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Unformatted text preview: Chapter 29 Plant Diversity I • Land plants arose 400 million years ago • Land plants probably evolved from a green algae called charophytes • Similarities between land plants and charophytes o Rosette- shaped cellulose- synthesizing complexes- petal shaped arrays in the plasma membrane that synthesize the cellulose microfibrils of the cell wall o Peroxisome enzymes- help minimize the loss of organic products as a result of photorespiration o Flagellated sperm- in species of land plants that have flagellated sperm, the structure of the sperm is like a charophyte’s o Formation of a phragmoplast- a group of microtubules known as the phragmoplast forms between the daughter nuclei of a dividing cell. A cell plate then develops in the middle of the phragmoplast, across the midline of the dividing cell. • In charophytes, a layer of a durable polymer called sporopollenin prevents exposed zygotes from drying out. A similar chemical adaptation is found in the tough sporopollenin walls that encases the spores of plants. • Differences between land plants and charophytes o Apical meristems on shoots and roots o Walled spores produced in sporangia Sporangia- multicellular organs that produce spores Sporocytes- diploid cells in a sporangia that undergo meiosis and produce the spores o Multicellular gametangia Gametangia- multicellular organs that produce gametes Archegonia- female gametangia that produce non-motile eggs Antheridia- male gametangia that produce sperm and release them into the environment o Alternation of Generations Sporophyte (diploid) undergoes meiosis to form spores Spore undergoes mitosis and forms a gametophyte (haploid) Gametophyte undergoes mitosis and produces gametes Gamete is fertilized by another and produces a zygote Zygote undergoes mitosis and makes a sporophyte o Placental transfer cells- cells an embryo has which enhance the transfer or nutrients from parent to embryo through elaborate ingrowths of the wall surface o Gametophyte- plant life generation which is named for its production of haploid gametes—eggs and sperm—that fuse during fertilization, forming diploid zygotes o Sporophyte- plant life generation which produces haploid spores o Spores- reproductive cells that can develop into a new haploid organism without fusing with another cell • How did plants overcome problems of living on land? o Plants developed a waxy coating called a cuticle to avoid drying out, prevent microbial attack, and help waterproof. o Formed symbiotic relation ( mycorrhizae ) with fungi to aid in nutrient uptake o Secondary compounds and pigments that prevent against herbivores, parasites, and UV radiation....
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This note was uploaded on 08/07/2009 for the course BY 124 taught by Professor Cusic during the Spring '08 term at University of Alabama at Birmingham.
- Spring '08