Well-defined nucleus is absent in

Draw a diagram of $Euglena$ and label the following parts:
Flagellum,photoreceptor,eyespot,chloroplast,nucleus,contractile vacuole.

$(a)$ Associate any three phyla of Animalia with triploblastic body organisation and bilateral symmetry.
$(b)$ State the meaning of triploblastic body organisation and bilateral symmetry.
$(c)$ On the basis of presence or absence of coelom,compare the three phyla answered in $(a)$.

$(a)$ State two characteristic features of nematodes.
$(b)$ Identify the phylum with the help of the following features:
$(i)$ Spiny-skinned,radially symmetrical,and have tube feet.
$(ii)$ Triploblastic,worm-like,having a segmented body.

Which one is the most striking or common character of the vertebrates?

Associate the following features with the groups in which they first appeared:
$(a)$ Vascular tissues
$(b)$ Notochord
$(c)$ Seeds inside fruits