Biology, Eighth Edition (Raven)

Chapter 42: Plant Reproduction

Post Test

When the wild-type (normal) EMF gene is mutated (thereby losing function), flowering occurs exceptionally early. What does this suggest about the effect of the EMF protein? (p. 829)
A)Flowering is a function of leaves converting into petals, and loss of the EMF gene causes petal formation.
B)The shoot apical meristem's natural inclination is to form vegetative structures, and is modified by the EMF protein to become a flower.
C)Phase change is reversible, depending on how much EMF protein is available.
D)Plants have juvenile and mature stages which are genetically controlled.
E)The "default" state of a shoot apical meristem is to form a flower, and the EMF gene creates a protein which inhibits this.
Sepals, petals, the androecium and the gynoecium have been shown to be produced through the action of just three genes, which can have additive effects which modify organ identity. Mutations in each of those genes give rise to predictable phenotypes. What would you predict if both the B and C gene products (found central to the A expression) were both knocked out? (p. 835)
A)There would only be anthers and carpels in the flower.
B)The flower would consist of sepals in all layers.
C)The flower would have male parts only.
D)The flower would have female parts only.
E)No flower could form because phase change would be blocked.
Some evolutionists have suggested that degradation of three of the four meiotic products, which leaves the cells of the embryo sac with only one genotype, was essential for double-fertilization to evolve. Why might this be important? (p. 838)
A)Having the same genotype means that the embryo will grow faster within the ovule.
B)Natural selection normally causes competition. When the haploid cells compete, only the healthiest ones remain, which allows the species to select only the best genotypes for the next generation.
C)The polar nuclei are of the same genotype as the embryo. Because they sacrifice themselves as endosperm, their "altruistic" genes will be selected for in the embryo, which benefits and passes on those genes.
D)Human oogenesis involves keeping only one haploid cell from each meiosis, so angiosperms, which are the epitome of plant evolution, show a similar pattern as the most advanced mammals.
E)The megaspores degenerate because they would compete with the "special" megaspore which remains behind. By dying out, they leave behind cellular reserves helpful to the megaspore which survives.
Dichogamous flowers offset the maturation of stamens and pistils to prevent selfing. In the 18th century, the pattern of bee flight was noted to proceed from the bottom of a panicle (a cluster of flowers) from the bottom to the top which, when reached, lead to the bee going to the bottom of another panicle and repeating the behavior. This is helpful for outcrossing, as the "top" flowers shed pollen, and the "bottom" flowers are receptive to pollination. What might account for this remarkable complementation of strategies? (p. 843)
A)The bees know that if they promote outcrossing by carrying the pollen from one plant to another, they'll be creating robust varieties that have enough genetic diversity to flourish under many conditions.
B)In the plants, genetic variety helps the plants under varied conditions, so the timing of maturation has been offset through natural selection. Bees which travel "up" the panicle do so because of their own genetics, and have coevolved with the plant because they themselves benefit by the plant's success.
C)Nectar tends to drip down to the bottom of the panicle, so bees that start there will get the easily-accessed food first, and work their way upwards until they no longer have enough nectar.
D)Bees find it hard to fly for long distances. When they're tired, they naturally end up at the bottom of flowers. They can climb up the inflorescence and feed as they go. Once they're at the top of the plant, they have rested and fed enough to go on another journey.
When a callus is generated in the laboratory in order to regenerate missing parts, what kind of ground tissue is it usually composed of? (p. 847)
Why are many commercial biennial plants harvested in their first year, rather than waiting until the second when they've had even more time to "bulk up"? (p. 848)
A)In the second year, the storage tissues (such as a tap root or thickened leaves) are depleted in order to power flowering behaviors.
B)An additional year will result in lots of secondary growth, which makes the product woody and undesirable for consumers.
C)A large number of biennials can't over-winter, and so there would be too few plants left after mortality for the farm to be economically viable.
D)The plants are harvested in the first year before the first annual flowering cycle, which uses up a lot of their reserves. In the second annual flowering cycle, there's not much left in the plant, even after another year's vegetative growth.
E)Commercial farmers need to watch out for their profits and so cannot wait the additional year to get paid.
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