Since homologous means same structure different functions, it shows that animals evolve to have the same structure as their ancestors but, have different uses to the part
Homology in bat wings, alligator leg, and a human arm represents their divergent evolution from common ancestor.
Explanation:
Homologous organs share a common basic structure but are adapted to perform different functions according to the need of organisms. Wings of bats (flying mammal), leg of alligator (reptile) and human (terrestrial mammal) arm share common basic developmental plan but are adapted to serve in flight, movement and holding things respectively.
Presence of homologous organs in these organisms from different group represents their evolution from a common ancestor. This means that bats, human, and alligators should have a common ancestor. Divergent evolution of the descends from the common ancestor must have given rise to homologous structures.
In this, the controlled variables are stirring and type of sugar. As more stirring might elevate the amount of sugar that dissolves, and different kind of sugars might dissolve in distinct concentrations. So, in order to make sure a fair test, there is a need to keep these variables similar for each cup of water.