A concentration gradient exists when one area has a higher concentration of a substance than another area does. True or false.

Heredity has an impact on personal health, but environmental factors are important as well. select the best answer from the choices provided

Which of these statements are true about scientific theories and hypothesis

Which is an advantage of having memory cells when a pathogen is encountered for a second time. a) the memory cells are what proliferate into clones of cells in response to the binding of an antigen. b) memory cells are vital to the primary immune response in that they immediately recognize pathogens even at the first encounter. c) memory cells are essentially effector cells that are short lived and attack antigens even without having a receptor specific to that antigen. d) it ensures that more lymphocytes with a receptor specific to a particular antigen will be present than in a host that had never encountered that pathogen.