Chondrichthyes is characterised by

• Placoid scale

• Ventral mouth

• Ctenoid scale and ventral mouth

• Placoid scale and ventral mouth

Animals of class-Mammalia have

• Seven cervical vertebrae

• Seven cranial nerve

• Single ventricular chamber

• Fourteen cervical vertebrae

The echinoderms are

• arborial insects

• marine animals

• terrestrial insects

• freshwater forms

Tube feet is the locomotory organ in 

• starfish

• jelly fish

• silver fish

• Scoliodon

Sea gulls excrete excess of NaCl from

• liver

• lungs

• nasal activity

• kidney

Connecting link between annelids and molluscs is

• Neopilina

• Peripatus

• Periplaneta

• Limulus

Ruminants belong to order

• Proboscida

• Artiodactyla

• Marsupials

• Edentata

138.

Which of the following have notochord throughout life?

• Birds

• Fish

• Snake

• Amphioxus

During unfavourable conditions, the sponges form

• cyst

• encyst

• spicule

• Gemmule

Shell of molluscs is derived from

• foot

• mantle

• ctenidia

• placoid