Chapter 25

Chapter 25 - NOTES FOR BIOLOGY 1002 SECTIONS 001 and 002...

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NOTES FOR BIOLOGY 1002 SECTIONS 001 and 002 Spring 2008 DR. STEVEN POMARICO Outline 3B CHAPTER 25 Plant Reproduction and Development Sexual versus Asexual Reproduction Many plant species can reproduce both sexually and asexually. Asexual reproduction can occur via fragmentation Fragmentation can be an artificial process (cuttings) or a natural process. The parent plant sends out horizontal stems ( runners ) that can lead to completely new plants. Asexual reproduction is natural cloning where all the offspring are genetically identical to the parent plant. Sexual offspring combine the genes from two parents and are genetically different from their parents Plant Life Cycles Alternation of generations revisited (see fig 25-1) 2 distinct multicellular adult forms sporophyte : diploid plant which produces haploid spores
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gametophyte : haploid plant which produces gametes In mosses and ferns the gametophyte is small and independent Water is essential for sexual reproduction In seed plants, gymnosperms and angiosperms, the gametophyte is very small and relies on the sporophyte (it’s part of the sporophyte) Water no longer needed for transporting the gametes Two types of spores are seen in the flowering plants. They are heterosporous (see fig 25-2) Megaspores - gives rise to the female gametophyte Microspores - gives rise to the male gametophyte The two different gametophytes produce two types of gametes female gametophyte is an embryo sac containing an egg cell male gametophyte is a pollen grain (sperm) After fertilization the zygote develops into the seed (plant embryo), which will grow into a new sporophyte.
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Chapter 25 - NOTES FOR BIOLOGY 1002 SECTIONS 001 and 002...

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