(a) Homologous structures are the organs which are similar in basic structure and have a common origin but perform different functions.
(i) They have same basic structure but are used for different functions i.e. swimming and flying respectively. So they are homologous.
(ii) Tuber of potato is a stem modification while the tuber of sweet potato is a root modification. But their function is same i.e food storage, so they are analogous.
(iii) Eyes of octopus and mammals have different basic structures but their function is same so they are analogous.
(iv) Thorns of Bougainvillea and tendrils of Cucurbita are both stem modifications but their functions are different i.e. protection and climbing respectively. So they are homologous.
(b) This type of evolution is called divergent evolution because the origin of homologous organs are same but they diverged into different directions to perform different functions.
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