Maarg Manthan · Topic 3.3

Reproductive System: Asexual and Sexual Reproduction in Plants, Animals and Humans

Science & Technology › Human Physiology – Organ Systems · Topic 3.3

Reproduction is the production of new individuals of the same species, and it is of two kinds. In asexual reproduction a single parent produces offspring that are genetically identical, by methods such as binary fission in amoeba, budding in yeast and Hydra, fragmentation in Spirogyra, spore formation in Rhizopus and vegetative propagation in plants. In sexual reproduction two parents contribute gametes that fuse in fertilisation, which gives variation. In humans, the male reproductive system makes sperm and the hormone testosterone in the testes, and the female system makes eggs and the hormones oestrogen and progesterone in the ovaries. Pregnancy lasts about 40 weeks, and the placenta nourishes the foetus.

5 min read · UPSC Prelims · Science & Technology · Human Physiology – Organ Systems

At a Glance

Asexual One parent; identical offspring
Sexual Two gametes; variation
Male gland Testes (testosterone)
Female gland Ovaries (oestrogen, progesterone)
Pregnancy About 40 weeks
Exam link UPSC Prelims, Science & Technology: Human Physiology – Organ Systems

Where Does It Fit?

This is the third topic of the macro on human physiology and organ systems. It extends the cell-level topic on sexual reproduction to whole organisms and to the human reproductive system. Previous topic: Muscular System (Myology). Next topic: Excretory System: Excretion in Plants and Animals.

How Do Organisms Reproduce Asexually?

Method	Example
Binary fission	Amoeba and bacteria divide into two equal cells
Multiple fission	Plasmodium divides into many daughter cells
Budding	Yeast and Hydra form a bud that grows into a new individual
Fragmentation	Spirogyra breaks into pieces that grow into new filaments
Regeneration	Planaria and starfish regrow lost parts
Spore formation	Rhizopus and ferns produce spores that grow into new individuals
Vegetative propagation	Runners in strawberry, tubers in potato, bulbs in onion, rhizomes in ginger and turmeric, leaves in Bryophyllum, and cuttings in rose and sugarcane
Artificial methods	Grafting, layering and tissue culture, used to grow plants with desired traits

What Are the Parts of the Human Reproductive Systems?

Testes: a pair of organs in the scrotum, which keeps them 2 to 3 degrees Celsius below body temperature, needed for sperm production. They make sperm in the seminiferous tubules and testosterone from Leydig cells.
Male ducts and glands: the epididymis stores sperm, the vas deferens carries it, and the seminal vesicles and prostate add fluids to make semen.
Ovaries: a pair of organs that release one egg about every month and make oestrogen and progesterone.
Fallopian tubes: carry the egg to the uterus and are the usual site of fertilisation.
Uterus: a muscular organ where the embryo implants and grows, opening through the cervix into the vagina.
Placenta: an organ that joins the foetus to the mother and supplies food and oxygen and removes wastes, and it also makes hormones such as human chorionic gonadotropin.

What Else Should You Remember?

Menstrual cycle: lasts about 28 days. Menstruation lasts for the first 3 to 5 days, ovulation occurs around the 14th day, and the uterine lining thickens under progesterone and is shed if there is no pregnancy. The first cycle, menarche, begins at puberty, and the cycles stop at menopause.
Hormones of the pituitary: follicle stimulating hormone and luteinising hormone control the ovary and testis, as in Endocrine System: Hypothalamus, Pineal Body, Pituitary Gland, Thyroid, Adrenal Glands, Reproductive Glands.
Implantation and development: the fertilised egg divides into a blastocyst that implants in the uterus about a week after fertilisation, and in the later stages the foetus develops organs.
Contraception: barrier methods such as condoms, oral pills, intrauterine devices and surgical methods such as vasectomy and tubectomy. Condoms also protect against sexually transmitted infections.
Sexually transmitted infections: gonorrhoea, syphilis, chlamydia, genital herpes, hepatitis B and HIV.
Infertility and ART: treated by methods such as IVF, intrauterine insemination and ICSI, regulated in India by the Assisted Reproductive Technology (Regulation) Act, 2021.
Medical Termination of Pregnancy: governed in India by an Act of 1971, amended in 2021 to allow termination up to 24 weeks in certain cases.
Link to cells: gametes are made by meiosis, as in Sexual Reproduction at the Cellular Level.
Puberty: sexual maturity begins at puberty, around 10 to 14 years in girls and 12 to 16 years in boys, under the control of hormones from the pituitary and gonads.

Why Does It Matter for the Exam?

Method matching: which organism reproduces by which asexual method.
Anatomy and hormone questions: functions of testes, ovaries, placenta and the hormones they make.
Health and policy link: contraception, family planning, ART and the MTP Act.
Agriculture link: vegetative propagation and tissue culture for banana, potato and orchids.
Common errors: mixing up ovulation and menstruation, and thinking that the egg is released from the uterus.

As an analytical point, asexual reproduction gives fast growth of useful traits, while sexual reproduction gives variation. Farmers use the first, and nature relies on the second to cope with change.

Why Is This Topic Important?

Facts Methods and examples asked
Anatomy Organs and hormones
Link Contraception and law

What Came Next?

The next topic covers the excretory system in plants and animals. Next topic: Excretory System: Excretion in Plants and Animals.

Key People and Terms

Budding Outgrowth that forms a new individual
Vegetative propagation New plants from stems, roots or leaves
Ovulation Release of egg
Placenta Organ linking mother and foetus
Vasectomy Cutting of the vas deferens
Tubectomy Cutting of fallopian tubes

Exam Corner

Points to Remember

Scrotum keeps testes 2 to 3 degrees cooler.
Ovulation about day 14.
Fertilisation in the fallopian tube.
Pregnancy about 40 weeks.
Potato tuber, onion bulb, ginger rhizome.

Do Not Confuse With

Vasectomy and tubectomy Male versus female sterilisation
Ovulation and menstruation Egg release versus shedding of lining
Fission and budding Equal division versus outgrowth

Memory Hook

Fission, budding, spore, cuttings: one parent’s way; testes make sperm, ovary eggs, placenta feeds the foetus in the womb to stay.

Mains Angle

Questions ask about reproduction and reproductive health. These points add depth.

Types Asexual and sexual
Human system Organs and hormones
Health Contraception and ART

A Question You May Face

An original practice question, not a past paper question.

“Distinguish between asexual and sexual reproduction and describe the human reproductive system and its hormonal control.”

How to Answer

Types Two modes.
Methods Fission, budding.
Human Organs, cycle.
Health Contraception.

GS Relevance

Prelims: types of asexual reproduction, parts and hormones of the human system, menstrual cycle, contraception. GS Paper 3: science and technology, health.

Frequently Asked Questions

What is the difference between asexual and sexual reproduction?

In asexual reproduction a single parent produces offspring that are genetically identical to it, as in budding in yeast or runners in strawberry. In sexual reproduction two gametes from two parents fuse in fertilisation, which gives offspring with new combinations of genes and more variation to help populations to adapt.

What is vegetative propagation?

Vegetative propagation is a form of asexual reproduction in plants in which new plants grow from vegetative parts such as stems, roots and leaves. Examples are runners in strawberry, tubers in potato, bulbs in onion, rhizomes in ginger and leaves in Bryophyllum, and farmers also use cuttings, grafting and tissue culture.

What is the menstrual cycle?

The menstrual cycle is a monthly cycle of about 28 days in which the ovary releases an egg around day 14, called ovulation, and the lining of the uterus thickens to prepare for pregnancy. If the egg is not fertilised, the lining is shed as menstruation, controlled by the hormones oestrogen, progesterone, FSH and LH.

What is the function of the placenta?

The placenta is an organ that develops in the uterus during pregnancy and connects the foetus to the mother through the umbilical cord. It supplies oxygen and nutrients, removes carbon dioxide and wastes, makes hormones such as human chorionic gonadotropin, and acts as a barrier to many harmful substances.

What are the main methods of contraception?

The main methods are barrier methods such as condoms, oral contraceptive pills, intrauterine devices that are placed in the uterus, and sterilisation by vasectomy in men or tubectomy in women. Condoms also lower the risk of sexually transmitted infections, and the choice depends on health and family planning needs.

PYQ Practice — Statement Analysis

1 Yeast reproduces asexually by budding.

True

A bud grows into a new cell.

2 Fertilisation in humans usually takes place in the uterus.

False

In the fallopian tube.

3 Testosterone is made by the testes.