A zygote will not undergo meiosis
in an environmental state that is not favorable for the zygote’s survival i.e.
the chance of the zygote to survive is not certain. Take for example, chlamydomonas
will form a zygote under normal asexual mitotic reproduction in a favorable environmental
condition. However, under unfavorable environmental conditions the organism
also reproduce sexually to form a zygote but will never proceed to meiotic
division because of the unfavorable environmental state.