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.
Porifera, Cnidaria and Ctenophora
Phylum Porifera
Poriferans are commonly called sponges. Most are marine, and adults are generally attached to a substratum.
- They show a cellular level of organisation.
- The body has numerous pores called ostia through which water enters.
- Water circulates through a canal system and leaves through the osculum.
- Choanocytes or collar cells help generate water currents and capture food.
- The skeleton consists of spicules or spongin fibres.
- Reproduction may be asexual or sexual.
Examples: Sycon, Spongilla and Euspongia.
Phylum Cnidaria or Coelenterata
- They are aquatic, mostly marine, and show tissue-level organisation.
- They are diploblastic and generally radially symmetrical.
- Cnidocytes contain nematocysts used in prey capture and defence.
- The gastrovascular cavity generally has a single opening.
- Polyp and medusa forms occur in different members.
- Metagenesis occurs in organisms such as Obelia.
Examples: Hydra, Aurelia, Adamsia, Physalia and Meandrina.
Phylum Ctenophora
- Commonly called comb jellies or sea walnuts.
- They are exclusively marine and diploblastic.
- Eight rows of ciliated comb plates help in locomotion.
- Bioluminescence is a characteristic feature.
- Sexual reproduction is common.
Examples: Pleurobrachia and Ctenoplana.
| Phylum | Identifying feature | Example |
|---|---|---|
| Porifera | Water canal system and choanocytes | Sycon |
| Cnidaria | Cnidocytes containing nematocysts | Hydra |
| Ctenophora | Eight rows of comb plates | Pleurobrachia |
NEET focus: Water canal system indicates Porifera; cnidocytes indicate Cnidaria; eight comb rows indicate Ctenophora.
