Question

In the following question a statement of assertion is followed by a statement of reason.

Assertion: Thorns of Bougainvillea and tendrils of Cucurbita represent homology.
Reason: Homologous organs have similar functions but are different in their structural details and origin.

Answer 1

The organs in different organisms which have the same fundamental (anatomical) structure due to same ancestral origin but are different in functions are called homologous organs. These organs follow the same basic organisation, but organs are modified to perform different functions as an adaptation to different environments.

Axillary buds of Bougainvillea and Cucurbita have similar anatomical structures during their development, but in adult condition, these organs are modified to perform different functions as an adaptation to different environments. In Bougainvillea, the axillary bud has been modified into a thorn to provide protection. In Cucurbita, the axillary buds are modified into a tendril to provide support. Therefore, thorns of Bougainvillea and tendrils of Cucurbita represent homology.