Chapter 30Wednesday, March 9, 20166:20 PMChapter 30 - Plant Diversity 2: The Evolution of Seed Plants Reproductive Adaptations of Seed Plants-Reduced and Retained GametophytesoSeed plants are heterosporous:-Megaspores (female)-Microspores (male)oBoth gametophytes mature within sporangia-Highly reduced in size (microscopic in size)-Protected from drying and UVChart [30.2] Mosses and other nonvascular plantsGametophyte DominantSporophyte Reduced, dependent on gametophyte for nutritionEx. Sporophyte (2n)Gametophyte (n)oNot released immediately, go through a maturation processoReleased as male gametophytes, not as spores-OvuleoDerived from a megasporangium on a sporophylloThree are degenerate, one becomes-receives a substantial cytoplasm in itoMegaspore grows into female gametophyteoEgg produced and fertilized within ovule-PollenoComes from microsporangium - retains microspores while they mature-Modified leaf, each has -Microspores stay inside microsporangium-Coats with sporopolleninoPollen grains = mature male gametophytes with sporopollenin (protective coating)-Help them to disperseoPollen grains travel (through air) to reach ovule-bearing parts = pollination-New step in sex, the actual arrival of male gametophyte to location of ovule-bearing partsoPollen grain then grows pollen tube toward egg within ovuleoSperm released within pollen tube-No flagella in conifers and angiospermsoFertilization occurs within ovule-Note: no rain/dew needed-SeedoDevelops from fertilized ovule-Includes: embryo, food supply, seed coatoSeed 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 CycleoOvules borne "exposed" on sporophylls-Usually arranged in cones (strobili)-No flower, no fruitoPollen typically carried by windoPine 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 - GinkgosoOne extant tree: Ginkgo bilobaoHerbal medicine (helps with memory)-Female sporophylls, not cones-Fleshy seeds, not fruitsoWith flagellated sperm, male sporophylls in strobili-Phylum Cycadophyta - CycadsoPalm-like fronds radiate from central stem (look like ferns in shrubs)o~100 species-Ex. Zamia species in Florida-Ex. "Sago Palm" Cycas speciesoDecorative plantoCentral female and male cones-Seeds are naked and exposed on the surfaceoWith flagellated sperm-Phylum Gnetophyta - Gnetophyteso3 distinct genera, ~70 speciesoStrobili; 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 - ConifersoMost 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 AngiospermsoSporophylls completely surrounds the ovuleoAngio - refers to "a vessel"-Derived CharacteristicsoFlower-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 fruitoFruit-Enhances seed dispersal-Protects dormant seed-About Flowerso4 whorls of modified leaves (sporophylls)oLearn 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 beoFloral 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 (pollinatebetter)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 FruitoSecond characteristic that makes angiosperms specialoDerived 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