Question

Is sweet potato homologous to turnip?

Answer 1

Change in an organism adapted due to some specific environmental condition is known as evolution. It requires a really long time for species to develop these kinds of physiological changes. There are various environmental stresses that cause the process to occur.

Complete answer:
Homologous structures are the ones which have similar embryonic origin but in the course of evolution they adopted some genetic changes that appear in their phenotype, making them morphologically different. On the other hand there are some organisms that are not related but somehow resemble each other due to environmental conditions.
If you take an example of the limbs of a frog, man and flippers of a whale. These structures have different functions but have the same origin. So we call them homologous organs
Now coming back to the question, these sweet potatoes and turnips are actually the modifications of their roots. The roots of these plants have been modified from their basic functions, which is to absorb water to other functions. The root of sweet potato is an adventitious root while the turnip root is a tap root. So despite the close resemblance of the origin they perform different functions, hence they are called homologous organs.

Note:
One can also notice that the wings of birds and the wings of bats perform the same function which is to fly but they have different origins. Wings of birds are the modification of their limbs while the wings of bats are extensions of their skin. These can also be considered analogous organs.