BIO 200 Lecture Notes - Lecture 27: Aphid, Gymnosperm, Secondary Growth
7 Dec 2017
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Document Summary
First tracheophytes all have swimming sperm but lack seeds: e. g. whisk ferns, horsetails, club mosses, ferns. Fern life cycle: spore produce underneath fern via meiosis. If the spores land in moist area they will germinate. Swimming sperm and eggs are produced underneath, the swimming sperm fertilizes and zygotes grow into embryo: parasitic for 9 months then it becomes independent. Diploid (sporophyte) generation is dominant in tracheophytes: the fern life cycle is an example of alternation of generation. In bryophytes: the haploid (n) generation is dominant. In tracheophytes: the diploid (2n) generation is dominant. Homosporous life cycle: e. g. bryophytes and ferns, one kind of spore, one kind of gametophyte. Selective advantages to land: less competition for light, less predation, problem with new environment, physical support, water loss and availability, reproduction, temperature fluctuations. Roots: anchor plants in soil & acquire nutrients & h2o. Stems: turgor pressure in cells and cell walls, lignin wood, secondary growth: i. e. growth in width (rings of xylem)
