Chapter 30: Plant Diversity II: The Evolution of Seed Plants

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Chapter 30Plant Diversity IIThe Evolution
ofSeed Plants
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Free-Living Gametophytes
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Reduced Gametophytes
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Some Seed-Bearing-Plant Anatomy
Gender Female Male
Sporangia Megasporangia Microsporangia
Spores Megaspores Microspores
Gametophyte Megagametophyte Microgametophyte
Gametangia Archegonia Antheridia
Gametes Egg Sperm
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Ovules

• Megasporangium gives rise (meiotically) to
  megaspores
• Integument envelopes, protecting the
  megasporangium
• An ovule consists of integument surrounding a
  megasporangium which in turn surrounds a
  megaspore
• The female gametophyte develops mitotically from
  the megaspore
• The female gametophyte gives rise mitotically to
  the female gamete, the egg
• Once fertilized the egg develops into an
  embryonic sporophyte
• The sporophyte embryo surrounded by the parental
  megagametophyte which, in turn, is surrounded by
  grandparental sporophyte tissue is a seed

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Seeds (are complicated)
Gametophyte (haploid parent)
Sporophyte (next generation)
Sporophyte (grandparent)
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Gymnosperms
Gymnosperms have seeds and vasculature but not
flowers nor fruit
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Gymnosperms
Gymnosperms are plants that have naked seeds
that are not enclosed in ovaries. Their seeds are
exposed on modified leaves that usually form
cones. p. 593, Campbell Reece (2005)
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Gymnosperm
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Pollen Heterospory
This is pollen!
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Pollen Pollen Tube
Pollen freed plants from flagellated sperm so no
more need for water for fertilization to take
place
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Grains of Pollen
Seed-bearing plants disseminate their sperm/male
gametophyte as pollen
Pine pollen
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Gymnosperm Life Cycle
Overall this life cycle takes about three years
(not including growth to sexual maturity of the
resulting tree)
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Angiosperms
Angiosperms are vascular plants that produce
seeds via flowers and distribute those seeds via
fruit
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A Flower
Male part
Female part
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Flower Cross Section
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Pigmented Sepals
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Flying Penises!
One of the great advantages of flowering is the
potential for pollination by animals
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Origin of Flower Structure
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Primitive Flowers
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Fruit
A fruit typically consists of a mature ovary,
although it can include other flower parts as
well
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Various Fruits
As seeds develop from ovules after
fertilization, the wall of the ovary thickens. A
pea pod is an example of a fruit, with seeds
(mature ovules, the peas)
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Even More Fruits
encased in the ripened ovary (the pod). Fruit
protects dormant seeds and aid in their
dispersal. p. 598, Campbell Reece (2005)
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Angiosperm Life Cycle
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Embryo Sac 7-Cell Gametophyte
Synergids
antipodal cells
Egg
Double fertilization is of these two cells
Formation of embryo sac the angiosperm female
gametophyte
Polar Nuclei
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Double Fertilization
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Monocots vs. Eudicots
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Monocots vs. Eudicots
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Monocots vs. Eudicots
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Overview Bryophytes (moss)
name? sporophyte? spores? gametophyte? gamete?
terminating event? meiosis? mitosis? mitosis? syngamy?
ploidy? diploid haploid haploid haploid
Bryophyta inconspicuous wind dispersed conspicuous germinates apart from parental sporophyte sperm is motile egg stays in association with gametophyte
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Overview Pterophytes (ferns)
name? sporophyte? spores? gametophyte? gamete?
terminating event? meiosis? mitosis? mitosis? syngamy?
ploidy? diploid haploid haploid haploid
Pterophyta conspicuous wind dispersed inconspicuous germinates apart from parental sporophyte sperm is motile egg stays in association with gametophyte
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Overview Coniferophytes (pines)
name? sporophyte? spores? gametophyte? gamete?
terminating event? meiosis? mitosis? mitosis? syngamy?
ploidy? diploid haploid haploid haploid
Conifero-phyta Conspic-uous embryos disperse, packaged associated with grand-parental sporophyte tissue (seeds) megaspore not dispersed microspore is wind dispersed with/as pollen inconspicuous microspore germinates as pollen tube, once associated with female sporophyte tissue, associated with ovule megaspore germinates in parental sporophyte sperm is non-motile both gametes stay in close association with parental gameto-phytes
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Overview Anthophytes (flowering)
name? sporophyte? spores? gametophyte? gamete?
terminating event? meiosis? mitosis? mitosis? syngamy?
ploidy? diploid haploid haploid haploid
Antho-phyta conspicuous seeds plus seeds packaged within grand-parental-sporophyte tissue (fruit) megaspore not dispersed microspore is wind dispersed with/as pollen inconspicuous same as pines except ovule is surrounded by a grandparental-sporophyte ovary (i.e., ovary and ovule are of same generation) sperm is non-motile both gametes stay in close association with parental gameto-phytes
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The End