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Fig. 30-2a
Gametophyte
Sporophyte(2n)
Gametophyte(n)
Sporophyte
Example
Dominant
Reduced, dependent ongametophyte for nutrition
Mosses and othernonvascular plants
Fig. 30-2b
Reduced, independent(photosynthetic andfree-living)
Sporophyte(2n)
Gametophyte(n)
Dominant
Ferns and other seedlessvascular plants
Example
Gametophyte
Sporophyte
Fig. 30-2c
Reduced (usually microscopic), dependent on surroundingsporophyte tissue for nutrition
Dominant
Seed plants (gymnosperms and angiosperms)
Gymnosperm AngiospermMicroscopic femalegametophytes (n) inside ovulate cone
Microscopic malegametophytes (n) inside pollencone
Sporophyte (2n) Sporophyte (2n)
Microscopic femalegametophytes (n) insidethese partsof flowers
Microscopic malegametophytes (n) insidethese partsof flowers
Example
Gametophyte
Sporophyte
Fig. 30-2
Reduced (usually microscopic), dependent on surroundingsporophyte tissue for nutrition
Reduced, independent(photosynthetic andfree-living)
Gametophyte
Sporophyte(2n)
Sporophyte(2n)
Gametophyte(n)
Sporophyte
Example
Gametophyte(n)
Dominant
Dominant DominantReduced, dependent ongametophyte for nutrition
Mosses and othernonvascular plants
Ferns and other seedlessvascular plants
Seed plants (gymnosperms and angiosperms)
PLANT GROUP
Gymnosperm Angiosperm
Microscopic femalegametophytes (n) insideovulate cone
Microscopic malegametophytes (n) inside pollencone
Sporophyte (2n) Sporophyte (2n)
Microscopic femalegametophytes (n) insidethese partsof flowers
Microscopic malegametophytes (n) insidethese partsof flowers
Pollen and Production of Sperm
Microspores develop into pollen grains, which contain the male gametophytes
Pollination is the transfer of pollen to the part of a seed plant containing the ovules
Pollen eliminates the need for a film of water and can be dispersed great distances by air or animals
If a pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule
The Evolutionary Advantage of Seeds
A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat
Seeds provide some evolutionary advantages over spores:– They may remain dormant for days to years, until
conditions are favorable for germination– They may be transported long distances by wind or
animals
Fig. 30-6-1
Microsporangium (2n)
Microsporocytes(2n)
Pollengrains (n)
Pollencone
Microsporangia
MEIOSIS
Maturesporophyte(2n)
Haploid (n)Diploid (2n)
Key
Fig. 30-6-2
Microsporangium (2n)
Microsporocytes(2n)
Pollengrains (n)
Pollencone
Microsporangia
MEIOSIS
Maturesporophyte(2n)
Haploid (n)Diploid (2n)
Key
MEIOSIS
Survivingmegaspore (n)
Pollengrain
Megasporangium(2n)
Megasporocyte (2n)
Ovule
Integument
Ovulatecone
Fig. 30-6-3
Microsporangium (2n)
Microsporocytes(2n)
Pollengrains (n)
Pollencone
Microsporangia
MEIOSIS
Maturesporophyte(2n)
Haploid (n)Diploid (2n)
Key
MEIOSIS
Pollengrain
Megasporocyte (2n)
Ovule
Integument
Ovulatecone
FERTILIZATION
Pollentube
Femalegametophyte
Spermnucleus (n)
Egg nucleus (n)
Archegonium
Megasporangium(2n)
Fig. 30-6-4
Microsporangium (2n)
Microsporocytes(2n)
Pollengrains (n)
Pollencone
Microsporangia
MEIOSIS
Maturesporophyte(2n)
Haploid (n)Diploid (2n)
Key
MEIOSIS
Survivingmegaspore (n)
Pollengrain
Megasporocyte (2n)
Ovule
Integument
Ovulatecone
FERTILIZATION
Pollentube
Femalegametophyte
Spermnucleus (n)
Egg nucleus (n)
Archegonium
Seedling
Seeds
Seed coat(2n)
Foodreserves(n)
Embryo(2n)
Megasporangium(2n)
Fig. 30-3-3
Seed coat(derived fromintegument)
(c) Gymnosperm seed
Embryo (2n)(new sporophyte)
Food supply(femalegametophyte tissue)
Angiosperms
Angiosperms are seed plants with reproductive structures called flowers and fruits
They are the most widespread and diverse of all plants
Flowers
The flower is an angiosperm structure specialized for sexual reproduction
Many species are pollinated by insects or animals, while some species are wind-pollinated
A flower is a specialized shoot with up to four types of modified leaves:
– Sepals, which enclose the flower – Petals, which are brightly colored and attract
pollinators– Stamens, which produce pollen on their terminal
anthers– Carpels, which produce ovules
Fig. 30-7
Carpel
Ovule
Sepal
Petal
Stigma
Style
Ovary
Stamen Anther
Filament
(or Pistil)(Male)
(Female)
A carpel (or pistil) consists of an ovary at the base and a style leading up to a stigma, where pollen is received
Video: Flower Blooming (time lapse)Video: Flower Blooming (time lapse)
Fruits
A fruit typically consists of a mature ovary but can also include other flower parts
Fruits protect seeds and aid in their dispersal
Mature fruits can be either fleshy or dry
Animation: Fruit DevelopmentAnimation: Fruit Development
Various fruit adaptations help disperse seeds
Seeds can be carried by wind, water, or animals to new locations
The Angiosperm Life Cycle
• The flower of the sporophyte is composed of both male and female structures
• Male gametophytes are contained within pollen grains produced by the microsporangia of anthers
• The female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma
• Most flowers have mechanisms to ensure cross-pollination between flowers from different plants of the same species
• A pollen grain that has landed on a stigma germinates and the pollen tube of the male gametophyte grows down to the ovary
• The ovule is entered by a pore called the micropyle
• Double fertilization occurs when the pollen tube discharges two sperm into the female gametophyte within an ovule
The Angiosperm Life Cycle (cont)
• One sperm fertilizes the egg (now a zygote (2n)), while the other combines with two nuclei in the central cell of the female gametophyte and initiates development of food-storing endosperm (3n)
• The endosperm nourishes the developing embryo
• Within a seed, the embryo consists of a root and two seed leaves called cotyledons
The Angiosperm Life Cycle (cont)
Fig. 30-10-1
MEIOSIS
Key
MicrosporangiumMicrosporocytes (2n)
Generative cell
Anther
Tube cell
Pollengrains
Microspore(n)
Male gametophyte(in pollen grain)(n)
Mature flower onsporophyte plant(2n)
Haploid (n)Diploid (2n)
A diploid microsporocyte, or microspore mother cell, divides to
give rise to four haploid microspores.
Each microspore divides by mitosis to
form two haploid nuclei (the tube nucleus and the
generative nucleus);
After landing on the stigma, the pollen germinates forming a pollen tube; the generative nucleus then divides by mitosis to form two haploid sperm nuclei.
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Fig. 30-10-2
MEIOSIS
Key
MicrosporangiumMicrosporocytes (2n)
Generative cell
Anther
Tube cell
Pollengrains
Microspore(n)
Male gametophyte(in pollen grain)(n)
Mature flower onsporophyte plant(2n)
Haploid (n)Diploid (2n)
MEIOSIS
Ovule (2n)
Ovary
Megasporangium(2n)
Megaspore(n)
Female gametophyte(embryo sac)
Antipodal cells
Central cell (or polar bodies that form endosperm)
Synergids
Egg (n)
A diploid megasporocyte (megaspore mother cell) undergoes meiosis, giving rise to four haploid megaspore nuclei (3
of which disintegrate).
The remaining megaspore nucleus
undergoes three mitotic divisions to form eight haploid
nuclei.
Nuclear migration and cytokinesis occur to form the mature megagametophyte
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Fig. 30-10-3
MEIOSIS
Key
MicrosporangiumMicrosporocytes (2n)
Generative cell
Anther
Tube cell
Pollengrains
Microspore(n)
Male gametophyte(in pollen grain)(n)
Mature flower onsporophyte plant(2n)
Haploid (n)Diploid (2n)
MEIOSIS
Ovule (2n)
Ovary
Megasporangium(2n)
Megaspore(n)
Female gametophyte(embryo sac)
Antipodal cells
Central cell
Synergids
Egg (n)
Pollentube
Pollentube
Stigma
Sperm(n)
Discharged sperm nuclei (n)
FERTILIZATION
Eggnucleus (n)
Style
Sperm
Fig. 30-10-4
MEIOSIS
Key
MicrosporangiumMicrosporocytes (2n)
Generative cell
Anther
Tube cell
Pollengrains
Microspore(n)
Male gametophyte(in pollen grain)(n)
Mature flower onsporophyte plant(2n)
Haploid (n)Diploid (2n)
MEIOSIS
Ovule (2n)
Ovary
Megasporangium(2n)
Megaspore(n)
Female gametophyte(embryo sac)
Antipodal cells
Central cell
Synergids
Egg (n)
Pollentube
Pollentube
Stigma
Sperm(n)
Discharged sperm nuclei (n)
FERTILIZATION
Germinatingseed
Embryo (2n)Endosperm (3n)Seed coat (2n)
Seed
Nucleus ofdevelopingendosperm(3n)
Zygote (2n)Eggnucleus (n)
Style
Sperm
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