What is IVF and when is it used?

IVF (In Vitro Fertilisation): eggs collected from ovary, fertilised by sperm in lab dish → resulting embryo transferred into uterus (ET = Embryo Transfer). Used for: blocked fallopian tubes, male infertility (low sperm count), unexplained infertility. Also called 'test-tube baby' technique (first success: Louise Brown, 1978, UK).

Samacheer Kalvi 12th Zoology Chapter 13 Exercise Solutions

Exercise Solutions Available

Step-by-step answers for all textbook questions in this chapter

View Solutions →

Chapter 13 — Reproductive Health

Key Concepts Quick Recap

Term	Definition
Reproductive health	Total well-being — physical, emotional, behavioural aspects of reproduction
Contraception	Prevention of pregnancy
STD/STI	Sexually transmitted disease/infection
Infertility	Inability to conceive after 1 year of unprotected intercourse
ART	Assisted Reproductive Technology (IVF, GIFT, ICSI, etc.)
MTP	Medical Termination of Pregnancy (legal abortion)
Amniocentesis	Prenatal diagnosis via amniotic fluid analysis
Vasectomy	Surgical cutting/tying of vas deferens in males
Tubectomy	Surgical cutting/tying of fallopian tubes in females
IVF	In Vitro Fertilisation — fertilisation outside the body

I. Choose the Best Answer (MCQs)

1. Which contraceptive method has the highest effectiveness? (a) Condom (b) Oral contraceptive pills (c) Rhythm method (d) Tubectomy

Answer(d) Tubectomy Tubectomy (female sterilisation): bilateral ligation (cutting and tying) of fallopian tubes → permanently prevents eggs from reaching uterus. Effectiveness ~99.9%. Vasectomy (male) is equally effective. Oral pills: ~91-99% (if taken correctly). Condom: ~85-98%. Rhythm method: ~76-88% (least effective hormonal-free method).

2. The oral contraceptive pill works by: (a) Preventing fertilisation only (b) Inhibiting ovulation (c) Killing sperm (d) Preventing implantation only

Answer(b) Inhibiting ovulation Combined OCP (oestrogen + progesterone): inhibit GnRH from hypothalamus → suppress FSH and LH → no follicle development → no ovulation. Also thickens cervical mucus and alters endometrium. Emergency contraceptive pills (high-dose progesterone) taken within 72 hours of unprotected sex.

3. Copper-T works as a contraceptive primarily by: (a) Releasing hormones (b) Creating toxic environment for sperm and preventing implantation (c) Preventing fertilisation in the fallopian tube (d) Covering the cervix

Answer(b) Creating toxic environment for sperm and preventing implantation Copper-T (IUD): copper ions are spermicidal (toxic to sperm). Also alters uterine environment to prevent implantation. Non-hormonal, reversible, effective for 5-10 years. Ideal for women who cannot use hormonal methods.

4. Which of the following is a sexually transmitted disease caused by a virus? (a) Gonorrhoea (b) Syphilis (c) HIV/AIDS (d) Chlamydia

Answer(c) HIV/AIDS

Viral STDs also include: Herpes simplex virus (HSV), Human Papillomavirus (HPV → cervical cancer), Hepatitis B.

HIV/AIDS: Caused by Human Immunodeficiency Virus → destroys CD4+ T cells → immunodeficiency.
Gonorrhoea: caused by Neisseria gonorrhoeae (bacterium).
Syphilis: Treponema pallidum (bacterium).
Chlamydia: Chlamydia trachomatis (bacterium; most common STI globally).

5. The first test-tube baby was born in: (a) USA (b) India (c) UK (d) Australia

Answer(c) UK Louise Brown — world's first IVF baby — born July 25, 1978, in Oldham, UK. IVF was pioneered by Robert Edwards (Nobel Prize 2010) and Patrick Steptoe. In India, the first test-tube baby (Durga/Kanupriya Agarwal) was born in Kolkata in 1978 (just 67 days after Louise Brown).

6. Amniocentesis is used for: (a) Contraception (b) Prenatal sex determination and genetic diagnosis (c) Treatment of infertility (d) Prevention of STDs

Answer(b) Prenatal sex determination and genetic diagnosis Amniocentesis: sampling of amniotic fluid (10-16 weeks of pregnancy) → foetal cells analysed for chromosomal abnormalities (Down syndrome, Edwards syndrome, spina bifida), genetic disorders (cystic fibrosis, sickle cell disease). Note: Used for sex determination in India is banned under the Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act, 1994.

7. ICSI (Intracytoplasmic Sperm Injection) is used in cases of: (a) Blocked fallopian tubes (b) Severe male infertility (very few sperms) (c) Hormonal imbalance in females (d) Premature ovarian failure

Answer(b) Severe male infertility (very few sperms) ICSI: a single sperm is directly injected into the cytoplasm of an egg under a microscope. Used for: oligospermia (very few sperms), azoospermia (no sperms in ejaculate — surgically retrieved from testis), poor sperm motility. Part of Assisted Reproductive Technology (ART).

II. Short Answer Questions

Q1. Compare different methods of contraception.

Answer

Method	Type	How it works	Effectiveness
Condom	Barrier	Physical barrier; prevents sperm reaching egg; also prevents STDs	85-98%
OCP (oral pill)	Hormonal	Oestrogen + progesterone; suppresses ovulation	91-99%
Copper-T	IUD	Copper toxic to sperm; prevents implantation	99%
Vasectomy	Surgical	Vas deferens cut/tied; permanent	99.9%
Tubectomy	Surgical	Fallopian tubes cut/tied; permanent	99.9%
Rhythm method	Natural	Avoid sex during fertile days (day 8-17)	76-88%
Lactational amenorrhoea	Natural	Breastfeeding suppresses ovulation	98% (up to 6 months)
Emergency pill	Post-coital	High-dose progesterone; within 72 hours	75-85%

Q2. List the major sexually transmitted diseases and their causative agents.

Answer

Disease	Causative agent	Type
HIV/AIDS	Human Immunodeficiency Virus (HIV)	Virus
Herpes genitalis	Herpes Simplex Virus-2 (HSV-2)	Virus
Genital warts/HPV	Human Papillomavirus (HPV)	Virus
Hepatitis B	Hepatitis B Virus	Virus
Gonorrhoea	Neisseria gonorrhoeae	Bacterium
Syphilis	Treponema pallidum	Bacterium
Chlamydia	Chlamydia trachomatis	Bacterium
Trichomoniasis	Trichomonas vaginalis	Protozoan

Prevention of STDs:

Abstinence or faithful partner.
Use of condoms (only method that also prevents STD transmission).
Avoid sharing needles.
Voluntary testing and early treatment.
HPV and Hepatitis B vaccines available.

Common Mistakes

Saying OCP prevents fertilisation — OCPs primarily prevent OVULATION (no egg released).
Confusing vasectomy (male, vas deferens) and tubectomy (female, fallopian tubes).
Saying amniocentesis is used for contraception — it is a prenatal DIAGNOSTIC test.
Forgetting condom is the ONLY contraceptive that prevents both pregnancy AND STDs.

Exam Checklist

Most effective contraception: tubectomy/vasectomy (surgical sterilisation).
OCP: inhibits ovulation (oestrogen + progesterone suppress LH/FSH).
Copper-T: spermicidal + prevents implantation (non-hormonal IUD).
Condom: only method preventing STDs AND pregnancy.
IVF = in vitro fertilisation; ICSI = inject sperm into egg; GIFT = gamete intrafallopian transfer.
Louise Brown: first IVF baby (1978, UK); Robert Edwards: Nobel Prize 2010.
Amniocentesis: prenatal genetic diagnosis (not for sex determination in India — banned under PCPNDT Act).

Frequently Asked Questions

1. Barrier methods: condom, diaphragm, cervical cap. 2. Chemical methods: spermicides, oral contraceptive pills (OCP — oestrogen + progesterone inhibit ovulation). 3. Intrauterine devices (IUD): copper-T, LNG-IUS. 4. Surgical: vasectomy (male), tubectomy (female — most effective). 5. Natural: rhythm method (safe period days 8-17), lactational amenorrhoea.