SOQ_22_evolution - SOQ 22 1 Plant ancestors were limited...

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SOQ 22 – 1. Plant ancestors were limited because of the need for water to reproduce and as shelter. The defining feature of plants is their protected embryos. This is essential for survival on land. They all have multicellular haploid and diploid stages. (smaller haploid stage). Can be described as vascular and nonvascular based on whether or not they have water conducting xylem and food conducting phloem. They possess a waxy cuticle that protects them from water loss to air (it is secreted on to their surfaces. Gas diffusion occurs through the stomata, tiny, mouth shaped openings. The addition of leaves increased the surface area for photosynthesis, and the shift to a more prominent diploid generation allowed plants to grow vertically and more complex (trees) There are 300,000 species of plants currently living. 2. The group that is the suspected ancestor of plants is the fresh-water green algae. See page 526 for really not important details. 3. For plants: A diploid sporophyte produces haploid spores by meiosis. Takes place in sporangia, where the diploid mother cells, (sporocytes) undergo meiosis to form four haploid spores. Spores divide to form a multi cellular haploid gametophyte generation. There is alteration of generations. 4. Non-vascular Plants: bryophytes (24,700 species) live in many terrestrial environments. a.
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This note was uploaded on 04/17/2008 for the course HUMANITIES 111 taught by Professor Blume during the Winter '08 term at Union.

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SOQ_22_evolution - SOQ 22 1 Plant ancestors were limited...

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