Exercise 12.6
Reproduction — asexual and/or sexual methods.
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
This item's stored line is a stray fragment of the §$\displaystyle 12.3.1$ criteria list. The chapter's Pause and Ponder $\displaystyle 6$ (page $\displaystyle 242$) asks how a beetle's hard external skeleton helps it survive, given that an earthworm is segmented too.
It protects the body. The rigid outer covering shields the soft parts underneath from injury and from predators — an earthworm has no skeleton at all (Fig. $\displaystyle 12.16$ marks Annelida with an X for skeleton).
It reduces water loss. The hard covering seals the body surface, so the beetle does not dry out. This is the decisive difference: the earthworm must stay in moist soil or water, while the beetle can live on open, dry land.
It supports powerful muscles. Muscles anchor to the exoskeleton, giving the beetle strong, precise movement — walking, digging, flying.
Segmentation plus the exoskeleton together give flexibility with strength: the segments allow bending and controlled movement, the hard plates supply protection.
Net effect, in the chapter's own terms: the exoskeleton lets arthropods survive in dry and exposed environments that annelids cannot enter.
