Reproduction in Human Beings Questions in English

(B) The secretions from the seminal vesicles and prostate glands serve two primary functions:
$1$. They provide a fluid medium that facilitates the easy transport of sperms.
$2$. They provide essential nutrients to the sperms,including fructose,calcium,and various enzymes,which help in their survival and motility.

(N/A) During puberty,girls undergo several physical and physiological changes due to the secretion of hormones like estrogen and progesterone:
$1$. Breast development: There is an increase in breast size and the skin of the nipples becomes darker.
$2$. Hair growth: Appearance of hair in the genital area and other parts of the body such as underarms,face,hands,and legs.
$3$. Reproductive system maturation: Increase in the size of the uterus and ovaries.
$4$. Menstruation: The beginning of the menstrual cycle (menarche).
$5$. Skin changes: Increased secretion of oil from the skin glands,which often leads to the appearance of pimples.

(N/A) The embryo develops inside the mother's body for about nine months. Inside the uterus,the outer tissue surrounding the embryo develops finger-like projections called villi. These villi are surrounded by uterine tissue and maternal blood. They provide a large surface area for the exchange of oxygen and nutrients. Also,there is a special tissue called the placenta,which is embedded in the uterine wall. The embryo receives oxygen and nutrients from the mother's blood via the placenta. The waste materials produced by the embryo are also removed through the placenta.

(B) The female reproductive system in humans consists of the ovaries, fallopian tubes, uterus, cervix, and vagina.
Vas deferens is a part of the male reproductive system, which transports sperm from the epididymis to the ejaculatory duct.
Therefore, $Vas \text{ } deferens$ is not a part of the female reproductive system.

(N/A) The testes are the primary male reproductive organs located outside the abdominal cavity within a pouch called the $scrotum$.
Functions of the testes:
$1$. $Spermatogenesis$: The testes are responsible for the production of male gametes, known as $sperms$.
$2$. Hormone production: The testes secrete the male sex hormone, $testosterone$. This hormone is responsible for the development of secondary sexual characteristics in boys during puberty, such as the deepening of the voice, growth of facial hair, and increased muscle mass.

(B) Menstruation is a process in which blood and mucous flow out every month through the vagina.
This process occurs because one egg is released from the ovary every month,and simultaneously,the uterus (womb) prepares itself to receive a fertilized egg.
The inner lining of the uterus becomes thick and is supplied with blood to nourish the potential embryo.
If the egg is not fertilized,the thickened lining of the uterus is no longer needed,so it breaks down and is released in the form of blood and mucous through the vagina.

(D) Puberty is the period during which adolescents reach sexual maturity and become capable of reproduction.
These changes are primarily driven by sex hormones.
In males,the testes secrete $testosterone$,which is responsible for the development of secondary sexual characteristics such as facial hair,deepening of the voice,and muscle growth.
In females,the ovaries secrete $estrogen$ (and progesterone),which is responsible for the development of secondary sexual characteristics such as breast development and the onset of the menstrual cycle.
Therefore,the correct answer is $D$.

(C) In sexually reproducing organisms,the process of meiosis occurs during gamete formation.
Meiosis is a reductional division that reduces the chromosome number to half $(n)$ in the gametes compared to the parent cell $(2n)$.
When the male gamete $(n)$ and female gamete $(n)$ fuse during fertilization,the diploid chromosome number $(2n)$ is restored in the zygote.
This ensures that the chromosome number remains constant across generations in a particular species.

(D) Sexual reproduction involves the fusion of male and female gametes,which are produced by two parents of the same species.
During the formation of gametes,the process of meiosis occurs,which includes recombination and crossing over of genetic material.
This results in new combinations of genes in the offspring,leading to genetic variation.
Since the genetic material is contributed by two different individuals of the same species,the offspring possess a unique combination of traits,which is different from both parents.

(B) During adolescence,the human body undergoes significant physical and hormonal changes.
Sexual maturation in boys is characterized by specific secondary sexual characteristics.
$A$. Loss of milk teeth occurs during childhood,not adolescence.
$B$. Cracking of voice (deepening of the voice) is a primary secondary sexual characteristic in boys caused by the enlargement of the larynx under the influence of testosterone.
$C$. Increase in height occurs in both boys and girls during adolescence,but it is a general growth spurt rather than a specific sign of sexual maturation.
$D$. Weight gain is a general physiological change associated with overall growth and development,not specifically sexual maturation.
Therefore,the correct option is $B$.

(C) In human females,the onset of the reproductive phase is marked by the beginning of the menstrual cycle,which is known as menarche.
This process involves the periodic shedding of the uterine lining and is a clear indicator that the female reproductive system has become functional.
While body growth,changes in hair pattern,and voice changes are secondary sexual characteristics that occur during puberty,they do not specifically mark the onset of the reproductive phase as clearly as the first menstruation.

(D) In human males,the testes are located outside the abdominal cavity in a pouch-like structure called the scrotum.
This is because the process of spermatogenesis (formation of sperm) requires a temperature that is $2-2.5^{\circ}C$ lower than the normal body temperature.
The scrotum provides this cooler environment,which is essential for the healthy development and survival of sperm.

(A) The testes are the primary male reproductive organs. Their main functions at puberty include:
$1$. Formation of germ cells (spermatozoa),which is the process of spermatogenesis.
$2$. Secretion of the male sex hormone,testosterone,which is responsible for secondary sexual characteristics in males.
Conversely,the development of the placenta is a function associated with the female reproductive system during pregnancy,and the secretion of estrogen is primarily a function of the ovaries in females.
Therefore,$(iii)$ and $(iv)$ are not functions of the testes.

(B) In the male reproductive system,sperms are produced in the $Testis$.
From the $Testis$,sperms are transported through the $Vas$ $deferens$ (also known as the sperm duct).
The $Vas$ $deferens$ then joins the $Urethra$,which acts as a common passage for both urine and sperms.
Therefore,the correct sequence is $Testis \to Vas$ $deferens \to Urethra$.

(N/A) During sexual reproduction,the process of meiosis (reduction division) occurs during gamete formation. This process reduces the chromosome number to half in both male and female gametes. When these two haploid gametes fuse during the process of fertilization,the diploid number of chromosomes,which is identical to that of the parents,is restored in the zygote and subsequently in the offspring.

(N/A) Yes,the chromosome number remains constant in the zygote,embryonal cells,and the adult of a particular organism.
This constancy is maintained because all these cells are formed through mitotic cell division.
In mitosis,the parent cell divides to produce two daughter cells that have the same number of chromosomes as the parent cell,ensuring genetic stability across these developmental stages.

(D) General growth refers to the overall developmental processes in the body,such as an increase in height,weight gain,and changes in the shape and size of the body.
Sexual maturation is specific to the changes that occur during puberty,such as the cracking of the voice,the appearance of new hair patterns,and the development of breasts in females.
While general growth is a continuous process of physical development,sexual maturation marks the transition toward reproductive maturity.

(N/A) The path of sperm during ejaculation is as follows: $Testis \rightarrow Epididymis \rightarrow Vas \ deferens \rightarrow Urethra \rightarrow Penis$.
Associated glands and their functions:
$1$. $Seminal \ vesicles$: They secrete a fluid that provides nutrition to the sperms and makes their transport easier.
$2$. $Prostate \ gland$: It secretes a fluid that nourishes the sperms and helps in their motility.
$3$. $Bulbourethral \ glands$: They secrete a lubricating fluid that neutralizes the acidity of the urethra.

(B) If fertilisation does not occur,the egg dies and the thick,spongy lining of the uterus,which was prepared to nourish the embryo,is no longer needed. Consequently,this lining slowly breaks down and is discharged from the body through the vagina in the form of blood and mucus,a process known as menstruation.

(B) Following the implantation of the embryo,the uterine wall undergoes significant changes to support the developing fetus.
$1$. The uterine lining (endometrium) thickens and becomes highly vascularized,meaning it is richly supplied with blood to provide nourishment.
$2$. $A$ specialized tissue called the $placenta$ develops,which acts as a structural and functional connection between the embryo and the mother's uterine wall.
$3$. The $placenta$ facilitates the exchange of nutrients,oxygen,and waste products between the maternal blood and the fetal blood.

(N/A) Ovary: It is responsible for the production of the egg (ovum).
$(b)$ Oviduct (Fallopian tube): It is the site where fertilisation occurs.
$(c)$ Uterus: It is the site of implantation where the embryo develops.
$(d)$ Vagina: It serves as the passage for the entry of sperms into the female reproductive tract.

(N/A) $gamete$ is a specialized sex cell or germ cell involved in sexual reproduction. There are two types of gametes: male and female.
$A$ $zygote$ is the diploid cell formed as a result of fertilization, where a male gamete and a female gamete fuse together.
The two fusing gametes carry genetic information from their respective parents in their $DNA$. Fertilization combines the genetic material of both parents into a single $zygote$ cell.
The $zygote$ serves as the first cell of the next generation. It undergoes repeated mitotic divisions to form an embryo, which subsequently develops into a new individual.

(N/A) The placenta is a special disc-like tissue embedded in the uterine wall that connects the developing embryo to the mother.
Its roles during pregnancy are:
$1$. It possesses villi on the embryo's side of the tissue,which increases the surface area for glucose and oxygen transfer from the mother to the embryo.
$2$. It facilitates the passage of essential nutrients and oxygen from the mother's blood to the embryo.
$3$. It acts as an excretory organ by removing waste substances and carbon dioxide produced by the embryo into the mother's blood for excretion.

(N/A) During sexual intercourse,sperm enters through the vaginal passage and moves upwards into the fallopian tube (oviduct).
$(b)$ An egg is released from the ovary and reaches the oviduct.
$(c)$ The sperm encounters the egg in the oviduct,where fusion occurs,resulting in fertilization.
$(d)$ Fertilization occurs once a month because the ovary releases only one egg every month during the menstrual cycle.

(A) At the time of puberty,the body undergoes significant developmental changes.
In boys,the testes begin to secrete the hormone $Testosterone$,which is responsible for the development of secondary sexual characteristics such as facial hair,deepening of the voice,and muscle growth.
In girls,the ovaries begin to secrete the hormone $Oestrogen$,which is responsible for the development of secondary sexual characteristics such as breast development,widening of the pelvis,and the onset of the menstrual cycle.

(N/A)

Estrogen	Testosterone
$(i)$ It is the female sex hormone.	$(i)$ It is the male sex hormone.
$(ii)$ It is secreted by female gonads (ovaries).	$(ii)$ It is secreted by male gonads (testes).
$(iii)$ It helps in the development of female reproductive organs and also imparts female secondary sexual characteristics.	$(iii)$ It helps in the development of male reproductive organs and also imparts male secondary sexual characteristics.

(A) During puberty,the human body undergoes significant physiological and physical changes.
These changes are primarily regulated by sex hormones.
In males,the testes secrete $Testosterone$,which is responsible for the development of secondary sexual characteristics such as facial hair,deepening of the voice,and muscle growth.
In females,the ovaries secrete $Estrogen$,which is responsible for the development of secondary sexual characteristics such as breast development and the onset of the menstrual cycle.
Therefore,the correct combination is $Testosterone$ from the testes and $Estrogen$ from the ovary.

(N/A) $(i)$ Production of female gametes (ova).
$(ii)$ Secretion of female sex hormones (estrogen and progesterone).

(B) Chromosomes are composed of $DNA$ and proteins. During the interphase of the cell cycle,the genetic material exists as a loose network called chromatin. However,when the cell enters the process of cell division (mitosis or meiosis),the chromatin condenses into highly organized,thread-like structures known as chromosomes. Therefore,chromosomes can be clearly identified and observed under a microscope only during the phase of cell division.

(B) The testes are located outside the abdominal cavity in the scrotal sac because the process of spermatogenesis (the production of sperms) requires a temperature that is approximately $2\,^{\circ}C$ to $2.5\,^{\circ}C$ lower than the normal internal body temperature. This lower temperature is essential for the survival and maturation of sperm cells.

(C) If the egg is not fertilized,the thick and spongy lining of the uterus is no longer needed. Consequently,this lining slowly breaks down and comes out through the vagina as blood and mucus. This process is known as menstruation.

(N/A) The lining of the uterus becomes thick and spongy every month to prepare itself to receive and nurture the growing embryo in case fertilization occurs. This rich,vascularized lining provides the necessary blood supply and nutrients to support the development of the zygote.

(N/A) $(i)$ $DNA$ is primarily located within the nucleus of a cell,specifically within the chromosomes.
$(ii)$ Genes are segments of $DNA$ located on the chromosomes.
$(b)$ The expansion of $DNA$ is Deoxyribonucleic Acid.

(N/A) The primary difference is that sperms are motile,while eggs are non-motile.
The importance of this difference is that the motility of the sperm allows it to travel through the female reproductive tract to reach the egg for fertilization.
Alternatively,another significant difference is in their chromosomal content:
Sperms contain either an $X$ or a $Y$ chromosome.
Eggs contain only an $X$ chromosome.
The importance of this difference is that it determines the sex of the offspring upon fertilization:
If an $X$-bearing sperm fertilizes the egg,the zygote becomes $XX$ (female).
If a $Y$-bearing sperm fertilizes the egg,the zygote becomes $XY$ (male).

(N/A) $(i)$ In sexual reproduction, the fusion of male and female gametes takes place. These germ cells/gametes contain half the number of chromosomes compared to the somatic (body) cells.
$(ii)$ When male and female gametes fuse during fertilization, the zygote formed receives one set of chromosomes from each parent, which restores the original diploid number of chromosomes, thereby ensuring the stability of the species.

(N/A)

Male gamete	Female gamete
$(i)$ It is smaller in size compared to the female gamete.	$(i)$ It is larger in size.
$(ii)$ It is generally motile.	$(ii)$ It is generally non-motile.

(N/A) Placenta: $(i)$ It facilitates the transport of glucose,oxygen,and nutrients from the mother to the developing embryo. $(ii)$ It helps in the removal of waste products generated by the embryo by transferring them into the mother's blood.
$(b)$ Fallopian tube: $(i)$ It acts as a pathway for the egg (ovum) to travel from the ovary to the uterus. $(ii)$ It is the site where fertilization of the egg by the sperm typically occurs.

(N/A) Testes: They are the primary male reproductive organs responsible for the production of sperms (spermatogenesis) and the secretion of the male sex hormone,testosterone.
$(b)$ Prostate gland: It is an accessory reproductive gland that secretes a milky,alkaline fluid which forms a significant part of the semen,helping to nourish and transport the sperms.

(N/A) The path of sperm is as follows: $\text{Testes} \rightarrow \text{Epididymis} \rightarrow \text{Vas deferens} \rightarrow \text{Ejaculatory duct} \rightarrow \text{Urethra} \rightarrow \text{Exterior}$.
$(b)$ The secretions of the prostate gland and seminal vesicles provide a fluid medium for the sperm,which makes their transport easier. Additionally,these secretions provide nutrition to the sperm and contain enzymes that help in the activation and survival of the sperm.

(N/A) Papaya,Watermelon
$(b)$ Insects,Wind (Air)
$(c)$ $(i)$ Appearance of pubic hair.
$(ii)$ Skin becomes oily and may develop pimples.

(N/A) The testes are located outside the abdominal cavity within the scrotum because the process of spermatogenesis (sperm formation) requires a temperature that is $1-3\,^{\circ}C$ lower than the normal internal body temperature.
Endocrine function: The testes act as an endocrine gland by secreting the male sex hormone,$testosterone$,directly into the bloodstream.
Exocrine function: The testes act as an exocrine gland by producing and releasing male gametes,known as $sperms$,through the duct system.

(N/A) Chromosomes are thread-like structures composed of $DNA$ and proteins,found within the nucleus of a cell.
In sexually reproducing organisms,the process of meiosis occurs during gamete formation. This process reduces the number of chromosomes to half $(n)$ in the gametes compared to the parent cell $(2n)$.
When fertilization occurs,the male gamete $(n)$ and the female gamete $(n)$ fuse to form a zygote $(2n)$. This fusion restores the original diploid number of chromosomes in the progeny,ensuring the stability of the species across generations.

(A) $(i)$ $DNA$ copying that is not perfectly accurate leads to variations in the offspring,which is the basis of evolution.
$(ii)$ In sexually reproducing organisms,specialized germ cells (gametes) are produced through meiosis,which contain only half the amount of $DNA$ or half the number of chromosomes compared to the parent cell.
$(iii)$ When these haploid germ cells fuse during fertilization,the resulting zygote restores the original amount of $DNA$ characteristic of the species,ensuring the amount remains constant across generations.

(N/A) In the provided diagram,the labels for 'Testis' and 'Penis' are swapped. The structure labeled as 'Testis' is actually the 'Penis',and the structure labeled as 'Penis' is actually the 'Testis' (within the scrotum).
$(b)$ The urethra serves as a common passage for both sperms and urine in the male reproductive system.
$(c)$ The testis releases the hormone 'Testosterone',which is responsible for the development of secondary sexual characteristics in males.

(N/A) Vagina: It serves as the birth canal and the passage for the entry of sperms into the female reproductive tract during sexual intercourse.
$(b)$ Ovary: It is responsible for the production of female gametes (ova or eggs) and the secretion of female sex hormones like estrogen and progesterone.

(N/A) $(i)$ The function of the pollen tube is to provide a pathway for the male gametes to travel from the stigma to the ovule for fertilization.
$(ii)$ The function of the ovary is the production of female gametes (ova) and the secretion of female sex hormones like estrogen and progesterone.
$(b)$ Two changes observed in the body of a female during puberty are:
$(i)$ Development and enlargement of mammary glands (breasts).
$(ii)$ Onset of the menstrual cycle (menarche).

(N/A) is the Seminal vesicle,and $B$ is the Prostate gland.
$(b)$ The hormone produced by organ $X$ (testis) is Testosterone. Its role is to control the formation of gametes (sperms) and regulate the development of secondary sexual characteristics in human males.
$(c)$ $(i)$ Tube $C$ (Vas deferens) transports sperms.
$(ii)$ Tube $D$ (Urethra) transports both sperms (semen) and urine.

(N/A) The human male reproductive organ is the $Testis$. It secretes the hormone $Testosterone$.
Functions of $Testosterone$:
$(i)$ It regulates the production of sperms.
$(ii)$ It brings about the development of secondary sexual characteristics in males during puberty.
$(b)$ $(i)$ Fertilisation takes place in the $Fallopian tube$ (or $Oviduct$).
$(ii)$ Implantation occurs in the $Uterus$.
Nourishment of the embryo: The embryo receives nourishment from the mother's blood through a special tissue called the $Placenta$. The $Placenta$ is a disc-like structure embedded in the uterine wall. It provides a large surface area for the transfer of glucose, oxygen, and other essential nutrients from the mother's blood to the developing embryo, and also facilitates the removal of waste products produced by the embryo.

(N/A) Diagram: Refer to the sectional view of the human female reproductive system in the textbook.
Labels:
$(i)$ Ovary: The site where eggs (ova) develop.
$(ii)$ Fallopian tube (Oviduct): The site where fertilization takes place.
$(iii)$ Uterus: The site where the fertilized egg (embryo) gets implanted.
$(b)$ $(i)$ To receive the zygote,the inner lining of the uterus (endometrium) becomes thick,soft,and richly supplied with blood vessels to nourish the developing embryo.
$(ii)$ If the zygote is not formed,the thickened uterine lining is no longer needed. It breaks down and is shed along with blood and mucus through the vagina,a process known as menstruation.

(N/A) Placenta: It is a specialized structural and functional unit that connects the developing embryo to the uterine wall of the mother.
Structure: It is a disc-like tissue embedded in the uterine wall. On the embryo's side,it possesses finger-like projections called villi. On the mother's side,there are blood spaces (lacunae) that surround these villi,allowing for the exchange of materials.
Functions:
$1$. It provides a large surface area for the transfer of nutrients like glucose and respiratory gases like oxygen from the mother's blood to the embryo.
$2$. It facilitates the removal of metabolic waste products and carbon dioxide produced by the developing embryo by transferring them into the mother's blood.