Phylum Porifera: The Simplest Multicellular Animals
Sponges sit at the very base of Kingdom Animalia. They are primitive multicellular animals with a cellular level of organisation — specialised cells that never assemble into true tissues or organs. Yet this modest body plan works beautifully, powered by one elegant mechanism: a continuous flow of water.
In this quiz you will test your understanding of:
- Water entering through ostia, filling the spongocoel, and leaving via the osculum
- The three duties of the canal system — food gathering, respiratory exchange and waste removal
- Choanocytes (collar cells), intracellular digestion, and the skeleton of spicules or spongin fibres
- The hermaphrodite condition, asexual fragmentation, and indirect development through a distinct larval stage
Work carefully through each question — the details of the canal system explain almost everything else about sponge biology.
Q1. Members of Phylum Porifera are commonly known as:
Members of Phylum Porifera are commonly known as sponges.
Q2. Which level of organisation is exhibited by sponges?
Sponges are primitive multicellular animals with the cellular level of organisation, the lowest grade in the animal kingdom.
Q3. Sponges are generally marine and mostly:
Sponges are generally marine and mostly asymmetrical animals.
Q4. Water enters the body wall of a sponge through minute pores called:
Water enters through minute pores called ostia in the body wall.
Q5. The central cavity of a sponge into which water passes from the ostia is called the:
Water enters through ostia into a central cavity called the spongocoel.
Q6. Water leaves the body of a sponge through the:
From the spongocoel, water goes out through the osculum.
Q7. The water transport pathway of sponges is helpful in:
The pathway of water transport is helpful in food gathering, respiratory exchange and removal of waste.
Q8. Choanocytes, also called collar cells, are found:
Choanocytes or collar cells line the spongocoel and the canals.
Q9. In sponges, digestion takes place:
Digestion in sponges is intracellular.
Q10. The skeleton that supports the body of a sponge is made up of:
The body is supported by a skeleton made up of spicules or spongin fibres.
Q11. Sponges are described as hermaphrodite because:
Sexes are not separate (hermaphrodite), i.e., eggs and sperms are produced by the same individual.
Q12. Asexual reproduction in sponges takes place by:
Sponges reproduce asexually by fragmentation and sexually by formation of gametes.
Q13. In sponges, fertilisation is internal and development is:
Fertilisation is internal and development is indirect, having a larval stage which is morphologically distinct from the adult.
Q14. Which of the following is a fresh water sponge?
Spongilla is the fresh water sponge; Euspongia is the bath sponge and Sycon (Scypha) is another sponge genus.
Q15. Which statement best explains why sponges are placed at the base of Kingdom Animalia?
Sponges are primitive multicellular animals exhibiting the cellular level of organisation, the lowest grade recognised in the animal kingdom, which places them at the base of the classification scheme.