Past Entrance Papers

Hint

[NCERT pg 44]

Natural methods work on the principle of avoiding chances of ovum and sperms meeting. Periodic abstinence is one such method in which the couples avoid or abstain from coitus from day 10 to 17 of the menstrual cycle when ovulation could be expected. As chances of fertilisation are very high during this period, it is called the fertile period. Therefore, byabstaining from coitus during this period, conception could be prevented. Withdrawal or coitus interruptus is another method in which the male partner withdraws his penis from the vagina just before ejaculation so as to avoid insemination. Lactational amenorrhea (absence of menstruation) method is based on the fact that ovulation and therefore the cycle do not occur during the period of intense lactation following parturition. Therefore, as long as the mother breast-feeds the child fully, chances of conception are almost nil. However, this method has been reported to be effective only upto a maximum period of six months following parturition. As no medicines or devices are used in these methods, side effects are almost nil.

Hint

[NCERT pgno 44]

The correct option is \(\mathrm{C} a-2, b-3, c-4, d-1\)
Non-medicated IUD- Lippes loop Non-medicated IUDs work by immunomodulating the environment of the uterus. It initiates a sterile inflammatory response in the uterus which stimulates accumulation of macrophages. This results in the phagocytosis of the sperms. Examples include Lippes loop.

Copper releasing IUD- Multiload 375 Copper releasing IUDs releases copper ions in the uterus which suppress the motility and fertilising ability of sperms and prevent fertilisation. Examples include CuT, Cu7, Multiload 375.

Hormone releasing IUD- LNG-20 Hormone-releasing IUDs release hormones such as progesterone in the uterus which make the cervix hostile by making the mucus thick and sticky due to which sperm are not able to reach the uterus. Besides, it makes the uterus unsuitable for allowing implantation. Examples include LNG-20 and progestasert.
Barrier contraceptive methods- Vaults Barrier contraceptive methods prevent the physical meeting of sperm and ovum. Examples include condoms, diaphragms, cervical caps etc. Vault is a barrier used by the females to cover their cervix during coitus to prevent fertilisation.

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Answer (3)

(i) Vasectomy is a surgical method of contraception
(ii) Coitus interruptus is a natural method of contraception
(iii) Cervical cap is a barrier method of contraception
(iv) Saheli is an oral method of contraception which is a non-steroidal pill

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Answer (3)
Sol. Option (3) is the correct answer because the intrauterine device (IUD) presently available as the nonmedicated IUDs, is Lippe’s loop.
Option (4) is incorrect as copper releasing IUDs are CuT, Cu7 and multiload 375.
Option (1) and (2) are incorrect as diaphragms, cervical caps and vaults are included in barrier method of contraception.

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Answer (2)

Sol. Option (2) is the correct answer because
Diaphragms are barrier methods of contraception. They cover the cervix and block the entry of sperms.
– Contraceptive pills are preparations containing either progestogens alone or combination of progestogen and oestrogen. They inhibit ovulation and implantation as well as alter the quality of cervical mucus to prevent entry of sperms.
– Intra uterine devices increase the phagocytosis of sperms within the uterus.
– Lactational amenorrhoea is a natural method of contraception and it is based on the fact that the ovulation and therefore menstrual cycle do not occur during the period of intense lactation following parturition.

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(d)

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(d) : Copper releasing IUDs (i.e., CuT, LNG-20) are placed in the uterus of the females. They are an efficient birth control methods. Copper ions released by them suppress motility and fertilising capacity of the sperms.

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(b, c)

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(a): LNG-20 is the hormone releasing IUD, multiload 375 and \(\mathrm{Cu} 7\) are copper releasing IUDs and Lippes loop is a non-medicated IUD.

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(b) : Vasectomy is a surgical contraception method performed in males. In vasectomy, a small part of the vas deferens is removed or tied up through a small cut on the scrotum. This prevents sperm transport. Vasectomy has a poor reversibility. There is no effect on libido and erectile functioning. Seminal vesicles are one pair of sac like structures which join vasa deferentia to form ejaculatory duct. They secrete seminal fluid which contains fructose, prostaglandins and clotting protein, but no sperms. In a male who has undergone vasectomy, the ejaculatory duct will receive seminal fluid but due to cut in vasa deferentia sperms will not be transported from epididymis hence the semen will lack sperms.

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(b) : Vasectomy is a sterilisation technique for the males in which a small part of the vas deferens is removed or tied up through a small cut on the scrotum to prevent passage of sperms. Spermatogenesis is the series of cell division in the testis that results in the production of spermatozoa or sperms.

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(a) : Embryo with more than 16 blastomeres formed due to in vitro fertilisation is transferred into uterus (intra-uterine transfer, IUT).

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(b) : Amniocentesis is fetal sex determination and disorder test based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo. It can be used to determine the sex of the infant, to identify some abnormalities in the number of chromosomes and to detect certain biochemicals and enzymatic abnormalities. It is usually done when woman is 14-16 weeks pregnant. Cleft palate can be detected by ultrasound.

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(d) : Gamete Intra Fallopian Transfer (GIFT) is an assisted reproductive technology in which both the sperm and unfertilised oocytes are transferred into the Fallopian tubes. Fertilisation takes place in vivo (inside the body of the female).

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(b)

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(a) : Chikungunya virus is transmitted through an Aedes aegypti mosquito.

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(a) : Sterilization provides a permanent and sure birth control. In females, it is called tubectomy. Tubectomy involves the blocking of the Fallopian tubes. A small part of the Fallopian tube is removed or tied up through a small incision in the abdomen or through vagina.

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(b) : Intra uterine devices (IUDs) are plastic or metal objects which are inserted by doctors in the uterus through vagina. These are available as nonmedicated IUDs (i.e., Lippes loop), copper releasing IUDs (CuT, Cu7, Multiload 375) and hormone releasing IUDs (progestasert, LNG-20). Vault cap is hemispheric dome like rubber or plastic cap with a thick rim which is meant for fitting over the vaginal vault over the cervix.

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(b) : Assisted reproductive technologies (ART) include a number of special techniques which assist infertile couples to have children. An important technique of ART is test tube baby programme. The baby produced by conceiving in a culture dish and nursing in the uterus is called a test tube baby. This method involves in vitro fertilization (IVF), i.e., fertilization of male and female gamete outside the body in almost similar conditions as that in the body followed by embryo transfer (ET). Zygote or embryo upto 8 blastomeres is transferred into the Fallopian tube (ZIFT – Zygote Intra Fallopian Transfer) and mature embryo with more than 8 blastomeres is transferred to uterus to complete its further development.

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(a) : In artificial insemination technique, the semen of a healthy donor male is collected and is introduced artificially through a flexible polyethylene catheter into the vagina or into uterus called intrauterine insemination (IUI). Best results are obtained when the motile sperm count is more than 10 million. The fertilizing capacity of spermatozoa (sperms) is for 24 – 48 hours. The procedure may be repeated 2 3 times over a period of \(2-3\) days.

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(c) : Intentional or voluntary termination of pregnancy by taking an appropriate medicine before full term is called medical termination of pregnancy (MTP) or induced abortion. Nearly 45 to 50 million MTPs are performed in a year all over the world whichaccount to \(1 / 5\) th of the total number of conceived pregnancies in a year. MTP has a significant role in decreasing the population though it is not meant for that purpose. Government of India legalized MTP in 1971 with some strict conditions to avoid its misuse. Such restrictions are all the more important to check indiscriminate and illegal female foeticides.

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(c) : Cleavage divisions produce a solid ball of cells called morula. It has 8-16 cells, occasionally 32 cells. It is transferred into uterus (IUT-Intra-uterine transfer) for further development.

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(b) : Oxytocin is a birth hormone and vasopressin (anti-diuretic hormone) reabsorbs water from the renal tubules to conserve water in the body. They have no role in contraception.

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(c): Tubectomy involves blocking of the Fallopian tubes. The Fallopian tube are tied twice and cut between the knot. It prevents the sperms from reaching the ovum and thus prevents fertilization. It is a permanent method of sterilization.

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(d) : In in vitro fertilization method, popularly known as test tube baby programme, ova from the wife/donor (female) and sperms from the husband/ donor (male) are collected and are induced to form zygote under simulated conditions in the laboratory. The zygote or early embryos (with upto 8 blastomeres) could then be transferred into the Fallopian tube (ZIFT-zygote intra Fallopian transfer) and embryos with more than 8 blastomeres, into the uterus (IUTintra uterine transfer), to complete its further development.

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(d) : At present the most widely accepted method of contraception in India is IUDs. These Intra Uterine Devices (IUDs) are presently available as the nonmedicated IUDs (e.g., lippes loop), copper releasing IUDs (CuT, Cu7, Multiload 375) and the hormones releasing IUDs (Progestasert, LNG-20). IUDs increase phagocytosis of sperms within the uterus and the \(\mathrm{Cu}\)-ions released suppress sperm motility and the fertilizing capacity of sperms. The hormone releasing IUDs make the uterus unsuitable for implantation and cervix hostile to the sperms.

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(b) : Medical termination of pregnancy (MTP) or abortion is the termination of pregnancy before the foetus becomes viable. MTP is comparatively safe upto 12 weeks (the first trimester) of pregnancy. It becomes more risky after the first trimester period of pregnancy as the foetus becomes intimately associated with the maternal tissues.

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(a) : Gamete Intra Fallopian Transfer (GIFT) is transfer of an ovum collected from a donor into theFallopian tube of another female who cannot produce ova but can provide proper environment for fertilization and further development.

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(b) : Assisted reproductive technologies (ART) include a number of special techniques which assist infertile couples to have children. An important technique of ART is test tube baby programme. The baby produced by conceiving in a culture dish and nursing in the uterus is called a test tube baby. This method involves in vitro fertilization (IVF), i.e., fertilization of male and female gamete outside the body in almost similar conditions as that in the body followed by embryo transfer (ET). Zygote or embryo upto 8 blastomeres is transferred into the Fallopian tube (ZIFT – Zygote Intra Fallopian Transfer) and mature embryo with more than 8 blastomeres is transferred to uterus to complete its further development.

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(d) : Amniocentesis is withdrawal of a sample of the fluid (amniotic fluid) surrounding a foetus in the uterus by piercing the amniotic sac through the abdominal wall, under direct ultrasound guidance. As the amniotic fluid contains cells from the foetus, cell cultures enable chromosome patterns to be studied so that prenatal diagnosis of chromosomal abnormalities can be made. Certain metabolic errors and other abnormalities, such as spina bifida, can also be diagnosed prenatally from analysis of the cells or of the fluid.
As this technique also helps in detection of sex of the unborn foetus, it has been banned in order to legally check increasing female foeticides.

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(c)  Copper releasing IUDs (i.e., CuT, LNG-20) are placed in the uterus of the females. They are an efficient birth control methods. Copper ions released by them suppress motility and fertilising capacity of the sperms.

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(a) : Intrauterine devices like copper \(T\) are effective contraceptives for birth control. It suppresses sperm motility and the fertilising capacity of the sperm. Medical termination of pregnancy or induced abortion is voluntary or intentional termination of pregnancy before full term of foetus. It is comparatively safe upto 12 weeks (the first trimester) of pregnancy.

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(a) : Nearly all populations will tend to grow exponentially as long as there are resources available. The formula for exponential population growth is \(d N /\) \(d t=r N\). In this equation \(d\) is the rate of change, \(N\) is the number of existing individuals, \(r\) is the intrinsicgrowth rate, \(t\) is time, and \(\mathrm{dN} / \mathrm{dt}\) is the rate of change in population size.

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(c): By in vitro fertilization, the ovum is fertilized with sperm outside the body of a woman, providing the ovum with the same environmental conditions as it would have got inside the uterus. The zygote is grown inside a culture and when embryo is formed, it is then implanted into uterus where it develops into foetus and then into a child. This is called test tube baby.
Methodology involves the following steps :
– Removal of unfertilised ovum from reproductive tract of a female.
– Ovum is kept under aseptic conditions.
– Fusion of sperm and ovum in a culture medium, outside the female body to form the zygote.
– Zygote is stimulated to develop in vitro upto 32-celled stage.
– Developing embryo is implanted on the endometrium of the uterus at 32 -celled stage. So the pregnancy in the woman starts and further the development of the child continues in the womb till it is born.

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(b): The environmental factors which can check the growth of population size constitute the environmental resistance. These include predators, food, water, nesting sites, similar competitors, etc. All living things tend to reproduce until the point at which their environment becomes a limiting factor. No population, human or otherwise, can grow indefinitely; eventually, some biotic or abiotic variable will begin to limit population growth.

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(a) : Biotic potential is defined as the physiological capacity of organisms to produce their offspring under natural conditions. It is also called reproductive potential. In nature, the biotic potential of organisms is enormous but all the organisms do not survive due to the lack of food and space. There are also a number of diseases and the predatory organisms, that feed upon other organisms. The carrying capacity is the maximum number of individuals which the environment can support or sustain.

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(b, c) : Copper-T is an intrauterine device (IUD) used by women as a birth control. An IUD is a small device which is placed inside the uterus. The vertical and horizontal arms of the Copper – T contain copper which is slowly released into the uterine cavity. Copper stops sperm from making their way upthrough the uterus into the tubes, and it reduces the ability of sperm to fertilize the egg. It also prevents a fertilized egg (blastocyst) from successfully implanting in the lining of the uterus if fertilization has occurred.

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(a) : Pills also called contraceptive pills contain small doses of either progestogens or progestogenoestrogen combinations. They inhibit ovulation and implantation.

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(d) : Male contraceptives work by interfering with sperm production or delivery, that means they inhibit the spermatogenesis as well as the function of male sex hormone testosterone.
\(\mathrm{LH}\) and FSH (both called gonadotropic hormone are secreted from anterior pituitary) have specific functions in the testis. FSH stimulates male germ cells for spermatogenesis and \(\mathrm{LH}\) stimulates accessory cells, called Leydig cells to produce sex steroids, especially testosterone. Thus, these two hormones (FSH and \(\mathrm{LH}\) ) prevent male contraception.

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(c) : The most common type of pill is the so called “combined pill”. It contains a combination of synthetic progestins (acting like progesterone) and estrogen. Combined pills inhibit ovulation by inhibiting the normal release of FSH and LH from the pituitary. They mimic the hormones produced by the corpus luteum, causing the uterine walls to thicken, as during normal menstrual cycle, and suppressing the release of FSH and \(\mathrm{LH}\).

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(b) : As this question appeared in 1997 , so the population of world in mid 1997 was 5, 840, 324, 240 i.e., approximately 6 billion.

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(c) : Barr body is a structure consisting of a condensed \(\mathrm{X}\) chromosome that is found in nondividing nuclei of female mammals. Amniotic fluid contains foetal skin cells, that are stained to determine the presence of sex chromatin (barr body). The presence of barr body indicates that the developing foetus is female with two X-chromosome.

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(b) :

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(a) : A population having mostly younger age group means its birth rate is high. If death rate is increased then the proportion of old age group will be increased. But in this case death rate has increasing trend thence in a human population which is heavily weighted towards the younger age groups, there will be short life span and high birth rate.

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(a):