Human ovulation cycle and plant double fertilization

BiologyHuman & Animal PhysiologyAges 16–17

A 28-day cycle clock runs through in about ten seconds: four curves for FSH, LH, estrogen, and progesterone change day by day, and the ovary shows a follicle growing and then ovulation exactly as LH peaks on day 14, after which a corpus luteum forms and the uterine lining thickens. Turn on the fertilized case to see progesterone stay high, the lining maintained, and no menstruation. Switch to the plant view to see a pollen tube grow down to the embryo sac for double fertilization: one sperm cell fuses with the egg to form a 2n zygote, and the other fuses with the diploid nucleus to form 3n endosperm.