What research method is used in order to establish what causes a behavior? an experiment What is the first step of the scientific method? pose a question In the science of human development, &quot;nurture&quot; refers to: environmental influences.
Vertical lines on one's nails, like those the writer seems to have, are a common phenomenon that often get more pronounced with age. There are many reasons for ridged nails but the most common is aging, says Dr. Phoebe Rich, M.D., FAAD, clinical adjunct professor of dermatology at Oregon Health Science University.
Dark Skin â If you have dark skin (African American or black people) it is not uncommon to have tan or dark lines running down your fingernails or toenails. Thought the possibility for cancer should not be ignored. Fungus â A fungal nail infection can cause discoloration of fingernails and toenails. Toenail fungus can cause the nail to appear dark even black. Often though there will be other shades of yellow and green associated with fungus.