Chapter 1: Reproduction in Organisms

Q1. Define reproduction. What are its two main types?

Solution

Reproduction is the biological process by which new individual organisms (offspring) are produced from their parents.

Asexual reproduction: Involves single parent, no gamete fusion (e.g., binary fission, budding)
Sexual reproduction: Involves two parents, fusion of male and female gametes

Q2. What is the difference between asexual and sexual reproduction?

Solution

Asexual: One parent, no gametes, offspring are clones, faster
Sexual: Two parents, gamete fusion, genetic variation, slower

Q3. Define the following: (i) Spermiation (ii) Ovulation (iii) Implantation

Solution

(i) Spermiation: Release of sperm from Sertoli cells into the lumen of seminiferous tubules
(ii) Ovulation: Release of mature ovum from the Graafian follicle
(iii) Implantation: Embedding of blastocyst into the uterine wall

Q4. What is vegetative propagation? Give two examples.

Solution

Vegetative propagation is a form of asexual reproduction in plants where new plants arise from vegetative parts (roots, stems, leaves).

Examples: (1) Potato - from tubers (2) Bryophyllum - from leaf buds

Q5. What are hermaphrodites? Give examples.

Solution

Organisms that possess both male and female reproductive organs.

Examples: Earthworm, Leech, Hydra, Tapeworm, Sponge

Q6. Describe the process of binary fission in Amoeba.

Solution

Binary fission in Amoeba is an asexual method where the parent cell divides into two identical daughter cells.

Steps: (1) Nucleus divides by mitosis (2) Cytoplasm constricts at the centre (3) Two daughter cells form, each with a nucleus and organelles

Q7. What is budding? Give two examples of organisms that reproduce by budding.

Solution

Budding is a type of asexual reproduction where a new organism develops from an outgrowth or bud due to cell division at one particular site.

Examples: (1) Hydra - bud develops on body wall and detaches (2) Yeast - bud forms on parent cell surface

Q8. Explain spore formation in Rhizopus.

Solution

Rhizopus (bread mould) reproduces asexually by forming spores called sporangiospores inside sporangia.

Process: (1) Sporangium develops at tip of sporangiophore (2) Spores formed inside by cell division (3) Sporangium bursts, releasing spores (4) Spores germinate under favourable conditions

Q9. What are the three phases of sexual reproduction?

Solution

Pre-fertilization: Gametogenesis (formation of gametes) and gamete transfer
Fertilization (Syngamy): Fusion of male and female gametes to form zygote
Post-fertilization: Embryogenesis (development of embryo from zygote)

Q10. What is fragmentation? In which organisms does it occur?

Solution

Fragmentation is a type of asexual reproduction where the body breaks into two or more fragments, each developing into a new organism.

Examples: (1) Spirogyra (2) Flatworms like Planaria (3) Starfish (regeneration)

Q11. What is the difference between external and internal fertilization?

Solution

External: Gametes fuse outside the body (e.g., fish, amphibians, most invertebrates)
Internal: Gametes fuse inside the female body (e.g., reptiles, birds, mammals)

Q12. What is cloning? Is it a form of sexual or asexual reproduction?

Solution

Cloning is the production of identical copies of an organism. It is a form of asexual reproduction since it involves a single parent and produces genetically identical offspring.

Example: Dolly the sheep - first mammal cloned from an adult somatic cell using nuclear transfer technique (1996)

Q13. What is the difference between oviparous and viviparous organisms?

Solution

Oviparous: Lay eggs that hatch outside the body (e.g., birds, reptiles, most fish, insects)
Viviparous: Give birth to young ones that develop inside the mother's body (e.g., mammals, some sharks)

Q14. Why is reproduction essential for organisms?

Solution

1. Continuation of species on Earth
2. Maintenance of population size
3. Source of genetic variation for evolution
4. Replacement of dead organisms
5. Ensures survival in changing environments

Q15. What is the difference between parthenogenesis and parthenocarpy?

Solution

Parthenogenesis: Development of embryo from unfertilized egg (e.g., honeybee drones, aphids)
Parthenocarpy: Development of fruit without fertilization, seedless fruits (e.g., banana, grapes)

Chapter 2: Sexual Reproduction in Flowering Plants →

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