How come similar physical features don’t always indicate a close evolutionary relationship?

Question

Most of the time, when two species or groups of organisms are compared, their physical features reveal a lot about their evolutionary relationship, but then how come similar physical features don’t always indicate a close evolutionary relationship?

Answer 1

Nature hits upon the same solution to solve problems because there are only so many efficient, effective ways to tackle most problems. No matter how many times you invent the wheel, it's always going to be a wheel. In the same way, the best way to fly is to evolve wings, though nature has created a variety of different wing types (think of flies, birds, and bats).

If organisms have the same trait because of shared common ancestry, as you suggested, we refer to the feature as "homology" (homo means same). However, sometimes animals evolve similar traits independently. There are two different concepts that we employ to describe this. One is "convergence." There are many pouched animals (marsupials) in Australia that have developed forms that are similar to placental mammals like us. For example, there are Australian squirrel-like marsupials, a recently extinct marsupial wolf-like animal, and many other examples. Why did the animals evolve similar forms? Well, because if you're going to live the life of a squirrel or a wolf, there are some best ways to do it, and natural selection is such a powerful process that it often hits upon similar solutions. Of course, even an amateur biologist would quickly recognize that these animals are substantially different.

The second concept we employ is known as "parallel evolution." Parallel evolution is a little different from convergence in that it's harder to recognize because in it we start with two very similar species or even populations of the same species and then they evolve, independently, in the same direction. This process usually happens on a smaller scale so it's hard for me to think of a good example as an illustration but it has been observe to happen in separate lakes in fish species where the local environment is changing and all of the fish evolve the same traits in response. Parallel evolution is thus similar to convergence, but differs in that the animals start in the same place and move the same direction, whereas in convergence the animals might start in very different places and end in a superficially similar, but fundamentally different place.

Answer 2

Different species might hae come from different ancestors but developed similar characteristics to survive in their respective environments.

Answer 3

that's right
species that live in similar environments develop traits or features that facilitate that lifestyle.