The menstrual cycle in a nonpregnant human female. Use this graph to answer part a and part b of this question. Describe the events that occur during period I as the immune system responds to the initial exposure to the antigen. Describe the events that occur during period II following a second exposure to the same antigen. Select three of the following, and for each of the three that you have chosen, explain how the process of recognition occurs and give an example.
Organisms recognize others as members of their own species.
Antigens trigger antibody responses. Nucleic acids are complementary. Some plants flower in response to changes in day length. Some mammals may run or fight when frightened. For both of these examples, describe the physiological mechanism involved in the response.