Phylum Porifera, Biology tutorial

Introduction to Phylum Porifera:

The members of phylum Porifera are exciting and are situated extensively distributed in both fresh and salt water. They differ significantly in size and shape; few reach the size of 80cm to 2 meters in diameter where as others form thin incrustation on rocks, sponges as porifera are known as, has very large number of microscopic pores on surface of the body by which water passes constantly in from this stream of water, the sponges are able to strains out the microscopic organisms, that are used as food.

Distinctive Features of Phylum Porifera:

Structure of multicellular animals, poriferas called as sponges are simplest and most primitive. Main distinctive characters of Phylum that is called as Parozoa are given below:

  • They are asymmetrical
  • Well grown tissues and organs are not present.
  • Digestive system is absent and digestion of food is intracellular.
  • Body wall surrounding central cavity is only 2 layers outer layer called as dermal layer and inner layer as gastral layer.
  • Gastral layer has flagellated collared cells or choanocytes. They don't include respiratory and excretory organs. Nerves cells are absent. Pores or Ostia opening into gastral cavity are enclosed by contractile cells.
  • The complete outer surface of body illustrates presence of large number of Ostia by which constantly flowing stream of water is kept.

Categorization of Poriferas:

Different types of spicules in wall of Poriferas are utilized in Classification. Thus Porifera is separated into following classes:

  • CALCAREA OR CALCISPONGIAE eg. Leucosolenia, Scypha, Grantia, etc.
  • HEXACTINELLIDA e.g. Euplectella, Hyalonema
  • DEMOSPONGIA eg. Spondilla, Spongia

Leucosolenia (A Simple Coconial Sponge)

  • Phylum - Porifera
  • Class - Callerea
  • Order - Homocoela
  • Genus - Leucosolenia

External Organizations:

Leucosolenia is whitish or Yellow in colour. Comprises of the cluster of vase-shaped individuals. Every individuals are related to common horizontal branches with the base. Individuals are free above and open to exterior by the large opening known as osculum, present at the tip. Osculum is enclosed by the oscular fringed that is made up of circlet of monaxim catcareous spicules. Every individual cylinder has several pores, known as Ostia, in surface and it may achieve the height of about 25cm.

Ecological Adaptation:

Habit and Habitat:

Leucosolenia is small, delicate branching, colonial marine springe. It is global in distribution and found joined to stones and rocks of sea-shore water. For the life activities, it relies completely on water.

Structural Adaptation of Leucosolenia:

Body wall of leusolenia is extremely thin and unfolded comprising of two Layer (choanodern). These layers are divided by gelatinous layers of Mesoglea or Mensenchyme.

Dermal layer is protective layer. Constant movement of flagella, located in gastral layer, set in continuous water current in one direction. Mesoglea has kinds of cells that together form the Mesenchyme. Amoebocytes that are most significant cells in mesenchyme perform given functions:

  • They take food from choanocytes and supply it to other cells,
  • They carry on intracellular digestion of food and also help in the storage.
  • They carry on transport of waste matter.
  • They form scleroblasts which produce spicules or sponging fibre.
  • These form the endoskeleton.
  • They also function as germ cells.

Sensitivity:

Though sponge has no nervous system but still they illustrate response to contact, chemicals light and heat.

Reproduction:

Sponges carry in reproduction by given method:

1. Regeneration

2. Asexual reproduction

3. Sexual reproduction

Canal Systems in Sponges:

i) Passages through which water travels from outside body to interior of body and then outside again, form canal systems in sponges. Canal system is beneficial as follows;

ii) It brings the constant supply of water. Continuous current of water passing through the sponge furnishes plenty supply of oxygen for all cells.

iii) Continuous current water passing through the sponge carries away carbon dioxide and waste nitrogenous substances.

iv) Water that leaves sponge has been filtered off much of the food and oxygen and is loaded with poisonous waste resulting from metabolism.

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