Hard calcium carbonate structures are used as a skeleton by

Explain how,'Two areas of study namely $evolution$ and $classification$ are interlinked'. Justify this statement.

Which organism is more complex and evolved among Bacteria,Mushroom,and Mango tree? Give reasons.

State appropriate terms for the following:
$(i)$ Amphibians of the plant kingdom.
$(ii)$ Plants not having well-differentiated body design.
$(iii)$ Single-celled,eukaryotic,and photosynthetic organism.

Identify the plant bodies,which are commonly named as 'cryptogamae'. State and explain two characteristics,which are exhibited by each category of these plant bodies.

Label $X$ and $Y$ in the given diagram of Hydra.