BIOL 1120 Lecture Notes - Lecture 16: Pollen Tube, Monocotyledon, Eudicots

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31 May 2016
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Chapter 31: Seed Plants
I. Adaptations of the Seed-Bearing Plants
A. The most successful of the vascular plants which have escaped dependency on water for fertilization, relying instead on
wind or animal pollinators.
B. Sporophyte is the dominant stage
C. Seed bearing plants (i.e. gymnosperms and angiosperms) differ from the seedless vascular plants in three ways:
1. They produce Microspores à
pollen grains.
a. Deposited on the female parts of the plant = pollination.
b. Delivers sperm to the egg = fertilization.
2. They also produce megaspores à ovules (Fig. 31.1, p. 601).
a. Mature ovules become seeds.
b. Seeds are composed of the embryo sporophytes and seed coats.
3. They have different leaf anatomy.
a. Thicker cuticles than seedless plants
b. Stomata are recessed below the surface of the leaf
c. Other competitive traits
II. Gymnosperms –Plants with "Naked" Seeds
A. General characteristics:
1. Sporophytic stage are conspicuous trees and shrubs
2. “Naked seeds” are rather unprotected.
a. Perched at the surface of reproductive parts
b. Not contained within fruits
3. No flowers
4. Pollen is wind blown
B. Conifers (Coniferophyta) (Fig. 31.3, p. 603)
1. Conifers (cone-bearers) are woody trees with needle-like or scale-like leaves.
2. Most are evergreens, some are deciduous.
3. Conifers produce 2 kinds of cones:
a. Male cones produce sporangia à microspores à pollen grains (male gametophyte).
b. Female cones produce ovules à megaspores (female gametophyte).
4. Upon pollination a pollen tube grows toward the egg.
5. Fertilization results in a zygote that develops into an embryo within the conifer seed.
C. Lesser Known Gymnosperms (Fig. 31.4, p. 604)
1. Cycods (Cycadophyta)
a. These palm-like trees flourished during the Mesozoic era.
b. Only about 100 species still exist.
c. Confined to the tropics and subtropics.
2. Ginkgos (Ginkgophyta)
a. They also flourished during the Mesozoic era.
b. Only one species has survived.
c. They are remarkably hardy, showing resistance to insects, disease, and air pollutants.
III. Angiosperms (Anthophyta) – The Flowering, Seed-Bearing Plants
A. Characteristics of Flowering Plants (Fig. 31.12, p. 609)
1. Angiosperms ("vessel seed") are the most successful and diverse division.
2. Produce specialized reproductive structures called flowers (Fig. 31.11, p. 608).
3. Most flowering plants coevolved with pollinators–insects, bats, birds, etc.
4. Disperse their seeds via mature ovaries called fruits (Fig. 31.17, p. 613).
5. Have broader leaves than gymnosperms
a. Intercept more sunlight
b. Can be shed during adverse conditions
B. There are 2 major groups of flowering plants
1. Eudicots (Class Dicotyledoneae)
a. Includes familiar shrubs, trees (except conifers), and herbaceous plants
b. 2 seed leaves (cotyledons)
c. 175,000 species
2. Monocots (Class Monocotyledoneae)
a. Includes grasses, lilies, and the major food-crop grains
b. 1 seed leaf
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c. 70,000 species
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