The 'Origin of Species' was written by:

Which among the following is exclusively marine?

What is haemocoel?

Name the phylum to which the following organisms belong:
$(a)$ Organisms which have a peculiar water-driven tube system that they use for moving around.
$(b)$ Organisms which have a foot that is used for moving around and have an open circulatory system.
$(c)$ These organisms have holes or pores all over the body. These lead to a canal system that helps in circulating water throughout the body.

On the basis of the following features,identify the group and give one example of each:
$(i)$ Presence of notochord at some stage of life.
$(ii)$ Unicellular,microscopic,and eukaryotic.
$(iii)$ Seeds are enclosed in fruits.

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.