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Chapter 30
Are Ulva gametes formed by meiosis? Explain your response. (Figure 30.5)
Answer: The diploid sporophyte of Ulva produces sporangia in which meiosis occurs.
The resultant haploid spores develop into either plus or minus strains of multicellular
gametophytes which, in turn, produce haploid gametangia. The gametangia produce
haploid gametes. Meiosis is involved in the formation of Ulva gametes, but not directly.
Explain why tracheophytes may have had a selective advantage during the evolution of
land plants. (Page 588)
Answer: Tracheophytes developed vascular tissue, enabling them to have efficient waterand food-conducting systems. Vascular tissue allowed tracheophytes to grow larger,
possibly then able to out-compete smaller, nonvascular land plants. A protective cuticle
and stomata that can close during dry conditions also conferred a selective advantage.
If the endosperm failed to develop in a seed, how do you think the fitness of that seed’s
embryo would be affected? Explain your answer. (Page 600)
Answer: Endosperm provides nutrients for the developing embryo in most flowering
plants. The embryo cannot derive nutrition from soil prior to root development, therefore
without endosperm, the embryo is unlikely to survive.