What are some factors that contribute to the constancy or change of a species' traits?
The DNA has many backup and buffering systems to catch and correct genetic errors for constancy but environmental stress can cause a change in the species traits.
The information in the DNA is protected in multiple ways that provide constancy in the traits of species. The genetic laws developed by Mendel show that no new information is produced in normal sexual or a sexual reproduction. Cell theory states that cells produce cells that are the same as the parent cells.
Errors and losses of information can causes changes in the species traits. Traits that are better adapted to the changes in the environment will be preserved and the traits in the original population can be lost. Examples are :resistance to antibiotics in bacteria. Traits that allow the antibiotics to attack the bacteria are lost. This "sacrifice" of genetic information allows the bacteria to survive in a "hostile" environment: The loss of eye tissue in the blind cave fish: The weakening of the red blood cell in sickle cell anemia that allows the resistance to the invasion of malaria.
The constancy and changes in the traits of a species can be studied using information theory and codes in the DNA.