Wednesday, July 29, 2020

Animal Kingdom - Notes | Class 11 | Part 2: Porifera

4. ANIMAL KINGDOM

PHYLUM PORIFERA (SPONGES): GENERAL CHARACTERS

  1. Grades of organization:
    • Cellular grade.
  2. Symmetry:
    • Asymmetrical. Some are radial.
  3. Coelom:
    • Acoelomate
  4. Habit and habitat:
    • Aquatic (mostly marine). Sedentary. Solitary/colonial.
  5. Digestive system:
    • Absent. Intracellular digestion.
  6. Respiratory system:
    • Absent
  7. Circulatory system:
    • Absent
  8. Reproduction:
    • Asexual (fragmentation) & Sexual.
    • Hermaphrodite (Monoecious): Male and female sex organs are seen in same individual.
    • Internal fertilization.
    • Development is indirect.
  9. Unique features:
    • Water canal (water transport) system. Millions of ostia (pores).
    • Water canal system: Here, water enters through minute pores (ostia) in the body wall into a central cavity (spongocoel), from where it goes out through osculum. Canal system is used for food gathering, gas exchange and removal of wastes.
    • Spongocoel & canals are lined with choanocytes (collar cells).
    • Body is supported by spicules and spongin fibres.
  10. Examples:
    • Sycon (Scypha), Spongilla (fresh water sponge), Euspongia (Bath sponge)


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