Extra 20 long-answer questions from the chapter:7 "How Do Organisms Reproduce?" for Class 10 CBSE Science, along with detailed answers.
1. Explain the different modes of asexual reproduction with examples.
Answer:
Asexual reproduction is the mode of reproduction where a single parent produces offspring without the involvement of gametes. The different types are:
Binary Fission
– The parent cell splits into two identical daughter cells.
(Example: Amoeba, Bacteria)
Budding
– A small outgrowth (bud) develops on the parent body and detaches when mature.
(Example: Hydra, Yeast)
Fragmentation
– The body breaks into fragments, each developing into a new organism.
(Example: Planaria, Spirogyra)
Spore Formation
– Organisms produce spores that develop into new individuals.
(Example: Rhizopus, Fungi)
Vegetative Propagation
– New plants grow from vegetative parts like roots, stems, and leaves.
(Example: Potato,
Bryophyllum
, Rose)
2. Explain the process of sexual reproduction in flowering plants.
Answer:
Sexual reproduction in flowering plants involves:
Pollination
– Transfer of pollen from the anther to the stigma.
Self-pollination
(within the same flower or plant).
Cross-pollination
(between different plants of the same species).
Fertilization
– The male gamete (pollen) fuses with the female gamete (egg) in the ovule.
Post-Fertilization Changes:
The
zygote
develops into an
embryo
.
The
ovule
becomes the
seed
.
The
ovary
develops into a
fruit
.
Petals, sepals, and stamens fall off.
3. What is vegetative propagation? Describe different types with examples.
Answer:
Vegetative propagation is an asexual method of reproduction where new plants grow from vegetative parts.
Types of Vegetative Propagation:
Natural Vegetative Propagation:
By roots:
Sweet potato, Dahlia.
By stems:
Potato (tubers), Ginger (rhizomes).
By leaves:
Bryophyllum
(leaf buds).
Artificial Vegetative Propagation:
Cutting:
Stem cuttings are planted to grow a new plant (e.g., Rose, Hibiscus).
Layering:
Lower branches are bent and covered with soil (e.g., Jasmine).
Grafting:
A part of one plant is attached to another plant (e.g., Mango, Apple).
Advantages: Faster growth, preservation of traits, and propagation of seedless plants.
4. What is fertilization? Explain the process of fertilization in humans.
Answer:
Fertilization is the fusion of male and female gametes to form a zygote.
Process of Fertilization in Humans:
Sperm Production:
Testes produce sperm, which travels through the vas deferens and is released through the penis.
Egg Production:
The ovary releases an egg every month (ovulation).
Fertilization:
Occurs in the
fallopian tube
when sperm meets the egg.
The sperm penetrates the egg, and their nuclei fuse to form a
zygote
.
Zygote Development:
The zygote divides and forms an
embryo
, which implants in the
uterus
.
The embryo develops into a
fetus
inside the uterus.
5. What are the male and female reproductive organs in humans? Describe their functions.
Answer:
Male Reproductive System:
Testes
– Produce sperm and testosterone hormone.
Vas Deferens
– Transports sperm from testes to the urethra.
Seminal Vesicles & Prostate Gland
– Secrete fluid that nourishes sperm.
Penis
– Transfers sperm to the female body.
Female Reproductive System:
Ovaries
– Produce eggs and
estrogen
hormone.
Fallopian Tubes
– Transport egg and site of fertilization.
Uterus
– Supports
fetal
development.
Vagina
– Receives sperm and is the birth canal.
6. Explain the different methods of contraception and their importance.
Answer:
Methods of Contraception:
Barrier Methods:
Prevent sperm from reaching the egg (e.g., Condoms, Diaphragms).
Hormonal Methods:
Regulate ovulation using pills, injections, or implants (e.g., Oral pills, Contraceptive patches).
Intrauterine Devices (IUDs):
Devices like
Copper-T
prevent implantation.
Surgical Methods:
Vasectomy
(males) – Vas deferens is cut.
Tubectomy
(females) – Fallopian tubes are blocked.
Importance: Prevents unwanted pregnancy and sexually transmitted diseases (STDs).
7. Explain the menstrual cycle in human females.
Answer:
The menstrual cycle is a 28-day cycle in females that prepares the body for pregnancy.
Menstrual Phase (Days 1-5):
The uterine lining sheds if fertilization does not occur.
Follicular Phase (Days 6-13):
Egg matures in the ovary, and the uterus lining thickens.
Ovulation Phase (Day 14):
The ovary releases a mature egg.
Luteal Phase (Days 15-28):
The uterus prepares for implantation; if fertilization does not occur, the cycle repeats.
8. What are sexually transmitted diseases (STDs)? Name two bacterial and two viral STDs.
Answer:
STDs are infections transmitted through sexual contact.
Bacterial STDs:
Syphilis,
Gonorrhea
.
Viral STDs:
HIV/AIDS, Genital Herpes.
Prevention: Safe sex practices, use of condoms, regular medical check-ups.
9. What is placenta? What are its functions?
Answer:
The placenta is an organ that connects the fetus to the mother's uterus.
Functions:
Provides oxygen and nutrients
to the
fetus
.
Removes waste products
from the
fetus
.
Acts as a barrier
against harmful substances.
Secretes hormones
needed for pregnancy.
10. Explain the significance of DNA copying in reproduction.
Answer:
DNA copying ensures genetic continuity.
Passes genetic information
to the next generation.
Maintains species characteristics.
Allows variations
that help in evolution.
Errors in DNA copying
can lead to mutations.
11. Differentiate between internal and external fertilization.
Answer:
Fertilization is the fusion of male and female gametes. It is of two types:
|
Feature |
Internal Fertilization |
External Fertilization |
|---|---|---|
|
Site of fertilization |
Inside the female body |
Outside the female body (in water) |
|
Gamete protection |
Well protected inside the body |
Gametes are exposed to environmental risks |
|
Number of gametes |
Fewer gametes produced |
Large number of gametes released |
|
Survival rate |
High as the embryo is protected |
Low due to predators and environmental hazards |
|
Examples |
Humans, birds, reptiles |
Frogs, fishes, amphibians |
12. Explain the advantages and disadvantages of sexual reproduction.
Answer:
Advantages:
Genetic Variation
– Offspring are genetically different, leading to better adaptability.
Evolutionary Benefit
– Helps in the survival of species in changing environments.
Elimination of Harmful Mutations
– Natural selection removes weak traits over generations.
Disadvantages:
Slow Process
– Requires two parents, which takes more time than asexual reproduction.
Energy Consuming
– Gamete production, mating, and development require high energy.
Uncertainty
– Fertilization may not always occur successfully.
13. Describe the development of a zygote into an embryo in humans.
Answer:
Fertilization:
The sperm fuses with the egg in the fallopian tube to form a
zygote
.
Zygote Cleavage:
The zygote undergoes repeated mitotic divisions to form a
morula
.
Blastocyst Formation:
The morula develops into a
blastocyst
with a fluid-filled cavity.
Implantation:
The blastocyst implants in the
uterus
lining.
Embryo Development:
The embryo develops
limbs, brain, and other organs
over time.
Fetal
Stage:
By the
8th week
, the embryo is called a
fetus
, which grows until birth.
14. What are the advantages of vegetative propagation?
Answer:
Fast Growth:
New plants develop quickly without seeds.
Genetic Stability:
Offspring are genetically identical to the parent plant.
Propagation of Seedless Plants:
Plants like banana and sugarcane can be grown without seeds.
Disease Resistance:
Desirable traits can be retained through artificial methods.
Economic Benefits:
Useful for large-scale farming of fruit plants like mango and rose.
15. Describe the role of hormones in the human reproductive system.
Answer:
Male Hormones:
Testosterone
– Produced by testes, responsible for sperm production and male secondary sexual characteristics (facial hair, deep voice).
Female Hormones:
Estrogen
– Produced by ovaries, responsible for female secondary sexual characteristics (breast development, menstruation).
Progesterone
– Prepares the uterus for pregnancy and maintains it.
Follicle-Stimulating Hormone (FSH)
– Stimulates egg development in ovaries.
Luteinizing Hormone (LH)
– Triggers ovulation.
16. What are the structural adaptations of a flower for pollination?
Answer:
For Wind Pollination:
Small, light, and dry pollen grains.
Large feathery stigma to capture pollen.
For Insect Pollination:
Brightly
colored
petals to attract insects.
Presence of nectar and scent.
For Water Pollination:
Pollen grains are waterproof.
Flowers remain close to the water surface.
17. Why is variation important in reproduction?
Answer:
Better Adaptability:
Variations help species survive in changing environments.
Disease Resistance:
Some individuals may have natural resistance to diseases.
Evolutionary Benefit:
Variations accumulate over generations, leading to new species.
Survival Advantage:
Organisms with beneficial variations are more likely to reproduce.
Example: Giraffes with longer necks could reach more food, helping them survive.
18. Explain the function of different parts of a flower in reproduction.
Answer:
Stamen (Male Part):
Anther:
Produces pollen (male gametes).
Filament:
Supports the anther.
Carpel/Pistil (Female Part):
Stigma:
Receives pollen.
Style:
Connects stigma to ovary.
Ovary:
Contains ovules, which develop into seeds after fertilization.
Petals:
Attract pollinators.
Sepals:
Protect the bud before blooming.
19. How do contraceptive methods help in population control?
Answer:
Contraceptive methods help prevent unwanted pregnancies and control population growth.
Methods:
Barrier Methods:
Condoms, diaphragms prevent sperm entry.
Hormonal Methods:
Birth control pills regulate ovulation.
Intrauterine Devices (IUDs):
Copper-T prevents implantation.
Surgical Methods:
Vasectomy (Males)
– Sperm transport blocked.
Tubectomy (Females)
– Egg transport blocked.
Importance:
Reduces overpopulation.
Lowers maternal and infant mortality rates.
Prevents sexually transmitted diseases (STDs).
20. What are the differences between artificial and natural propagation?
Answer:
|
Feature |
Natural Propagation |
Artificial Propagation |
|---|---|---|
|
Origin |
Occurs naturally |
Done by humans |
|
Methods |
Budding, Fragmentation, Spores |
Grafting, Cutting, Layering |
|
Genetic Variation |
No variation |
Can create hybrids |
|
Example |
Bryophyllum, Potato |
Rose, Mango, Sugarcane |
