key characteristics include bilateral symmetry, a post-anal tail, a closed circulatory system, and the presence of pharyngeal gill slits.

Subphyla within Chordata: An In-depth Look

1. Subphylum Urochordata: Also known as Tunicata, these marine animals develop a leathery covering. The notochord is present only in the larval tail, and they transition to sessile adults after settling on the seabed.
2. Subphylum Cephalochordata: Comprising small, fish-like marine animals, this subphylum features an extended notochord along the entire body. The presence of numerous gill slits and separate sexes distinguishes them.
3. Subphylum Vertebrata: In this subphylum, the notochord is present in embryonic stages and is replaced by a vertebral column in adulthood. Vertebrates exhibit a true vertebral column, internal skeleton, and various chambered hearts.

Vertebrates Classification: Exploring the Five Classes

1. Class Pisces (Fishes):

   • Streamlined aquatic animals.
   • Possess fins for propulsion.
   • Cold-blooded, with exceptions like the opah.
   • Examples: Dogfish, Rohu.

2. Class Amphibia:

   • Cold-blooded organisms requiring an aquatic habitat for egg-laying.
   • Characterized by two pairs of limbs and smooth, moist skin.
   • Examples: Frog, Toad, Salamander.

3. Class Reptilia:

   • Ectothermic organisms with osteoderms forming scales.
   • Lack external ears; some snakes are "deaf," relying on thermoception.
   • Examples: Tortoise, Wall lizard, Snake.

4. Class Aves (Birds):

   • Streamlined body for low air resistance during flight.
   • Forelimbs modified into wings; feathers for various functions.
   • Warm-blooded with the ability to regulate body temperature.
   • Examples: Parrot, Pigeon, Duck.

5. Class Mammalia:

   • Distinguished by mammary glands.
   • Two pairs of limbs with digits equipped with claws, nails, or hooves.
   • Covered in hair with external ears (pinnae).
   • Warm-blooded animals.
   • Examples: Monkeys, Lions, Bats, Humans.

Conclusion: The classification of animals into chordates and non-chordates, further branching into subphyla and classes within Chordata, provides a systematic framework for understanding the incredible diversity within the animal kingdom.