The Parazoa Flashcards
Parazoans are
The simplest and most primitive multicellular animals
Despite this their cells are not organised into tissues and organs
Metazoan are
Multicellular animals whose cells are organised into tissues and organs
Parazoa has only one Phylum:
Phylum porifera
The most primitive and simplest multicellular animals are
Poriferans
Poriferans are at what level of organisation
Cellular level
Poriferans are predominantly -
Marine
Central body cavity of sponges is known as
Spongocoel or paragaster
Cells in sponges are arranged in
Two layers around a central cavity
Gastral layer or choanoderm is
The layer lining the internal cavity in sponges
What are choanocytes
These are collared flagellated cells that line the choanoderm in sponges
What are ostia
These are numerous pores that perforate the body of sponges for which they are named porifera
Ostia are linked to
Inhalant canals
How does water enter into sponges
Water enters by the ostia and passes into the inhalant canals into the spongocoel. It carries along with it minute organisms that serve as food
Major opening in sponges is
An exhalant not mouth
This is the osculum
Food particles are engulfed by
Choanocytes where digestion takes place
Indigested food is injected into the space within the collar
Sponges are often coloured due to
Interaction with symbiotic algae
Individual sponges are
Hermaphrodites
Reproduction in sponges is by
Sexual and asexual means
What is amphiblastula
One of different larval forms of sponges
Phylum porifera is divided into
Four classes
Class calcarea
Class hexactinellida
Class Demospongiae
Class Scelerospongiae
Xtics of Class calcerea
These are sponges with skeletons consisting solely of calcerous spicules
They have large choanocytes
Eg leucoslenia, sycon
Xtics of Hexactinellida
These sponges have purely siliceous skeleton composed of six rayed spicules
Choanocytes are small and lack jelly
They are deep sea group
Eg euplectella, hyalonema
Xtics of Demospongiae
They lack skeleton
If present may be siliceous without six rayed spicules
Choanocytes are small and possess jelly
Eg spongilla, oscarella
Xtics of scelerospongiae
Very small class of leuconoid sponges
Similar to dermospongiae
Found in association with coral reef
