CBSE Class 10 Science Reproduction Assignment

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.

(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.

(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

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

(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.

(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.

REPRODUCTION IN A FLOWERING PLANT :

(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 :
• It is located in the center of a flower.
• It is composed of one or more carpals.
• The freely occurring units of the carpals in a flower are called pistils.
• 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.

(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 :
• It maintains purity of race.
• 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.
• The transfer of pollen grains occurs through various ways, which may be biotic or abiotic.

(i) Abiotic factors       Technical terms
            Wind                    Anemophily
            Water                   Hydrophily

(ii) Biotic           factors
      Insects        Entomophily
      Birds           Ornithophily
      Bats            Chiropterophily
      Snails          Malacophily.

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.

(c) Fertilization is a Flowering Plant :
• Fertilization is a process of fusion of male gamete with the female gamete.
• The process of formation of male gametophyte in case of plants is called as microsporogenesis.
• The process of formation of female gametophyte in case of plants is called as megasporogenesis.
• The process of pollination occurs, due to which the anther get stuck up to the stigma.
• After reaching to stigma pollen grains develops a pollen tube.
• This pollen tube grown through the length of style, from where it reaches to ovule.
• Pollen tube comprise of two male gametes, which is later on released in the embryo sac through an opening called as micropyle.
• 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.
• 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.”
• 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.

• After fertilization sepals and petals fall and zygote undergoes a series of mitotic division to from a multinuclear embryo.
• 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.

DIFFERENCES BETWEEN SELF POLLINATION AND CROSS POLLINATION

SEXUAL REPRODUCTION IN HUMANS :
• Mammals are unisexual.
• Reproductive system of each organism consists of many reproductive organs.
• These can be primary sex organs or secondary sex organs.
• The primary sex organs are called as gonads. They produce sex cells or gametes and also secrete sex hormones.
• The gonads of males are called a testis, which produce sperms.
• The gonads of females are called as ovaries, which produce ova or female gametes.
• 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.
• e.g., In males : Vasa efferentia, epididymis, seminal vesicles, ejaculatory duct, urethra etc. In females : Fallopian tube, uterus, vagina, mammary glands etc.
• Accessory or external sec characters help to distinguish the two sexes of a species externally.
• e.g., In male : Muscular body, more height, low pitched voice, moustaches etc. In female : High pitched voice, breast development, lateral pubic hairs etc.
• Puberty : Beginning of sexual maturity is known as puberty.
• At this stage primary sex organs start functioning.
• Secondary sex organs develop dully under the influence of sex hormones produced by primary sex organs.
• In the stage of puberty body growth is very rapid.
• It occurs at the age of 10 - 14 years in girls and 13 - 15 years in boys.

(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 : 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.
• It’s inner covering is called as tunica albuginea.
• Ingrowths of tunica albuginea are called as septa, that divide the testis into 200-300 lobules.
• It also consist of convoluted somniferous tubules.
• These somniferous tubules at one end join to form tubules which open into a network of irregular cavities known as rete testis.
• This rete testis comes out from a dorsal surface of the testis with the help of vesa efferentia.
This vasa efferentia combines to form a single tube which becomes highly coiled and from epididymis.
• This vasa efferentia combines to form a single tube wihich becomes highly coiled and form epididymis.
• Epididymis peon into a narrow tube vas deferens.
• Somniferous tubules from the spermatogenic tissue of the testis.
• It consists of a germinal epithelial layer at the periphery. Spermatogenesis occurs at the center.
• 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.
• The later (i.e. spermatids) metamorphose into spermatozoa.
• This process of formation of spermatozoa from spermatogonia is called as spermatogenesis.
• 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.
• It is divided internally into two compartments by a muscular partition called as septum scroti.
• Scrotum possesses smooth involuntary dortus muscles.
• Scrotum sac is connected to the abdominal cavity through inguinal canal.
• Function of dortus muscle is to change the position of testis to keep them at proper temperature.
• Scrotum has temperature 1 - 3 lower than body temperature which favours the formation of sperms.
• 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 : Vasa efferentia from epididymal duct finally opens into vas deferens.
• It comes out through inguinal canal passing over urinary bladder to receive ducts from seminal vesicles.
• 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.

(b) Semen :
it is milky, viscous and alkaline fluid, ejaculated by reproductive system of males during copulation
• It’s quantity is 2.5 - 4.0 ml at a time having about 40 million sperms.
• Semen has chemical for nourishment of sperms neutralizing the acidity of urethra and vagina, stimulating their movement in female tract.
• Spermatogenesis starts at puberty under the influence of gonadotropin secreted from anterior pituitary gland.

(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.

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.
• Ovary is covered by two layers outer is made up of germinal epithelial cells.
• Inner layer is called as tunica albuginea which is made up of fibrous connective tissues.
• The ovary consists of inner part called as stroma.
• It’s outer peripheral pat is called as cortex while inner part is called a medulla.
• Medulla consists of connective tissues containing numerous blood vessels, lymphatic vessels and nerves.
• Cortex consists of graffian follicles in all the stages of development.
The developing oocyte is called as primary oocyte
This primary follicle undergoes maturation to form secondary follicle or secondary oocyte
It later on forms follicular layer
This follicular layer undergoes mitotic division to form secondary egg membrane.
This stage is called as secondary follicle
This is called as graffian follicle

FLOW CHART SHOWING THE FORMATION OF GRAFFIAN FOLLICLE
• 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.
• It is situated in a pelvic cavity.
• It is attached to the fallopian tube from the sides and below it opens into vagina through cervix.
• 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 :
• Bartholin’s gland : it secretes a clear, viscous fluid under sexual excitement.
• The fluid serves as a lubricant during copulation or mating.

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

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

(ii) Proliferative phase :
• In this phase F.S.H. stimulate development and maturation of graffian follicles.
• In this phase oestrogen level rises which leads to formation of new endometrium.
• It lasts for about 10 - 14 days. Thinnest endometrium is found in this phase.
• It is also called as follicular phase.

(iii) Ovulation phase :
• At this phase ovulation occurs.
• Ovulation occurs in the presence of FSH and LH.
• Thicket endometrium found in this stage.
• It also lasts for about 14 days.

(iv) Secretory phase :
In this sage both oestrogen and progesterone levels are high.
• If fertilization takes place, this stage extends till to the parturition (giving birth to a child)
• If, fertilization does not take place, this stage completes on 28th day of menstrual cycle.
• The commencement of menstruation of puberty is called as menarche.
• It’s stoppage around the age of 50 years is called as menopause.
• The period between menarche and menopause is the reproductive phase in human female.

(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.

FERTILIZATION :
• It included release of ovum from the ovary, where it remains viable for 12 - 24 hours.
• At the time of sexual intercourse the sperm enters in to the vagina.
• Only one sperm is required for fertilization of the ovum.
• The head of the sperm penetrates the corona radiate layer of ovum and then the zona pellucida layer.
• This process if facilitated by acrosome and proteolytic enzymes.
• After penetration the tail and body of the sperm is lost, only head remains inside the ovum.
• It’s head begins to swell and forms male pronucleus.
• 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. Sperm
With the help of acrosomes & proteolytic enzymes enter the ovum
Tail & body of the sperm is lost after it’s entry in the ovum
Head of sperm swells up to form male pronucleus
This male pronucleus fuses with female pronucleus
Forms a new resultant nucleus with 46 chr. Each contributing about 23 of chromosomes.
Zygote Embryo
• Fusion of male & female gametes is called as fertilization. Zygote starts developing in fallopian tube and forms embryo, this later on moves to uterus. It gets attached to uterine walls and the whole process is called as implantation
• Placental formation occurs between uterine wall and the foetus, which provides nourishment to the foetus.
• 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.
• The process of giving birth to baby is called as parturition.

ARTIFICIAL INSEMINATION :
• It is a technique to make a female pregnant by artificially introduction semen into vagina.
• In this process semen from a good quality male is collected, preserved by freezing and used when required.
• In case of humans it is also being used for improving the chances of fertility.
• 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.
• In this case husband’s semen is collected, concentrated and introduced artificially into the wife’s vagina. this is called as artificial insemination.
• If the husband’s sperms are faulty, some donors sperm can be used. This is called as artificial insemination donor.

Artificial insemination has following two advantages.
(i) Semen of good quality male animal is used to inseminate a umber of females.
(ii) Preserved semen can be transported to distant places, excluding the need for sending the male animal there.

Differences between asexual and sexual reproduction

POPULATION GROWTH:
• The term population refers to the total number of individuals of a species occupying particular geographical area at a given time.
• 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

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 : They involve use of condoms.
• Use of cervical or diaphragm cap which is fitted in the vagina that checks the entry of sperms.
• 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.

Question. Cleistogamous condition is present in
(a) Brassica oleracea
(b) Solanum tuberosum
(c) Arachis hypogea
(d) Allium cepa

Answer: C

Question. Graffian follicles are found in
(a) testis of mammas
(b) ovary of frog
(c) ovary of cockroach
(d) ovary of mammals

Answer: D

Question. Which of the following regenerated with the help of layering?
(a) Cactus
(b) Rose
(c) Mango
(d) Jasmine

Answer: D

Question. Development of egg without fertilization is
(a) parthenocarpy
(b) polyembryo
(c) parthenogenesis
(d) adventive embryony

Answer: C

Question. Site of fertilization in mammals is
(a) ovary
(b) uterus
(c) vagina
(d) fallopian tube

Answer: D

Question. Anemophily is pollination by
(a) air
(b) water
(c) insects
(d) animal

Answer: A

Question. The process of reproduction which involves only a single parent to form an individual
(a) sexual reproduction
(b) asexual reproduction
(c) none of these
(d) Both A & B are correct

Answer: B

Question. Pollination between different flowers of same plant is called
(a) autogamy
(b) geitonogamy
(c) allogamy
(d) xenogamy

Answer: B

Question. Cowper’s glands are found in
(a) male mammals
(b) female mammals
(c) male amphibians
(d) female amphibians

Answer: A

Question. Double fertilization is
(a) fusion of two male gametes with egg
(b) fusion of one male gamete with egg and the other male gamete with the polar bodies
(c) both are correct
(d) both are incorrect

Answer: B

Question. Loss of reproductive capacity in women after age of 45 years is
(a) menstruation
(b) ageing
(c) menopause
(d) menarche

Answer: C

Question. The structure meant for the nourishment of developing embryo in case of plant is
(a) pollen tube
(b) endosperm
(c) both A & B are correct
(d) none of these

Answer: B

Question. Release of oocytes from ovary is
(a) gestation
(b) ovulation
(c) parturition
(d) implantation

Answer: B

Question. The embryo sac of a typical dicot at the time of fertilization is -
(a) 8 called
(b) 7 celled
(c) 6 called
(d) 5 celled

Answer: B

Question. Acrosome is made up of
(a) mitochondria
(b) centrioles
(c) golgi bodies
(d) ribosomes

Answer: C

Question. The genetic information is stored in -
(a) DNA
(b) RNA
(c) Ribosome
(d) ER

Answer: A

Question. Acrosome aids the sperm to
(a) penetrate vitelline membrane of ovum
(b) find ovum
(c) swim
(d) higher activity

Answer: A

Question. Each female flower consist of
(a) ovary
(b) stigma
(c) ovary, style and stigma
(d) thalamus

Answer: C

Question. In mammals, the testes lies in scrotal sacs due to
(a) presence of urinary bladder
(b) presence of rectum
(c) long vas-deference
(d) requirement of low temperate for spermatogenesis

Answer: D

Question. Progesterone is secreted by
(a) corpus luteum
(b) thyroid
(c) thymus
(d) testis

Answer: A