Double Fertilisation Questions in English

(A) The life of all sexually reproducing organisms begins as a single cell called the $Zygote$.
This $Zygote$ is formed by the fusion of male and female gametes during fertilization.
It contains the complete genetic blueprint necessary for the development of the entire organism.

(C) Double fertilization is a characteristic feature of $Angiosperms$ (flowering plants).
It involves two fusion events:
$1$. Syngamy: One male gamete fuses with the egg cell to form a diploid zygote $(2n)$.
$2$. Triple fusion: The second male gamete fuses with the two polar nuclei (or secondary nucleus) to form the primary endosperm nucleus $(PEN)$,which is triploid $(3n)$.
This process ensures the development of the embryo and the formation of nutritive tissue (endosperm) for the developing seed.

(A) Double fertilization is a unique and defining characteristic of $Angiosperms$ (flowering plants).
In this process, one male gamete fuses with the egg cell to form a diploid zygote $(syngamy)$, and the second male gamete fuses with the two polar nuclei to form a triploid primary endosperm nucleus $(triple \text{ } fusion)$.
Together, these two events are known as double fertilization.

(A) Assertion $(A)$ is true: In angiosperms like roses,the endosperm is formed by the fusion of a male gamete with two polar nuclei (triple fusion),which occurs only after fertilization.
Reason $(R)$ is true: Double fertilization (syngamy and triple fusion) is a unique characteristic feature of angiosperms.
Explanation: The formation of the endosperm is a direct result of the triple fusion process,which is a part of the double fertilization event. Therefore,$R$ is the correct explanation of $A$.

(B) In angiosperms,the endosperm is formed as a result of double fertilization,specifically through the fusion of one male gamete with two polar nuclei (triple fusion).
Sunflower $(Helianthus \ annuus)$ is an angiosperm.
In gymnosperms like Pinus and Thuja,the endosperm is haploid and forms before fertilization.
Nephrolepis is a pteridophyte and does not produce seeds or endosperm.

(B) The plant shown in the figure is a sunflower,which belongs to the group of Angiosperms (flowering plants).
Angiosperms are characterized by a unique process known as double fertilization.
In this process,one male gamete fuses with the egg cell to form a diploid zygote (syngamy),and the other male gamete fuses with the two polar nuclei to form a triploid primary endosperm nucleus (triple fusion).
Therefore,double fertilization is the characteristic feature of angiosperms.

(C) The correct answer is $C$. Double fertilisation is a unique and characteristic feature of angiosperms.
In this process,two male gametes are released into the embryo sac.
One male gamete fuses with the egg cell to form a diploid zygote,which develops into the embryo.
The second male gamete fuses with the secondary nucleus (or two polar nuclei) to form the primary endosperm nucleus $(PEN)$,which is triploid $(3n)$ and develops into the endosperm.

(D) The $Zygote$ is the vital link that ensures the continuity of species between organisms of one generation and the next.
It is a diploid cell formed by the fusion of two haploid gametes (male and female) during the process of fertilization.
This single-celled $Zygote$ contains the genetic material from both parents, which then undergoes repeated mitotic divisions to develop into a new individual, thereby maintaining the continuity of the species.

(A) Double fertilization is a characteristic feature of angiosperms.
It involves two fusion events:
$1$. Syngamy: One male gamete fuses with the egg cell to form a diploid zygote $(n + n = 2n)$.
$2$. Triple Fusion: The second male gamete fuses with the two polar nuclei (or the secondary nucleus) to form the primary endosperm nucleus $(PEN)$,which is triploid $(n + 2n = 3n)$.
Together,these two processes are known as double fertilization.

(A) Before fertilization, a mature embryo sac (polygonum type) contains $7$ cells and $8$ nuclei.
After fertilization, the following events occur:
$1$. The egg cell fuses with one male gamete to form a diploid zygote $(2n)$, which contains $1$ nucleus.
$2$. The central cell, which contains two polar nuclei, fuses with the second male gamete to form a primary endosperm nucleus $(PEN)$, which is triploid $(3n)$ and contains $1$ nucleus.
$3$. The three antipodal cells and two synergids usually degenerate.
However, the question asks for the total number of nuclei present in the embryo sac structure. The $PEN$ ($1$ nucleus) and the zygote ($1$ nucleus) are present. The degenerating synergids and antipodal cells still contain their nuclei for a period. Specifically, the $PEN$ is $1$ nucleus, the zygote is $1$ nucleus, the $3$ antipodal cells have $3$ nuclei, and the $2$ synergids have $2$ nuclei.
Total nuclei = $1 (PEN) + 1 (Zygote) + 3 (Antipodals) + 2 (Synergids) = 7$ nuclei.

(B) During the process of double fertilization in angiosperms,the pollen tube enters one of the synergids through the filiform apparatus.
Upon entering the synergid,the pollen tube ruptures and releases two male gametes into the cytoplasm of that synergid.
One male gamete fuses with the egg cell to form a zygote (syngamy),and the other male gamete fuses with the two polar nuclei to form the primary endosperm nucleus (triple fusion).
Therefore,the correct sequence is that the pollen tube enters one synergid and releases two male gametes.

(B) Double fertilization is a unique and defining characteristic of $Angiosperms$ (flowering plants).
In this process, one male gamete fuses with the egg cell to form a diploid zygote $(syngamy)$, and the second male gamete fuses with the two polar nuclei to form a triploid primary endosperm nucleus $(triple \text{ } fusion)$.
This combined process of syngamy and triple fusion is known as double fertilization.

(B) Double fertilization is a unique and defining characteristic of angiosperms (flowering plants). It involves the fusion of one male gamete with the egg cell to form a zygote (syngamy) and the fusion of another male gamete with the two polar nuclei to form the primary endosperm nucleus (triple fusion). This process is universal in all angiosperms. Vessels are absent in some primitive angiosperms,secondary growth is absent in monocots,and while most angiosperms are autotrophic,some are parasitic (e.g.,Cuscuta),making double fertilization the only exceptionless feature among the choices.

(A) Syngamy is the process of fusion of two haploid gametes to form a diploid zygote. This is a fundamental event in sexual reproduction. Therefore,the correct definition is the fusion of gametes.

(D) Double fertilization is a characteristic feature of angiosperms.
It involves two fusion events:
$1$. Syngamy: One male gamete fuses with the egg cell to form a diploid zygote $(n + n = 2n)$.
$2$. Triple Fusion: The second male gamete fuses with the two polar nuclei (or the secondary nucleus) to form a triploid primary endosperm nucleus $(n + 2n = 3n)$.
Thus,double fertilization is the fusion of one male gamete with the egg cell and another male gamete with the secondary nucleus.

(B) Double fertilization and triple fusion were discovered by $S.G. \text{Nawaschin}$ and $L. \text{Guignard}$ in $1898$ in the plants $Lilium$ and $Fritillaria$.
Double fertilization involves the fusion of one male gamete with the egg cell to form a diploid zygote,and the fusion of the second male gamete with two polar nuclei to form the primary endosperm nucleus (triple fusion).

(B) In angiosperms,the process of double fertilization involves two events: syngamy and triple fusion.
Syngamy involves the fusion of one male gamete with the egg cell to form a diploid zygote $(2n)$,which develops into the embryo.
Triple fusion involves the fusion of the second male gamete $(n)$ with two polar nuclei $(n+n)$ or the secondary nucleus $(2n)$ to form the primary endosperm nucleus $(PEN)$ which is triploid $(3n)$.
The $PEN$ subsequently develops into the endosperm,which provides nourishment to the developing embryo.
Therefore,triple fusion is essential for the formation of the endosperm.

(B) In angiosperms,double fertilization involves two processes: syngamy and triple fusion.
During triple fusion,one male gamete $(n)$ fuses with two polar nuclei $(n + n)$ or the secondary nucleus $(2n)$ present in the central cell.
This fusion results in the formation of the Primary Endosperm Nucleus $(PEN)$,which is triploid $(3n)$.
This $PEN$ subsequently develops into the endosperm,which provides nourishment to the developing embryo.

(D) Double fertilization is a characteristic feature of $Angiosperms$ (flowering plants).
In this process, one male gamete fuses with the egg cell to form a diploid zygote $(syngamy)$, and the second male gamete fuses with the two polar nuclei to form a triploid primary endosperm nucleus $(triple \text{ } fusion)$.
Together, these two events are known as double fertilization.

(D) Double fertilization is a characteristic feature of angiosperms.
It involves two distinct fusion events:
$1$. Syngamy: One male gamete fuses with the egg cell to form a diploid zygote $(2n)$.
$2$. Triple fusion: The second male gamete fuses with the two polar nuclei (or the secondary nucleus) to form a primary endosperm nucleus $(PEN)$,which is triploid $(3n)$.
Therefore,double fertilization is the combination of syngamy and triple fusion.

(D) In angiosperms,the process of double fertilization occurs.
After the pollen tube enters the synergid,it releases two male gametes into the cytoplasm of the synergid.
One male gamete moves towards the egg cell and fuses with its nucleus to form a diploid zygote $(n + n = 2n)$,a process known as syngamy.
The second male gamete moves towards the two polar nuclei located in the central cell and fuses with them to form a triploid primary endosperm nucleus $(PEN)$ $(n + n + n = 3n)$,a process known as triple fusion.
Thus,one male gamete fuses with the egg and the other fuses with the central cell nuclei.

(A) Double fertilization is a unique and characteristic feature of angiosperms.
It involves two distinct fusion events:
$1$. Syngamy: One male gamete fuses with the egg cell to form a diploid zygote $(2n)$.
$2$. Triple Fusion: The second male gamete fuses with the two polar nuclei (or the diploid secondary nucleus) to form the primary endosperm nucleus $(PEN)$,which is triploid $(3n)$.
Since the process is defined by these two specific fusion events,the Reason correctly explains the Assertion.

(N/A) $(i)$ Red algae and brown algae

$(1)$ Red algae belong to class Rhodophyceae.	$(1)$ Brown algae belong to class Phaeophyceae.
$(2)$ Stored food is floridean starch.	$(2)$ Stored food is mannitol or laminarin.
$(3)$ Pigments are chlorophyll $a, d$ and phycoerythrin.	$(3)$ Pigments are chlorophyll $a, c$ and fucoxanthin.
$(4)$ Cell wall contains cellulose,pectin,and phycocolloids.	$(4)$ Cell wall contains cellulose and algin.
$(5)$ Flagella are absent.	$(5)$ Two flagella are present.

$(ii)$ Liverworts and moss

$(1)$ Rhizoids are unicellular.	$(1)$ Rhizoids are multicellular.
$(2)$ Scales are often present.	$(2)$ Scales are absent.
$(3)$ Thalloid body with dichotomous branching.	$(3)$ Foliage body with lateral branching.
$(4)$ Gemma cups are present.	$(4)$ Gemma cups are absent.
$(5)$ Sporophyte has little photosynthetic tissue.	$(5)$ Sporophyte has abundant photosynthetic tissue.

$(iii)$ Homosporous and heterosporous pteridophytes

$(1)$ Produce spores of the same type.	$(1)$ Produce two types of spores: microspores and megaspores.
$(2)$ Produce bisexual gametophytes.	$(2)$ Produce unisexual gametophytes.

$(iv)$ Syngamy and triple fusion

$(1)$ Fusion of male gamete with egg.	$(1)$ Fusion of male gamete with secondary nucleus.
$(2)$ Forms a diploid zygote.	$(2)$ Forms a triploid primary endosperm nucleus.

(B) Double fertilization is a unique process characteristic of Angiosperms. It involves two distinct fusion events:
$1$. Syngamy: One male gamete fuses with the egg cell to form a diploid zygote $(2n)$.
$2$. Triple Fusion: The second male gamete fuses with the two polar nuclei (or the secondary nucleus) in the central cell to form a triploid primary endosperm nucleus ($PEN$,$3n$).
Together,these two processes are known as double fertilization.

(N/A) Triple fusion is the fusion of one male gamete with two polar nuclei inside the embryo sac of an angiosperm.
This process takes place inside the central cell of the embryo sac.
When pollen grains land on the stigma,they germinate to form a pollen tube that grows through the style and enters the ovule. The pollen tube enters one of the synergids and releases two male gametes. One male gamete fuses with the egg cell to form a diploid zygote (syngamy). The second male gamete moves towards the central cell and fuses with the two polar nuclei to form a triploid primary endosperm nucleus $(PEN)$. This process is called triple fusion because it involves the fusion of three haploid nuclei. It leads to the development of the endosperm.
The nuclei involved are one male gamete nucleus and two polar nuclei.

(N/A) Double fertilisation is a complex fertilization mechanism unique to angiosperms.
$1$. Pollen deposition and tube growth: After pollination,the pollen grain germinates on the stigma to form a pollen tube. This tube grows through the style and enters the ovary,eventually reaching the ovule. Two male gametes are carried within the pollen tube.
$2$. Entry into the embryo sac: Upon entering one of the synergids,the pollen tube releases the two male gametes into the cytoplasm of the synergid.
$3$. Syngamy: One of the male gametes moves towards the egg cell and fuses with its nucleus. This fusion is called syngamy,resulting in the formation of a diploid zygote $(2n)$.
$4$. Triple fusion: The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them. This fusion of three haploid nuclei $(n + n + n)$ is termed triple fusion,resulting in a triploid primary endosperm nucleus ($PEN$,$3n$).
$5$. Conclusion: Since both syngamy and triple fusion occur within the embryo sac,the process is known as double fertilisation. The central cell,after triple fusion,becomes the Primary Endosperm Cell $(PEC)$ and develops into the endosperm,while the zygote develops into the embryo.

(N/A) $\rightarrow$ In angiosperms,out of the two male gametes,one male gamete fuses with the egg cell to form a diploid zygote (syngamy),while the other male gamete fuses with the two polar nuclei (or diploid secondary nucleus) to form a triploid primary endosperm nucleus $(PEN)$ (triple fusion).
$\rightarrow$ Since two types of fusion events occur in the embryo sac,this process is known as double fertilisation.
$\rightarrow$ This phenomenon is a unique characteristic of angiosperms.

(B) In angiosperms,during the process of double fertilization,one of the male gametes fuses with the two polar nuclei located in the central cell to form a triploid $(3n)$ structure known as the Primary Endosperm Nucleus $(PEN)$.
This nucleus subsequently develops into the endosperm,which provides nourishment to the developing embryo.

(N/A) In angiosperms,the process of fertilization involves two distinct fusion events:
$1$. Syngamy (Fertilization): One of the two male gametes released by the pollen tube fuses with the egg cell to form a diploid zygote $(2n)$.
$2$. Triple Fusion: The second male gamete fuses with the two polar nuclei (or the secondary nucleus) located in the central cell to form a triploid Primary Endosperm Nucleus ($PEN$,$3n$).
Since these two fusion events occur simultaneously in the embryo sac,the process is collectively known as double fertilization. Following these events,the zygote develops into an embryo,and the $PEN$ develops into the endosperm,which provides nourishment to the developing embryo.

(N/A) $\rightarrow$ After pollination,the pollen grain germinates on the stigma,and the pollen tube grows through the style to reach the ovule.
$\rightarrow$ The pollen tube enters the embryo sac and releases two male gametes.
$\rightarrow$ One male gamete fuses with the egg cell to form a diploid zygote,a process known as $Syngamy$.
$\rightarrow$ The second male gamete fuses with the two polar nuclei (or the diploid secondary nucleus) to form a triploid primary endosperm nucleus $(PEN)$,a process known as $Triple$ $Fusion$.
$\rightarrow$ Since two types of fusions occur within the embryo sac,this phenomenon is called $Double$ $Fertilization$,which is a unique characteristic of angiosperms.

(N/A) After entering one of the synergids,the pollen tube releases the two male gametes into the cytoplasm of the synergid.
One of the male gametes moves towards the egg cell and fuses with its nucleus,thus completing the $syngamy$. This results in the formation of a diploid cell,the $zygote$.
The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid $primary$ $endosperm$ $nucleus$ $(PEN)$.
As this involves the fusion of three haploid nuclei,it is termed $triple$ $fusion$.
Since two types of fusions,$syngamy$ and $triple$ $fusion$,take place in an embryo sac,the phenomenon is termed $double$ $fertilisation$.

(N/A) The triploid tissue in a fertilised ovule is the Primary Endosperm Nucleus $(PEN)$,which develops into the endosperm.
This triploid condition is achieved through a process called triple fusion.
During this process,one of the male gametes (haploid,$n$) fuses with the two polar nuclei (each haploid,$n$) present in the central cell.
This fusion of three haploid nuclei $(n + n + n)$ results in a triploid $(3n)$ nucleus.

(A) In angiosperms,each pollen grain produces two male gametes.
$1$. The first male gamete fuses with the egg cell (syngamy) to form a diploid zygote $(2n)$,which eventually develops into an embryo.
$2$. The second male gamete fuses with the two polar nuclei (or the secondary nucleus) in the central cell to form the primary endosperm nucleus $(PEN)$,which is triploid $(3n)$. This process is known as triple fusion.
Together,syngamy and triple fusion constitute the process of double fertilization.

(A) The process of fusion of a male gamete with an egg cell (female gamete) is known as $Syngamy$. This fusion results in the formation of a diploid cell called the $Zygote$. This is a key event in sexual reproduction.

(D) In angiosperms,during double fertilization,one of the male gametes fuses with the two polar nuclei located in the central cell to form a triploid $(3n)$ structure known as the Primary Endosperm Nucleus $(PEN)$.
This process is called triple fusion.
The $PEN$ subsequently develops into the endosperm,which provides nourishment to the developing embryo.

(C) In angiosperms,the process of double fertilization involves the fusion of one male gamete with two polar nuclei to form the Primary Endosperm Nucleus $(PEN)$.
Since the male gamete is haploid $(n)$ and the two polar nuclei are also haploid $(n + n)$,their fusion results in a triploid $(3n)$ structure.
Therefore,the ploidy level of $PEN$ is $3n$.

(B) In angiosperms,double fertilization occurs. One male gamete fuses with the egg cell (syngamy) to form a diploid zygote $(2n)$. The other male gamete fuses with the two polar nuclei (triple fusion) to form the Primary Endosperm Nucleus $(PEN)$. Thus,the fusion of a male gamete with the egg cell nucleus results in the formation of a zygote.

(B) Triple fusion is a key event in the process of double fertilization in angiosperms.
It involves the fusion of one male gamete $(n)$ with two polar nuclei (or a secondary nucleus formed by the fusion of two polar nuclei,each $n$) present in the central cell.
Since the male gamete is haploid $(n)$ and the two polar nuclei are also haploid $(n + n)$,their fusion results in the formation of a triploid $(3n)$ primary endosperm nucleus $(PEN)$.
Therefore,it is the fusion of three haploid nuclei.

(D) In angiosperms,double fertilization involves two fusion events:
$1$. Syngamy: One male gamete fuses with the egg cell to form a diploid zygote $(2n)$.
$2$. Triple Fusion: The second male gamete fuses with the two polar nuclei (or the secondary nucleus) present in the central cell to form the primary endosperm nucleus ($PEN$,$3n$).
Therefore,the male gametes fuse with the nuclei of the egg cell and the central cell.

(D) In flowering plants (angiosperms),the process of fertilization occurs within the embryo sac,which is the female gametophyte located inside the ovule.
$1$. The pollen tube enters the ovule through the micropyle.
$2$. It then enters one of the synergids.
$3$. The two male gametes are released into the cytoplasm of the synergid.
$4$. One male gamete fuses with the egg cell (syngamy) to form a zygote,and the other fuses with the two polar nuclei (triple fusion) to form the primary endosperm nucleus $(PEN)$.
Therefore,the site of fertilization is the female gametophyte.

(A) Double fertilization is a unique and characteristic feature of $Angiosperms$ (flowering plants).
In this process, one male gamete fuses with the egg cell to form a diploid zygote $(Syngamy)$, and the other male gamete fuses with the two polar nuclei to form a triploid primary endosperm nucleus $(Triple \text{ } Fusion)$.
Together, these two events are known as double fertilization.

(B) In angiosperms,double fertilization involves two processes: syngamy and triple fusion.
Triple fusion occurs when one male gamete $(n)$ fuses with two polar nuclei or the secondary nucleus $(2n)$ present in the central cell.
This fusion results in the formation of the Primary Endosperm Cell $(PEC)$,which is triploid $(3n)$.
Therefore,the correct answer is $PEC$.

(D) The correct answer is $D$.
Triple fusion is a characteristic feature of angiosperms (flowering plants) only,where one male gamete fuses with two polar nuclei to form the primary endosperm nucleus $(PEN)$.
It is not observed in gymnosperms,pteridophytes,bryophytes,or algae.
Therefore,the statement that triple fusion is observed in all plants is incorrect.
Wheat and maize are monocots where the endosperm persists in the mature seed.
Bean seeds are dicots and possess two cotyledons.
The radicle is protected by a root cap in all root systems.

(A) During fertilisation in angiosperms,one male gamete fuses with the egg cell to form a diploid zygote,a process known as syngamy.
The second male gamete fuses with the two polar nuclei (or the secondary nucleus) located in the central cell to form the primary endosperm nucleus $(PEN)$.
This fusion of three haploid nuclei is called triple fusion.
Together,syngamy and triple fusion constitute the process of double fertilisation.

(B) In angiospermic sexual reproduction,the process of syngamy involves the fusion of one male gamete with the egg cell to form a diploid zygote $(2n)$.
This event is specifically termed as syngamy or generative fertilisation.
Therefore,$A$ is the zygote and $B$ is syngamy.

(A) Double fertilisation is a characteristic feature of angiosperms,not gymnosperms. It involves syngamy (true fertilisation) and triple fusion. It was first demonstrated by $Nawaschin$ in $Fritillaria$ and $Lilium$. Therefore,the statement that it is unique to gymnosperms and monocotyledons is incorrect.

(A) Double fertilization is a process in which one male gamete fuses with the egg cell to form a zygote,and the second male gamete fuses with the two polar nuclei to form the primary endosperm nucleus $(PEN)$. This phenomenon is exclusive to angiosperms and is not observed in any other group of plants.

(D) $Eucalyptus$ is an angiosperm,which is characterized by the process of double fertilization,including triple fusion. In contrast,$Cedrus$ is a gymnosperm,which lacks triple fusion and does not produce flowers or fruits. Therefore,the presence of triple fusion is a distinguishing feature of $Eucalyptus$ compared to $Cedrus$.

(D) Endosperm is formed as a result of double fertilisation,specifically through the process of triple fusion where one male gamete fuses with two polar nuclei to form the Primary Endosperm Nucleus $(PEN)$.
Endosperm provides nourishment to the developing embryo during seed development.
In plants such as bean,gram,and pea,the endosperm is not present in the mature seed because it is completely consumed during seed development. Such seeds are called non-endospermic or exalbuminous seeds.
In monocots and castor bean (a dicot),the embryo does not consume all the endosperm during seed development,so it persists in the mature seeds. Such seeds are called endospermic or albuminous seeds.