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Transcript
Chapter 38. Plant Reproduction AP Biology 2005-2006 Animal vs. Plant life cycle Animal Plant multicellular 2n multicellular sporophyte 2n gametes 1n unicellular gametes 1n AP Biology spores 2n multicellular gametophyte 1n 2005-2006 alternation of generations Alternation of generations diploid haploid AP Biology 2005-2006 Alternation of generations AP Biology 2005-2006 Alternation of generations Fern sporophyte leafy plant you are familiar with Fern spores AP Biology haploid cells that will sprout into gametophyte 2005-2006 Alternation of generations Fern gametophyte AP Biology small diploid plant which produces gametes 2005-2006 AP Biology 2005-2006 Alternation of generations Archegonium female gamete-producing structure produces a single egg cell in a vase-shaped organ AP Biology 2005-2006 Alternation of generations Antheridia male gamete-producing structure produces many sperm cells that are released to the environment flagella = swimming sperm AP Biology 2005-2006 Evolutionary trends Alternation of generations dominant haploid plant bryophytes - mosses dominant diploid plant pteridophytes - ferns gymnosperm - conifers angiosperm - flowering plants Evolutionary advantage? AP Biology reduction of gametophyte protects delicate egg & embryo in protective sporophyte 2005-2006 Moss sporophytes AP Biology 2005-2006 Reduction of gametophyte AP Biology 2005-2006 Gametophytes of seed plants Gymnosperm Angiosperm male gametophyte male gametophyte pollen in male cone female gametophyte develops in female cone seed naked in cone female gametophyte develops in ovaries of flower seed AP Biology pollen in anthers of flower protected in ovary ovary wall can develop into fruit 2005-2006 Gymnosperm life cycle female gametophyte in cone male gametophyte in pollen sporophyte in seed AP Biology 2005-2006 Angiosperm life cycle male gametophyte in pollen female gametophyte in ovary sporophyte in seed AP Biology 2005-2006 Flowers AP Biology 2005-2006 Flower Modified shoot with 4 rings of modified leaves sepals petals stamens male carpals female AP Biology 2005-2006 pistil AP Biology 2005-2006 Male & female parts of flower AP Biology 2005-2006 Parts of flower Male stamens = male reproductive organs stamens have stalks (filament) & terminal anthers which carry pollen sacs pollen sacs produce pollen pollen grain = gametophyte sperm-producing structure AP Biology 2005-2006 Parts of flower Female carpels = female reproductive organs ovary at the base slender neck = style within the ovary are 1 or more ovules within ovules are embryo sacs female gametophyte = embryo sac egg-producing structure AP Biology 2005-2006 AP Biology 2005-2006 AP Biology 2005-2006 Fertilization Pollination pollen released from anthers is carried by wind or animals to land on stigma pollen grain produces a pollen tube pollen tube grows down style into ovary & discharges 2 sperm into the embryo sac 1 sperm fertilizes egg = zygote zygote develops into embryo AP Biology ovule develops into a seed ovary develops into a fruit containing 1 or more seeds 2005-2006 Preventing self-pollination Various mechanisms stamens & carpels may mature at different times arranged so that animal pollinator won’t transfer pollen from anthers to stigma of same flower biochemical self-incompatibility = block pollen tube growth AP Biology 2005-2006 Preventing self-fertilization This model involves the “S” allele Pollen (male) with same allele cannot germinate on stigma (female) Matching alleles interact & inhibit RNA production AP Biology 2005-2006 Biochemical mechanism Preventing self-fertilization AP Biology pollen produces signal → receptor → kinase → signal transduction path → effector protein produced → block pollen tube growth 2005-2006 Fertilization in flowering plants Double fertilization 2 sperm from pollen 1 sperm fertilizes egg = diploid zygote 1 sperm fuses with 2 polar nuclei to form 3n endosperm endosperm = food tissue in seed coconut milk grains AP Biology 2005-2006 Pollen tube growth grow down style to ovule path for sperm nuclei AP Biology 2005-2006 Fertilization in flowering plants Development of the new sporophyte AP Biology 2005-2006 Plant embryo endosperm seed coat cotyledons ovary wall embryo AP Biology 2005-2006 Seed Anatomy Sporophyte in seed Sets stage for structure of plant Roots Shoots Leaves AP Biology 2005-2006 Germination How does the dicot differ from the monocot? AP Biology 2005-2006 Mobilization of nutrients Seed germination AP Biology 1. seed imbibes water 2. gibberellin release signals aleurone layer 3. amylase is released which hydrolyzes starch 4. sugar is absorbed by embryo 2005-2006 Fruit Fruit is a mature ovary AP Biology seeds develop from ovules wall of ovary thickens to form fruit fruits protect dormant seeds & aid in their dispersal 2005-2006 Fruit development Pea (legume) AP Biology 2005-2006 Fruit development Peach (stone fruit or drupe) AP Biology 1 flower : 1 carpel : 1 ovary : 1 seed 2005-2006 Fruit development Apple (pome fruit) AP Biology 1 flower : 5 carpels : many ovaries : many seeds 2005-2006 Fruit development Citrus fruit (berry) AP Biology 1 flower : many carpels : many ovaries : many seeds 2005-2006 Fruit development Raspberry (aggregate fruit) AP Biology 1 flower : many ovaries : many seeds 2005-2006 Reproduction in angiosperm Sporophyte plant produces unique reproductive structure = the flower male gametophyte = pollen grain develop within anthers of flower female gametophyte = embryo sac develop within ovaries of flower pollination by wind or animals brings pollen grain to female gametophyte fertilization takes place within ovary double fertilization = embryo & endosperm seeds contain sporophyte embryo development of seeds in ovary ovary develops into fruit around the seed AP Biology 2005-2006 Coevolution of plants & animals Angiosperms & animals have shaped one another’s evolution Natural selection reinforced the interactions because they improved the reproductive success of both partners AP Biology 2005-2006 Seed dispersal Plants produce enormous numbers of seeds to compensate for low survival rate AP Biology a lot of genetic variation for natural selection to screen 2005-2006