Chapter 30 - CR

Chapter 30 - CR - Chapter 30 Plant Diversity II: The...

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Page 1 of 40 Chapter 30 Chapter 30 Plant Diversity II: The Evolution of Seed Plants
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Page 2 of 40 30.1: The reduced gametophytes of 30.1: The reduced gametophytes of seed plants are protected in ovules seed plants are protected in ovules and pollen grains and pollen grains Seeds changed the course of plant evolution This enabled their bearers to become the dominant producers in most terrestrial ecosystems In addition to seeds, the following are common to all seed plants Reduced gametophytes Heterospory Ovules Pollen Figure 30.1
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Page 3 of 40 Advantages of Reduced Gametophytes The gametophytes of seed plants develop within the walls of spores retained within tissues of the parent sporophyte Heterospory Megasporangia produce megaspores that give rise to female gametophytes Microsporangia produce microspores that give rise to male gametophytes Pollen and Production of Sperm Microspores develop into pollen grains which contain the male gametophytes of plants Pollination is the transfer of pollen to the part of a seed plant containing the ovules Eliminated the water requirement for fertilization
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Page 4 of 40 Ovules and Production of Eggs Ovules and Production of Eggs An ovule consists of a megasporangium , megaspore , and protective integuments If a pollen grain germinates it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule (a) Unfertilized gymnosperm ovule. (Angiosperms have two integuments.) Integument Spore wall Megasporangium (2 n ) Megaspore ( n ) Figure 30.3a Figure 30.3b (b) Fertilized ovule. Male gametophyte (within germinating pollen grain) ( n ) Female gametophyte ( n ) Egg nucleus ( n ) Discharged sperm nucleus ( n ) Pollen grain ( n ) Micropyle
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Page 5 of 40 The Evolutionary Advantage of Seeds Seeds A seed develops from the whole ovule It is a sporophyte embryo , along with its food supply, packaged in a protective coat Figure 30.3c Gymnosperm seed. Fertilization initiates the transformation of the ovule into a seed (c) Seed coat (derived from integument) Food supply (female gametophyte tissue) ( n ) Embryo (2 n ) (new sporophyte)
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Page 6 of 40 30.2: Gymnosperms bear 30.2: Gymnosperms bear
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This note was uploaded on 04/07/2008 for the course BIO 103 taught by Professor Mannino during the Fall '08 term at Long Island U..

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Chapter 30 - CR - Chapter 30 Plant Diversity II: The...

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