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Plant Diversity II: The Evolution of Seed Plants

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Plant Diversity II: The Evolution of Seed Plants Campbell, 5th Edition, Chapter 30 Nancy G. Morris Volunteer State Community College – PowerPoint PPT presentation

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Title: Plant Diversity II: The Evolution of Seed Plants


1
Plant Diversity II The Evolution of Seed
Plants
  • Campbell, 5th Edition, Chapter 30
  • Nancy G. Morris
  • Volunteer State Community College

2
Evolution of Seed Plants
  • Gametophytes of seed plants continue pattern of
    reduction
  • Sporophytes continue pattern of dominance
  • (Figure 30.1)

3
Reproductive Adaptations of Seed Plants
  • Gametophyte develops within the spore retained in
    the tissues of the parent sporophyte.
  • (Figure 30.1)

4
Trend in Dominance of Sporophyte
5
Reproductive Adaptations of Seed Plants
  • The seed replaced the spore as the main means of
    dispersing offspring. (Figure 30.2)
  • The seed, which is the fertilized ovule, consists
    of a sporophyte embryo packaged along with a food
    supply within a seed coat.

6
Figure 30.2 From Ovule to Seed
7
Reproductive Adaptations of Seed Plants
  • Pollen became the vehicles for sperm cells in
    seed plants.
  • The pollen grain, which is the immature male
    gametophyte, can be dispersed through the air by
    wind or transported by animals.

8
Gymosperms
  • Bear their seeds naked on the surfaces of
    sporophylls.
  • Pine Life Cycle -- key reproductive adaptation of
    seed plants (Figure 30.4)
  • 1) Dominance of the sporophyte
  • 2) Development of seed from fertilized ovules
  • 3) Flagellated sperm replaced by pollen

9
4 Divisions of Gymnosperms
  • Division Cycadophyta sago palms
  • Division Ginkgophyta ginkgo
  • Division Gnetophyta Welwitshia
  • Division Coniferophyta pines, firs,
    redwoods, spruce, hemlock, bald cypress
  • (Figure 30.3)

10
Figure 30.4 Gymnosperm Life Cycle
11
Angiosperms
  • Terrestrial adaptation continued with the
    refinement of vascular tissue
  • both xylem vessel elements fibers evolved from
    tracheids, a type of xylem. (Figure 30.5)

12
Figure 30.5 Tracheids
13
Angiosperms
  • The flower is the defining reproductive
    adaptation (Figure 30.6)
  • Sepals, petals, stamens (which produce pollen),
    carpels (which produce ovules), are whorls of
    modified leaves that make up flowers.

14
Figure 30.6 Flower Anatomy
15
Angiosperms
  • Fruits help disperse the seeds of angiosperms
    (Figure 30.7)
  • Ovaries ripen into fruits, which when opened
    disperse seeds to new locations.

16
Life Cycle of the Angiosperm
  • Alternation of Generations Life Cycle Figure 30.8
  • Double fertilization occurs when a pollen tube
    discharges two sperm into the embryo sac (the
    female gametophyte within an ovule). One sperm
    fertilizes the egg, the other combines with two
    nuclei to produce the food-storing endosperm.

17
Figure 30.8 Life Cycle of Angiosperm
18
Consider this
  • Angiosperms animals have shaped one anothers
    evolution.
  • Pollination of flowers by animals transport of
    seeds by animals are two important relationships
    in terrestrial ecosystems.
  • Agriculture is based almost entirely on
    angiosperms.
  • Human cultures depend on the cultivation
    harvest of angiosperms, especially the fruits of
    grains.

19
Consider this
  • Plants transform the atmosphere and the climate.
  • By lowering the concentration of CO2, plants
    probably contribute to the cooling of the Earth.
  • Plants are a renewable resource.
  • Plant diversity is a nonrenewable resource.
  • Destruction of the tropical rainforests is an
    especially urgent problem because they contain
    the greatest diversity of plants on Earth.

20
Embryological Development of a Plant
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