Chapter 30

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Chapter 30 Plant Diversity II  The Evolution
of Seed Plants
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I.  Overview of seed plant evolution ? There were
three (3) major reproductive adaptations in the
evolution of seed plants A.  Reduction of the
gametophyte continued with the evolution of seed
plants 1.  In seed plants, the very small female
gametophyte develops from spores retained in the
sporangia of the sporophyte. Why?? a.  Delicate
female gametophytes are protected from
environmental stress. Nourished by the
sporophyte. b.  Embryos that are produced are
also protected from drought and UV
radiation.                        
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2.  Gametophytes of seed plants are microscopic,
so they can exist within the sporophyte.   Figure
30.1c (p. 598, ed. 6 Fig. 30.2, p.592, ed. 7)
Three variations on gametophyte/sporophyte
relationships.
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B.  Seeds became an important means of
dispersal                         1.  Seeds are
resistant to environmental stress, multicellular,
complex structures that consist of a sporophyte
embryo, a food supply, and a protective
coat.   2.  The embryo develops from the spore
retained within the sporangium.  
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 3.  All seed plants are heterosporous à Female
spores give rise to female gametes male spores
give rise to male gametes.                        
             a.  The megasporangia produce
megaspores (female) and the microsporangia
produce microspores (male).   4.  The
megasporangium is enveloped by layers of tissue
called integuments.  The whole structure
(integuments megasporangium) is called the
ovule.    Figure 30.2 (p. 599) From ovule to
seed (ed. 6) Fig. 30.3, p. 593, Ed. 7).   Know
the structures and sequence in Figure 30.2
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            C.  Pollen (Sperm cells) eliminated
the liquid-water requirement for
fertilization                         1.  Pollen
travels by air or on animals.  It eliminates the
need for water to be present during
fertilization.
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D.  Two clades of seed plants   Figure 30.4 (p.
601) Hypothetical phylogeny of the seed
plants.                                        
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II.  Gymnosperms             A.  Mesozoic era was
the age of gymnosperms 1.  Gymnosperms were the
most common plants during the Mesozoic era (the
age of dinosaurs).               B.  Four phyla
of extant gymnosperms   Figure 30.5 (p. 602)
Phylum Ginkgophyta  Ginkgo biloba. Figure 30.6
(p. 602) Phylum Cycadophyta cycads. Figure
30.7 (p. 603) Phylum Gnetophyta. Figure 30.8
(p. 604) Phylum Coniferophyta  A sampling of
conifer diversity.    Know the common names of
phyla discussed For ed. 7 - Fig. 30.4, p.
394-5.
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1.  Gymnosperms are vascular plants that bear
naked seeds seeds not enclosed in specialized
chambers.        Examples  Ginkgo, Cycads,
Gnetophyta (Welwitschia, Gnetum, Ephedra), and
Conifers (Common names)
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            C.  Life cycle of a pine demonstrates
the key reproductive adaptations of seed
plants                         Figure 30.9 (p.
605, ed 6 Fig. 30.6, p. 597, ed. 7) The life
cycle of a pine.               1.  The tree is
the sporophyte.   2.  Female gametophyte develops
within the sporangium.   3.  Pollen cone has
microsporangium that develops into pollen (male
gametophyte).   4.  After fertilization, the
embryo develops and is surrounded by food
reserves and a seed coat.   5.  Embryo grows to
produce a new sporophyte.
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2.  Angiosperms are flowering plants that form
seeds inside a protective chamber called an
ovary.                                     A. 
Systematists are identifying angiosperm
clades                         1.  Monocots are
angiosperms that possess one embryonic seed leaf
(cotyledon).   2.  Dicots are angiosperms that
possess two embryonic seed leaves
(cotyledons).   3.  However, Angiosperms are
still being divided into new taxonomic groups as
we learn more about them.
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B.  The flower is the defining reproductive
adaptation of angiosperms                        
1.  Flowers are made up of four types of
modified leaves à sepals, petals, stamens, and
carpels.                                     a. 
Stamens are the male reproductive organs that
produce microspores.   b.  Carpels are female
reproductive organs that produce
megaspores.   Figure 30.13 (p. 608, ed. 6 Fig.
30.7, p. 598, ed.7) The structure of a
flower.                                    
Know the different flower parts
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 2.  A fruit is a mature ovary                    
                 a.  Protect dormant seeds.   b. 
Fruit aids in seed dispersal.                     
- Wind dispersal                      -
Attachment and transportation                     
- Consumption berries contain seeds to be
passed in feces   Figure 30.16 (p. 609) Fruit
adaptations that enhance seed dispersal.
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            C.  Life cycle of an
angiosperm                         1.  Mature
plant is the sporophyte   2.  Some plants easily
self-pollinate, but most have mechanisms to
ensure cross-pollination.    3.  Male
gametophytes reach female gametophytes by
producing a pollen tube.        Figure 30.17 (p.
611, ed.6 Fig. 30.10, p. 600, ed.7) The life
cycle of an angiosperm.
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 D.  Angiosperms dominated the earth at the end
of the Mesozoic era                         1. 
Radiation of angiosperms represents the
transition from Mesozoic to Cenozoic   E. 
Angiosperms and animals have affected one
anothers evolution                         1. 
Coevolution is the mutual influence on the
evolution of two different species interacting
with each other and reciprocally influencing each
others adaptations.                              
       a.  Pollinator-plant relationships
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IV.  Plants and Human Welfare A.  Agriculture is
almost totally dependent on angiosperms           
    B.  Plant diversity is a nonrenewable
resource                         1.  Many
medicines are obtained from plant
materials   Table 30.2 (p. 613) A sampling of
medicines derived from plants.  
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 2.  Deforestation eliminates Biodiversity, which
cannot be regained.
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