SCIENTIFIC INQUIRY Draw IT As will be described in detail in Chapter 38, the female

Chapter 30, Problem 8

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SCIENTIFIC INQUIRY Draw IT As will be described in detail in Chapter 38, the female gametophyte of angiosperms typically has seven cells, one of which, the central cell, contains two haploid nuclei. After double fertilization, the central cell develops into endosperm, which is triploid. Because magnoliids, monocots, and eudicots typically have female gametophytes with seven cells and triploid endosperm, scientists assumed that this was the ancestral state for angiosperms. Consider, however, the following recent discoveries: Our understanding of angiosperm phylogeny has changed to that shown in Figure 30.14b. Amborella trichopoda has eight-celled female gametophytes and triploid endosperm. Water lilies and star anise have four-celled female gametophytes and diploid endosperm. a. Draw a phylogeny of the angiosperms (see Figure 30.14b), incorporating the data given above about the number of cells in female gametophytes and the ploidy of the endosperm. Assume that all of the star anise relatives have fourcelled female gametophytes and diploid endosperm. b. What does your labeled phylogeny suggest about the evolution of the female gametophyte and endosperm in angiosperms?