Exercise 12.1
Meena and Hari observed an animal in their garden. Hari called it an insect while Meena said it was an earthworm. Choose the correct option which confirms that it is an insect. (i) Bilateral symmetrical body (ii) Body with jointed legs (iii) Cylindrical body (iv) Body with little segmentation
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
NCERT’s answer
(ii)
(ii) Body with jointed legs.
Jointed legs are the defining feature of Arthropoda, the phylum insects belong to — the name itself comes from arthro (limbs) and poda (appendages). An earthworm has no legs at all.
(i) is wrong because it does not separate them: both an insect and an earthworm are bilaterally symmetrical, with distinct head-tail and front-back regions.
(iii) is wrong — a cylindrical body describes the earthworm (Annelida), not the insect.
(iv) is wrong in both directions: the earthworm's body is clearly divided into segments, and arthropods are segmented too, with different segments specialised for different jobs.
Quick check for Hari: an insect also carries a hard exoskeleton, which Fig. $\displaystyle 12.16$ marks for Arthropoda and marks absent (X) for Annelida.
