Lab 6 - Seedless plants - Student

Lab 6 - Seedless plants - Student - BSC2011 Lab 6 Seedless...

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1 The extant seedless plants consist of the “bryophytes”, the “fern allies” and the ferns. The term “bryophyte” refers to those plants that lack vascular tissue, and the term “fern allies” refers to seedless plants that contain vascular tissue but are not ferns. As their name suggests, none of these plants produce seeds or flowers, although some of them do produce “flower -like" reproductive structures, such as strobili (cones) or specialized stems that have collections of sporangia. Seedless plants vary greatly in size (centimeters to meters in height) and exhibit the typical alternation of generations lifecycle found in all plants. The alternation of generations refers to a life cycle that exhibits separate multi-cellular diploid individuals and multi-cellular haploid individuals. Thus, two separate generations, the gametophyte and the sporophyte , are needed to complete one cycle of life. The gametophyte is a multi-cellular individual that may be unisexual (male or female) or bisexual (male and female) that produces haploid gamete cells (flagellated sperm or eggs). Male gametophytes release sperm into the surrounding environment to fuse with the retained female gametes (fertilization). The resulting zygote develops into the diploid, multi-cellular sporophyte , which releases haploid spores into the environment that germinate and grow to become a multicellular haploid gametophyte (see figure below for clarification). In all seedless plants, gametes are produced in jacketed multi-cellular structures ( gametangia ). Two types of gametangia exist: antheridia that produce many flagellated sperm, which swim to an archegonium that contains a single egg. The new sporophyte grows out of the archegonium and is usually anchored to the gametophyte by a “foot”. The sporophyt e is initially dependent on the gametophyte (zygote to early embryo) for sustenance. Objectives Understand the basic life cycle of seedless plants Recognize key differences in the growth patterns and reproductive strategies of both life cycle stages in different plant groups BSC2011 Lab 6 Seedless Plants
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BSC2011 Lab 6 Seedless Plants 2 Materials Compound microscope Dissecting microscope Live specimens : Marchantia Conocephalum Bazzania Polytrichum Sphagnum Lycopodium Selaginella Equisetum Prepared slides : Marchantia antheridiophore Marchantia archegoniophore Mnium antheridia Mnium archegonia Lycopodium strobilus Selaginella strobilus Preserved specimen : Polytrichum Land plants alternate between a diploid stage and a haploid stage throughout their life cycle. Plants in the diploid stage are called Sporophytes and plants in the haploid stage are called Gametophytes. In some plant species, the sporophyte generation dominates the lifecycle, while in other plants, the gametophyte generation dominates the life cycle.
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