Algae, phytoplankton, or any green plants.
Cell wall because their has to be something protecting it.
Current estimations are that one in five Americans will develop skin cancer in their lifetime. It is estimated that approximately 9,500 people in the U.S. are diagnosed with skin cancer every day. Which adds up to over 3.3 million persons each year.
Hope this helps! :)
I believe the answer is receptor sites, but correct me if I'm wrong.
Hope this helps!