Question

Section 28.1

1. Briefly describe the general body plan of a typical sponge. Also describe the germ layer and symmetry.

2. What is the purpose of the choanocytes and amoebocytes?

3. How do sponges obtain nutrients?

4. Mode of locomotion.

Answer 1

1. Sponges formed from ectoderm and endoderm so they are diploblastic. Asymmetric means they don’t have any symmetry like other higher organisms. The basic body plan is called asconoid. They have a body cavity called spongocoel. Water pumped directly through pores (these pores are called Ostia) into spongocoel. The spongocoel is lined with digestive cells called choanocytes. synconoid body plan is a little more complex. Here ostia lead to a network of canals and before the connection at spongocoel. Digestion takes place in canals. so there is no digestive cells surrounds spongocoel. The most complex form is leuconoid, the canal system is a branched type here. Moreover, leads to the digestive chamber. Then leads to osculum.

  

2. Amoebocytes deliver nutrients from choanocytes to other cells of the sponge. They give nutrients to eggs for sexual reproduction. They are totipotent. store digest and transport food and excrete waste.

3.Choanocytes otherwise called collar cells. line interior of ascanoid, synconoid, and leuconoid body types sponges. contain a central flagellum. Choanocytes filter particles out of the water and into spongocoel. improves respiratory digestive function of sponges.

4. They have Ostia. Water flow in through Ostia, cells in walls filter nutrients from water when water is pumped through the osculum. Digestive cells are present in osculum. water flow is only one direction regulated by the beating of flagella.

5.Sponges are sessile generally. They attaches to their substratum. they are devoid of movements. They can creep along substrata by organizational plasticity.