Arrange the steps of natural selection to describe the evolution of armor among stickleback fish in freshwater lakes.

1. Marine stickleback fish had heavy armor.
2. Some freshwater environments became closed systems of lakes with few or no predators.
3. A mutation in the Eda gene gave rise to the low-Eda allele, resulting in variation in armor plating.
4. Marine sticklebacks carrying the recessive low-armor Eda mutation spread into freshwater habitats.
5. In freshwater lakes, sticklebacks with less armor produced more offspring than sticklebacks with more armor.
6. Most stickleback populations in lakes evolved a predominance of light armor.

The sequence of events leading to armored evolution in sticklebacks includes a mutation in the Eda gene, migration to freshwater habitats, environmental changes leading to fewer predators, and natural selection, eventually favoring lighter armor in lake populations.

The evolution of armor in stickleback fish through natural selection can be arranged in the following sequence:

Mutation in the Eda gene occurred, giving rise to variation in armor plating through the low-Eda allele.
Marine sticklebacks carrying the recessive low-armor Eda mutation spread into freshwater habitats.
Some freshwater environments became closed systems of lakes with few or no predators.
In these freshwater lakes, selection favored sticklebacks with less armor, as they produced more offspring than those with more armor.
Eventually, these changes led to a predominance of sticklebacks with light armor in most lake populations, demonstrating an instance of evolution through natural selection.

The three-spined stickleback is a prime example of how natural selection acts on both gene expression and coding region mutations. Studies demonstrated that mutations in regulatory regions played a significant role in the evolution of adaptive phenotypes such as the lighter armor of freshwater sticklebacks.