Human ovulation cycle and plant double fertilization
BiologyHuman & Animal PhysiologyAges 16–17
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Human & Animal Physiology
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. The Contraception screen shows how the combined pill keeps FSH and LH low by negative feedback so there is no LH surge and no ovulation, and compares progestogen-only methods, the copper IUD and barrier methods in a table of effectiveness; the Infertility treatment screen runs a fertility drug and the steps of IVF with age-dependent success rates.
Lesson: Sexual reproduction in animals and in flowering plants; controlling human fertility: contraception, fertility drugs and IVF
What it shows
The ovarian cycle is controlled by feedback between the pituitary gland and the ovary. FSH makes a follicle grow and secrete estrogen; high estrogen triggers the LH surge that releases the egg around day 14, and the corpus luteum then secretes progesterone. Without fertilization the lining is shed. The Contraception screen shows how the combined pill holds FSH and LH down by negative feedback so that no egg is released, and compares other methods; the Infertility treatment screen covers fertility drugs and IVF. In flowering plants, double fertilization produces a 2n zygote and 3n endosperm.
How to use
Press Pause and drag the Day slider to key days such as 1, 14 and 21 and read the four hormone curves. Open Contraception, choose a Method and compare the LH curve and the ovary with the natural cycle; use the table to compare typical and perfect use. In Infertility treatment, choose In vitro fertilization (IVF), set Woman's age and Embryos transferred, follow one cycle and press Run 100 cycles. Press View plant on the first screen for double fertilization.
Parameters you can change
- Subject Human – 28-day ovulation cycle, Flowering plant – double fertilization
- Day of the cycle 1–28 day
- Auto-play over time
- Case: egg is fertilized
- Simulation speed 1–8 days/s
- Screen Natural cycle, Contraception, Infertility treatment
- Contraceptive method Combined pill, Progestogen only (implant, injection, mini-pill), Copper IUD, Barrier (condom, diaphragm)
- Treatment Fertility drug (FSH + LH), In vitro fertilization (IVF)
- Woman's age 25–45 years
- Embryos transferred 1–2 embryos
Questions to explore
- Why does progesterone fall at the end of the cycle when the egg is not fertilized?
- How would a contraceptive pill containing estrogen and progesterone affect the LH surge, and why?
- Why is the endosperm triploid (3n), and what is its role in the seed?
