Gymnosperms Flashcards
How many species of gymnosperms are there compared to angiosperms
1500
300,000
Seeds
Mature, fertilized ovule that contains and embryo
An embryonic plants that had its food supply encapsulated in a protective coat
Adaptations of seeds
-survive extended periods of drought and cold
-embryo protected from fungi or bacteria
-dispersal
-food supply:head start
Ovule
Megasporangium surrounded by integument
Evolution of ovules
-retention of megaspores within megasporangium: fleshy, nucellus
-reduction in the number to one megasporcyte
-survival of one megaspore
-formation of female gametophyte within megaspore (endospory)
-development of embryo within female gametophyte within mega sporangium
-integument completely envelopes megasporangium except for micropyle
-apex of megasporangium modified to receive microspores
Start at mega and microsporangium to egg and sperm cells
Megasporangium -> mega sporocyte-> meiosis->megaspore-> mitosis->Megagametophyte->archegonia-> egg cells
Characterisitcs of seed plants
-reduction of gametophytes (protected and nourished by sporophyte)
-sperm delivered to egg by pollen tube
-fertilization is independent of water
-non-flagellated sperm (except cycads and ginkgo)
-non hollow pollen tube
-bifacial vascular cambium (secondary growth)
Seeds of gymnosperms
-formed on surface of Sporophylls
-exposed
-result from single fertilization of egg cells by sperm
-developing embryo nourished by nucellus
-Megagametophyte tissues develop at the expense of the nucellus (megasporangium)
Progymnosperms
-did not produce seeds
-wood
-some are heterosporous
Ex: archaeophytales, aneurophytales
Pteridosperms
Seeds ferns
-ancestors to cycads
-ovules protected by integument-variation
-may be ancestor to bennettitales
Microgametophyte of pinus development
Microspore -> first prothallial cell and meristematic initial
Meristematic initial->second prothallial cell and antheridial initial
Antheridial initial->tube cell and generative cell
Generative cell->sterile cell and spermatogenous cell
Spermatogenous cell->2 make gametophytes
How many archegonia are within the ovule?
2-only one’s egg gets fertilized
Synonym for nucellus
Megaspornagium
What phyla has most diversity in gymnosperms
Coniferophyta
Habitat of gymnosperms
-long cold and dry seasons
-mostly northern hemispheres
-higher elevations
Characteristics of gymnosperms
-no vessels
-simple, narrow, reduces stomata leaves with hypodermics, and transfusion tissue, cuticle on epidermis
Why don’t coniferophyta have vessels
-vessels lead to freezing damage
Sporophylls of coniferophyta are where
In cones (mega and micro strobili)
Are conifers monoecious or dioecious
Monoecious
Megastrobili of conifers vary in which ways
-aril (fleshy covering of seed)
-cones (scale covering)
Deciduous species of conifers
Larch, dawn redwood, taxodium
Transfusion tissue
In endodermis and surrounds vascular bundles in conifers
Prevent water loss, prevent freezing
Resin canals purpose
Anti herbivory secondary metabolites that is sticky
Cycadophyta leaves
-compound, frond like leaves
Very rigid
