The Parazoa

Question 1

Parazoans are

Answer 1

The simplest and most primitive multicellular animals
Despite this their cells are not organised into tissues and organs

Question 2

Metazoan are

Answer 2

Multicellular animals whose cells are organised into tissues and organs

Question 3

Parazoa has only one Phylum:

Answer 3

Phylum porifera

Question 4

The most primitive and simplest multicellular animals are

Answer 4

Poriferans

Question 5

Poriferans are at what level of organisation

Answer 5

Cellular level

Question 6

Poriferans are predominantly -

Answer 6

Marine

Question 7

Central body cavity of sponges is known as

Answer 7

Spongocoel or paragaster

Question 8

Cells in sponges are arranged in

Answer 8

Two layers around a central cavity

Question 9

Gastral layer or choanoderm is

Answer 9

The layer lining the internal cavity in sponges

Question 10

What are choanocytes

Answer 10

These are collared flagellated cells that line the choanoderm in sponges

Question 11

What are ostia

Answer 11

These are numerous pores that perforate the body of sponges for which they are named porifera

Question 12

Ostia are linked to

Answer 12

Inhalant canals

Question 13

How does water enter into sponges

Answer 13

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

Question 14

Major opening in sponges is

Answer 14

An exhalant not mouth
This is the osculum

Question 15

Food particles are engulfed by

Answer 15

Choanocytes where digestion takes place
Indigested food is injected into the space within the collar

Question 16

Sponges are often coloured due to

Answer 16

Interaction with symbiotic algae

Question 17

Individual sponges are

Answer 17

Hermaphrodites

Question 18

Reproduction in sponges is by

Answer 18

Sexual and asexual means

Question 19

What is amphiblastula

Answer 19

One of different larval forms of sponges

Question 20

Phylum porifera is divided into

Answer 20

Four classes
Class calcarea
Class hexactinellida
Class Demospongiae
Class Scelerospongiae

Question 21

Xtics of Class calcerea

Answer 21

These are sponges with skeletons consisting solely of calcerous spicules
They have large choanocytes
Eg leucoslenia, sycon

Question 22

Xtics of Hexactinellida

Answer 22

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

Question 23

Xtics of Demospongiae

Answer 23

They lack skeleton
If present may be siliceous without six rayed spicules
Choanocytes are small and possess jelly
Eg spongilla, oscarella

Question 24

Xtics of scelerospongiae

Answer 24

Very small class of leuconoid sponges
Similar to dermospongiae
Found in association with coral reef

Question 25

Skeleton of scelerospongiae is made of

Answer 25

Siliceous spicules and sponging fibres confined to a thin superficial layer on top of a huge mass of calcium carbonate