Chapter 30 Wednesday March 9 2016 6 20 PM Chapter 30 Plant Diversity 2 The Evolution of Seed Plants Reproductive Adaptations of Seed Plants Reduced and Retained Gametophytes o Seed plants are heterosporous Megaspores female Microspores male o Both gametophytes mature within sporangia Highly reduced in size microscopic in size Protected from drying and UV Chart 30 2 Mosses and other nonvascular plants Gametophyte Dominant Sporophyte Reduced dependent on gametophyte for nutrition Ex Sporophyte 2n Gametophyte n o Not released immediately go through a maturation process o Released as male gametophytes not as spores Ovule o Derived from a megasporangium on a sporophyll o Three are degenerate one becomes receives a substantial cytoplasm in it o Megaspore grows into female gametophyte o Egg produced and fertilized within ovule Pollen o Comes from microsporangium retains microspores while they mature Modified leaf each has Microspores stay inside microsporangium Coats with sporopollenin o Pollen grains mature male gametophytes with sporopollenin protective coating Help them to disperse o Pollen grains travel through air to reach ovule bearing parts pollination New step in sex the actual arrival of male gametophyte to location of ovulebearing parts o Pollen grain then grows pollen tube toward egg within ovule o Sperm released within pollen tube No flagella in conifers and angiosperms o Fertilization occurs within ovule Note no rain dew needed Seed o Develops from fertilized ovule Includes embryo food supply seed coat o Seed advantages Enhanced dispersal safe from desiccation Underground germination possible Stored food allows embryo growth without photosynthesis May stay dormant until conditions are OK Gymnosperms naked seed plants Gymnosperm Life Cycle o Ovules borne exposed on sporophylls Usually arranged in cones strobili No flower no fruit o Pollen typically carried by wind o Pine Life Cycle Alternate between haploid and diploid Plants outside we see are sporophytes having sporangia Two types megaspores females and microspores pollen cones males New structures called ovule megasporangium produces megaspore Goes through meiosis forms four daughter cells The rest disintegrates while one moves on Microsporangium has a meiosis of cells has microspores go through development Sporopollenin to protect them Carried by air or beetle to reach ovule Female cone has sap and as the pollen grain hits the cones and sticks to the sap and draws it into the micropile Eventually the pollen grain grows pollen tube and sperm nucleus Fertilization occurs back to diploid cycle Female gametophyte starts packing on calories oils carbohydrates Eventually the seed matures Once seed releases eventually lands on the ground Underground and germinate Start over again Phylum Ginkgophyta Ginkgos o One extant tree Ginkgo biloba o Herbal medicine helps with memory Female sporophylls not cones Fleshy seeds not fruits o With flagellated sperm male sporophylls in strobili Phylum Cycadophyta Cycads o Palm like fronds radiate from central stem look like ferns in shrubs o 100 species Ex Zamia species in Florida Ex Sago Palm Cycas species o Decorative plant o Central female and male cones Seeds are naked and exposed on the surface o With flagellated sperm Phylum Gnetophyta Gnetophytes o 3 distinct genera 70 species o Strobili sperm not motile Find male strobilus and strobilus with naked ovules Seeds with fleshy seed coats not fruit Ex Gnetum in tropics Ex Welwitschia in SW Africa deserts most of plant is underground Ex Ephedra in U S deserts no leaves Male cones visible giveaway that it is a gymnosperm Phylum Coniferophyta Conifers o Most diverse gymnosperms today Cone bearers Male pollen cone sperm not motile Female ovulate cone Dominate high altitudes and latitudes in N Hemisphere Can take conditions Cone shape allows shed snow needles allow to shed snow High surface area allow Most are evergreens with needle like leaves Examples include Pine fir spruce Cedar juniper cypress Redwood sequoia Pacific yew source of cancer drug taxol Include record breakers Tallest organism Coast Redwoods of California The oldest organism 4750 years Bristlecone pine Most massive organism 5 5 million kg Sequoias of California Angiosperms o Sporophylls completely surrounds the ovule o Angio refers to a vessel Derived Characteristics o Flower Protects ovules within ovary Ovules while developing can be vulnerable Promotes efficient pollen transfer especially by animal pollinators Once pollination and fertilization occurs flower develops further to produce fruit o Fruit Enhances seed dispersal Protects dormant seed About Flowers o o o 4 whorls of modified leaves sporophylls Learn parts and functions from 30 8 and text Outermost is the sepal Next inward most set of leaves are petals Provide some sort of attraction for pollinator Base of petal nectar and scent glands Inward from petals are fertile leaves sporophyll stamen Actual location where microsporangium will be Floral anatomy relates to successful pollination Complete flowers have all parts Flowers can be incomplete missing parts First flowers are male flowers only have anthers Later female flowers come out and ovules are fertilized once pollen Unisex flowers only carpels or stamens promotes outcrossing pollinate better No petals if wind pollinated Lack petals petals get in the way and not needed complete male female parts Groups of flowers can form an inflorescence More attractive to visual pollinators A flower with little flowers The petals are just modified sepals Floral color and scent attracts pollinators Flower shape and color adapted to the pollinator Nectar and pollen are rewards promoting loyalty for pollinator Coevolution of plants and pollinators Competing pressures in this mutualism Some pollinators totally depend on flowering plants Sometimes pollinators are tricked and end up pollinating the plant for no reward Ex Orchids imitate scent of female wasp so they can get a male to pollinate them Ex Dead horse flower smells like dead horse Attracts flesh flies About Fruit o Second characteristic that makes angiosperms special o Derived from ovary tissue after fertilization may include other flower parts Fleshy fruit developed from ovary wall Ex Peach Peach pit is also part of the fruit contains seed from ovule o Fleshy fruits are adapted to be eaten by animals Seeds are scattered or pass through gut into feces tough seed coat protects it o Dry fruits help dispersal by wind water or