Double Fertilisation Questions in English

(A) In all sexually reproducing organisms,life begins from a single-celled zygote.
When a haploid male gamete $(n)$ fuses with a haploid female gamete $(n)$,they form a diploid $(2n)$ single-celled structure known as the zygote.
This zygote serves as the vital link that ensures the continuity of species between organisms of one generation and the next.
Therefore,the zygote is the first cell of a new individual.

(C) The fusion of male and female gametes results in the formation of a diploid zygote.
This process is known as syngamy.
In biological terminology,the terms syngamy and fertilization are often used interchangeably to describe this fusion event.

(A) In flowering plants (Angiosperms),the process of fertilization occurs within the embryo sac,which is located inside the ovule. The fusion of the male gamete and the egg cell results in the formation of a zygote. Therefore,the zygote is formed inside the ovule.

(C) The vital link between two generations that ensures the continuity of species is the $Zygote$.
$1$. The $Zygote$ is a single-celled structure,so it cannot be multicelled $(b)$.
$2$. The $Zygote$ is diploid $(2n)$,meaning it contains two sets of chromosomes,so it cannot have only one set of chromosomes $(c)$.
$3$. The $Zygote$ is formed by the fusion of gametes and is not a $Meiocyte$ (a cell that undergoes meiosis) $(d)$.
$4$. The $Zygote$ is generally not thick-walled $(a)$ or a resting stage $(e)$ in most organisms,although some zygotes (like in algae or fungi) may develop a thick wall to survive unfavorable conditions.
However,based on standard biological definitions,the $Zygote$ is $1n$ (haploid) in some organisms,but it is fundamentally a $2n$ structure in sexual reproduction. The features it cannot show are being multicelled $(b)$,having one set of chromosomes $(c)$,being a $Meiocyte$ $(d)$,and being a resting stage $(e)$ (in the context of active development). The most appropriate combination of features that the $Zygote$ does not possess is $(b), (c), (d),$ and $(e)$. Given the options,$(b)$ and $(c)$ are the most definitive characteristics it lacks.

(D) Double fertilization was discovered by $S. G. Nawaschin$ $(1898)$ and $Guignard$ in $Lilium$ and $Fritillaria$. Double fertilization is a characteristic feature restricted only to angiosperms.
When the pollen tube enters the ovule,it releases two male gametes into the embryo sac. These gametes fuse with two different structures in the same female gametophyte:
$1.$ Syngamy: Fusion of one male gamete with the egg cell to form a diploid zygote $(2n)$.
$2.$ Triple Fusion: Fusion of the second male gamete with the two polar nuclei (or the secondary nucleus) to form the primary endosperm nucleus $(PEN)$,which is triploid $(3n)$.

(B) Double fertilization involves two processes: syngamy and triple fusion.
$1$. Syngamy: One male gamete fuses with the egg cell (one female nucleus).
$2$. Triple fusion: The second male gamete fuses with two polar nuclei (two female nuclei) present in the central cell.
Therefore,the total number of female nuclei involved is $1$ (egg cell) + $2$ (polar nuclei) = $3$ female nuclei.

(D) In angiosperms,fertilization occurs within the embryo sac. The pollen tube enters the embryo sac and releases two male gametes. One male gamete fuses with the egg cell (syngamy) to form a zygote,while the other fuses with the two polar nuclei to form the primary endosperm nucleus. Since the egg cell is located within the embryo sac,the fertilization process is completed inside it.

(A) Double fertilization is a characteristic feature of angiosperms. It was discovered by $S.G. Nawaschin$ in $1898$ in the plants $Lilium$ and $Fritillaria$. During this process, 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).

(A) clone is an individual genetically identical to its parent,produced through asexual means such as apomixis,vegetative reproduction,or tissue culture.
Double fertilization is a characteristic feature of angiosperms involving the fusion of two male gametes with the egg cell and the central cell,respectively.
Since double fertilization is a part of sexual reproduction,it involves meiosis and genetic recombination,which leads to genetic variation rather than the formation of clones.
It was discovered by $Nawaschin$ in $1898$.

(A) The Primary Endosperm Cell $(PEC)$ is formed as a result of triple fusion.
During double fertilization in angiosperms,one male gamete fuses with the egg cell to form a diploid zygote (syngamy).
The second male gamete fuses with the two polar nuclei located in the central cell to form a triploid Primary Endosperm Nucleus $(PEN)$.
This process of fusion of three haploid nuclei is known as triple fusion.
Following this fusion,the central cell,which contains the $PEN$,is referred to as the Primary Endosperm Cell $(PEC)$.

(C) In angiosperms,the endosperm is formed by the fusion of two polar nuclei (from the female gametophyte) and one male gamete (from the pollen grain).
This process is known as triple fusion,resulting in a triploid $(3n)$ structure.
Given the endosperm genotype is $ZZA$,it implies that the two polar nuclei contributed $ZZ$ and the male gamete contributed $A$.
Since the polar nuclei are derived from the female plant,the female plant must have a genotype of $ZZ$.
Since the male gamete is derived from the male plant,the male plant must have a genotype of $AA$.

(C) Double fertilization is a characteristic feature of angiosperms. It was discovered by $S. G. Nawaschin$ in $1898$.
In double fertilization,one male gamete fuses with the egg cell to form a diploid zygote,and the second male gamete fuses with the diploid secondary nucleus to form the triploid primary endosperm nucleus $(PEN)$.
Since the secondary nucleus is diploid $(2n)$ and the male gamete is haploid $(n)$,the resulting primary endosperm nucleus is triploid $(3n)$.
Therefore,the statement that the endosperm nucleus is diploid is incorrect.
The endosperm provides nutrition to the developing embryo.

(B) Fertilization is the process in which the fusion of male and female gametes occurs. In flowering plants,this process takes place within the embryo sac,which is located inside the ovary $(C)$. Therefore,the ovary is the site where fertilization occurs.

(A) In flowering plants,double fertilization involves two processes:
$1$. Syngamy: The fusion of one male gamete with the egg cell to form a diploid $(2n)$ zygote,which subsequently develops into an embryo $(B)$. Thus,$A$ is Syngamy and $B$ is Embryo.
$2$. Triple Fusion: The fusion of the second male gamete with two polar nuclei (or the central cell) to form a triploid $(3n)$ primary endosperm nucleus,which develops into the endosperm $(C)$. Thus,the process is Triple fusion $(C)$ and the product is Endosperm $(D)$.
Therefore,$A-$Syngamy,$B-$Embryo,$C-$Triple fusion,$D-$Endosperm.

(B) In angiosperms,the process involving both syngamy (fusion of male gamete with egg) and triple fusion (fusion of male gamete with two polar nuclei) is collectively known as double fertilization $(A)$.
After triple fusion,the central cell becomes the Primary Endosperm Nucleus $(PEN)$ $(B)$.
The $PEN$ subsequently develops into the endosperm $(C)$,which provides nutrition to the developing embryo.
The zygote,formed by syngamy,develops into the embryo $(D)$.

(D) Double fertilization in angiosperms involves two distinct processes: syngamy and triple fusion.
$1$. Syngamy: One male gamete $(n)$ fuses with the egg cell $(n)$ to form a diploid zygote (2n). This involves $2$ nuclei.
$2$. Triple Fusion: The second male gamete $(n)$ fuses with the two polar nuclei (n + n) present in the central cell to form the primary endosperm nucleus $(PEN)$ (3n). This involves $3$ nuclei.
Therefore,the total number of nuclei involved in double fertilization is $2 + 3 = 5$.

(B) In angiosperms,double fertilization involves two processes: syngamy and triple fusion.
Triple fusion occurs when one of the two male gametes fuses with the two polar nuclei (or the secondary nucleus) located in the central cell of the embryo sac.
Since the male gamete is $n$ and the two polar nuclei are $n + n$,the resulting structure is triploid $(3n)$.
This structure is known as the Primary Endosperm Nucleus $(PEN)$.
The $PEN$ subsequently develops into the endosperm,which provides nourishment to the developing embryo.

(A) During double fertilization,the central cell contains two haploid polar nuclei.
One male gamete fuses with these two polar nuclei to form a triploid nucleus,which is known as the Primary Endosperm Nucleus $(PEN)$.
The entire central cell,after this fusion,is referred to as the Primary Endosperm Cell $(PEC)$.

(A) Double fertilization involves two processes: syngamy and triple fusion.
$1$. Syngamy: The fusion of one male gamete $(n)$ with the egg cell $(n)$ results in the formation of a diploid $(2n)$ Zygote.
$2$. Triple fusion: The fusion of the second male gamete $(n)$ with two polar nuclei $(n + n)$ results in the formation of a triploid $(3n)$ Primary Endosperm Nucleus $(PEN)$.
Therefore,the diploid product is the Zygote and the triploid product is the Primary Endosperm Nucleus $(PEN)$.

(D) Triple fusion is a characteristic feature unique to angiosperms (flowering plants) and does not occur in gymnosperms,even though both are spermatophytes.
Therefore,the Assertion is incorrect.
Triple fusion involves the fusion of one male gamete with two polar nuclei (or a secondary nucleus) to form the primary endosperm nucleus $(PEN)$,which develops into the endosperm,not a 'definitive nucleus' as nutritive tissue.
Thus,the Reason is also incorrect.

(C) In angiosperms,the process of double fertilization occurs.
One male gamete $(n)$ fuses with the two polar nuclei $(n + n)$ present in the central cell of the embryo sac.
This process is known as triple fusion.
As a result of triple fusion,the Primary Endosperm Nucleus $(PEN)$ is formed,which is triploid $(3n)$.

(A) 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) to form the primary endosperm nucleus $(PEN)$,which is triploid $(3n)$.
Thus,the two male gametes fuse with the egg cell and the secondary nucleus,respectively.

(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 $(n + n = 2n)$.
$2$. Triple Fusion: The second male gamete fuses with the two polar nuclei (or the secondary nucleus) to form the primary endosperm nucleus $(n + n + n = 3n)$.
Since two male gametes are involved in these processes,the total number of gametes participating is $2$ (male gametes) + $1$ (egg cell) + $2$ (polar nuclei) = $5$ gametes in total.

(C) In the mature embryo sac,double fertilization occurs.
One male gamete fuses with the egg cell (labeled $R$) to form a diploid zygote.
The other male gamete fuses with the two polar nuclei (labeled $Q$) to form the primary endosperm nucleus $(PEN)$.
Therefore,the male gametes fuse at $Q$ and $R$.

(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 $(2n)$.
$2$. 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 $(3n)$.
Thus,the correct description is that one male gamete fuses with the egg cell and one male gamete fuses with the secondary nucleus.

(A) In angiosperms,double fertilization involves two processes:
$1$. Syngamy: The fusion of the male gamete with the egg cell to form a diploid zygote $(P = \text{Syngamy})$.
$2$. Triple fusion: The fusion of the second male gamete with the two polar nuclei (secondary nucleus) to form a triploid primary endosperm nucleus $(Q = \text{Triple fusion})$.
Therefore,the correct option is $A$.

(D) Synergids are cells of the female gametophyte and are therefore haploid $(n)$.
Zygote is formed by the fusion of a male gamete $(n)$ and an egg cell $(n)$,making it diploid $(2n)$.
Primary endosperm nucleus $(PEN)$ is formed by the fusion of a diploid secondary nucleus $(2n)$ with a male gamete $(n)$,making it triploid $(3n)$.
Thus,the sequence of haploid,diploid,and triploid structures is Synergids,Zygote,and Primary endosperm nucleus.

(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 $(2n)$.
$2$. 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 $(3n)$.
Thus,a total of $3$ gametes are involved: two male gametes and one egg cell (the polar nuclei are considered part of the female gametophyte structure,but the fusion involves $3$ haploid nuclei in total,specifically $2$ male gametes and $1$ egg cell for syngamy,and $1$ male gamete and $2$ polar nuclei for triple fusion).
However,in terms of distinct gametic cells participating,there are $2$ male gametes and $1$ egg cell,totaling $3$ gametes.

(C) In most angiosperms,pollen grains are shed at the $2$-celled stage. These $2$ cells consist of one vegetative cell and one generative cell. The generative cell later divides to form $2$ male gametes. Therefore,at the time of fertilization (when the pollen tube reaches the micropyle),the pollen grain contains $3$ haploid nuclei: $1$ vegetative nucleus and $2$ male gamete nuclei.

(A) In angiosperms,double fertilization involves two main processes:
$1$. Syngamy: One male gamete fuses with the egg cell to form a diploid zygote.
$2$. Triple fusion: The second male gamete fuses with the two polar nuclei (or the secondary nucleus) to form the primary endosperm nucleus $(PEN)$.
Therefore,in triple fusion,$1$ male gamete is involved.
In double fertilization (which is the sum of syngamy and triple fusion),a total of $2$ male gametes are involved.
Thus,the correct sequence is $1$ and $2$.

(A) Syngamy involves the fusion of a haploid female gamete $(n)$ and a haploid male gamete $(n)$ to form a diploid zygote $(2n)$,which develops into the embryo.
Triple fusion involves the fusion of the second haploid male gamete $(n)$ with the diploid secondary nucleus $(2n)$ to form the Primary Endosperm Nucleus ($PEN$,$3n$),which develops into the triploid endosperm $(3n)$.

(A) Double fertilization is a characteristic feature of angiosperms. It was first discovered by $S.G. \text{Nawaschin}$ in $1898$ in the plants $Lilium$ and $Fritillaria$. In this process,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).

(C) The dominance of angiosperms on Earth is primarily attributed to the process of $Double \ fertilization$.
Double fertilization involves the fusion of one male gamete with the egg cell to form a zygote and the other male gamete with the central cell to form the primary endosperm nucleus $(PEN)$.
This process ensures the development of a nutritive tissue called endosperm,which provides nourishment to the developing embryo.
Furthermore,it leads to the formation of seeds enclosed within fruits,which protects the embryo and aids in dispersal,contributing significantly to their evolutionary success.

(D) In angiosperms, the process of double fertilization involves two fusion events.
$1$. Syngamy: The fusion of one male gamete with the egg cell to form a diploid zygote.
$2$. Triple Fusion: The fusion of the second male gamete with the two polar nuclei (or the secondary nucleus) to form a triploid primary endosperm nucleus $(PEN)$.
Because this second fusion event involves three haploid nuclei (two polar nuclei and one male gamete), it is often referred to as "triple fusion" or the "second fertilization" event in the embryo sac.

(D) In angiosperms,the endosperm is formed by the process of triple fusion,which involves the fusion of a diploid secondary nucleus and a haploid male gamete.
$1$. The female plant has $2n = 24$,so its gamete (egg cell and polar nuclei) will have $n = 12$ chromosomes.
$2$. The male plant has $2n = 12$,so its gamete (male gamete) will have $n = 6$ chromosomes.
$3$. The secondary nucleus is formed by the fusion of two polar nuclei,each having $n = 12$ chromosomes,resulting in a diploid secondary nucleus with $2n = 24$ chromosomes.
$4$. During double fertilization,the diploid secondary nucleus $(2n = 24)$ fuses with one haploid male gamete $(n = 6)$ to form the triploid endosperm $(3n = 30)$.

(C) The process of double fertilization in Angiosperms involves the following steps:
$1$. $Porogamy$: The entry of the pollen tube into the ovule through the micropyle.
$2$. $Syngamy$: The fusion of one male gamete with the egg cell to form a diploid zygote.
$3$. $Triple$ fusion: The fusion of the second male gamete with the two polar nuclei (or the secondary nucleus) to form the primary endosperm nucleus $(PEN)$.
Therefore, the correct sequence is $Porogamy$, $Syngamy$, $Triple$ fusion.

(A) Syngamy is the process of fusion of a male gamete $(n)$ with a female gamete $(n)$ to form a diploid zygote $(2n)$.
This process is a fundamental part of fertilization in both plants and animals.
In angiosperms,syngamy is one of the two events of double fertilization,the other being triple fusion which results in the formation of a triploid primary endosperm nucleus $(3n)$.

(A) In flowering plants,the process of double fertilization involves two events: syngamy and triple fusion. During triple fusion,one of the two male gametes released from the pollen tube fuses with the two polar nuclei (or the secondary nucleus) located in the central cell of the embryo sac. This fusion involves three haploid nuclei,hence it is called 'triple fusion'. This process results in the formation of the primary endosperm nucleus $(PEN)$,which is triploid $(3n)$.

(C) In angiosperms,the process of double fertilization involves the fusion of one male gamete $(n)$ with two polar nuclei $(n + n)$ or a secondary nucleus $(2n)$ present in the central cell.
This fusion results in the formation of the Primary Endosperm Nucleus $(PEN)$,which is $3n$ or triploid.
Therefore,the correct option is $C$.

(D) In angiosperms,the egg cell is a female gamete formed through meiosis,so it is haploid $(n)$.
The endosperm is formed by the fusion of one male gamete $(n)$ with two polar nuclei $(n + n)$,a process known as triple fusion,resulting in a triploid $(3n)$ structure.
Therefore,the egg cell is haploid and the endosperm is triploid.

(A) The correct answer is $A$.
In the embryo sac, the $Egg$ $cell$ is haploid $(n)$ before fertilization and becomes a diploid $(2n)$ zygote after fertilization.
The $Central$ $cell$ contains two polar nuclei (each $n$) and is effectively diploid $(2n)$ before fertilization; after fusion with a male gamete $(n)$, it becomes a triploid $(3n)$ primary endosperm nucleus $(PEN)$.
$Synergids$ and $Antipodals$ are haploid cells that degenerate after fertilization without undergoing a change in ploidy.

(B) The correct answer is $B$.
In angiosperms,the process of double fertilization involves two events: syngamy and triple fusion.
The primary endosperm nucleus $(PEN)$ is formed by the fusion of two haploid polar nuclei (which form the diploid secondary nucleus) and one haploid male gamete.
Since this process involves the fusion of three haploid nuclei,it is termed as triple fusion.
This results in the formation of a triploid $(3n)$ primary endosperm nucleus.

(D) During double fertilisation in angiosperms,one male gamete fuses with the egg cell to form a zygote (syngamy).
Another male gamete fuses with the two polar nuclei located in the central cell to form the primary endosperm nucleus $(PEN)$.
This process is known as triple fusion.
Therefore,the central cell is the cell of the female gametophyte that is involved in the formation of the $PEN$.