Which among the following is exclusively marine?

Study the figure and answer the following questions:
$(a)$ Label $A$ and $B$.
$(b)$ Identify the organism and its kingdom.
$(c)$ Name two organisms (other than the one shown here) belonging to the same kingdom.

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.

Which among the following phyla is exclusively marine?

Bacteria and Cyanobacteria are included under kingdom Monera. Explain in detail the structure of $E.$ Coli bacteria. What kind of body design does it have? State its mode of nutrition.

Explain by giving three reasons,how the work done by earlier scientists with respect to classification is helpful to the present generation.