BIOL 2004 Lecture Notes - Lecture 4: Transpiration, Polyembryony, Larch
Document Summary
Conifers such as pine, spruce and fir trees are the most familiar gymosperms. Gymnosperms are also characterized by having storable or cones. Most species display recognizable pollen cones and ovulate cones. Gingko: used for city planning (only male plants) Gingko named living fossil by charles darwin. Gymnosperm seeds result from a single fertilization of sperm and egg. Angiosperm seed results from a double fertilization of sperm with egg and with two nuclei of the megagametophyte endosperm. In gymnosperms seeds, megagametophyte tissue nourishes the developing embryo. In angiosperm seeds, the nourishment is provided by endosperm. In gymnosperms and other seed plants, dependent gametophytes develop within the parent sporophyte. The evolution of seeds is closely ties to the evolution of sporophylls and sporangia on sporophytes. The evolution of seed plants with dependent gametophytes from seedless plants that had separate and independent gametophytes involved a number of developments. Two precursors to the emergence of seeds were.
