Animal Kingdom
NCERT Class 11 Biology | CBSE | NEET-UG Preparation
Study the basis of animal classification, the major non-chordate phyla, chordate characteristics and vertebrate classes. Revise important definitions, identifying features, examples and comparisons for CBSE examinations and NEET-UG.
Mollusca, Echinodermata and Hemichordata
Phylum Mollusca
- The body is generally soft and unsegmented.
- Typical body regions include the head, muscular foot and visceral hump.
- The mantle often secretes a calcareous shell.
- The radula is a rasping feeding organ in many molluscs, but is absent in bivalves.
- Respiration commonly occurs through gills.
Examples: Pila, Unio, Sepia, Loligo, Octopus and Pinctada.
Phylum Echinodermata
- They are exclusively marine.
- Adults generally show pentaradial symmetry; larvae are bilaterally symmetrical.
- The calcareous endoskeleton consists of ossicles.
- The water vascular system is a distinctive feature.
- Tube feet assist locomotion, food capture and respiration.
Examples: Asterias, Echinus, Ophiura and Antedon.
Phylum Hemichordata
- They are marine, worm-like animals.
- The body is divided into proboscis, collar and trunk.
- Pharyngeal gill slits are present.
- The circulatory system is open.
- A stomochord is present; it is not homologous to the chordate notochord.
Example: Balanoglossus.
| Phylum | Distinctive feature | Example |
|---|---|---|
| Mollusca | Muscular foot, mantle and visceral mass | Pila |
| Echinodermata | Water vascular system | Asterias |
| Hemichordata | Proboscis, collar and trunk | Balanoglossus |
NEET focus: The water vascular system identifies Echinodermata. The radula occurs in many molluscs, while the stomochord is characteristic of Hemichordata.
