Seed Plants

1. Seed Plants Crystal Nam Ms. Moore AP Biology 8 October 2013

2. Seed Plants- plants with seeds • The vast majority of living plant species. • Origin: about 360 million years ago • seed= an embryo(2n) packaged with a supply of nutrients inside a protective coat <Seeds> • Can resist harsh environments and spread offspring more widely • Multicellular -> much more resistant and complex than a single-celled spore • A seed may remain dormant even for years until it meets favorable conditions

3. Traits of Seed Plants • Reduced(microscopic) gametophytes ->the tissue of the sporophyte shield the gametophytes from drought conditions and from UV radiation • Aerobic (air enters/exits through stomata) - inhale carbon dioxide and exhale oxygen when photosynthesize - exhale carbon dioxide constantly • Photoautotroph

5. Heterospory - Heterosporous Seed plants: the two types of spores are produced by separate cones, small pollen cones, and large ovulate cones. - megasporophylls (contain) diploid megasporangia (produce) haploid megaspores (develop into) haploid female gametophytes - microsporophylls (contain) diploid microsporangia (produce) haploid microspores (develop into) haploid male gametophytes - Each megasporangium has a single megaspore - Each microsporangium has vast numbers of microspores

6. Ovules (from the Latin ovulum, little egg) -Ovule: the whole structure consisted of megasporangium(2n), megaspore(n), and their integument(s) -Inside each ovule, a female gametophyte produces one or more egg cells -Integuments: layers of sporophyte tissue -> envelop and protect the megasporangium *Gymnosperm megaspores: surrounded by one integument *Angiosperm megaspores: surrounded by two integuments

7. Pollen -Microspores develop into pollen grains ->protected by a tough coat ->contain male gametophytes ->the male gametophytes can be carried long distances by the wind or by pollinators -Pollination: the transfer of pollen to the part of a seed plant containing the ovules • If a sperm fertilizes an egg of a seed plant, the zygote grows into a sporophyte(2n) embryo

8. Groups of Seed Plants- based on the absence or presence of enclosed chambers in which seeds mature • Gymnosperms (gymnos: naked, sperm:seed) : plants that have “naked” seeds that are not enclosed in ovaries-> exposed on leaves • Consist primarily of conifers ex. pines, firs, redwoods • The first seed-bearing plants • Dominated terrestrial ecosystem during Mesozoic era

9. Unfertilized ovule- a megasporangium is surrounded by an integument • Fertilized ovule- a megaspore develops into a female gametophyte - The opening is called micropyle - Pollen grains develops a pollen tube that discharges sperm • Gymnosperm seed - Transformation into a seed

11. Phyla of Gymnosperm • Cycadophyta (Cycads) • second largest group of gymnosperms • Have large cones and palm-like leaves • Thrived during the Mesozoic era • Aerobic • Photoautotroph • Sexual Reproduction->Dioecious: an individual produces either male or female cones • Vector of pollination: wind • Thick stems, not made of true wood often equal diameter with taproot • Ex. Cycasrevoluta(Japanese Sago Palm) Boweniaserrulata(Byfield fern)

13. Xylem: tissue that carries water and mineral salts from the roots to all other parts • Phloem: tissue that carries synthesized organic nutrients from leaves to all other parts • Cambium: a meristem created by additional xylem and phloem

14. Ginkgophyta (Ginkgo) • Ginkgo biloba, also known as maidenhair tree, is the only extant species • Deciduous fanlike leaves, turn gold in autumn • tolerates air pollution well • seeds smell rancid as they decay • Vector of pollination: wind • Aerobic, Photoautotroph • Sexual reproduction-> Dioecious: produce either male or female cones

16. Gnetophyta (Gnetophytes) • Consists of three genera: Gnetum, Ephedra, Wlwitschia • Gnetum: tropical trees, shrubs, and vines. leaves look similar to those of flowering plants, and seeds look like fruits • Ephedra: desert shrubs Ex. Mormon tea • Wlwitschia: one species Welwitschiamirabilis. its strap-like leaves are among the largest leaves known. Lives in desert • Some species are tropical, others live in deserts • Vectors of pollination: insects and wind • Aerobic, Photoautotroph, Sexual reproduction • Stem system Xylem: water is carried from the root to other parts Phloem: nutrients is carried from the leaves to other parts

17. Coniferophyta (Conus=cone, ferre=to carry • The largest of the gymnosperm phyla consisting of 600 species of conifers • Many large trees and evergreens • Stem system: xylem, phloem, cambium • Reproduction: can be sexual or asexual -> most species have both ovulate and pollen cones • Aerobic, Photoautotroph • Ex. cypresses, redwoods, douglas fir, common juniper, wollemia pine, pacific yew, bristlecone pine, sequoia

18. Groups of Seed Plants • Angiosperms (angion=container): seed plants that produce the reproductive structures called flowers and fruits - Seeds develop inside chambers called ovaries - Single phylum: Anthophyta (anthos=flower) • The most diverse and widespread of all plants, more than 250,000 species • Some flowers self-pollinate(asexual reproduction), most cross-pollinate(sexual reproduction) • Aerobic, Photoautotroph • Ex. roses, peas, maples, wheat, rice

19. < Lineages of Angiosperm> • Basal angiosperms: Amborella, Water Illies, and Star anise and relatives • Magnolids: a lineage that includes both woody and herbaceous species <Clades of Angiosperm> • Monocots: species with one cotyledon • Dicots: species with two cotyledon

20. Based on the number of cotyledons, seed leaves, divided into monocots and dicots

21. Flowers • Flower: an angiosperm structure specialized for sexual reproduction • Vectors of pollination: wind, Insects or other animals -> more directed than wind-dependent pollination • Floral Organs • Sepals: enclose the flower before it opens • Petals: brightly colored, aid in attracting pollinators • Stamens: the microsporophylls, produce microspores

22. Stamen consists of • Filament: a stalk • Anther: a terminal sac where pollen is produced • Carpels: megasporophylls, produce megaspores Carpel consists of • Stigma: receives pollen at the tip of the carpel • Style: leads to the ovary at the base of the carpel • Ovary: contains one or more ovules • The whorls of floral organs are attached to the receptacle • Some angiosperms have flowers with a single carpel, others have separate carpels • Pistil: a single carpel or a group of fused carpel

25. Double Fertilization of Angiosperms • Each pollen grain has two haploid cells: a generative cell- divides, forming two sperm a tube cell- produces a pollen tube • Embryo sac: a female gametophyte containing the egg • Micropyle: a pore in the integuments of the ovule • Discharges two sperm cells into the female gametophyte • One sperm fertilizes the egg, forming a diploid zygote • The other sperm fuses with the nuclei in the central cell of the female gametophyte ->develops into endosperm: tissue rich in starch and other food resources

26. Fruits • Consists of a mature ovary, can include other flower parts as well • Protect inactive seeds and aid in their dispersal • The wall of the ovary becomes the pericarp: the thickened wall of the fruit • Fleshy fruits: oranges, strawberries, grapes -> pericarp layer(s) becomes soft • Dry fruits: beans, nuts, grains-> winds-dispersed fruits of grasses -> the ripening involves the aging and drying out of the fruit tissues