Reproduction and its type Questions in English

(D) Viviparity is the condition where the embryo develops inside the body of the mother and the mother gives birth to live young ones.
Among the given options,Mammals (including whales) are exclusively viviparous,with the exception of monotremes (egg-laying mammals like platypus and echidna).
While many cartilaginous fishes (Chondrichthyes) are viviparous,some are oviparous or ovoviviparous. Bony fishes are primarily oviparous.
Therefore,Mammals are the group that is considered exclusively viviparous in the context of general biological classification.

(D) $Gynandromorph$ is an organism that contains both male and female tissues. In the context of humans,this term is often used to describe individuals who exhibit secondary sexual characteristics of both sexes. While 'Intersex' is a broader term for variations in sex characteristics,'Gynandromorph' specifically refers to the presence of both male and female phenotypic traits.

(D) Polyestrous mammals are those that exhibit multiple estrous cycles within a single breeding season.
Examples of polyestrous animals include mice,cows,sheep,pigs,and horses.
In contrast,monoestrous animals have only one estrous cycle per breeding season.
Therefore,among the given options,the horse is a polyestrous mammal.

(D) Viviparity is a reproductive strategy where the embryo develops inside the body of the mother,and the offspring is born alive.
Among the given options,$A$ (Frog),$B$ (Lizard),and $C$ (Snake) are primarily oviparous,meaning they lay eggs.
$D$ (Rabbit) is a mammal,and mammals are characterized by viviparity,where the fetus receives nourishment directly from the mother through the placenta.

(A) Binary fission is a type of asexual reproduction where a single parent cell divides into two equal-sized daughter cells.
In this process,the parent cell replicates its genetic material and then divides into two distinct individuals.
Therefore,one fission event results in the production of two individuals.

(B) In a $Diplontic$ life cycle,the diploid sporophyte is the dominant,photosynthetic,and independent phase of the plant. The gametophytic phase is represented by the single to few-celled haploid gametophytes. Since the entire life cycle is dominated by the diploid phase and the haploid stage is restricted only to the gametes,this pattern is known as a $Diplontic$ life cycle.

(C) Sexual dimorphism is the condition where the two sexes of the same species exhibit different morphological characteristics beyond the differences in their sexual organs. This can include differences in size,color,markings,or other physical traits.

(C) Fertilization is the process of fusion of male and female gametes.
In $Toads$ and $Frogs$ (Amphibians),fertilization is external,occurring in water.
In $Cat$ $fish$ (Teleost fish),fertilization is also external.
In $Dog$ $fish$ (Scoliodon,a cartilaginous fish),fertilization is internal,as the male possesses claspers to transfer sperm into the female's body.

(D) Sexual dimorphism refers to the condition where the two sexes of the same species exhibit different characteristics beyond the differences in their sexual organs.
$1$. $Ascaris$ (roundworm) is dioecious,meaning sexes are separate,and the male is distinctly smaller than the female with a curved posterior end.
$2$. $Oryctolagus$ (rabbit) is a mammal that shows clear sexual dimorphism in body size and external genitalia.
$3$. $Hydra$ is generally hermaphroditic (monoecious).
$4$. $Pheretima$ (earthworm) is also hermaphroditic.
Therefore,both $Ascaris$ and $Oryctolagus$ exhibit clear sexual dimorphism.

(B) $Arrhenotoky$ is a specific type of parthenogenesis in which unfertilized eggs develop into haploid males $(drones)$.
In honey bees,the queen lays both fertilized and unfertilized eggs.
Fertilized eggs develop into diploid females ($workers$ or $queens$),while unfertilized eggs develop into haploid males $(drones)$ through the process of $arrhenotoky$.

(A) Arrhenotoky is a form of parthenogenesis in which unfertilized eggs develop into males.
In many Hymenoptera,such as honey bees,arrhenotoky is the mechanism of sex determination where haploid males (drones) develop from unfertilized eggs,while diploid females (queens and workers) develop from fertilized eggs.
Therefore,it is a specific type of parthenogenesis.

(B) . Eutherian mammals are viviparous placental mammals that give birth to relatively well-developed young ones.
Eutherians constitute the vast majority of living mammals,which are characterized by the presence of a complex placenta for the nourishment of the fetus during gestation.

(C) Earthworms are hermaphrodites (bisexual),meaning they possess both male and female reproductive organs.
However,self-fertilization is prevented by a phenomenon known as $Protandry$.
In $Protandry$,the male reproductive organs (testes) mature and release sperm before the female reproductive organs (ovaries) mature.
This temporal separation in the maturation of gametes ensures cross-fertilization between two different individuals.

(B) The correct answer is $B$. Incomplete or cyclic parthenogenesis is a phenomenon observed in certain animal species where sexual reproduction and parthenogenesis occur in alternating generations or cycles. This allows the population to benefit from both genetic recombination during sexual reproduction and rapid population growth through parthenogenesis.

(C) Haploid parthenogenesis (also known as arrhenotoky) is a phenomenon where unfertilized eggs develop into haploid males,while fertilized eggs develop into diploid females. This process is characteristic of the order $Hymenoptera$,which includes bees,ants,and wasps. In honey bees ($Apis$ $mellifera$),for example,the queen lays unfertilized eggs that develop into drones (males) via parthenogenesis,while fertilized eggs develop into workers or queens.

(B) Parthenogenesis is a form of asexual reproduction where an embryo develops from an unfertilized egg.
In honeybees $(Apis \ mellifera)$,the queen lays two types of eggs: fertilized eggs,which develop into female workers or queens,and unfertilized eggs,which develop into male drones via parthenogenesis.
Therefore,natural parthenogenesis is a characteristic feature of honeybee drone production.

(B) The correct answer is $B$.
Periblastula,also known as a superficial blastula,is formed by superficial meroblastic cleavage.
This type of cleavage occurs in centrolecithal eggs,which are characteristic of insects.
In this process,the blastoderm forms a single layer of epithelial cells surrounding the centrally located yolk mass.
Unlike other types of blastulae,a periblastula lacks a central cavity or blastocoel.

(C) The eggs of reptiles and birds are classified as $Telolecithal$.
In these eggs,a large amount of yolk is present,which is concentrated at the vegetal pole,while the active cytoplasm is restricted to a small disc at the animal pole.
This distribution of yolk is characteristic of birds and reptiles.

(C) Insects possess $Centrolecithal$ eggs.
In $Centrolecithal$ eggs,the yolk is concentrated in the center of the egg,surrounded by a peripheral layer of cytoplasm.
These eggs are also classified as $Megalecithal$ (or $Polylecithal$) because they contain a large amount of yolk to support the development of the embryo.
Therefore,insect eggs are characterized as both $Megalecithal$ and $Centrolecithal$.

(B) In a $telolecithal$ egg,the yolk is very abundant and is concentrated at one pole,known as the $vegetal$ pole,while the active cytoplasm is restricted to the opposite pole,known as the $animal$ pole. This type of egg is commonly found in birds and reptiles.