101. Which tissue forms the central mass of cells in the ovule and encloses the embryo sac?
ⓐ. integument
ⓑ. funicle
ⓒ. nucellus
ⓓ. endothecium
Correct Answer: nucellus
Explanation: Nucellus is the central tissue of the ovule and surrounds the embryo sac. It is a nutritive sporophytic tissue and should not be confused with the embryo sac itself, which is the female gametophyte. The integuments lie outside the nucellus as protective coverings. This distinction between nucellus and embryo sac is a common source of confusion.
102. Which statement correctly compares nucellus and embryo sac?
ⓐ. Nucellus is sporophytic tissue, whereas embryo sac is the female gametophyte.
ⓑ. Nucellus is the pollen-bearing tissue, whereas embryo sac forms the exine.
ⓒ. Nucellus is a male gametophyte, whereas embryo sac is a female sporophyte.
ⓓ. Nucellus and embryo sac are two names for the same structure.
Correct Answer: Nucellus is sporophytic tissue, whereas embryo sac is the female gametophyte.
Explanation: Nucellus belongs to the diploid sporophytic body of the plant and provides surrounding tissue within the ovule. The embryo sac develops inside it and represents the haploid female gametophyte. These two structures are closely associated spatially, but they are not identical. Keeping this distinction clear is essential for correct interpretation of ovule structure.
103. Which set includes only parts of a typical ovule?
ⓐ. filament, connective, tapetum, raphe
ⓑ. stigma, style, ovary, placenta
ⓒ. endothecium, middle layers, epidermis, tapetum
ⓓ. funicle, micropyle, chalaza, integuments
Correct Answer: funicle, micropyle, chalaza, integuments
Explanation: Funicle, micropyle, chalaza, and integuments are all parts of an ovule. The other options include parts of the pistil or anther rather than the ovule itself.
104. Choose the correct completion.
Inside a typical ovule, the embryo sac lies embedded within the ______, while the outer protective coverings are the ______.
ⓐ. placenta, funicle
ⓑ. nucellus, integuments
ⓒ. raphe, chalaza
ⓓ. hilum, micropyle
Correct Answer: nucellus, integuments
Explanation: The embryo sac is situated within the nucellus, which forms the central tissue of the ovule. Outside the nucellus are one or two integuments that protect the ovule while leaving a micropyle. This arrangement is fundamental to the structure of the megasporangium in flowering plants. Identifying inner tissue and outer coverings together helps build a clear spatial picture of the ovule.
105. Which part of the ovule mainly serves as the protective covering around the nucellus?
ⓐ. Integuments
ⓑ. Funicle
ⓒ. Raphe
ⓓ. Hilum
Correct Answer: Integuments
Explanation: Integuments are the outer coverings of the ovule. They surround the nucellus and protect the developing female reproductive structures inside. These coverings do not completely close, leaving a small opening called the micropyle. Their protective role is one of the defining features of an ovule as an integumented megasporangium.
106. A structure in the ovary is described as having a stalk-like attachment, a small opening at one end, and a chalazal region at the opposite end. This description best fits the
ⓐ. anther
ⓑ. pollen grain
ⓒ. ovule
ⓓ. stigma
Correct Answer: ovule
Explanation: The ovule is attached to the placenta by the funicle, has a micropyle at one end, and a chalaza at the opposite end. These landmarks are commonly used to identify it. The ovule also contains the nucellus and embryo sac within integuments. Together, these features make the ovule easy to distinguish from other floral structures.
107. If the integuments of an ovule completely closed without leaving any gap, which structure would be absent?
ⓐ. hilum
ⓑ. raphe
ⓒ. chalaza
ⓓ. micropyle
Correct Answer: micropyle
Explanation: The micropyle is formed because the integuments do not fuse completely at one end of the ovule. This small opening remains important later for pollen tube entry. Hilum, raphe, and chalaza are different structural regions and do not depend on such an opening. So complete closure of integuments would specifically eliminate the micropyle.
108. Which pair is correctly matched?
ⓐ. Hilum — opposite end of the ovule from the micropyle
ⓑ. Micropyle — small opening left by integuments
ⓒ. Raphe — central tissue enclosing the embryo sac
ⓓ. Nucellus — stalk attaching the ovule to placenta
Correct Answer: Micropyle — small opening left by integuments
Explanation: The micropyle is the small opening left by the integuments. Hilum marks the point of attachment, raphe is the ridge formed by fusion of the funicle with the ovule body, and nucellus is the central tissue.
109. During megasporogenesis, the cell that undergoes meiosis is the
ⓐ. antipodal cell
ⓑ. egg cell
ⓒ. megaspore mother cell
ⓓ. synergid
Correct Answer: megaspore mother cell
Explanation: Megasporogenesis begins when a diploid megaspore mother cell differentiates in the nucellus. This cell then undergoes meiosis to form haploid megaspores. The egg cell, synergids, and antipodals appear much later during embryo sac development. So the megaspore mother cell is the starting point of the female spore line.
110. What is the chromosome number of the megaspore mother cell and the megaspores formed from it, respectively?
ⓐ. $2n$ and $n$
ⓑ. $n$ and $2n$
ⓒ. $2n$ and $2n$
ⓓ. $n$ and $n$
Correct Answer: $2n$ and $n$
Explanation: The megaspore mother cell belongs to the diploid sporophytic tissue of the ovule. Through meiosis, it produces haploid megaspores. This reduction in chromosome number is parallel to the formation of microspores on the male side. The ploidy shift is essential because the later female gametophyte develops from a haploid megaspore.
111. The immediate product of meiosis in a megaspore mother cell is usually a
ⓐ. four-celled embryo sac
ⓑ. triploid endosperm
ⓒ. single diploid functional megaspore
ⓓ. linear tetrad of haploid megaspores
Correct Answer: linear tetrad of haploid megaspores
Explanation: After meiosis, the megaspore mother cell generally forms four haploid megaspores arranged in a linear tetrad. This is the direct product of megasporogenesis. The embryo sac develops later from only one surviving megaspore in most angiosperms. Endosperm is formed only after fertilisation, so it is not related to this stage.
112. In most flowering plants, how many megaspores of the tetrad usually remain functional?
ⓐ. Four
ⓑ. Three
ⓒ. Two
ⓓ. One
Correct Answer: One
Explanation: Although four megaspores are formed by meiosis, usually only one remains functional in most angiosperms. The remaining three degenerate. This single surviving megaspore later develops into the embryo sac. The pattern is therefore both selective and highly characteristic of typical angiosperm reproduction.
113. Which statement correctly describes the usual fate of the four megaspores formed during megasporogenesis?
ⓐ. Three degenerate and one remains functional.
ⓑ. All four fuse to form the embryo sac.
ⓒ. Two form pollen grains and two degenerate.
ⓓ. All four directly act as female gametes.
Correct Answer: Three degenerate and one remains functional.
Explanation: The usual angiosperm pattern involves formation of four haploid megaspores, but only one of them survives. The other three generally degenerate. The surviving functional megaspore gives rise to the female gametophyte. This selective survival is a major feature distinguishing the usual course of megasporogenesis from simple retention of all meiotic products.
114. Which sequence correctly represents the usual order of events in megasporogenesis?
ⓐ. embryo sac formation → megaspore mother cell → meiosis → tetrad
ⓑ. functional megaspore → meiosis → megaspore mother cell → tetrad
ⓒ. nucellar cell differentiation → megaspore mother cell → meiosis → functional megaspore
ⓓ. meiosis → nucellar differentiation → tetrad → functional megaspore
Correct Answer: nucellar cell differentiation → megaspore mother cell → meiosis → functional megaspore
Explanation: A cell in the nucellus first differentiates into the megaspore mother cell. This diploid cell undergoes meiosis to produce a tetrad of haploid megaspores. Out of these, one usually remains functional. The sequence is important because it links sporophytic origin with haploid spore formation.
115. Which feature is characteristic of megasporogenesis in most angiosperms?
ⓐ. Formation of four equally persistent embryo sacs
ⓑ. Mitotic division of the egg cell before pollination
ⓒ. Production of diploid megaspores inside the ovary
ⓓ. Degeneration of three megaspores after meiosis
Correct Answer: Degeneration of three megaspores after meiosis
Explanation: The typical angiosperm pattern does not retain all four meiotic products. Instead, only one megaspore survives while the other three degenerate. This makes the later female gametophyte effectively monosporic in origin. The process is therefore defined not only by meiosis, but also by the usual degeneration pattern that follows it.
116. Choose the correct completion.
Megasporogenesis produces a tetrad of haploid megaspores, of which usually ______ survives to form the female gametophyte.
ⓐ. all four
ⓑ. only one
ⓒ. only two
ⓓ. none
Correct Answer: only one
Explanation: In most flowering plants, a single megaspore remains functional after meiosis. This surviving megaspore develops into the embryo sac, which is the female gametophyte. The other three usually degenerate and do not contribute further. This is why the common embryo sac of angiosperms is described as arising from one megaspore.
117. In most angiosperms, the embryo sac develops from
ⓐ. one functional megaspore
ⓑ. all four megaspores of the tetrad
ⓒ. the nucellus directly
ⓓ. the pollen mother cell
Correct Answer: one functional megaspore
Explanation: The usual embryo sac in angiosperms arises from a single surviving megaspore. After megasporogenesis, three megaspores generally degenerate and only one remains functional. This surviving megaspore undergoes mitotic divisions to form the female gametophyte. Because the embryo sac develops from one megaspore, it is described as monosporic.
118. The most common type of embryo sac development in flowering plants is the
ⓐ. bisporic type
ⓑ. tetrasporic type
ⓒ. Polygonum type
ⓓ. Oenothera type
Correct Answer: Polygonum type
Explanation: The Polygonum type is the common pattern of embryo sac development in angiosperms. In this type, the embryo sac is monosporic and develops from a single functional megaspore.
119. How many mitotic divisions does the functional megaspore usually undergo to form the typical embryo sac?
ⓐ. One
ⓑ. Two
ⓒ. Four
ⓓ. Three
Correct Answer: Three
Explanation: The functional megaspore undergoes three successive mitotic divisions. These divisions produce eight nuclei within the developing embryo sac. Afterward, these nuclei are arranged into specific cells at the micropylar and chalazal ends and in the center. The three mitotic divisions are therefore crucial for building the typical female gametophyte.
120. A typical mature angiosperm embryo sac is
ⓐ. eight-celled and seven-nucleate
ⓑ. seven-celled and eight-nucleate
ⓒ. eight-celled and eight-nucleate
ⓓ. seven-celled and seven-nucleate
Correct Answer: seven-celled and eight-nucleate
Explanation: The mature embryo sac has seven cells but contains eight nuclei. This happens because the central cell contains two polar nuclei, while the other cells each contain one nucleus. The arrangement is therefore seven-celled yet eight-nucleate at the same time. Both descriptions are correct together and should not be treated as contradictory.
