Fern plants. Like all other vascular plants, the diploid sporophyte is the dominant phase or generation in the life cycle. The gametophytes of ferns, however, are very different from those of seed plants. They are free-living and resemble liverworts, whereas those of seed plants develop within the spore wall and are dependent on the parent sporophyte for their nutrition. A fern gametophyte typically consists of: Ferns first appear in the fossil record in the early Carboniferous period. By the Triassic, the first evidence of ferns related to several modern families appeared. The great fern radiation occurred in the late Cretaceous, when
Second-generation immigrants in the United States dominant norm of mainstream U.S. society. Despite the barriers that come from being born to immigrants who are generally low skilled, have little education, and have less knowledge of the English language compared to U.S. natives, second-generation immigrants are doing better than U.S. native groups of comparable racial backgrounds, contradicting the concept of downward assimilation. A major factor that contributes to second-generation immigrants doing so well is the drive to succeed and do better than their predecessors that is commonly instilled in these immigrants from childhood by their families. The theory of segment assimilation undermines such early socialization. Second-generation immigrants