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Slide 1 : How do Organisms Reproduce

Introduction : Introduction Reproduction is defined as the production of new individuals of the same species that is the next generation of the species from an existing individual. This is one of the fundamental characteristics of living things; it is not an essential life process.

Slide 3 : Reproduction is necessary to maintain the number of individuals of a species or to prevent their extinction. Variations Organisms look similar because their body designs are similar. If body designs are to be similar, the blue prints for these designs should be similar. Thus, reproduction involves making copies of the blue prints of body design.

Slide 4 : The chromosomes in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA (Deoxyribo Nucleic Acid) molecules. The DNA in the cell nucleus is the information source for making proteins. If the information is changed, different proteins will be made. Different proteins will eventually lead to altered body designs.

Slide 5 : A basic process even in reproduction is the creation of a DNA copy. Cells use chemical reactions to build copies of their DNA. The process of copying DNA will have some variations each time due to some mistakes created by replication machinery during the copying process. The DNA copies generated will be similar but may not be identical to the original.

Slide 6 : The Importance of Variation The consistency of DNA copying during reproduction is important, which leads to the stability of population species. The organisms maintain their body designs and this helps the organism to exist in a particular niche.

Slide 7 : Changes in ecological system, which are beyond our control like varying temperature, varying water levels and natural calamities, can wipe out the population species. So if there is some variations are present in some individuals of the population species then there is a chance for the survival of these species over time.

Methods of Reproduction : Methods of Reproduction Asexual Reproduction A type of reproduction which does not involve the fusion of two sex cells (gametes). Only one parent is involved in this kind of reproduction. Sexual Reproduction It is characterized by the fusion of a male and a female reproductive cell or gamete. It involves two parents—a male and a female parent.

Slide 9 : All organisms are made up of cells. The cells are of two types: (1) Vegetative (2) Reproductive Vegetative cells are those that are present everywhere in the body of the organism whereas reproductive cells are those that are present in the reproductive structures and are associated with sexual reproduction.

Slide 10 : The vegetative cells only show mitotic division where the number of chromosomes in every division remains the same (diploid). However, the reproductive cells show mitotic and meiotic division. Meiotic division results in the formation of gametes that have only half the number of chromosomes (haploid). Each mitotic division results in two daughter cells whereas meiotic division results in four daughter cells that are called gametes.

ASEXUAL REPRODUCTION : ASEXUAL REPRODUCTION Asexual reproduction is the production of new individuals by mitotic divisions from a single parent. It does not involve the fusion of gametes or sex cells. There are many types of asexual reproduction, all producing individuals that are genetically identical to the parent.

Slide 12 : Types of Asexual Reproduction Fission, Budding, Spore formation, Regeneration, Fragmentation, Vegetative propagation

Fission : Fission This type of reproduction is of two types Binary fission Multiple fission Fission occurs in lower plants and animals such as the bacteria, blue-green algae and protozoa.

Slide 14 : Binary fission In this process, the cell divides after the genetic material has divided. If the cell divides into two it is called binary fission. The DNA or the nucleus of a mature cell divides first and then the cell divides into two daughter cells of almost the same size. It is seen in bacteria and protozoans like amoeba, leishmania and paramoecium.

Slide 15 : Amoeba attains a fully grown size and it divides to form two daughter cells forming daughter amoeba. These feed and again grow in size. When fully grown they again divide. When the division occurs through transverse plane it is known as transverse fission.

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Slide 18 : Binary Fission

Slide 19 : Leishmania causes kala azar. The animal has flagella at one end and it divides by binary fission in longitudinal plane thus such a type of fission which occurs in longitudinal axis is also known as longitudinal fission. It is type of binary fission.

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Slide 21 : Multiple fission If the parent cell divides into many daughter cells, it is called multiple fission. It is seen in the life cycle of the protozoa, plasmodium (the malarial parasite). The nucleus divides many times and then the cytoplasm divides and surrounds the nuclei. The parent cell may get covered by a protective coat called the cyst under unfavourable conditions.

Slide 22 : The nucleus divides multiple times to form daughter nuclei with a little cytoplasm around each nuclei. Thin membranes are formed around these small cells and when the favourable conditions arrive the cyst bursts to release the daughter cells. Multiple fission is also seen in Chlamydomonas, an alga.

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Slide 24 : Multiple Fission

Budding : Budding It is seen in certain fungi and multicellular animals. In budding, the parent cell or body gives out a lateral outgrowth called the bud. The nucleus divides and one of the daughter nuclei passes into the daughter cell. The bud grows in size while being attached to the parent body. It then gets separated from the parent by the formation of a wall. It then falls off and germinates into a new individual.

Slide 26 : Thus budding results in the formation of daughter cells of unequal sizes that later grow to adult size. For example, yeast, a fungus and Hydra, a coelenterate animal. In case of hydra, the bud develops as a result of multiple divisions and the daughter hydra even develops hypostome and tentacles develop around the hypostome before being detached from the parent body.

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Spore Formation : Spore Formation Spores are microscopic asexual reproductive bodies which are covered by a hard protective coat. The presence of hard coat enables the spores to survive in unfavourable conditions. These develop into new individuals when favourable conditions arrive. They are light weighted and microscopic and thus float in air. It is generally seen in bacteria and most fungi.

Slide 30 : One of the cells enlarges and forms the sporangium or spore sac. In multicellular forms sporangia are borne on sporangiophores or the stalk of the sporangia. The nucleus divides many times and then the daughter nuclei are surrounded with protoplasm bits to form daughter cells called spores. The spores are covered with a thick wall called the cyst.

Slide 31 : On maturation, the sporangium bursts and releases the spores. The spores germinate on getting favourable conditions. For example, fungi such as Mucor and Rhizopus (bread mould)

Slide 32 : A Sporangium

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Fragmentation : Fragmentation It takes place in some lower plants and animals such as some worms. The mature organism breaks up into two or more pieces or fragments. The fragments then grow into complete organisms. For example: Spirogyra, an alga and worms such as ribbon-worms (Nemertinea) and flatworms (Turbellaria). Fragmentation takes places in hydra, planaria, sea anemone and sponges. The fragments regenerate to form an entire individual.

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Regeneration : Regeneration Regeneration is one of the methods of asexual reproduction in lower or less evolved animals where the body has relatively simple organization and only very few specialized cells. When the parent body breaks into pieces, each piece can grow into a new organism. It is the process of developing into a fully grown organism from its body parts e.g. Hydra and Planaria.

Slide 37 : Regeneration occurs by the process of growth and development by some specialized cell. This happens as follows: The cells of the cut body part divide rapidly to form a ball of cells. This process is called as wound healing. The cells from the ball of cells move to their proper places within the ball where they have to form various organs and body parts. This is called as dedifferentiation. The cells then change their shape and differentiate to form specific tissues. This process is known as redifferentiation. At the end of this process a new individual is formed

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Vegetative Reproduction : Vegetative Reproduction Regeneration of new plants from the vegetative parts of the parent plant is called vegetative propagation or vegetative reproduction. Vegetative propagation is done with the help of vegetative parts such as roots, stem or leaves. These parts may also be variously modified for vegetative propagation.

Slide 40 : Example-Vegetative Propagation by Leaves This is not very common and is seen in plants such as Bryophyllum. It has succulent (fleshy) leaves and adventitious buds present at the margins of the leaves. These buds fall off and grow into new plants.

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Tissue Culture : Tissue Culture Tissue culture is the propagation of plants in artificial lab conditions in artificial growth medium. Tissue culture is based on the concept of cellular totipotency. That is all the multicellular organisms basically are formed from a single cell (the zygote), by repeated multiplication and differentiation. Thus a single cell can develop into a whole organism or in other words, the cell is totipotent.

Slide 46 : This is because it contains the full set of genetic information needed to make the organism. This is called cellular totipotency. Thus, a tissue can be taken from any part of the plant (explant) and put in a suitable nutrient medium. The nutrient medium is jelly-like and is taken in a test-tube. The tissue starts dividing mitotically and produces a mass of cells. This structure is undifferentiated and is called the callus (The undifferentiated mass of cells obtained from the single cell is called the callus.).

Slide 47 : Differentiation refers to the formation of different tissues like the roots, stem, leaves, etc. The callus is transferred to other medium that contains different hormones for differentiation to occur. This differentiated mass of tissue is called the embryoid which grows into the new plantlet. The plantlets are then planted in pots and then in the fields. A single cell can also be separated and cultured to give rise to a new plantlet. This is called cell culture.

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Sexual Reproduction : Sexual Reproduction In the higher organisms, sexual reproduction involves the production of sex cells or gametes and their subsequent fusion to produce a new individual. Whether plant or animal, sexual reproduction follows a basic pattern. The organisms that follow sexual reproduction have the specific reproductive organs.

Slide 50 : The reproductive organs produce the haploid sex cells (half number of chromosomes than normal cells) called the gametes by the process of meiosis. There are two types of gametes - male and female. Male gametes are called sperm cells and the female gametes are called ova or eggs. The eggs are bigger as they contain the reserve food for the growing embryo.

Slide 51 : The male reproductive organs produce the sperm cells and the female reproductive organs produce the eggs. The organisms that have only the male reproductive organs are called the males and those with the female reproductive organs are called the females. Such type of organisms where the male and female reproductive organs are on different individuals are called dioecious or monosexual.

Slide 52 : There are certain organisms which have both the male and female reproductive organs in the same organism. These organisms are called monoecious or bisexual. Both the male and female gametes fused to form a single cell that is zygote. Zygote is the first cell in the whole process of development of an organism. Zygote develops into an embryo and then into whole organism.

Slide 53 : This offspring produced is different from its parents. The following factors are responsible for these variations: The genes present in progeny are the mixture of two different parents. The gametes carry variations already accumulated in previous generations. Recombination process in which new arrangement of genes arise during the process of meiosis or gamete formation. The chromosomes exchange their material and new combination of characters arises.

SEXUAL REPRODUCTION IN PLANTS : SEXUAL REPRODUCTION IN PLANTS The plants that sexually reproduce have the reproductive structures called the flowers. The flower is a condensed shoot with the nodes present very close to each other. The different parts of the plant are attached to the nodes.

Slide 55 : All the structures present at one node are collectively called the whorl. The first or the outermost two whorls are called the non-reproductive whorls. They are the calyx and corolla. The inner two whorls are androecium and gynoecium, the reproductive whorls.

Flower : Flower Calyx is the outermost and most often green in colour. The individual units of calyx are called the sepals. It protects the inner whorls at bud stage. Corolla is the next inner whorl and is often coloured brightly. The individual units of corolla are called petals. They serve to attract bees, birds, etc which are the agents of pollination.

Slide 57 : Androecium is the male reproductive part of the flower. The individual units of androecium are called the stamens. Each stamen has a thread-like filament at the free end of which is attached the four-lobed anther. The anther has four pollen-sacs, one in each lobe. The pollen-sacs contain cells microspores, also called the pollen grains. Each microspore divides once mitotically to produce two male gametes or sperm cells.

Slide 58 : Gynoecium is the female reproductive part of the flower. The individual units are called the carpels or pistils. Each carpel is made up of the basal ovary, middle style and the upper stigma. The ovary is the chamber where there are many ovules that are attached to an axis.

Slide 59 : Each ovule consists of a haploid egg, two polar nuclei and other associated cells. The stigma is a sticky structure that receives the pollen grains. The style is hollow and provides a passage for the male gametes to reach the female gametes, the eggs.

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Slide 63 : Pollination Transfer of pollen grains to the stigma is called pollination. If the pollen grains are transferred to the stigma of the same flower, the pollination is called self-pollination or autogamy. If the pollen grains are transferred to the stigma of another flower of the same species, the pollination is called cross-pollination or allogamy.

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Slide 65 : Fertilisation On reaching the stigma, the pollen grains put out a tube. This is called germination of the pollen grain. Male gamete reaches to the ovular part of the ovary through this tube and then two processes are occur: Syngamy Double Fertilization

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Slide 67 : The fusion of the one male gamete with the female gamete(egg) is called fertilization or Syngamy. This results in the formation of zygote that is diploid. The zygote develops into the embryo. The other male gamete fuses with the polar nuclei. This result in the formation of a triploid nucleus called the endosperm nucleus. Since the process of fertilisation involves two fusions, it is called double fertilisation.

Slide 68 : The divisions of the endosperm nucleus result in the formation of the endosperm that nourishes the growing embryo. The ovule then becomes the seed and the ovary changes into fruit. Male gamete + Egg Cell =Zygote (Form Embryo) Male Gamete + 2 Polar nuclei =Endosperm Nucleus

Slide 69 : After fertilization the Ovary develops into the fruit. The ovules develop in to seeds. The zygote develops into the embryo of a seed. The rest of the parts of the flower like sepals, petals, stamens, stigma and style of carpel wither away.

Human Reproduction : Human Reproduction The human beings are unisexual with two separate sexes - male and female. Puberty The individuals of the two sexes show distinctive features called the secondary sexual characteristics. Some of the male secondary sexual characteristics are facial hair, cracking of voice, etc.

Slide 71 : Female secondary sexual characteristics include development of breasts, broadening of hips, etc. Such distinguishing features are present in all the animals. These characteristics serve to identify and attract sex partners

Male Reproductive System : Male Reproductive System A pair of testes, organs that produce the male gametes i.e., sperms A network of tubules and tubes for passage of the sperms called the duct system Associated glands A mating organ called the penis.

Slide 73 : Testes The male reproductive system comprises of a pair of testes that are present in a thin-walled sac called the scrotum. The scrotum is contained within the abdominal cavity in the embryonic stage. Shortly before birth, they come down and remain outside throughout life. This is because the testes cannot produce sperms at the body temperature. A temperature 2-3 degrees lower is ideal for the production of sperms.

Slide 74 : Each testis is covered by a thick connective tissue layer. Internally, the testis is lobed. There are 15-20 lobes, each having a network of seminiferous tubules and the interstitial cells between the tubules. The seminiferous tubules produce sperms that are passed along the tubules to the posterior region of the testis. The sperms are produced by a process called the spermatogenesis.

Slide 75 : The interstitial cells are also called the Leydig cells and they secrete the hormone testosterone. In addition they also form a packing tissue between the seminiferous tubules.

Slide 76 : Duct System From the seminiferous tubules, the sperms are passed into a network of 10-12 ducts called the efferent ducts or the vasa efferentia. They are then passed into a highly coiled tubular part called the epididymis. Epididymis is an organ that extends from the top of the testis along its side to its back.

Slide 77 : The sperms from the epididymis pass into a distinct tube called the vas deferens, also called the sperm duct. Vas deferens is also coiled though not much. It rises into the abdominal cavity and loops over the ureter of that side. Vasa deferens connect to a tube originated from urinary bladder and opens combinely into penis.

Slide 78 : Glands The various glands associated with the male reproductive system are as follows: Seminal vesicles Prostategland Cowper's glands Penis glands Secretions from these glands nourish the sperm, lubricate their passage and provide suitable medium for fertilization.

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Human male reproductive tract : Human male reproductive tract See Fig. 46.10

Human male reproductive tract : Human male reproductive tract Testes (in scrotum) Sperm Testosterone See Fig. 46.10

Slide 82 : Accessory structures Seminal vesicles Prostate gland Bulbourethral gland (together produce semen) See Fig. 46.10

Human male reproductive tract : Human male reproductive tract Accessory structures Epididymis (sperm storage) See Fig. 46.10

Testes produce sperm & testosterone : Testes produce sperm & testosterone Sperm production occurs in seminiferous tubules See Fig. 46.12

Testes produce sperm & testosterone : Testes produce sperm & testosterone Sperm production occurs in seminiferous tubules At puberty, testosterone production begins in interstitial cells See Fig. 46.12

Testes produce sperm & testosterone : Testes produce sperm & testosterone Sperm production occurs in seminiferous tubules Sertoli cells regulate sperm production & nourish developing sperm See Fig. 46.12

Testes produce sperm & testosterone : Testes produce sperm & testosterone Sperm production occurs in seminiferous tubules Spermatozoa are produced by spermatogonia See Fig. 46.12

Human sperm – almost no cytoplasm; carries male DNA to egg DNA : Human sperm – almost no cytoplasm; carries male DNA to egg DNA Head Nucleus – DNA Acrosome – Enzymes See Fig. 46.12

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Slide 90 : Penis Penis is a muscular organ containing erectile tissue. The tissue is richly supplied with blood vessels. On sexual stimulation the penis is gorged excess with blood which causes it to become erect. During sexual intercourse, the penis is inserted into the vagina of the females before ejaculation. Ejaculation is the release of sperms by the penis to the outside.

Female Reproductive System : Female Reproductive System The female reproductive system consists of a pair of ovaries, a pair of oviducts, uterus, vagina and vulva. The main functions of the female reproductive system are to produce eggs, receive the sperms, provide the site for fertilisation, implantation of the growing embryo and development of the foetus. It also produces hormones that control the various stages of ovulation and maintenance of pregnancy.

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Slide 93 : Ovaries They are a pair of oval structures that are present one on either side. The ovaries produce eggs, one at a time, every alternate month. The eggs are produced by the germinal epithelial cells of the ovary.

Slide 94 : Oviducts Oviducts/Fallopian tubes are a pair of tubes of about 12cm in length. They run from the ovaries of each side to the uterus. At the ovarian end the tube is funnel-shaped with the end of the tube thrown into number of folds. These folds are ciliated which help to sweep the egg produced by the ovary into the fallopian tube. The fallopian tubes are the sites for fertilisation of the egg by the sperms.

Slide 95 : Uterus Uterus is a pear-shaped structure, broader on the upper end and narrower on the lower end. The upper end is called the body of the uterus and the lower end is called the cervix. At the upper end, it receives the oviducts of either side whereas the lower end the cervix opens into the vaginal canal that opens to the outside.

Slide 96 : Vagina Vagina is a 9cm long muscular tube that receives the penis during copulation. It is lined with epithelial cells. The secretions of the vaginal canal are acidic which is not conducive to the sperms as semen is alkaline.

Human female reproductive tract : Ovaries Eggs Estrogen / progesterone Accessory structures receive & move sperm to egg & nourish developing embryo Vagina – receives sperm Fallopian tubes – sites of fertilization Uterus – site of development of embryo fimbriae cervix Fallopian tubes, a.k.a. uterine tubes, a.k.a. oviducts ovary uterus vagina Human female reproductive tract See Fig. 46.9

Menstrual Cycle : Menstrual Cycle The menstrual cycle is linked with the periodical release of eggs from the ovary. The cycle is of 28 days. The release of egg from the ovary is called ovulation. Before the release of an egg, the wall of the uterus becomes thick. There is an increased blood supply to prepare the uterus to receive the fertilized egg. If the ovum is fertilized it gets implanted in the uterus

Slide 99 : If it is not fertilized, it is thrown out of the body through the vagina along with the lining of the uterus and blood. This outflow of blood with tissue is called menstruation. It lasts for 3 to 5 days. The menstrual cycle continues as long as a woman is reproductively active. It usually stops around the age of 45-50. This is called menopause.

Slide 100 : Fertilization The mature ovum is released from the ovary into the fallopian tube. When sperms are released into the female reproductive system, they move towards the ovum. Only one of these sperms fuse with the egg. The fusion of male and female sex cells is called fertilization.

Slide 101 : Fertilization takes place in the fallopian tube. The fertilized egg is called zygote. After fertilization, the zygote fixes itself to the wall of the uterus and starts developing as the embryo.

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Slide 103 : Sperm Sperm OVA Sperm Sperm Sperm

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Slide 106 : Development The fertilized egg develops into the embryo by repeated division. Initially, the zygote receives its nourishment from the yolk surrounding it. But as it grows and the requirement of food increases, it develops a cellular connection called placenta with the mother's body. The placenta is connected to the embryo by a tubular cord called umbilical cord.

Slide 107 : Blood vessels in the umbilical cord bring in nutrients and oxygen from the mother's blood to the embryo and take away the waste carbon dioxide and other wastes from the embryo to the mother's blood. The full term development of the embryo in the uterus is called gestation or pregnancy. In humans it lasts for about 280 days or a little over 9 months.

Slide 108 : The embryo develops into a baby before it comes out of the mother's body. After the body has been fully developed, the uterus wall contracts, pushing the baby out of the uterus through the vagina, and the child in born.

Slide 109 : FOETAL POSITIONS AND STAGES

Reproductive Health : Reproductive Health Sexual Transmitted Diseases The common diseases are syphilis and gonorrhoea. Syphilis is characterized by sores around the anus, vagina, penis, lips, fingers, nipples, etc. In the later stages it results in fever and skin rashes. If untreated, it can result in insanity, heart damage or blindness.

Slide 111 : Gonorrhoea is characterized by yellow discharge from urethra and burning sensation while passing urine. In females it affects the uterus and the fallopian tubes. It can result in sterility.

Slide 112 : Both syphilis and gonorrhoea are extremely infectious diseases. They spread through sexual contact. Indulging in unsafe and promiscuous sex with a person having frequent and diverse sexual relationships, esp. transient ones. Sexual relationships of this kind increases the risk of infection. Both diseases can be cured by antibiotics.

Slide 113 : AIDS It is the most serious and challenging health problem confronting the world today. It is also a sexually transmitted disease. AIDS stands for Acquired Immuno Deficiency Syndrome. It is caused by human immuno deficiency virus (HIV).

Slide 114 : It spreads through transfer of bodily fluids such as blood and semen. Thus the main causes are unprotected sexual activities, use of infected needles or transfusion of infected blood. The virus affects the immune system of the body by inactivating the white blood cells. This results in loss of resistance against infections. It is a fatal disease.

Population Control : Population Control Increasing population is a serious issue, particularly in developing countries. It is necessary for every generation to produce more off springs because many individuals do not survive to reach the reproductive age due to natural causes. However, man has upset this equation as he has been successful in bringing down the mortality rate.

Slide 116 : But a simultaneous decrease in the birth rate is also essential to maintain the balance in nature. Since this has not happened, there has been a tremendous increase in the population of human beings and also the animals and plants useful to them. This has created a strain on the natural resources that are shared by all creatures on earth.

Slide 117 : Having understood so much about the reproductive system, it is necessary to learn the possibilities of preventing and planning pregnancies. The need of the hour today is that every couple should understand that pregnancies can be prevented and that it is very important to plan them. This is called family planning.

Slide 118 : It involves restricting the number of children to two and spacing children by maintaining a gap of minimum three years between two children. This gives each child enough attention, nutrition and education.

Slide 119 : There are various ways in which pregnancy can be planned or prevented. Some of them are: Mechanical methods Hormonal methods Natural methods Sterilisation

Mechanical method : Mechanical method In this type of contraception, a physical barrier is placed to prevent the entry of sperms into the uterus. It includes condoms (such as Nirodh) used by males, intrauterine device (IUD) and diaphragm cap used by females. IUD is commonly called loop and copper T is inserted by a doctor into the uterus to prevent the implantation of the fertilized egg.

Hormonal method : It involves the intake of synthetic hormones by the females to prevent ovulation. These are called oral contraceptive pills and have to be taken as per doctor's advice. Hormonal method

Natural Method : Natural Method Total avoidance of sexual intercourse or abstinence is, of course, the only sure contraceptive method. However, there is a rhythm method which involves avoiding intercourse during the time of ovulation that is for about a week. However rhythm method is not a reliable method.

Sterlization : Sterlization Sterilisation is a surgical procedure that involves cutting of the tubes that conduct the gametes. In males it is called vasectomy in which each vas deferens is cut and the cut ends are tied back. In females, it is called tubectomy in which the oviducts are cut and the cut ends are tied back. Both the procedures are reversible to some extent. They are as good as permanent methods of prevention of pregnancy.

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Slide 125 : Thank You