Out breeding Devices Questions in English

(B) cross between an $F_1$ hybrid and one of its parents is known as a backcross.
When the $F_1$ hybrid is crossed with the dominant homozygous parent,it is specifically called an outcross.
In contrast,when the $F_1$ hybrid is crossed with the recessive homozygous parent,it is called a test cross.
Therefore,crossing an $F_1$ individual with a dominant homozygous parent is an outcross.

(A) In plants,self-pollination leads to the production of homozygous offspring over successive generations. This process is known as inbreeding. Inbreeding increases homozygosity,which is essential for developing pure lines in plant breeding programs. Therefore,inbreeding is the correct term associated with self-pollination.

(C) Cross-fertilisation is a mechanism to ensure genetic diversity in bisexual (hermaphrodite) organisms. Protandry is a condition where the male reproductive organs (testes) mature before the female reproductive organs (ovaries). Similarly,protogyny is where the ovaries mature before the testes. Since the gametes do not mature simultaneously,self-fertilisation is prevented,thereby favouring cross-fertilisation.

(D) Self-pollination is a process where pollen grains are transferred from the anther to the stigma of the same flower or another flower on the same plant.
Continued self-pollination in cross-pollinated species leads to the accumulation of recessive deleterious alleles, which reduces the fitness and vigor of the population.
This phenomenon is known as $Inbreeding \text{ } depression$.
Conversely, $Heterosis$ (or hybrid vigor) is the result of cross-breeding, and $Hybridisation$ is the process of crossing two genetically different individuals.

(A) Continued self-pollination leads to the accumulation of recessive deleterious alleles in the homozygous state.
This process reduces the genetic diversity within the population.
As a result,the fitness and productivity of the offspring decline,a phenomenon known as inbreeding depression.

(B) Self-incompatibility is a genetic mechanism in flowering plants that prevents self-pollination and self-fertilization by inhibiting the germination of pollen grains on the stigma of the same flower or other flowers of the same plant.
$I$. It ensures cross-pollination by preventing the success of self-pollen.
$II$. It acts as a device to prevent self-pollination.
$III$. It prevents self-fertilization, so statement $III$ is incorrect as it does not ensure it.
$IV$. It is a genetic control mechanism that prevents self-fertilization.
Therefore, statements $I, II,$ and $IV$ are correct.

(A) Homogamy is a condition in which the male reproductive part (anther) and the female reproductive part (stigma) of a flower mature simultaneously. This synchronization promotes self-pollination.

(D) Dioecious plants are those in which male and female flowers are present on different plants.
Because the male and female reproductive organs are on separate plants,the plant cannot perform self-pollination (autogamy) or pollination between flowers of the same plant (geitonogamy).
Therefore,the dioecious condition prevents both autogamy and geitonogamy.

(D) Papaya is a dioecious plant,meaning male and female flowers are borne on separate individuals.
Because the male and female reproductive structures are on different plants,self-pollination (autogamy and geitonogamy) is impossible.
Therefore,the only mode of pollination possible is cross-pollination between two different plants,which is known as xenogamy.

(D) Outbreeding devices are mechanisms that plants use to discourage self-pollination and encourage cross-pollination. These include:
$1$. Non-synchronization of pollen release and stigma receptivity.
$2$. Placement of anther and stigma at different positions.
$3$. Self-incompatibility (a genetic mechanism preventing self-pollen from fertilizing the ovules).
$4$. Production of unisexual flowers.
Therefore,all the given options are devices to discourage self-pollination.

(D) In monoecious plants like castor and maize,both male and female flowers are present on the same individual plant.
$1$. Autogamy (self-pollination within the same flower) is prevented because the flowers are unisexual.
$2$. Geitonogamy (pollination between two different flowers on the same plant) is not prevented because both male and female flowers are on the same plant.
Therefore,the correct statement is that geitonogamy is not prevented.

(B) Dichogamy is a condition in bisexual flowers where the stamens (anthers) and the carpels (stigma) mature at different times.
This temporal separation prevents self-pollination (autogamy) and encourages cross-pollination (allogamy).
Therefore,it acts as an outbreeding device to ensure genetic diversity.

(D) Outbreeding devices are mechanisms evolved by plants to discourage self-pollination and encourage cross-pollination.
$1$. By promoting cross-pollination,these devices facilitate outbreeding.
$2$. Continuous self-pollination often leads to inbreeding depression,which reduces the fitness and vigor of the plant population.
$3$. By preventing self-pollination,these devices provide relief from inbreeding depression.
Therefore,both $B$ and $C$ are correct outcomes of outbreeding devices.

(D) Outbreeding devices are mechanisms developed by flowering plants to discourage self-pollination and promote cross-pollination to increase genetic diversity.
$1$. $Dichogamy$: In this process,the stamen and stigma mature at different times,preventing self-pollination.
$2$. $Self-incompatibility$: This is a genetic mechanism that prevents pollen from the same flower or other flowers of the same plant from fertilizing the ovules.
$3$. $Heterostyly$: This refers to the condition where flowers have different lengths of styles and stamens,which physically hinders self-pollination.
Since all these methods are strategies to prevent self-pollination,the correct answer is $D$.

(B) Herkogamy is a genetic mechanism in bisexual flowers where a physical barrier exists between the anther and the stigma to prevent self-pollination.
This barrier can be structural,such as the presence of a hood or a flap,or spatial,where the anthers and stigma are placed at different positions or heights,making it impossible for the pollen to reach the stigma of the same flower.
- Heterostyly involves differences in the length of styles and stamens.
- Dichogamy refers to the maturation of anthers and stigma at different times.
- Self-incompatibility is a genetic mechanism that prevents pollen from fertilizing the ovules of the same flower.

(A) monoecious plant bears both male and female flowers on the same individual (e.g.,castor and maize).
In such plants,autogamy (self-pollination within the same flower) can be prevented by various mechanisms like herkogamy or dichogamy.
However,geitonogamy (pollination between two flowers on the same plant) cannot be prevented because the pollen grains from the male flower can easily reach the stigma of the female flower on the same plant.
Xenogamy (cross-pollination between different plants) also cannot be prevented as it is a natural process of cross-pollination.
Therefore,in monoecious plants,autogamy can be prevented,but geitonogamy and xenogamy cannot be prevented.

(C) In a dioecious plant,male and female flowers are present on different plants (e.g.,papaya).
Because the plants are separate,autogamy (self-pollination within the same flower) and geitonogamy (pollination between two flowers of the same plant) are naturally prevented.
However,xenogamy (cross-pollination between different plants) is the only mode of pollination possible in such plants.
Therefore,autogamy and geitonogamy are prevented,but xenogamy cannot be prevented.

(B) Outbreeding devices are mechanisms developed by plants to discourage self-pollination and promote cross-pollination.
$1$. Dichogamy: Anthers and stigma mature at different times.
$2$. Self-incompatibility: $A$ genetic mechanism that prevents pollen from fertilizing ovules of the same flower.
$3$. Heterostyly: Differences in the lengths of styles and stamens prevent self-pollination.
$4$. Homogamy: This is a condition where the anthers and stigma of a flower mature at the same time,which actually encourages self-pollination rather than preventing it.
Therefore,Homogamy is $NOT$ an outbreeding device.

(B) Dioecious plants are those in which male and female flowers are borne on separate individuals.
Since each individual plant bears only one type of reproductive organ (either staminate or pistillate),the flowers produced are unisexual.
This mechanism is an outbreeding device that prevents autogamy and geitonogamy.

(D) Self-incompatibility is a genetic mechanism that prevents self-pollen (from the same flower or other flowers of the same plant) from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil. This is a major outbreeding device used by many flowering plants to promote cross-pollination and ensure genetic diversity.

(D) Flowering plants have evolved several mechanisms,known as outbreeding devices,to prevent self-pollination and promote cross-pollination. This is because continued self-pollination leads to inbreeding depression,which reduces the genetic diversity and fitness of the offspring.
Examples of outbreeding devices include:
$1$. Dichogamy: Anther and stigma mature at different times.
$2$. Herkogamy: Spatial arrangement of anther and stigma prevents self-pollination.
$3$. Self-incompatibility: $A$ genetic mechanism that prevents pollen from fertilizing the same flower or other flowers on the same plant.
$4$. Production of unisexual flowers.
Since both the assertion and the reason are scientifically accurate,and the reason correctly explains why plants need outbreeding devices,the correct option is $(D)$.

(A) In monoecious plants,both male and female flowers are present on the same individual plant.
If the flowers are unisexual,the plant cannot perform autogamy because the pollen from the male flower cannot reach the stigma of the same flower (as it lacks the necessary reproductive organ).
However,the pollen from a male flower can still be transferred to the stigma of a female flower on the same plant,which is known as geitonogamy.
Therefore,monoecious plants with unisexual flowers prevent autogamy but do not prevent geitonogamy.

(C) Self-pollination requires the maturation of both male and female reproductive organs at the same time (homogamy) or the presence of flowers that remain closed (cleistogamy). Bisexuality provides the potential for self-pollination. Protandry is a condition where the androecium (male part) matures earlier than the gynoecium (female part),which prevents self-pollination and actively promotes cross-pollination.

(D) Statement $I$ is incorrect. Heteromorphic flowers (like in Primula) exhibit heterostyly,where anthers and stigmas are at different levels to prevent self-pollination,not the same level.
Statement $II$ is correct. Tobacco exhibits self-incompatibility,a genetic mechanism that prevents self-fertilization by inhibiting pollen germination or pollen tube growth on the stigma of the same flower.
Therefore,Statement $I$ is incorrect and Statement $II$ is correct.

(D) Statement $I$ is incorrect because self-incompatibility is a device that prevents inbreeding (self-pollination),not outbreeding.
Statement $II$ is correct because self-incompatibility is indeed a genetic mechanism that prevents the germination of pollen grains on the stigma of the same flower or other flowers of the same plant,thereby promoting cross-pollination.

(B) The correct matching is as follows:
$i$. Protandry: In this condition,the anthers mature before the stigma of the same flower. This is observed in $Sunflower$ $(i-c)$.
$ii$. Prepotency: Pollen grains of another flower germinate more rapidly over the stigma than the pollen grains of the same flower. This is observed in $Apple$ $(ii-d)$.
$iii$. Self sterility: In this condition,the pollen grains of a flower fail to germinate on the stigma of the same flower due to genetic incompatibility. This is observed in $Tobacco$ $(iii-b)$.
$iv$. Herkogamy: This is a mechanical device to prevent self-pollination where the stigma and anthers are placed in such a way that pollen cannot reach the stigma. This is observed in $Calotropis$ $(iv-a)$.
Therefore,the correct sequence is $i-c, ii-d, iii-b, iv-a$.

(A) Herkogamy is a mechanical device in bisexual flowers that prevents self-pollination by creating a physical barrier between the male $(anther)$ and female $(stigma)$ reproductive organs. This spatial separation ensures that pollen from the same flower cannot easily reach the stigma,thereby promoting cross-pollination.

(C) Heterostyly is a condition in flowers where styles and stamens are of different lengths. This structural arrangement acts as a mechanism to prevent self-pollination $(autogamy)$ and promote cross-pollination $(xenogamy)$. By ensuring that pollen from one flower does not easily reach the stigma of the same flower,it encourages the transfer of pollen to the stigma of a different flower,thereby facilitating $xenogamy$.

(C) Dichogamy is an outbreeding device in flowering plants where the stamens (male reproductive parts) and carpels (female reproductive parts) of a flower mature at different times.
This mechanism prevents self-pollination and promotes cross-pollination.
It can occur in two forms: Protandry (anthers mature before stigma) and Protogyny (stigma matures before anthers).

(B) Cleistogamous flowers are those that do not open at all. In such flowers,the anthers and stigma lie close to each other. When anthers dehisce in the closed flower buds,pollen grains come in contact with the stigma to effect pollination. Thus,cleistogamous flowers are invariably autogamous as there is no chance of cross-pollination. Therefore,the correct option is $B$.

(D) The phenomenon where the stigma and anther of a flower mature at different times is known as $Dichogamy$.
This mechanism ensures that the pollen grains from the same flower cannot fertilize the stigma of the same flower,thereby preventing self-pollination.
Consequently,this process promotes and facilitates cross-pollination,which increases genetic diversity in the offspring.
Therefore,the correct option is $D$.

(A) $1$. Monoecious plants $(i)$ have both male and female flowers on the same plant. This arrangement prevents autogamy (self-pollination within the same flower) but does not prevent geitonogamy (pollination between different flowers on the same plant). Examples include Castor and Maize $(y)$.
$2$. Dioecious plants (ii) have male and female flowers on different plants. This arrangement prevents both autogamy and geitonogamy. Examples include Papaya and Date palm $(x)$.
$3$. Therefore,the correct matching is: (i - q,y) and (ii - p,x).