CBSE Class 10 Science Reproduction Notes

REPRODUCTON

11.1 MEANING OF REPRODUCTION:

Reproduction is the ability of living organisms to produce new living organisms similar to them. It is one of the important characteristic of life.

11.1 (a) Purpose of Reproduction:

Reproduction is aimed sat multiplication and perpetuation (stability) of the species. In other words it proves group immortality by replacing the dead individuals with new ones.

11.1 (b) Basic Features of Reproduction:

The modes of reproduction vary is different organisms. However all the these have certain common basic features. These are -

(i) replication of DNA  (ii) cell division

(iii) Formation of reproductive bodies or units  (iv) development or reproductive bodies into offspring 

11.2 FORMS OF REPRODUCTION:

Animals reproduce in a variety of ways. Which are categorized in two categories i.e. Asexual and sexual reproduction.

11.2 (a) Asexual Reproduction:

Definition: Production of offspring by a single parent without the formation and fusion of gametes is called as asexual preproduction. It is more primitive type or reproduction. If ensures rapid increase in number.

Occurrence Asexual reproduction occurs in protozoans and some animals such as sponges, coelentrates, certain worms and tunicates. It is absent among the higher invertebrates and all vertebrates.

Type of Asexual Reproduction: Asexual reproduction takes place in the following principal ways :

(i) Fission : it is the simples form of reproduction in which unicellular organism either devised into two or many organisms.

It is also divided into two types:

(A) Binary fission: It is a type of reproduction in which nuclear division is followed by the appearance of a constriction in the cell membrane, which gradually deepens inward and divides the cytoplasm into two parts, each with one nucleus. Finally two daughter cells are formed.

E.g. Amoeba

(B) Multiple fission : Sometimes the nucleus several times into many daughter nuclei. The daughter nuclei arrange at the periphery of the parent cell, and a bit of cytoplasm around each daughter nuclei is present. nucleus develops an outer membrane. Finally the multinucleated body divides into many daughter cells. e.g. Plasmodium.

(ii) Budding : Formation of daughter individual from a small projection which is called as bud, arising on the parent body is called as budding.

Budding is also of two types :

(A) Exogenous budding : [External budding] In this, bud arises from the surface of parent body, e.g., Hydra.

(B) Endogenous budding :  [Internal budding] In this, bud arises inside or within the parent body e.g., Sponges.

NOTE : During the process of budding, the bud remains attached to the parent body so as to derive it’s nutrition from the parent but as it matures, it get’s detached form the parent body. 

(iii) Fragmentation : It is a type reproduction or the regeneration ability of the organisms to replace their lost part. In this process an entire new organism can grow from certain pieces or cells of the parent organisms. e.g. Flatworm.

(iv) Spore formation : It is a process of reproduction most commonly found in fungi, some cocci and bacillus bacteria. During this process a structure called as sporangium is formed. In this structure nucleus divides several times and each nucleus with a little trace of cytoplasm forms a spore. These spores are then liberated out and develop into a new hyphen, e.g. Rhizopus.

(v) Vegetative propagation : This is a type of reproduction found in higher plants in which a new plant is formed from vegetative part of the plant such as roots, stems or leaves.               

It is of following types :

(A) Cutting : This is the very common method of vegetative propagation practised by the gardeners all over the world. It is the process in which a vegetative portion from plant is taken and is rooted in the soil to form a new plant e.g. Grapes, Sugarcane etc.

(B) Layering : In this process the development of adventitious roots is induced on a stem before it gets detached from parent plant, e.g, Mango, roses etc.

It is of three types :

* Mound layering : In the process of layering the lower stem branch of plant is used. Leaves are removed from this stem. Then it is bent close to the ground, pegged and covered with the moist soil in such a way that it’s rowing tip remains above the solid surface. This pegged down branch is called as layer. After a few days the covered portion of stem develops roots. This stem is then detached from the parent plant and is grown separately from the parent plant and is grown separately into a new individual .e.g Jasmine

NOTE : The formation of adventitious roots in a layer can be hastened by injuring the ’layer’ by tonguing, ringing or notching.

Air layering : It is adopted in those plans where stem cannot be bent to the ground. In this process the stem is girdled (i.e. ring of the bark is removed). then it is covered with moist moss or cotton and wrapped with a polythene sheet to preserve the moisture. After few weeks adventitious roots develop from the injured part. The branch along with roots in then separated from the parent plant and planted to grow into a new plant. e.g. Orange, Pomegranate etc.

Grafting : The process of joining together of two different plants in such a manner that they live as one plant is called as grafting. Out of the two plans one is rooted in the soil and is known as the stock. The other part consist of a small shoot bearing one or more buds, it is known as scion. Their union is carried out in such a way that their cambium must overlap each other e.g. Mango, roses etc.

(vi) Micro propagation : It has now become possible due to recent techniques to produce a large number of plantlets from a small piece of tissue taken from the shoot tip or other suitable plant parts. This method of propagation  is called as micropropagation.  It involves the process of tissue culture. e.g., Orchids, ornamental plants etc.

Significance of vegetative propagation

(A) It is used to propagate a plant in which viable seeds are not formed or very few seeds are  produced e.g. Orange, pineapple, banana etc.

(B) Vegetative propagation helps us to introduce plants in new areas where the seed germination fails to produce mature plant due to change in environmental factors and the soil.

(C) Vegetative propagation is a more rapid, easier and cheaper method of multiplication  of plants.                            

(D) By this method a good quality of a race or variety can be preservers.

(E) Most of the ornamental plants are propagated through vegetative propagation. e.g. Rose, Tulip etc.

(vii) Parthenogenesis : It is a modification of sexual reproduction in which an egg develops into a

complete offspring without fertilization. It is monoparental (i.e. fusion of gametes does not occur, only a single parent gives rise to a new individual).

Significance of asexual reproduction : It brings about multiplication of the species only. It does not play a role in evolution as no variation is introduced into the new individual formed by it.

11.2 (b) Sexual Reproduction :

Definition : Production of offspring by formation and fusion of special haploid cells called as gametes. These are contributed generally by two parents. i.e. ,male gamete and female gamete is called as sexual reproduction.

Occurrence: Sexual reproduction occurs nearly in all animals including those which reproduce asexually. In most animals there are two sexes male and female, and the differences between them are genetically determined.

Types of sexual reproduction :

(i) Syngamy : It involves the complete and permanent fusion of two gametes to form a composite cell called as zygote. This is a common mode of sexual reproduction.

(ii) Conjugation : It involved temporary pairing of two parents which exchange their pronuclei and then undergo the process of separation .e.g Paramecium etc.               

Characteristics of sexual reproduction :

(i) It is generally biparental [i.e. it involves two parents ]

(ii) It involves formation and fusion of gametes.

(iii) Cell divisions are both meiotic & mitotic during gamete formation and mitotic during development of zygote  into an offspring.

(iv) The offspring’s are not genetically identical to the parents.

(v) Fertilization in case of humans is internal.

(vi) Infects can be fed on mother’s milk.

(vii) Parental care is very well developed,

Significance of sexual reproduction :

(i) It results in multiplication and perpetuation  of species.

(ii) It contributes to evolution of the species by introducing variation in a population much more rapidly than asexual reproduction.

General Terms :

(i) Fertilization : It is the process of fusion of gametes.

(ii) Unisexual organism : In case of humans male and female sex organs are separate and therefore called as unisexual.

(iii) Bisexual : In plants and some organisms like tapeworm, earthworm etc. both male an female organs are present in the same individual and therefore called as bisexual.

(iv) Gonads: Organs which are involved in the formation of gametes are called as gonads.

(v) Copulation or mating : The process of transfer of male gametes into female body.

11.3  REPRODUCTION IN A FLOWERING PLANT:

11.3 (a)A flower Consists of Following Parts :

(i) Calyx: The sepals collectively are called as calyx. They are usually green in colour and protect the inner whorls of a flower especially during bud formation.

(ii) Corolla : It consists of coloured petals. They are normally large often fragrant and bright coloured. Their primary function is to attract animals and insects for pollination.

(iii) Androecium / stamen/male reproductive organ : The stamens are referred to as the male reproductive organ. A typical stamen is differentiated into three parts, they are filament connective and anther.

(A) Filament : It forms the stalk that bears more or less cylindrical or avoid anther.

(B) Connective : It connects anther to filament.

(C) Anther : It is present on the top of filament. Each anther consists of two lobes that is why it is called as bilobed. Bed anther lobe has two pollen sacs which contain millions of tiny microscopic grains, called as microspores. The pollen grains are like yellow dusty powder in appearance.

(vi) Gynoecium / pistil / female reproductive organ :

1. It is located in the center of a flower.
2. It is composed of one or more carpals.
3. The freely occurring units of the carpals in a flower are called pistils.
4. Each pistil usually consist of three distinct parts - ovary, style and stigma.

(A) Ovary : It is a basal, swollen part of the pistil The ovary has one or more chambers called the loculi which is distributed in a special cushion like parechymatous tissue called the placenta, from which the ovule develops.

(B) Style : From the top of the ovary arises a long, elongated structure called as style.

(C) Stigma : The terminal end of style is called as stigma. The stigma is normally rough, hairy or sticky to hold pollen grains during pollination process.

11.3 (b) Pollination :

The transfer and deposition of pollen grains from the anther to the stigma of a flower is called as pollination.

Types of pollination : Pollination is of two type -

(i) self pollination : It is the process of transfer of the pollen grains from the anther to the stigma of either the same or genetically similar flower. It is further divided into two types :

(A) Autogamy: It is a type of self pollination in which the pollen grains are transferred from the anther to stigma of the same flower e.g. Wheat, rice pea etc.

(B) Geitonogamy : It is a type of self pollination in which the pollen grains are transferred from the anthers of one flower to the stigma of another flower borne either on the same plant or a genetically identical plant. 

Significance of self pollination :

1. It maintains purity of race.
2. It also maintains the superiority of variety once developed.

(ii) Cross pollination : it is the process of transfer of the pollen grains from the anther of one flower to the stigma of another flower borne on a different plant of the same species.

Significance of cross pollination :

(i)  Increase in yield and adaptability.

(ii) It eliminates defective traits and produces new varieties.

(iii) It also leads to the hybrid production.

11.3 (c) Fertilization is a Flowering Plant :

1. Fertilization is a process of fusion of male gamete with the female gamete.
2. The process of formation of male gametophyte in case of plants is called as microsporogenesis.
3. The process of formation of female gametophyte in case of plants is called as megasporogenesis.
4. The process of pollination occurs, due to which the anther get stuck up to the stigma.
5. After reaching to stigma pollen grains develops a pollen tube.
6. This pollen tube grown through the length of style, from where it reaches to ovule.
7. Pollen tube comprise of two male gametes, which is later on released in the embryo sac through an opening called as micropyle.
8. Here one male gamete fuses with the egg to form a diploid zygote and the other male gamete fuses with the polar bodies to form a triploid nucleus which later on produces the structure called as endosperm.
9. The process of fusion of one of the male gamete with egg and the other male gamete with polar bodies is called as “double fertilization.”
10. The fusion of one male gamete with the two polar bodies to form endosperm is called a “triple fusion” (at it involves one male gamete and two polar bodies).               

NOTE : The endosperm is meant to provide nourishment to the developing embryo.

1. After fertilization sepals and petals fall and zygote undergoes a series of mitotic division to from a multinuclear embryo.
2. At maturity wall of ovules changes to seed coat of which outer one is hard and is known as testa, while inner one is called as tegnum.
3. Ovule change into seed and ovary wall change into fruit wall.

12.1 SEXUAL REPRODUCTION IN HUMANS :

1. Mammals are unisexual.
2. Reproductive system of each organism consists of many reproductive organs.
3. These can be primary sex organs or secondary sex organs.
4. The primary sex organs  are called as gonads. They produce sex cells or gametes and also secrete sex hormones.
5. The gonads of males are called a testis, which produce sperms.
6. The gonads of females are called as ovaries, which produce ova or female gametes.
7. Secondary sex organs include the reproductive ducts which transport gametes and reproductive glands which help in process of reproduction. These organs do not produce gametes.
8. e.g., In males : Vasa efferentia, epididymis, seminal vesicles, ejaculatory duct, urethra etc. In females : Fallopian tube, uterus, vagina, mammary glands etc.
9. Accessory or external sec characters help to distinguish the two sexes of a species externally.
10. e.g., In male : Muscular body, more height, low pitched voice, moustaches etc.
11. In female : High pitched voice, breast development, lateral pubic hairs etc.
12. Puberty : Beginning of sexual maturity is known as puberty.
13. At this stage primary sex organs start functioning.
14. Secondary sex organs develop dully under the influence of sex hormones produced by primary sex organs.
15. In the stage of puberty body growth is very rapid.
16. It occurs at the age of 10 - 14 years in girls and 13 - 15 years in boys.

12.1 (a) Male Reproductive System : 

Male reproductive system comprises of following parts :

(i) Testis                                       (ii) Scrotum                                         (iii) Vasa efferent

(iv) Epididymis                         (v) Vas deference                               (vi) Ejaculatory duct

(vii) Urethra                                (viii) Accessory sex glands             (ix) Penis

(i) Testis :

1. They are soft, smooth, pinkish, oval organs. They are housed [present] in a sac like structure called as scrotum. Outer covering is called as as tunicavaginalis.
2. It’s inner covering is called as tunica albuginea.
3. Ingrowths of tunica albuginea are called as septa, that divide the testis into 200-300 lobules.
4. It also consist of convoluted somniferous tubules.
5. These somniferous tubules at one end join to form tubules which open into a network of irregular cavities known as rete testis.
6. This rete testis comes out from a dorsal surface of the testis with the help of vesa efferentia.
7. This vasa efferentia combines to form a single tube which becomes highly coiled and from epididymis.
8. This vasa efferentia combines to form a single tube wihich becomes highly coiled and form epididymis.
9. Epididymis peon into a narrow tube vas deferens.
10. Somniferous tubules from the spermatogenic tissue of the testis.
11. It consists of a germinal epithelial layer at the periphery. Spermatogenesis occurs at the center.
12. It forms spermatogonia which grows and form spermatocytes which further grow to form primary spematrocytes, which undergo meiosis to form secondary spermatocytes and then spematids.
13. The later (i.e. spermatids) metamorphose into spermatozoa.
14. This process of formation of spermatozoa from spermatogonia is called as spermatogenesis.
15. These spermatozoa are nourished during the development by nurse cells.

*In between somniferous tubules, there are interstitial cells known as Leydig cells which secrete male hormone called as testosterone. This hormone helps in the growth and development of male sex hormone.

(ii) Scrotum : It is a pouch of pigmented skin arising from the lower abdominal wall and hanging between the legs.

1. It is divided internally into two compartments by a muscular partition called as septum scroti.
2. Scrotum possesses smooth involuntary dortus muscles.
3. Scrotum sac is connected to the abdominal cavity through inguinal canal.
4. Function of dortus muscle is to change the position of testis to keep them at proper temperature.
5. Scrotum has temperature 1 - 3 lower than body temperature which favours the formation of sperms.
6. Duct system :

(iii) Vasa efferentia : Rete testis is connected to epididymis through a fine tubule called as vasa efferentia. They help in conduction of sperms.

(iv) Epididymis : They are long tubules which lie compacted along the testis from their upper ends to lower back side. Its walls are muscular and glandular to provide or secrete nutritive fluid which provides nourishment to the sperms.

(v) Vas deference :

1. Vasa efferentia from epididymal duct finally opens into vas deferens.
2. It comes out through inguinal canal passing over urinary bladder to receive ducts from seminal vesicles.
3. They are thick walled and muscular and conduct sperms.

(vi) Ejaculatory duct : They are short, straight, muscular tubes, each formed by the union of vas deferens and duct of seminal vesicles.

(vii) Urethra : it arises from urinary bladder forming a urinogenital canal. It carries urine, sperm and secretion of seminal vesicles, prostrate and cowper’s gland.

(vii) Accessory glands: They consist of prostrate gland, a pair of seminal vesicles, and a pair of cowper’s gland.

(A) Prostrate gland : It is a large pyramidal gland that encloses a part of urethra including it’s junction with the ejaculatory duct. It contains 30 - 40 alveoli which open separately into urethra by fine ducts. Secretion is thick, milky and alkaline which continue 20 - 30% semen.

(B) Cowper’s glands “ These are a pair of small glands, present below the prostrate and consist of separate opening. Their secretion provide lubrication to the reproductive track.

(C) Seminal vesicle : It is paired and present between urinary bladder and rectum. It’s secretion from a major part of semen (60-70%). It is thick, viscous, alkaline having proteins, fructose and prostaglandins.

(ix) Penis : It is a male copulatory organ which also passes urine. It consists of highly sensitive covering of skin called prepuce.

12.1 (b) Semen :

 it is milky, viscous and alkaline fluid, ejaculated by reproductive system of males during copulation

1. It’s quantity is 2.5 - 4.0 ml at a time having about 40 million sperms.
2. Semen has chemical for nourishment of sperms neutralizing the acidity of urethra and vagina, stimulating their movement in female tract.
3. Spermatogenesis starts at puberty under the influence of gonadotropin secreted from anterior pituitary gland.

12.1 (c) Structure of Sperm :

Each sperm consists of following parts :

(i) Head (ii) Neck         (iii) Middle piece     (iv) Tail

(i) Head : It is oval in structure. It is composed of a large nucleus and a small acrosome. The nucleus is compact. It consists of DNA and basic proteins. Acrosome lies at the tip of nucleus. It is formed of golgi complex. It consist of hydrolytic enzymes and is used to contact and penetrate the egg during fertilization.

(ii) Middle piece: It is cylindrical in human sperms. It consists of ATP and mitochondria in a thin layer of cytoplasm. Mitochondria is coiled round the axial filament, it provided energy and it is said to be the power house of the sperm.

(iii) Neck : It is very short and constrains two centrioles. These play an important role during the first cleavage of the zygote.

(iv) Tail : It is very long, slender and tapering. It is formed of cytoplasm. It’s main function is to provide mobility to the sperm. End piece consists of the exposed axial sheath, which forms a fine filament.

12.2     FEMALE REPRODUCTIVE SYSTEM :

Female reproductive system comprises of following parts :

(i) Ovaries            (ii) Fallopian tube              (B) Uterus

(iv) Vagina           (v) Glands

(i) Ovaries : These are oval shaped lying near the kidney. 

1. Ovary is covered by two layers outer is made up of germinal epithelial cells.
2. Inner layer is called as tunica albuginea which is made up of fibrous connective tissues.
3. The ovary consists of inner part called as stroma.
4. It’s outer peripheral pat is called as cortex while inner part is called a medulla.
5. Medulla consists of connective tissues containing numerous blood vessels, lymphatic vessels and nerves.
6. Cortex consists of graffian follicles in all the stages of development.

Cortex also consists of large mass of yellow cells termed as corpus luteum, formed in an empty graffian follicle after the release of it’s ovum.

The cells of corpus luteum secrete the hormones

(A) progesterone during pregnancy.     (B) Relaxing at the end of pregnancy.

Oestrongen is secreted by graffian follicle and intestinal cells. It’s secretion is maximum during ovulation. It is also secreted during pregnancy. 

(ii) Fallopian tube : It is about 10 cm. long muscular tube. It shows 4 regions :

(A) Infundibulum : It is the broad, funnel shaped proximal part of fallopian tube. It’s margin bears finger like processes called as fimbriae. This is meant to carry ovum by ciliary movement to the uterus.

(B) Ampulla : It is a long, wide part of the fallopian tube next to the Infundibulum.

(C) Isthmus : it is the narrow part that follows ampulla.

(D) Uterine part : It is also narrow and passes through the uterine wall.

(iii) Uterus : It is large, highly elastic sac specialized for the development of the embryo.

1. It is situated in a pelvic cavity.
2. It is attached to the fallopian tube from the sides and below it opens into vagina through cervix.
3. This uterus undergoes cyclic changes during phases of menstrual cycle.

(iv) Cervix: Lower narrow cervix that projects into the vagina. The cervix communicates above with the body of the uterus and below with the vagina.

(v) Vagina: It is a large, median, elastic, muscular tube. This canal opens externally into labia minora and labia majora. It’s folds consist of stratified squamous epithelium which has mucous lining It secretes a lubricant fluid. Labia majora is the innermost, thin, moist fold. Labia minora is outer large and hair covered. pH of vagina is 4.3 It is also called a “Birth canal”.

(vi) Gland:

1. Bartholin’s gland : it secretes a clear, viscous fluid under sexual excitement.
2. The fluid serves as a lubricant during copulation or mating.

12.2 (a) menstrual Cycle :

1. It is a cyclic phase of the flow of blood with mucus and tissues etc. from the uterus of a woman at monthly interval.
2. It occurs on average of 28 days interval.
3. It starts at the age of 12-14 years and stops at 45-50 years of life.
4. This cycle stops during pregnancy.
5. The menstrual cycle consists of following phases :

(i) Bleeding or menstrual phase :

1. It is the first stage of menstrual cycle.
2. It’s duration is of 5 days but normally bleeding is found for 2-3 days.
3. In this stage hormones estrogen, progesterone, follicle stimulating hormone and luteinizing hormone are found in minimum quantity.
4. Total 100 ml, of blood flows in a complete bleeding phase.

(ii) Proliferative phase:

1. In this phase F.S.H. stimulate development and maturation of graffian follicles.
2. In this phase oestrogen level rises which leads to formation of new endometrium.
3. It lasts for about 10 - 14 days. Thinnest endometrium is found in this phase.
4. It is also called as follicular phase. 

(iii) Ovulation phase:

1. At this phase ovulation occurs.
2. Ovulation occurs in the presence of FSH and LH.
3. Thicket endometrium found in this stage.
4. It also lasts for about 14 days. 

(iv) Secretory phase: In this sage both oestrogen and progesterone levels are high.

1. If fertilization takes place, this stage extends till to the parturition (giving birth to a child)
2. If, fertilization does not take place, this stage completes on 28^th day of menstrual cycle.
3. The commencement of menstruation of puberty is called as menarche.
4. It’s stoppage around the age of 50 years is called as menopause.
5. The period between menarche and menopause is the reproductive phase in human female. 

12.2 (b) Ooganesis :

Oogenesis is a process of formation of ovum. the ovum is a rounded, non-motile cell. It’s size varies in different animals depending upon the amount of yolk in it.            

Ovum consists of two types of coverings :

(i) Inner thin, transparent, non-cellular, covering called as zona pellucida. it is composed of protein and sugars. It is secreted y by follicle cells.

(ii) Outer thick covering is called as corona radiata.

12.3     FERTILIZATION:

1. Here the pronuclei of sperm and ovum fuse to from a new resultant nucleus each contributing 23 chromosome, so that the resultant may have 46 chromosomes.
2. It’s head begins to swell and forms male pronucleus.
3. After penetration the tail and body of the sperm is lost, only head remains inside the ovum.
4. This process if facilitated by acrosome and proteolytic enzymes.
5. The head of the sperm penetrates the corona radiate layer of ovum and then the zona pellucida layer.
6. Only one sperm is required for fertilization of the ovum.
7. At the time of sexual intercourse the sperm enters in to the vagina.       
8. It included release of ovum from the ovary, where it remains viable for 12 - 24 hours.
9. Fusion of male & female gametes is called as fertilization. Zygote starts developing in fallopian tube
10. and forms embryo, this later on moves to uterus. It gets attached to uterine walls and the whole process is called as implantation
11. Placental formation occurs between uterine wall and the foetus, which provides nourishment to the foetus.
12. The time period for which a developing fetus remains inside the mother’s womb is called as gestation period. it extends for about 9 months or 40 weeks or 280 days.
13. The process of giving birth to baby is called as parturition.

12.4     ARTIFICIAL INSEMINATION :

1. It is a technique to make a female pregnant by artificially introduction semen into vagina.
2. In this process semen from a good quality male is collected, preserved by freezing and used when required.
3. In case of humans it is also being used for improving the chances of fertility.
4. A man may be infertile due to insufficient number of sperms, weak or premature ejaculation, inability of penis to undergo and enter the vagina or nonmotile sperms.
5. In this case husband’s semen is collected, concentrated and introduced artificially into the wife’s vagina. this is called as artificial insemination.
6. If the husband’s sperms are faulty, some donors sperm can be used. This is called as artificial insemination donor.
7. Artificial insemination has following two advantages.

(i) Semen of good quality male animal is used to inseminate a number of females.

(ii) Preserved semen can be transported to distant places, excluding the need for sending the male animal there.

12.5     POPULATION GROWTH :

1. The term population refers to the total number of individuals of a species occupying particular geographical area at a given time.
2. The scientific study of human population is called as “demography”.

Factors that lead to increase in population are :

(i) Increase in protection from risk               (ii) Illiteracy

(iii) Desire of son          (iv) Decline in death rate

(v) Desire for more earning hands

(vi) Unawareness of various birth control measures

12.6     METHODS ADOPTED FOR POPULATION CONTROL 

(i)  Planned control of population :

(A)  By educating people about the advantages of small family.     

(B)   Raising the age of marriage can help in reducing population growth.

(C)   By family planning.

(ii)   Temporary methods :

(A) Safe period : A week before and after the menstrual cycle is considered to be infertile and fertilization, does not occur during this period.

(B) Coitus interrupts : It involves withdrawal by males before ejaculation so that semen is not deposited, in vagina.

(C) Chemical means : These includes certain jellies, paste, foam tables which when introduced into vagina cause immobilization of sperms and kill them. They also include contraceptive pills which inhibit secretion of F.S.H. and L.H. ovulation is inhibited.

(D) Mechanical means :

1. They involve use of condoms.
2. Use of cervical or diaphragm cap which is fitted in the vagina that checks the entry of sperms.
3. IUD (intrauterine device) called as copper-T is also fitted in the uterus which prevents fertilization.

(E) Surgical methods: It involves tubectomy in females which involves cutting of fallopian tube, and vasectomy in males which involves cutting of vas deference from both the sides. However, surgical removal of ovaries also occurs which is called as ovariectomy and in males removal of testis called as castration.

Abortion : Medical termination of pregnancy is called as abortion.

Case study questions

The male reproductive system consist of portions which produce the germ-cells and other portions that deliver the germ-cells to the site of fertilisation. Testes are located outside the abdominal cavity in scrotum because sperm formation requires a lower temperature than normal body temperature. It also has a role of secretion of male sex hormone which brings changes in appearance seen in boys at the time of puberty. Vas deferens unites wih a tube coming from urinary bladder. Urethra is a common passage for sperms and urine. Prostate gland and seminal vesicles add their secretions so that sperms are now in fluid.

Question. Testes are located outside the abdominal cavity in scrotum because
(a) sperms formation requires higher temperature than body temperature
(b) sperms formation requires lower temperature than body temperature
(c) it is easier to transport sperms from the scrotum
(d) None of these
Answer : B

Question. Name the sex hormone associated with males.
(a) Testosterone
(b) Progesterone
(c) Oestrogen
(d) None of these
Answer : A

Question. Which of the following statement is incorrect?
(a) Sperms and urine has a common passage from urethra.
(b) Sperms have long tail that helps them to move forward.
(c) Sperms contain genetic material.
(d) Sperms formation requires 1–3°C higher temperature than normal body temperature.
Answer : D

Question. Which of the following statements is incorrect ?
(a) Sperms are present in a fluid
(b) Fluid provides nutrition to sperms
(c) Fluid makes easier transportation of sperms
(d) Fluid helps to bind the sperms together
Answer : D

Question. What is the nature of semen?
(a) slightly acidic
(b) Neutral
(c) Slightly basic
(d) Strongly basic
Answer : C

Short Answer Type Questions

Question. What are the two roles of testosterone?
Answer : (i) Testosterone regulates formation of sperms.
(ii) The appearance of secondary sexual characteristics at puberty like beard, genital hair, change in voice is due to testosterone.

Question. Foetus derives its nutrition from the mother.
(i) Identify the tissue used for above purpose. Explain its structure.
(ii) Explain how wastes generated by developing embryo are removed.
(iii) How does the birth of child take place?
Answer : (i) Placenta is a disc like special tissue connection between embryo and uterine wall. It acts as an endocrine gland. It possesses villi that increases the surface area for absorption of nutrients.
Facilitates passage of nutrition and oxygen to embryo from mother through blood.
(ii) Waste substances produced by embryo are removed through placenta into mother’s blood.
(iii) Birth of child takes place after the gestation period (9 months inside the womb of mother). When the contractions in muscles of the uterine walls is at highest then the birth of child takes place by the birth canal.

Question. Name the parts A, B and C shown in the following diagram and state one function of each.
Answer : ‘A’ is anther. It contains pollen grains.
‘B’ is style. It allows growth in pollen tube up to the ovary from the stigma.
‘C’ is ovary. It contains ovules

Question. Mention the changes observed in flower after fertilisation.
Answer : (i) Ovary ripens and developed into fruit.
(ii) Ovules develop into seed.
(iii) Petals and sepals wither and drop.
(iv) Stigma, style and stamens dry up and fall off.

Question. Name the reproductive parts of an angiosperm. Where are these parts located? Explain in brief the structure of female reproductive parts.
Answer : The male reproductive part of an angiosperm is stamen. The female reproductive part is pistil/carpel, which consist of stigma, style and ovary.
Stigma: It is the site for deposition of pollen grains after pollination.
Style: It is a tube that allows growth of pollen tube to reach the ovary.
Ovary: It contains ovules that develops into seeds.

Question. What are changes seen in girls at the time of puberty?
Answer : (i) Change in voice.
(ii) Increase in size of breasts.
(iii) Appearance of hair in armpit and genital hair (pubic hair).
(iv) Widening of hips.
(v) Rapid physical growth.
(vi) Onset of menstruation.

Question. Describe the structure and function of placenta. 
Answer : Structure of placenta: It is a special disc like tissue embedded in mother’s uterine wall and connected to the foetus/embryo.
Functions of placenta: It provides a large surface area for glucose and oxygen/nutrients to pass from mother’s body to the developing/developed embryo/foetus and also helps in passing the waste from the foetus/embryo to the mother’s body.

Question. Explain what happens when:
(a) Testosterone is released in males. (b) Pollen grains falls on the stigma of flowers.
(c) Egg fuses with sperm cell. (d) Planaria is cut into many pieces.
(e) Buds are formed on notches of the bryophyllum leaf.
Answer : (a) (i) Formation of sperms and change in appearance.
(ii) Thick hair growth on face stet and pubic region and change in voice.
(b) A tube grows out of the pollen grain and travels through the style to the ovary.
(c) Zygote is formed i.e. fertilisation takes place.
(d) Each piece grows into new organism.
(e) Buds may fall on the soil and change into new organism.

Question. Why must pollination occur before fertilisation? How is pollination different from fertilisation? What does a pollen contain inside?
Answer : Pollination must occur before fertilisation as it has to reach the male gametes present in pollen grain which will germinate to form a pollen tube and carry the male gametes to the ovum. Pollination is different from fertilisation because here the pollen grain with its male gametes just reaches the stigma, whereas fertilisation of male gamete to ovum results in formation of diploid zygote which is the foundation of new generation.

Question. Differentiate between self pollination and cross pollination. 
Answer : Self pollination
(i) It involves transfer of pollen grains from anther to stigma within the same flower.
(ii) It occurs in same flower or in two flowers of same plant
(iii) Flowers should be genetically same.
Cross pollination
(i) Cross pollination is the transfer of pollen grains from anther to stigma in another flower of another plants.
(ii) It occurs between two flowers of different plants but of same species
(iii) It occurs between flowers which are genetically different.

Question. Suggest three contraceptive methods for birth control, which is essential for the health and prosperity of a country. State the basic principle involved in each.
Answer : (i) Barrier method: Condom is placed on the erect penis of male before sexual intercourse. In female, a thin rubber disc is placed in the vagina, which covers the opening of cervix.
(ii) Oral pills: Birth control pills can be taken to prevent pregnancy.
(iii) Surgical methods: Use of copper-T in females, surgically implanted at the opening of the cervix, prevents entry of sperms.
Vasectomy in males, tubectomy in females can also help in population control. In vasectomy, sperm ducts are cut. In tubectomy, oviducts are tied, blocked or cut. Sperms cannot reach the ova and thus pregnancy is avoided.

Question. Why are testes located outside the abdominal cavity? Mention the endocrine and exocrine functions of the testes.
Answer : Sperm formation takes place at a lower temperature than body temperature therefore testes are located outside the body and its temperature is 2°C below the body temperature.
Functions of Testes:
Endocrine Function: The production of testosterone hormone.
Exocrine Function: The production of sperms

Question. List three techniques that have been developed to prevent pregnancy. Which one of these is not meant for males? How does the use of these techniques have a direct impact on health and prosperity of a family? 
Answer : The three techniques which prevent pregnancy are:
(i) Barrier method, (ii) Chemical method (iii) Surgical method
Chemical methods are not for males.
The use of contraceptive have a direct effect on the health and prosperity of the family.
(i) To avoid unwanted pregnancy–if the woman is not physically or mentally prepared to bear a child her health gets adversely affected.
(ii) Contraception allows the parents to space the birth of two children and helps in family planning.
(iii) This way they can decide how many children to have and allows them to bring them up properly especially in case of limited resources. (or any other)

Question. (a) State in brief the functions of following female reproductive system
(i) Ovary, (ii) Fallopian tube, (iii) Uterus
(b) State in brief the functions of following male reproductive system
(i) Scrotum, (ii) Testes, (iii) Vas deferens 
Answer : (a) (i) Ovary: It produces ova and female sex hormones.
(ii) Fallopian tube: It is the site of fertilisation and transfer of female gamete from the ovary.
(iii) Uterus: Implantation of zygote and it keeps foetus till complete development.
(b) (i) Scrotum: It protects testes.
(ii) Testes: It produces sperms.
(iii) Vas deferens: It delivers sperms from testes to urethra

Question. List four points of significance of reproductive health in society. Name any two areas related to reproductive health which have improved over the past 50 years.
Answer : Significance of reproductive health in society are:
(i) Prevent STD (Sexually Transmitted Disease)
(ii) Advantages of small family
(iii) Less mortality among new borns
(iv) Reduces cases of maternal mortality
Two areas of Improvement are:
(i) Family planning. (ii) Decrease in STD cases.

Question. How do sperms reach the female genital tract? Where fertilisation and implantation of the embryo does take place? For how long does the embryo remain attached to uterine walls?
Answer : Sperms travel upwards through uterus to oviduct where they may meet an ovum and hence fertilise it. Fertilisation takes place in oviduct to give rise to single celled zygote. The zygote divides to become multicellular embryo which gets fixed in uterus. The embryo remains attached to uterine walls throughout gestation period which is about 40 weeks in humans

Question. List six specific characteristics of sexual reproduction. 
Answer : (i) Two parents are involved
(ii) Two dissimilar gametes are formed
(iii) Variations are produced
(iv) Occurs in higher and some of lower organisms
(v) Fertilisation is needed for zygote formation
(vi) It is a slow process.

Question. State the changes that take place in the uterus when:
(a) Implantation of embryo has occurred.
(b) Female gamete/egg is not fertilised. 
Answer : (a) When the implantation has occurred in uterus of the mother, the inner lining of the uterus thickens and is richly supplied with the blood vessels to provide nourishment to the growing embryo.
(b) If the egg is not fertilised, it lives for about one day. Since, the thickened uterus lining is no more required, it will slowly break down and come out through the vagina as blood and mucus known as menstruation which lasts for about two to eight days.

Question. Write one main difference between asexual and sexual mode of reproduction. Which species is likely to have comparatively better chances of survival – the one reproducing asexually or the one reproducing sexually? Give reason to justify your answer.
Answer : Any one of the following differences:
(i) In sexual reproduction two opposite sexes are involved whereas in asexual reproduction only one individual is involved.
(ii) In sexual reproduction male and female gametes formation take place whereas in asexual reproduction no gamete formation occurs.
• Sexually reproducing organisms have better chances of survival.
• This is because more variations are generated

Question. Write two causes of human population explosion. Explain with the help of a suitable examples how this explosion can be checked.
Answer : Two causes of human population explosion are:
(i) Reduced mortality rate due to better medical facilities.
(ii) Desire for male child.
(iii) Less awareness of birth control methods.
(iv) Illiteracy and poverty. (Any two)
Methods to check population explosion are:
(i) By using contraception methods.
(ii) Awareness among people of the advantage of small family.

Question. List three distinguishing features between sexual and asexual types of reproduction in tabular form.
Answer : Asexual reproduction
Only single parent is needed
Gametes are not produced.
Offsprings produced are identical to parent
No mixing of genetic material
It is not useful for natural selection in the evolution of species.
It is a rapid process, under proper conditions
Sexual reproduction
Two parents are involved.
Male and female gametes are produced
Offsprings are different from parent
Mixing of genetic material from both the parents.
It helps in natural selection in the evolution of species.
It is a slow process

Question. (i) Describe the role of prostate gland, seminal vesicle and testes in the human male reproductive system.
(ii) How is the surgical removal of unwanted pregnancies misused?
(iii) Explain the role of oral contraceptive pills in preventing conception.
Answer : (i) Prostate glands and seminal vesicle add their secretions so that the sperms are in a fluid state and it makes their transport easier and also provides nutrition to sperms. Testes secrete testosterone hormone which brings about changes in the appearance in the boys at the time of puberty.
(ii) Female foeticides/illegal sex selected abortion of female child.
(iii) Interfere in release of egg and eggs are not released.