Chapter 6: Reproduction in Animals

1. What is reproduction?

Process of producing new individuals (offspring) from parents.(Janakon se nayi santan paida karne ki prakriya).

2. Name the two main modes of reproduction in animals.

Sexual and Asexual reproduction.(Laingik aur Alaingik prajanan).

3. What are gametes?

Special reproductive cells (sperm and ovum/egg).(Vishesh prajanan koshikayein).

4. Name the male gamete.

Sperm.(Shukranu).

5. Name the female gamete.

Ovum (or Egg).(Andaanu (ya Anda)).

6. What is fertilization?

Fusion of sperm and ovum to form a zygote.(Sperm aur ovum ka milkar zygote banana).

7. Name the cell formed after fertilization.

Zygote.(Yugmanaj).

8. Give an example of an animal showing external fertilization.

Frog or Fish.(Mendhak ya Machhli).

9. Give an example of an animal showing internal fertilization.

Human, Cow, Dog, Hen.

10. What is an embryo?

The developing structure formed from the zygote.(Zygote se banne wali vikasit sanrachna).

11. What are viviparous animals?

Animals that give birth to young ones.(Bachhon ko janm dene wale janwar).

12. What are oviparous animals?

Animals that lay eggs.(Ande dene wale janwar).

13. What is metamorphosis?

Transformation of larva into adult through drastic changes.(Larva ka achanak badlavon se adult mein badalna).

14. Name the larva of a frog.

Tadpole.(Tadpole).

15. Name one method of asexual reproduction.

Budding or Binary Fission.(Mukulan ya Dwikhandan).

16. Name an organism that reproduces by budding.

Hydra or Yeast.(Hydra ya Yeast).

17. Name an organism that reproduces by binary fission.

Amoeba or Paramoecium.(Amoeba ya Paramoecium).

1. Why is reproduction essential for organisms?

• It ensures the continuation of species generation after generation. (Yeh prajatiyon ko peedhi dar peedhi banaye rakhna sunishchit karta hai).
• Without reproduction, a species would eventually become extinct 💀. (Prajanan ke bina, ek prajati antतः vilupt ho jayegi).
• It helps in replacing individuals lost due to death.

2. Differentiate between sexual and asexual reproduction.

• Sexual: Involves two parents (male & female), fusion of gametes (sperm & egg) occurs, offspring are genetically different from parents. (Do janak, gamete ka milan, santan alag).
• Asexual: Involves single parent, no gamete fusion, offspring are identical copies (clones) of the parent. (Ek janak, gamete ka milan nahi, santan bilkul copy).

3. What is a zygote? How is it formed?

• Zygote is the first single cell of a new individual formed during sexual reproduction. (Zygote laingik prajanan ke dauran banane wali naye jeev ki pehli ekal koshika hai).
• It is formed by the fusion (milna) of the male gamete (sperm) and the female gamete (ovum/egg). ♂️➕♀️➡️✨ (Yeh nar gamete (sperm) aur maada gamete (ovum) ke milan se banta hai).
• This process of fusion is called fertilization. (Is milan ki prakriya ko nishechan kehte hain).
• The zygote then divides repeatedly to form an embryo.

4. Differentiate between internal and external fertilization.

• Internal Fertilization: Fusion of sperm and egg occurs *inside* the female body 🏠. Ex: Humans, hens, cows. (Nishechan maada ke sharir ke andar hota hai).
• External Fertilization: Fusion of sperm and egg occurs *outside* the female body, usually in water 💧. Ex: Frogs, fish, starfish. (Nishechan sharir ke bahar hota hai, aam taur par paani mein).
• External fertilization requires producing large number of gametes due to lower survival chances.

5. Differentiate between Viviparous and Oviparous animals.

• Viviparous <0xF0><0x9F><0xA6><0xBD>: Give birth to live young ones. Embryo develops inside mother’s body. Ex: Humans, dogs, cows. (Bachhon ko janm dete hain. Bhroon maa ke andar vikasit hota hai).
• Oviparous 🥚: Lay eggs. Embryo develops inside the egg, outside mother’s body. Egg hatches to release young. Ex: Birds, frogs, insects, reptiles. (Ande dete hain. Bhroon ande ke andar vikasit hota hai. Ande se bachha nikalta hai).

6. Describe the process of budding in Hydra.

• Budding is a type of asexual reproduction. (Yeh alaingik prajanan ka ek prakar hai).
• In Hydra, one or more bulges, called **buds** 🌱, develop on the parent body wall. (Hydra mein, janak ke sharir par ek ya adhik ubhaar, jinhe **mukool (bud)** kehte hain, vikasit hote hain).
• Each bud grows using nutrients from the parent.
• It develops tentacles and a mouth.
• When fully grown, the bud detaches from the parent body and becomes a new, independent Hydra. (Jab poora vikasit ho jaata hai, bud janak se alag hokar naya Hydra ban jaata hai).

7. Describe binary fission in Amoeba.

• Binary fission is asexual reproduction where one cell divides into two. (Yeh alaingik prajanan hai jahan ek koshika do mein vibhajit hoti hai).
• Seen in single-celled organisms like Amoeba 🦠.
• First, the **nucleus** of the Amoeba elongates and divides into two nuclei ➡️✌️. (Pehle Amoeba ka nucleus lamba hokar do nuclei mein vibhajit hota hai).
• Then, the **cytoplasm** divides around each nucleus.
• Finally, the parent Amoeba splits into two daughter Amoebae, each with a nucleus. ➗(Ant mein, janak Amoeba do daughter Amoebae mein bant jaata hai).

8. Why do frogs and fish lay eggs in hundreds whereas a hen lays only one egg at a time?

• Frogs and fish exhibit **external fertilization** in water 💧. (Mendhak aur machhli mein baahya nishechan hota hai).
• The eggs and sperm released outside are exposed to many threats like water currents, predators, etc. (Bahar chhode gaye ande aur sperm ko paani ke bahav, shikariyon jaise kai khatron ka samna karna padta hai).
• Many eggs and sperm get destroyed before fertilization.
• Laying eggs in large numbers increases the chance that at least some will get fertilized and survive. (Adhik sankhya mein ande dene se kam se kam kuch ke fertilise hone aur bachne ki sambhavna badh jaati hai).
• Hens exhibit **internal fertilization** and lay eggs with hard shells 🥚🛡️, providing better protection. Therefore, fewer eggs are needed.

9. What is metamorphosis? Give an example life cycle.

• Metamorphosis is the process of transformation of a larva into an adult through drastic changes. (Larva ka achanak badlavon se adult mein badalna).
• The young one looks very different from the adult initially.
• Example: Life Cycle of Frog 🐸
  • Egg ➡️ Tadpole (larva – aquatic, gills, tail) ➡️ undergoes changes (limbs grow, tail disappears, lungs develop) ➡️ Adult Frog (terrestrial/aquatic, lungs).
• Example: Silkmoth 🐛➡️🦋: Egg ➡️ Larva (Caterpillar) ➡️ Pupa (in cocoon) ➡️ Adult.

10. How is a zygote different from a foetus?

• Zygote ✨: The single cell formed immediately after fertilization (fusion of sperm and egg). It is the beginning of a new organism. (Fertilization ke turant baad bani ekal koshika. Naye jeev ki shuruat).
• Foetus 👶: The stage of the embryo where all the main body parts (like hands, legs, head, eyes) can be identified. It develops from the embryo after considerable growth and differentiation. (Bhroon (embryo) ki vah avastha jab sabhi mukhya sharir ke ang pehchane ja sakte hain. Yeh embryo ke vikas ke baad banta hai).

1. Describe the process of fertilization in animals, including its types.

Fertilization is the fusion of male gamete (sperm) and female gamete (ovum/egg).

• Process: Sperm (produced by male) comes in contact with the ovum (produced by female). One sperm fuses with the ovum. (Sperm ovum ke contact mein aata hai. Ek sperm ovum ke saath mil jaata hai).
• Result: Formation of a single nucleus from the fusion of nuclei of sperm and egg. This results in a single fertilized egg cell called the Zygote ✨. (Sperm aur egg ke nuclei milkar ek nucleus banate hain. Isse ek fertilized egg cell banta hai jise Zygote kehte hain).
• Zygote is the beginning of a new individual.

Types of Fertilization:

• Internal Fertilization 🏠: Fusion occurs *inside* the female’s body. Sperm are deposited inside the female body where they travel to meet the egg. Ensures higher chance of fertilization. Ex: Humans, Mammals, Birds, Reptiles. (Maada ke sharir ke andar hota hai. Nishechan ka chance zyada).
• External Fertilization 💧: Fusion occurs *outside* the female’s body, usually in water. Both male and female release their gametes into the water. Chance plays a role. Large number of gametes released to increase odds. Ex: Frogs 🐸, Fish 🐠, Starfish. (Sharir ke bahar hota hai, aam taur par paani mein. Dono janak paani mein gametes chhodte hain. Bahut saare gametes chhodne padte hain).

2. Explain the difference between zygote, embryo, and foetus.

These are different stages in the development of a new individual in sexual reproduction:

• Zygote ✨: The very first stage. It’s the single cell formed immediately after the fusion of sperm and ovum (fertilization). Contains genetic material from both parents. (Fertilization ke turant baad bani pehli single cell. Naye jeev ki shuruat).
• Embryo 👶: The zygote undergoes repeated cell divisions (mitosis) to form a ball of cells, which then starts differentiating into various tissues and rudimentary organs. This developing structure is the embryo. It embeds itself in the wall of the uterus (in internal fertilization like humans). (Zygote ke divide hone se bana cells ka gola jo tissues/organs mein develop hone lagta hai. Yeh vikasit ho rahi sanrachna hai).
• Foetus 👶: The stage of the embryo where all major body parts like hands, legs, head, eyes, ears become distinct and identifiable. This stage comes after the embryo has developed significantly. The foetus continues to grow inside the uterus until birth. (Embryo ki woh stage jab haath, pair, sir jaise sabhi mukhya ang pehchane ja sakte hain. Yeh embryo ke kaafi vikas ke baad aata hai).

So, the sequence is: Fertilization → Zygote → Embryo → Foetus → Birth (in Viviparous animals).

3. Describe asexual reproduction methods: Budding and Binary Fission with examples.

Asexual reproduction involves a single parent producing identical offspring.

Budding (Mukulan):

• Seen in Hydra, Yeast 🌱.
• An outgrowth or **bud** develops on the parent body.
• The bud receives nucleus and cytoplasm from the parent.
• It grows in size.
• Eventually, it detaches from the parent to live as an independent organism (like in Hydra) or may remain attached forming chains (like in Yeast).
• Offspring is a clone of the parent.

Binary Fission (Dwikhandan):

• Seen in unicellular organisms like Amoeba 🦠, Paramoecium.
• Means ‘splitting into two’ ➗.
• The parent cell first divides its **nucleus** into two.
• Then, the **cytoplasm** divides, separating the two nuclei.
• Finally, the parent cell splits completely into two **daughter cells**, which grow into adults.
• Offspring are identical clones.

4. Draw and explain the life cycle of a frog.

(Diagram description): The life cycle shows metamorphosis.

1. Eggs 🥚: Female frog lays hundreds of eggs in water, often in clusters called ‘spawn’. Eggs are covered by a jelly layer for protection. External fertilization occurs.
(Maada paani mein saikdon ande deti hai (‘spawn’). Jelly ki parat hoti hai).
2. Tadpole (Larva) 🐛💧: Fertilized eggs hatch into tadpoles. Tadpoles look very different from adult frogs – they resemble small fish, have gills for breathing underwater, and a tail for swimming. They are usually herbivores.
(Andon se Tadpole nikalte hain. Woh adult mendhak se bilkul alag dikhte hain – machhli jaise, paani mein saans lene ke liye gills, tairne ke liye poonchh).
3. Metamorphosis 🔄: The tadpole undergoes drastic changes:
   • Hind legs appear, then front legs.
   • Lungs develop, gills disappear.
   • Tail gradually shortens and disappears (absorbed by body).
   • Mouth shape changes.
4. Adult Frog 🐸: The fully developed frog can live both on land and in water (amphibian), breathes through lungs (on land) and skin (in water), has limbs for jumping/swimming, and is usually carnivorous.
(Poora vikasit mendhak zameen aur paani dono mein reh sakta hai, phepde/tvacha se saans leta hai, koodne/tairne ke liye pair hain, maansahari hota hai).

5. What is IVF? Why is it performed?

IVF (In Vitro Fertilization):

• ‘In Vitro’ means ‘in glass’ (outside the body).
• IVF is a technique where fertilization occurs *outside* the female body, in a laboratory setting 🔬. (Yeh ek technique hai jahan nishechan maada ke sharir ke bahar, lab mein hota hai).
• Freshly collected egg from the female and sperm from the male are mixed in a test tube or petri dish containing suitable nutrient medium.
• Fertilization is allowed to occur (‘Test Tube Baby’ technique refers to this stage, though baby doesn’t grow in test tube!). (‘Test Tube Baby’ technique isi stage se judi hai).
• If fertilization occurs, the zygote develops into an early embryo over about a week.
• This embryo is then transferred into the mother’s uterus (womb) for further development. (Is embryo ko fir maa ke garbhashay mein daal diya jaata hai).
• Complete development then occurs inside the mother’s body like normal pregnancy.

Why Performed? (Kyun Kiya Jaata Hai?)

• IVF is an assisted reproductive technology used to help couples who are unable to conceive naturally.
• Reasons for infertility could be blocked oviducts (fallopian tubes) in females (where fertilization normally occurs), low sperm count in males, or other issues. IVF bypasses these problems by enabling fertilization outside the body. (Yeh unn couples ki madad ke liye hai jo prakritik roop se bachha paida nahi kar pa rahe hain, jaise maada mein oviducts block hona ya nar mein sperm count kam hona).

6. Differentiate between Gametes and Zygote.

Gametes vs. Zygote:

• Gametes (Sperm ♂️, Ovum ♀️): These are the specialized reproductive cells produced by male and female parents respectively. They are haploid (contain half the number of chromosomes of a body cell). They cannot develop into a new individual on their own. (Yeh nar/maada dwara banayi gayi khaas prajanan koshikayein hain. Yeh haploid hoti hain. Akele naya jeev nahi bana sakti).
• Zygote ✨: This is the single cell formed by the *fusion* of a male gamete (sperm) and a female gamete (ovum) during fertilization. It is diploid (contains the full set of chromosomes, half from each parent). It is the very first cell of the new individual and divides repeatedly to form the embryo. (Yeh sperm aur ovum ke milan se bani pehli single cell hai. Yeh diploid hoti hai. Naye jeev ki shuruaati koshika jo divide hokar embryo banati hai).

7. What happens during the development of an embryo?

After fertilization, the zygote starts developing into an embryo:

• Cell Division (Cleavage): The zygote undergoes repeated mitotic cell divisions, forming 2 cells, then 4, then 8, and so on, becoming a ball of cells (called morula, then blastocyst). (Zygote lagatar divide hokar cells ka gola banata hai).
• Implantation (in internal fertilization): The ball of cells travels down the oviduct and embeds itself into the thick lining of the uterus (womb). (Cells ka gola oviduct se neeche jakar uterus ki deewar mein chipak jaata hai).
• Differentiation: The cells within the ball start to differentiate and arrange themselves into layers. These layers will eventually form different tissues and organs. (Cells alag-alag hokar layers banate hain jo tissues aur organs banayenge).
• Organogenesis: Specific body parts like hands, legs, head, eyes, heart ❤️ start developing gradually. (Sharir ke khaas ang jaise haath, pair, sir, aankhein dheere dheere vikasit hone lagte hain).
• Growth: The embryo grows in size. When all major body parts are identifiable, it is called a foetus. (Embryo size mein badhta hai. Jab sabhi mukhya ang pehchaan mein aate hain, toh use foetus kehte hain).

8. Why do organisms reproduce?

Reproduction is a fundamental characteristic of living organisms and is essential for several reasons:

• Continuity of Species: It is the only way for a species to continue its existence over generations. Individual organisms have a limited lifespan, but reproduction ensures the species does not die out. ➡️👨‍👩‍👧‍👦 (Yeh prajati ko peedhi dar peedhi banaye rakhne ka ekmatra tareeka hai).
• Population Growth: Reproduction leads to an increase in the number of individuals in a population, helping the species thrive and occupy habitats. (Isse abadi mein vyaktiyon ki sankhya badhti hai).
• Replacement of Individuals: It replaces old and dying individuals with new ones, maintaining the population size. (Yeh purane aur mar rahe vyaktiyon ki jagah naye le aata hai).
• Variation (in Sexual Reproduction): Sexual reproduction combines genetic material from two parents, creating variations in offspring. This variation is crucial for adaptation and evolution, helping the species survive changing environments. 🧬🔄 (Laingik prajanan se santan mein vividhata aati hai, jo badalte mahaul mein survive karne mein madad karti hai).

In essence, reproduction ensures life continues on Earth.

9. Give two examples each of Oviparous and Viviparous animals.

• Oviparous Animals (Egg-laying) 🥚: Lay eggs where embryo develops outside mother’s body.
  • Example 1: Hen 🐔 (Birds)
  • Example 2: Frog 🐸 (Amphibians)
  • Other examples: Fish 🐠, Snakes 🐍, Lizards 🦎, Butterflies 🦋
  Ande dene wale. Bhroon ande ke andar bahar vikasit hota hai.
• Viviparous Animals (Giving birth to young) <0xF0><0x9F><0xA6><0xBD>: Give birth to live young. Embryo develops inside mother’s body.
  • Example 1: Human 🧍 (Mammals)
  • Example 2: Cow 🐄 (Mammals)
  • Other examples: Dog 🐕, Cat 🐈, Elephant 🐘, Whale
  Bachhon ko janm dene wale. Bhroon maa ke andar vikasit hota hai.

10. Can you differentiate between Budding and Binary Fission?

Budding vs. Binary Fission (Both Asexual):

• Number of Offspring: Binary Fission always produces two daughter cells ➗. Budding typically produces one new individual at a time (though multiple buds can form). (Binary Fission mein hamesha 2. Budding mein aamtaur par ek).
• Parent Identity: In Binary Fission, the parent cell disappears as it divides into two daughters. In Budding, the parent organism remains distinct, and the bud grows as an outgrowth before detaching (or remaining attached). (Binary Fission mein parent khatam ho jaata hai. Budding mein parent rehta hai, bud us par ugta hai).
• Site of Division/Growth: In Binary Fission, the whole cell divides. In Budding, growth occurs at a specific site (the bud). (Binary Fission mein poori cell divide hoti hai. Budding mein khaas jagah (bud) par growth hoti hai).
• Examples: Budding – Hydra, Yeast 🌱. Binary Fission – Amoeba, Paramoecium 🦠.