Lecture Notes on Seed Plant I Gymnosperm - Native Plants | BIO 406D, Study notes of Biology

Download Lecture Notes on Seed Plant I Gymnosperm - Native Plants | BIO 406D and more Study notes Biology in PDF only on Docsity! Seed Plants I - Gymnosperms Characteristics of Gymnosperms Eukaryotic Multi-celled (with cell walls composed of cellulose) Autotrophic Do have xylem and phloem Do produce seeds Do not produce flowers or fruits The Groups of Gymnosperms Ginkgos – Ginkgo Cycads – Cycas, Zamia, other genera Gnetophytes – Welwitschia, Gnetum, Ephedra Conifers – Abies (firs), Cedrus (cedar), Picea (spruce), Pinus (pine), Pseudotsuga (Douglas fir), Tsuga (hemlock), Araucaria (Norfolk Island pine; monkey puzzle tree), Metasequoia (dawn redwood), Sequoia (redwood), Sequoiadendron (giant sequoia), Taxodium (bald cypress), Chamaecyparis, Cupressus (cypress), Juniperus (juniper), Taxus (yew) Pine Life Cycle A mature pine tree, which is a diploid (2n) sporophyte, produces two kinds of cones, pollen cones (male) and ovulate cones (female) Inside of microsporangia located on the scales of the pollen cones, diploid (2n) cells divide by meiosis to produce haploid (n) microspores Haploid (n) microspores (immature pollen grains) develop by mitosis into haploid (n) male gametophytes (mature pollen grains), which contain a tube cell and two nonmotile sperm cells Inside of megasporangia (which, with a surrounding cell layer called the integument, are known as ovules) located on the scales of the ovulate cones, a diploid (2n) cell known as a megaspore mother cell divides by meiosis to produce a haploid (n) megaspore The haploid (n) megaspore develops by mitosis into a haploid (n) female gametophyte, which has two or three archegonia containing one egg each (note: the female gametophyte develops within the megasporangium in the ovule, which remains attached to the scale of the ovulate cone)