Post on 04-Jan-2016
2005-2006 AP Biology
Chapter 38.
Plant Reproduction
2005-2006AP Biology
Animal vs. Plant life cycle
multicellular2n
multicellularsporophyte
2n
multicellulargametophyte
1n
unicellulargametes
1n
spores2n
gametes1n
Animal Plant
alternation of generations
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diploid
Alternation of generations
haploid
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Alternation of generations
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Alternation of generations Fern sporophyte
leafy plant you are familiar with
Fern spores haploid cells that will sprout into
gametophyte
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Alternation of generations Fern gametophyte
small diploid plant which produces gametes
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Alternation of generations Archegonium
female gamete-producing structure produces a single egg cell in a
vase-shaped organ
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Alternation of generations Antheridia
male gamete-producing structure produces many sperm cells that are
released to the environment
flagella = swimming sperm
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Evolutionary trends Alternation of generations
dominant haploid plant bryophytes - mosses
dominant diploid plant pteridophytes - ferns gymnosperm - conifers angiosperm - flowering plants
Evolutionary advantage? reduction of gametophyte protects delicate
egg & embryo in protective sporophyte
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Moss sporophytes
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Reduction of gametophyte
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Gametophytes of seed plants
male gametophyte pollen in male cone
female gametophyte develops in female
cone
seed naked in cone
male gametophyte pollen in anthers of
flower
female gametophyte develops in ovaries
of flower
seed protected in ovary ovary wall can
develop into fruit
Gymnosperm Angiosperm
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Gymnosperm life cyclefemale
gametophytein cone
malegametophyte
in pollen
sporophytein seed
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Angiosperm life cycle
femalegametophyte
in ovary
malegametophyte
in pollen
sporophytein seed
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Flowers
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Flower Modified shoot
with 4 rings of modified leaves sepals petals stamens
male carpals
female
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pistil
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Male & female parts of flower
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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
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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
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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
ovule develops into a seed ovary develops into a fruit containing
1 or more seeds
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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 flowerbiochemical self-incompatibility = block pollen
tube growth
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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
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Biochemical mechanism Preventing self-fertilization
pollen produces signal → receptor → kinase → signal transduction path → effector protein produced → block pollen tube growth
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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
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Pollen tube growth
grow down style to ovule path for sperm nuclei
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Fertilization in flowering plants
Development of the new sporophyte
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Plant embryo
endosperm
cotyledons
embryo
seed coat
ovary wall
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Seed Anatomy Sporophyte in seed
Sets stage for structure of plant Roots Shoots Leaves
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Germination How does the dicot differ from the
monocot?
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Mobilization of nutrients Seed germination
1. seed imbibes water 2. gibberellin release signals aleurone layer 3. amylase is released which hydrolyzes starch 4. sugar is absorbed by embryo
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Fruit Fruit is a mature ovary
seeds develop from ovules wall of ovary thickens to form fruit fruits protect dormant seeds &
aid in their dispersal
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Fruit development
Pea (legume)
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Fruit development Peach (stone fruit or drupe)
1 flower : 1 carpel : 1 ovary : 1 seed
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Fruit development Apple (pome fruit)
1 flower : 5 carpels : many ovaries : many seeds
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Fruit development Citrus fruit (berry)
1 flower : many carpels : many ovaries : many seeds
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Fruit development Raspberry (aggregate fruit)
1 flower : many ovaries : many seeds
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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
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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
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Seed dispersal Plants produce enormous numbers of seeds to
compensate for low survival rate a lot of genetic variation for natural selection to screen