12) in developing the cell theory, virchow proposed the idea that cells come from pre-existing cells. this was contradictory to the beliefs of most scientists at the time. louis pasteur provided proof of this when he performed an experiment with sterilized nutrient broth. the broth in straight neck flasks grew bacteria, but the flasks with curved necks did not grow bacteria. how are scientific theories formed? a) from the opinions of very educated people b) from one experiment of a famous scientist c) from evidence gained by many experiments of many scientists d) ignoring any experimental evidence that does not fit the theory

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.

Describe the function of the endomembrane system? what organelles are involved?

This is one of the five kingdoms in the older biological succession. organisms in this kingdom are prokaryotic.