Natural selection causes what to occur? 1. evolution
2. survival of the fittest
The law of independent assortment
3. Mendel's law of segregation
4. genetic drift

(1.) Natural selection causes evolution to occur.

Explanation:

Over time, the naturally occurring variation within a population that arise from mutations, alter in frequency. Some of these variants or traits, may confer advantages to certain organisms, allowing them to reproduce and pass on genes more successfully. These traits become fixed within the population, and eventually the individuals evolve to form a species.

Natural selection, acts on evolution, for or against traits.  It ensures that individuals with traits well-suited to their environments and reproductive fitness survive.      

answer; a muscle cell, another neuron and a of the above