BIOL 2004 Lecture Notes - Lecture 5: Ginkgo Biloba, Selaginella, Gametophyte

• School: Dalhousie University
• Department: Biology
• Course: BIOL 2004
• Professor: Gunawardena Arunika

Document Summary

Spores from mature sporophyte are only one kind (homosporous) Sporangium releases spores that mature into gametophyte (gametophytes are only for reproduction) Fertilization occurs, zygote grows into embryo: once the embryo becomes independent, gametophyte disintegrates. Embryo grows into young sporophyte, which matures. In most ferns, sporangia are produced on the underside of leaves: sporangia have a thickened ridge of cells along the back, termed the annulus, when it dries, annulus snaps back violently, and the spores are flung. Gametophyte thallus may have both archegonia and antheridia. If they"re on the same gametophyte, the antheridia and archegonium mature at separate times, to prevent self-fertilization. Sperm are released when free water rushes over them, and they can swim into archegonium: upon fertilization, zygote grows in remnants of archegonium. Nutrients are taken from gametophyte, which disintegrates once embryo is independent. Spores produced via meiosis in sporangium: one 2n cell gives a rise to four 1n spores in sporangium.