Centrioles, cilia, flagella, and basal bodies have remarkably similar structural elements and arrangements. This leads us to which of the following as a probable hypothesis?
1. Disruption of one of these types of structure should necessarily disrupt each of the others as well.
2. Loss of basal bodies should lead to loss of all cilia, flagella, and centrioles.
3. Motor proteins such as dynein must have evolved before any of these four kinds of structure.
4. Natural selection for motility must select for microtubular arrays in circular patterns.