2 5 derived characteristics in land plants (not in ancestors) Apical meristems – localized areas of cell division in shoot & tipsAlternation of generations – separate slideWalled spores produced in sporangiatough wall resists drying2n spore mother cells go through meiosis to produce 4 haploid sporesMulticellular gametangiaArchegonium – (female) produces haploid egg & keeps itAntheridium – (male) produces & releases spermMulticellular, dependent embryosdevelop w/in archegonium from zygoteDerive nutrition from female parent tissue with specialized placenta- like cells
3 2 more traits that evolved in many plant groups CuticleMade of waxes on surface of epidermal cellsProtectionSecondary compoundsRepel herbivores & parasitesAbsorb UV radiationAttract symbionts
4 Basic Life Cycle of Plants – Alternation of Generations
6 Bryophytes Non-vascular – whole body can absorb water Gametophyte is larger (dominant) stageSporophyte dependent on gametophyteNo true leavesFlagellated spermMosses require water for fertilization. Why?
10 Vascular Seed Plants Common traits Seeds Integument – seed coat Female gametophyte – food supplyEmbryo sporophyte – baby plantAdvantage of seedsConsists of embryo and food supply contained in protective coatBetter resist harsh environmentsDisperse offspring more widely
11 Ovules – contains female gametophytes Reduced gametophytes – spores retained in sporangia, develop into gametophytesHeterospory –Megasporangium produce one megaspore & female gametophyteMicrosporangium produce many microspores & male gametophytesOvules – contains female gametophytesPollen – contain male gametophytes – transferred to female part of plant and will germinate into a pollen tube that finds the ovule and egg
12 GymnospermsBear “naked” cones – seeds are exposed on modified leaves that usually form conesPollen cones – produce pollenOvulate cones – produce eggsConiferophyta – pines, firs, redwoods
14 Angiosperms Anthophyta - Flowering plants used for sexual reproduction Megasporangium megaspore megagametophyte in ovule (all enclosed in ovary of flower)Microsporangium microspore microgametophyte in anther of flowerFruits - mature ovary – seed develops from ovules after fertilization, the wall of the ovary thickensEx – tomato, grapefruit, nectarine, milkweed, walnutPollination required for transfer of pollen from flower to the female sex organs of another flower
15 Double FertilzationOne sperm fertilizes the egg cell and the other sperm combines with the two polar nuclei of the large central cell of the embryo sac.Result - One sperm nucleus unites with the egg to form the diploid zygote, from which the embryo develops, and the other unites with two polar nuclei to form the triploid, primary endosperm nucleus (nutrition).
19 Germination Imbibation – taking in H2O ABA decreases (plant soluble hormone that causes dormancy)Embryo responds and releases gibberellin (stimulates release of amylase)Amylase breaks down starch for nutrition which allows for growthRoot extends downward while shoot extends upward