Concept explainers
Figure 14.19 At what stage does the diploid zygote form?
a. When the female cone begins to bud from the tree
b. When the sperm nucleus and the egg nucleus fuse
c. When the seeds drop from the tree
d. When the pollen tube begins to grow
Introduction:
The terrestrial plants mostly comprise of the small green plant vegetation. It consists of grasses, trees, mosses, ferns, gymnosperms, hornworts. All the land plants have specific reproductive organs. In biology, alternation of generations is also known as heterogenesis or metagenesis. It represents the alternation of an asexual phase and a sexual phase in the life cycle of an organism.
Answer to Problem 1ACQ
Correct answer:
The correct answer is the option (b) when the sperm nucleus and egg nucleus fuse.
Explanation of Solution
Explanation/justification for the correct answer:
The correct option (b) when the sperm nucleus and egg nucleus fuse. Fertilization is the process in which the fusion of haploid microsporangium or sperm nucleus and megasporangium or female nucleus takes place to form a diploid zygote. It is the phenomenon in which the haploid stages lead to the diploid stage. Hence, the option (b) is correct.
Explanation for incorrect answer:
Option (a) when the female cone starts to bud from the tree. The female cone on budding will produce several megasporocytes. These give rise to a megasporangium (female gamete) in the gymnosperm. The female cones occur on the higher branches of the tree to promote the pollination. Hence, the option (a) is incorrect.
Option (c) when the seed drops from the tree. The seed forms after the effective fertilization. The seed gets dispersed by several means that germinate and produce a new plant. Hence, the option (c) is incorrect.
Option (d) when the pollen tube starts to grow. The pollen tube is a hollow tube-like structure that runs through the style of a female reproductive system in a flower. It carries two sperm cells that take part in the double fertilization process. Hence, the option (d) is incorrect.
Fertilization is the process in which the fusion of haploid microsporangium or sperm nucleus and megasporangium or female nucleus takes place to form a diploid zygote. Hence, the option (b) is correct.
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