Two organisms occupying a particular geo | Class 12 Biology Chapter Evolution, Evolution NCERT Solutions

This phenomenon indicated in the question is convergent evolution where the unrelated animals converging on the same structure because they are adaptive in the same environment, this type of evolution is known as convergent evolution and this produces analogous structures. In the simple way we can say that analogous organs are those which have different origin or ancestors but performs similar functions.

Example:

1.  Streamlined shape of sharks and dolphins (their body shape, fins and flippers are same but they belongs to different lineages; shark is an elasmobranch fish belongs to Pisces and dolphin is an aquatic mammal). But both of them depends on swift movement through the water, so a streamlined shape is essential. Thus, it is a similar habitat that resulted in selection of similar adapted features in different groups of organisms, but towards the same function.
2. Spines (modified leaves) and thorns (modified stem); both looks similar and provide protection to the plant, the plants to which they belong are distantly related.