Biology reading for 3/16/15Pages 185-187Evolution of RootsRoots: organs that absorb water and nutrients from the soilRoots anchor vascular plants, hence the shoot system grows tallerEvolution of leavesLeaves: increase the surface area of the plant body and serve as the primary photosynthetic organ of the vascular plantsLeaves can either be classified as microphylls or megaphyllsLycophyte: the oldest lineage of extant vascular plantsMicrophylls: Small, often spine-shaped leaves supported by a single strand of vascular tissue. It is only found in lycophytes.Megaphylls: leaves with a highly branched vascular system. It is found in almost all other vascular plants.Sporophylls and Spore variationsSporophylls: modified leaves that bear sporangia.Sori: type of sporangia produced by fern sporophylls. It is usually found on the underside of the sporophyll.Strobili: cone-like structure that is formed by sporophylls in lycophytes and most gymnospermsHomosporous: most seedless vascular plants. Has one type of sporangium that produces one type of spore, which typically develops into a bisexual gametophyte.Heterosporous: species that has two types of sporangia: megasporangia, and microsporangia and produces two types of spores: megaspores, and microspores.Megaspores: produced by megasporangia on megasporophylls. They develop into female gametophytes.Microspores: Produced by microsporangia on microsporophylls. They develop into male gametophytes.Homosporous spore production: Sporangium on sporophyll → single type of spore → Typically bisexual gametophyte → eggs or spermHeterosporous spore production: megasporangium on megasporophyll or microsporangium onmicrosporophyll → megaspore or microspore → female or male gametophyte → eggs or spermClassification of seedless vascular plantsThe two clades of seedless vascular plants: lycophytes and monilophytesQuizlet link:
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