The system of scientific naming was introduced by

You are given leech,Nereis,Scolopendra,prawn,and scorpion; all have a segmented body organization. Will you classify them in one group? If no,give the important characters based on which you will separate these organisms into different groups.

Name the phylum to which the organism shown in the image belongs. Write any two characteristic features of this phylum.

State reasons for the following:
$(i)$ Tapeworms do not have a digestive tract.
$(ii)$ Frogs have both skin and lungs for breathing.
$(iii)$ $A$ whale is a mammal,not a fish.

$A$ well-defined nucleus is absent in

Echinoderms have a system that they use for moving around. Name the system. What is their skeleton made-up of?