LS1_Wk5_Demo - The Photosynthetic World From Algae to...

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The Photosynthetic World: From Algae to Angiosperms DEMO 5 Objectives In this demo section you will learn: The major groups of multicellular photosynthetic organisms; The general adaptations that each group has for survival in their environments; The changes in reproductive, structural, vascular, and gas exchange strategies that have allowed for the Transition of plants from aquatic to terrestrial environments; The major adaptations of gymnosperms and angiosperms that have allowed them to be successful in terrestrial environments; The adaptations that have allowed angiosperms to become the dominant terrestrial plants. Introduction Life and the world we know today primarily exist because of the evolution of aquatic and terrestrial organisms capable of photosynthesis. These organisms are capable of converting the energy of sunlight into energy rich organic chemical bonds. Heterotrophs depend on this source of chemical energy to carry out their metabolic activities. Photosynthetic organisms use pigments to capture light energy and build sugars from inorganic carbon dioxide. The chemical energy stored in the sugar molecules is subsequently released when the plants (or other organisms feeding on the plants) digest this food source. Additionally, a vital by-product of photosynthesis is oxygen. Most aquatic and terrestrial organisms require oxygen for their survival, and photosynthesis accounts for almost all of the free oxygen in the world today. In this lab, you will look at the major groups of both aquatic and terrestrial photosynthetic organisms, and will consider the various adaptations that each group has for success. When looking at the different algae and plants consider their specific adaptations for success in their environments. Plant Life Cycles Sexual species typically have haploid and diploid phases in their life cycle. The diploid phase contains cells that undergo meiosis creating haploid gametes, and haploid gametes fuse to form a diploid cell. During this process, new gene combinations are formed. One important aspect of life cycles in multicellular organisms is whether the haploid, diploid, or both phases of the life cycle is multicellular. In animals, only the diploid phase is multicellular, and the haploid phase (the gametes) only exists as single cells. This in not the case in many organisms, including plants and algae. In “alternation of generations,” both the diploid and haploid stages are multicellular. In all terrestrial plants and many groups of algae, a multicellular diploid generation called the sporophyte alternates with a multicellular haploid generation called the gametophyte .
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The sporophyte generation of plants does not produce gametes directly (as the diploid generation of most animals does), instead the sporophyte, via meiosis, produces haploid cells called spores . The haploid spores then divide mitotically to produce a multicellular haploid gametophyte . This haploid gametophyte produces haploid gametes
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This note was uploaded on 06/03/2011 for the course LS 1 taught by Professor Thomas during the Spring '05 term at UCLA.

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LS1_Wk5_Demo - The Photosynthetic World From Algae to...

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