El sistema inmune es una red compleja de células y proteínas que defiende al cuerpo contra las infecciones. El sistema inmune mantiene un registro de todos los gérmenes (microbios) que ha derrotado para poder reconocer y destruir el microbio rápidamente si ingresa nuevamente al cuerpo.
Crossing over – often, the sister homologous chromosomes of a cell exchange genetic material through recombination of genes.
Independent assortment/random fertilization – there are numerous variety of ways that the chromosomes of the gametes can combine, after meiosis, through fertilization to form a zygote
Mutation – on rare occasion, there is a slight and random change in the genes of a gametic cell caused by environmental factors.
Platelets would help the blood clot, therefore preventing blood loss. White Blood Cells would help protect against infection. So, I believe the answer would be platelets & white blood cells.