how do you determine the fraction of parent isotope remaining after 20,000 years if the isotope used has a half life of 5000 years

Cells tend to have a relatively small and uniform size. why aren’t cells larger?

Indica el nombre y la fucion de los vasos sanguineos que entran y salen de los riñones

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.