Reproduction: Reproduction in Plants, Animals and Humans — REET Science Notes
This page covers every method of asexual reproduction, the parts of a flower and pollination, fertilisation in animals, and the hormones and glands associated with human reproduction. REET 2024 carried 4 questions on Reproduction that went a little deeper than the Class 8 level, so this page covers exactly that depth.
- 4 questions in REET 2024
- Class 6-8 level
- 9 min read
How REET asks this topic
REET 2024 carried 4 questions from Reproduction, and 2 of these were directly about the method of asexual reproduction — Leishmania (binary fission) and Plasmodium (multiple fission). The other 2 came from human reproduction: the lubricating secretion of the male bulbourethral (Cowper's) gland, and oxytocin, the hormone that contracts the uterine muscles during childbirth. Notice that the difficulty level has crept slightly above Class 8 NCERT (toward Class 10-12 biology), so make sure the 'organism → reproduction method' and 'gland/hormone → function' pairings are firmly memorised.
What is reproduction, and what types does it come in?
The process by which organisms produce new organisms like themselves is called reproduction. It is not essential to the survival of any single organism, but it is essential for the continuity of a species.
Reproduction is of two kinds. In asexual reproduction, only one parent is involved, no gametes are formed, and the offspring is almost an exact copy of the parent. In sexual reproduction, male and female gametes — sperm and ovum — fuse to form a zygote; this fusion is called fertilisation. Sexual reproduction introduces variation in the offspring, which is the basis of evolution.
Methods of asexual reproduction — with organisms
| Method | What happens | Example |
|---|---|---|
| Binary fission | One cell splits into two roughly equal parts | Amoeba, Paramecium, bacteria; Leishmania (splits along a fixed plane defined by its flagellum) |
| Multiple fission | The nucleus divides many times, and then several daughter cells are formed all at once | Plasmodium (the malaria parasite) |
| Budding | A bud forms as an outgrowth on the parent's body and develops into a new organism | Hydra, yeast |
| Fragmentation | The body breaks into pieces, and each piece grows into a new organism | Spirogyra (an alga) |
| Regeneration | A cut-off part regrows into a complete organism | Planaria, Hydra |
| Spore formation | Light spores are released from a sporangium and germinate | Rhizopus/bread mould (a fungus), moss, fern |
| Vegetative propagation | A new plant grows from a root, stem, or leaf | The eye of a potato, ginger, turmeric; leaf buds of Bryophyllum; a rose cutting |
REET 2024 offered binary fission, multiple fission, budding and regeneration all as options in the same question.[Source 1]
Sexual reproduction in plants
The flower is the reproductive organ of a plant. The stamen is the male part — its anther produces pollen grains, which contain the male gametes. The pistil is the female part — it has a stigma, style and ovary; the ovary's ovule contains the female gamete (the egg cell). Flowers that have both parts are called bisexual (mustard, hibiscus, rose, petunia), and those with only one are called unisexual (maize, papaya, cucumber).
The transfer of pollen from the anther to the stigma is called pollination — self-pollination if it happens on the same flower or the same plant, and cross-pollination if it happens on a flower of a different plant. Pollination is carried by wind, water and insects. After fertilisation, the zygote develops into an embryo, the ovule becomes the seed, and the ovary becomes the fruit. Seeds are dispersed by wind (the winged seeds of drumstick and maple; the hairy seeds of madar/akand), by water (coconut), by animals (the spiny seeds of Xanthium, which stick to an animal's body) and through fruits that burst open (castor, balsam).
Sexual reproduction in animals and humans
When fertilisation happens inside the female's body, it is called internal fertilisation (humans, cows, dogs, hens); when it happens outside the body, usually in water, it is called external fertilisation (frogs, fish, starfish). In external fertilisation, gametes are far more likely to be lost, which is why frogs and fish lay hundreds of eggs. Animals that give birth directly to young are called viviparous (humans, cows), and those that lay eggs are called oviparous (hens, frogs, lizards). A dramatic change like a tadpole turning into a frog, or a caterpillar turning into a silk moth, is called metamorphosis.
In humans, the testes produce sperm and testosterone; the ovaries produce eggs and estrogen/progesterone. Fertilisation usually takes place in the fallopian tube; the zygote divides repeatedly to form an embryo, which implants itself in the wall of the uterus. Once all the organs can be recognised, this stage is called the foetus. The accessory glands in the male are the seminal vesicles, the prostate and the bulbourethral (Cowper's) gland; the secretion of the bulbourethral gland also assists in lubricating the penis.
In women whose fallopian tubes are blocked, the egg and sperm are made to fertilise outside the body — this is called in-vitro fertilisation (IVF), and such a baby is commonly called a 'test-tube baby' in everyday speech, even though the embryo actually develops inside the mother's uterus. The first mammal created by cloning was a sheep named Dolly, produced by Ian Wilmut and colleagues at the Roslin Institute in Scotland; she was born on 5 July 1996.
Hormones and glands linked to reproduction
| Hormone / gland | Source | Main function |
|---|---|---|
| Oxytocin | Posterior pituitary gland (produced in the hypothalamus) | Contracts the uterine muscles during childbirth; ejects milk from the breast |
| Prolactin | Anterior pituitary gland | Stimulates milk production in the mammary glands |
| Testosterone | Testes | Secondary sexual characteristics in males (beard/moustache, deeper voice) |
| Estrogen | Ovaries | Secondary sexual characteristics in females, breast development |
| Thyroxine | Thyroid gland | Controls metabolism; essential for metamorphosis in frogs |
| Bulbourethral gland | Male accessory reproductive gland | Its secretion provides lubrication |
The difference between prolactin (makes milk) and oxytocin (releases milk and aids childbirth) is asked repeatedly.[Source 2]
How to teach this to children
Activity: dissecting a flower (Class 7)
Using a Datura, hibiscus or mustard flower, have children separate the sepals, petals, stamen and pistil, examine pollen grains with a hand lens, and cut the ovary crosswise to identify the ovules. Compare this with the unisexual flowers of maize or cucumber.
Experiment: vegetative propagation
Have children plant a potato piece with an eye, a Bryophyllum leaf, and a rose or money-plant cutting in soil or water, and keep an observation diary for two weeks. Show budding under a microscope by keeping yeast in a sugar solution.
Teaching aids
Life-cycle charts of a frog and a silk moth; flash cards of asexual methods (organism on one side, method on the other); a model of the human reproductive system.
Common misconceptions
'A test-tube baby develops entirely inside a test tube' — incorrect, only fertilisation happens outside; 'all flowers have both male and female parts' — maize and papaya are unisexual; 'a seed and a fruit are the same thing' — a seed comes from the ovule, a fruit from the ovary.
Sensitivity and assessment
While teaching human reproduction, use scientific terminology naturally and keep a question box so children can ask questions anonymously without hesitation. For assessment, use an 'organism-reproduction method' matching exercise and have students draw a labelled diagram of a flower.
Memory trick / exam tip
Link the asexual method to the number of offspring: 'bi = two offspring (amoeba, Leishmania), multi = many offspring (Plasmodium — the malaria parasite spreads extremely fast)'. For hormones: 'pro-lactin = production (of milk); oxy-tocin = expulsion/push (childbirth and milk release)'.
REET 2024 questions (solved)
Question 138
Secretion of which gland also helps in lubrication of penis in man ?
- Aपिनियल ग्रंथि
- Bथाइमस ग्रंथि
- Cअधिवृक्क ग्रंथि
- Dबल्बोयूरेथ्रल ग्रंथि
Explanation
बल्बोयूरेथ्रल ग्रंथि (Bulbourethral / काउपर ग्रंथि) पुरुष की सहायक जनन ग्रंथि है, जिसका स्राव शिश्न के स्नेहन (lubrication) में सहायता करता है। पिनियल, थाइमस और अधिवृक्क अंतःस्रावी ग्रंथियाँ हैं जिनका जनन मार्ग के स्नेहन से संबंध नहीं है।
Question 142
Mode of reproduction in Leishmania is
- Aमुकुलन
- Bपुनरूद्धभवन
- Cद्विखंडन
- Dबहुखंडन
Explanation
लेस्मानिया (Leishmania, कालाजार रोग का परजीवी) एककोशिकीय जीव है जो द्विखंडन (binary fission) द्वारा प्रजनन करता है। इसमें कोशिका के एक सिरे पर स्थित कशाभ (flagellum) के कारण विभाजन एक निश्चित तल में (अनुदैर्ध्य) होता है। बहुखंडन प्लाज्मोडियम में और मुकुलन हाइड्रा/यीस्ट में होता है।
Question 145
Mode of reproduction in plasmodium is
- Aद्विखंडन
- Bबहुखंडन
- Cपुनरुद्भवन
- Dमुकुलन
Explanation
प्लैज्मोडियम (मलेरिया परजीवी) में बहुखंडन (multiple fission) द्वारा जनन होता है, जिसमें केन्द्रक कई बार विभाजित होकर एक साथ अनेक संतति कोशिकाएँ बनाता है। अमीबा व लेस्मानिया में द्विखंडन, यीस्ट व हाइड्रा में मुकुलन तथा प्लेनेरिया में पुनरुद्भवन होता है।
Question 149
Hormone that acts on the Uterine muscles during parturition
- Aप्रोलैक्टिन
- Bथायरॉक्सिन
- Cटेस्टोस्टेरॉन
- Dऑक्सीटोसिन
Explanation
ऑक्सीटोसिन हॉर्मोन पश्च पीयूष ग्रंथि (posterior pituitary) से स्रावित होता है और प्रसव (parturition) के समय गर्भाशय की पेशियों में संकुचन कराता है। प्रोलैक्टिन दुग्ध-निर्माण, थायरॉक्सिन उपापचय और टेस्टोस्टेरॉन नर लक्षणों से संबंधित है।
Practice questions
Question 1
In Hydra, asexual reproduction commonly takes place by —
- Aद्विखंडन
- Bमुकुलन
- Cबीजाणु निर्माण
- Dबहुखंडन
Explanation
In Hydra, a bud forms on the body, which grows and detaches to become a new Hydra. Yeast also reproduces by budding.
Question 2
Which part of a flower develops into the fruit after fertilisation?
- Aबीजांड
- Bपरागकोश
- Cअंडाशय
- Dवर्तिकाग्र
Explanation
After fertilisation, the ovary ripens into a fruit, while the ovule develops into the seed.
Question 3
Which of the following plants bears unisexual flowers?
- Aसरसों
- Bगुड़हल
- Cमक्का
- Dगुलाब
Explanation
Maize flowers have either only stamens or only a pistil, so they are unisexual. Mustard, hibiscus and rose flowers are bisexual.
Question 4
The common method of asexual reproduction in Spirogyra is —
- Aखंडन
- Bमुकुलन
- Cबहुखंडन
- Dकायिक प्रवर्धन (पत्ती द्वारा)
Explanation
The filament of Spirogyra breaks into pieces, and each piece grows into a new filament — this is fragmentation.
Question 5
The hormone that stimulates milk production in mammary glands is —
- Aऑक्सीटोसिन
- Bप्रोलैक्टिन
- Cथायरॉक्सिन
- Dइंसुलिन
Explanation
Prolactin (from the anterior pituitary) stimulates milk production; oxytocin acts in milk release and in contracting the uterus during childbirth.
Question 6
Which of the following animals is viviparous?
- Aमुर्गी
- Bमेंढक
- Cगाय
- Dछिपकली
Explanation
Viviparous animals give birth directly to a developed young one, such as a cow or a human. Hens, frogs and lizards all lay eggs (oviparous).
Question 7
A frog lays hundreds of eggs at a time because it has external fertilisation, since —
- Aसभी अंडे निश्चित रूप से निषेचित होते हैं
- Bपानी में अंडे और शुक्राणु बहने तथा दूसरे जंतुओं द्वारा खाए जाने से बहुत-से नष्ट हो जाते हैं
- Cमेंढक में आंतरिक निषेचन भी होता है
- Dअंडों से सीधे वयस्क मेंढक निकलते हैं
Explanation
In external fertilisation, gametes are lost in large numbers due to water currents, air, or being eaten by other animals, so a great many eggs are produced to ensure some offspring survive. Frog eggs hatch into tadpoles, not directly into adult frogs.
Question 8
Which is the most effective activity to clarify vegetative propagation in Class 7?
- Aपरिभाषा बोर्ड पर लिखकर याद कराना
- Bआलू की आँख, ब्रायोफिलम की पत्ती और गुलाब की कलम लगाकर बच्चों से अवलोकन-डायरी भरवाना
- Cपाठ्यपुस्तक से प्रश्न-उत्तर लिखवाना
- Dकेवल चित्र दिखाकर आगे बढ़ना
Explanation
Direct experience and an observation diary let children see for themselves that a new plant grows from a stem or a leaf. This is learning by doing, in line with what the NCF recommends.
Question 9
Which statement about a 'test-tube baby' (IVF) is correct?
- Aशिशु का पूरा विकास परखनली में होता है
- Bनिषेचन शरीर के बाहर होता है और भ्रूण का विकास माँ के गर्भाशय में होता है
- Cइसमें शुक्राणु की आवश्यकता नहीं होती
- Dयह अलैंगिक जनन का उदाहरण है
Explanation
In IVF, the egg and sperm are combined outside the body to form a zygote, and the early embryo is then implanted into the mother's uterus. Since gametes fuse, this is sexual reproduction.
Question 10
A teacher conducts a card game matching 'method of asexual reproduction – organism'. This mainly serves which purpose?
- Aकेवल मनोरंजन
- Bसक्रिय सहभागिता के साथ अवधारणाओं का सुदृढ़ीकरण और रचनात्मक आकलन
- Cबच्चों के बीच प्रतिस्पर्धा से डर पैदा करना
- Dयोगात्मक मूल्यांकन हेतु अंक देना
Explanation
In a matching card game, children actively participate, which reinforces concepts, and the teacher can immediately spot which pairing is causing confusion — this is a tool of formative assessment.
Frequently asked questions
What method of reproduction do amoeba and Plasmodium use?+
Amoeba reproduces by binary fission and Plasmodium (the malaria parasite) by multiple fission. Leishmania also reproduces by binary fission.
Which hormone acts during childbirth?+
Oxytocin causes contraction of the uterine muscles, assisting in childbirth; it also plays a role in the ejection of milk.
What is the difference between internal and external fertilisation?+
Internal fertilisation happens inside the female's body (humans, hens), while external fertilisation happens outside the body, usually in water (frogs, fish).
What are some examples of vegetative propagation?+
Potato (the eye of the stem), ginger-turmeric (underground stems), Bryophyllum (leaf buds) and rose (cuttings) are common examples of vegetative propagation.
How many questions come from Reproduction in REET?+
REET 2024 (Level 2 Science) carried 4 questions from Reproduction — 2 on asexual reproduction methods and 2 on human reproduction (gland and hormone).
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Change Log
- 17 September 2026 — English page published — mirrors the fact-checked Hindi page, independently bilingual-accuracy checked