Question

evolutionary relationship between spines of opuntia and Thorns of bougainvillea

Answer 1

omologous organs are those organs which have the same basic structure (or same basic design) but different functions. Hence, they have common ancestor or origin.

Both the thorns of bougainvillea and tendrils of cucurbita origin from the stem and are modified from the auxiliary buds but their functions are different. The thorns in bougainvillea provide protection while the tendrils in cucurbita provide support.

Since the thorns of bougainvillea and tendrils of cucurbita have same basic structure but are modified to perform different functions, they are homologous organs.