Answer The Following Question
1. What is the importance of DNA copying in reproduction?
Ans: DNA carries genetic information determining an organism’s traits.
DNA is copied during reproduction to pass on this information to offspring.
Ensures genetic continuity and inheritance of traits.
Provides instructions for making proteins essential for body structure and function.
2. Why is variation beneficial to the species but not necessarily for the individual?
Ans: Variations help species survive in changing environments.
If the environment changes drastically, variations increase the chances of some individuals surviving.
While beneficial for the species as a whole, variation may not always benefit the individual directly.
3. How does binary fission differ from multiple fissions?
Ans: Binary Fission:
A single parent cell divides into two equal daughter cells.
Occurs in organisms like bacteria, amoeba, and paramecium.
Simple and faster process.
Multiple Fission:
A single parent cell divides into multiple daughter cells.
Occurs in organisms like Plasmodium (causes malaria).
The parent cell undergoes division to form several smaller cells simultaneously, often in response to unfavorable conditions.
4. How will an organism be benefited if it reproduces through spores?
Ans: Benefits of Reproducing Through Spores:
Protection: Spores have thick, protective walls that shield them from harsh environmental conditions, such as extreme temperatures, dryness, or UV radiation.
Dispersal: Spores can be easily dispersed by wind, water, or animals, allowing the organism to colonize new areas and spread more effectively.
Survival in Unfavorable Conditions: Spores can remain dormant for long periods until they find favorable conditions for growth, ensuring the survival of the species even in challenging environments.
Rapid Colonization: Once they land in a suitable habitat, spores can germinate and grow quickly, allowing for the fast establishment of new individuals.
5. Can you think of reasons why more complex organism cannot give rise to new individuals through regeneration?
Ans: Complex organisms cannot give rise to new individuals through regeneration because:
Cell Specialization: Cells are specialized into different types and can’t form new individuals.
Organ-System Level: They have interconnected organ systems that can’t regenerate a whole new organism.
Coordination: Regenerating a complete organism requires complex systems working together, which is not possible.
Developmental Constraints: Only certain tissues can regenerate, not whole organs or systems.
Hence, regeneration in complex organisms is limited to repair, not reproduction.
6. Why is vegetative propagation practiced for growing some types of plants?
Ans: Vegetative propagation is practiced for growing certain plants because:
Faster Flowering and Fruiting: Plants raised by vegetative propagation can bear flowers and fruits earlier than those grown from seeds.
Propagation of Seedless Plants: It allows the propagation of plants like banana, orange, rose, and jasmine that cannot produce seeds.
Genetic Uniformity: Plants produced through vegetative propagation are genetically identical to the parent plant, ensuring all desired traits are passed on.
7. Why is DNA coping essential part of the process of reproduction?
Ans : DNA contains information for the inheritance of features from parents to next generation. DNA presents in nucleus of cells are the information source for making protein. If information is different, different protein will be made that lead to altered body design.
8. How is process of pollination different from fertilization?
Ans: Pollination:
Pollination is the transfer of pollen (containing male gametes) from the male reproductive organ (anther) to the female reproductive organ (stigma) of a flower.
It can be biological (insects, birds, wind) or mechanical (e.g., by water).
It does not involve fusion of male and female gametes.
Fertilization:
Fertilization occurs after pollination when the male gamete (sperm) fuses with the female gamete (egg) in the ovule.
This fusion results in the formation of a zygote, which eventually develops into a seed.
9. What is the role of the seminal vesicles and the prostate gland?
Ans: The role of the seminal vesicles and the prostate gland is as follows:
Seminal Vesicles:
They secrete a thick, nutrient-rich fluid that provides energy (mainly fructose) to the sperm.
This fluid also helps in the transportation and movement of sperm.
Prostate Gland:
It secretes a milky fluid that neutralizes the acidic environment of the urethra and female reproductive tract, providing a safer environment for the sperm.
The fluid also helps in the motility of sperm.
10. What are the changes seen in girls at the time of puberty?
Ans : The changes seen in girls during puberty include:
Breast Development: The breasts begin to grow, and the skin of the nipples darkens.
Menstruation: Girls start menstruating (menstrual periods) around this time, marking the onset of reproductive maturity.
Growth Spurts: Height increases as the body grows.
Widening of Hips: The hips become broader, and the body takes on a more rounded shape.
Pubic and Underarm Hair: Hair starts growing in the pubic area and underarms.
Increased Sweating: More sweat is produced, and the body odor changes due to hormonal changes.
These changes are part of the physical and hormonal development that prepares the body for reproduction.
11. How does the embryo get nourishment inside the mother’s body?
Ans: The embryo gets nourishment inside the mother’s body through the following process:
Placenta Formation: The placenta, a special tissue embedded in the uterine wall, connects the mother and the embryo.
Villi: The outer tissue surrounding the embryo forms finger-like projections called villi. These villi increase the surface area for nutrient and oxygen exchange.
Nutrient and Oxygen Transfer: The mother’s blood, which surrounds the villi, supplies the embryo with oxygen and nutrients.
Waste Removal: The placenta also helps remove waste products from the embryo’s blood to the mother’s bloodstream for excretion.
This connection allows the embryo to receive essential nutrients and oxygen while also getting rid of waste materials.
12. If a woman is using a Copper-T, will it help in protecting her from sexually transmitted diseases?
Ans: Copper-T is a form of intrauterine device (IUD) used to prevent unwanted pregnancies. However, it does not protect against sexually transmitted diseases (STDs). It only prevents pregnancy by altering the environment in the uterus to prevent fertilization. To protect against STDs, additional precautions like condoms are necessary.
13. Asexual reproduction takes place through budding in
(a) Amoeba
(b) Yeast
(c) Plasmodium
(d) Leishmania.
Ans : (b) Yeast
14. Which of the following is not a part of female reproductive system in human beings?
(a) Ovary(b) Uterus
(c) Vas deferens
(d) Fallopian tube
Ans : (c) Vas deferens
15. The anther contains
(a) Sepals
(b) Ovules
(c) Carpel
(d) Pollen grains.
Ans : (d) Pollen grains.
16. What are the advantages of sexual reproduction over asexual reproduction?
Ans: Advantages of sexual reproduction over asexual reproduction:
Genetic variation: Sexual reproduction results in variations due to the recombination of DNA.
Survival advantage: These variations help species adapt to changing environments, increasing survival chances.
Greater diversity: Offspring are genetically unique, which can lead to a stronger gene pool.
In contrast, asexual reproduction does not introduce genetic variation, which can limit adaptability.
17. What are the functions performed by the testis in human beings?
Ans: Functions of testis in human beings:
Production of sperms: Testes produce male gametes called sperms.
Secretion of testosterone: Testosterone, the male hormone, is responsible for secondary sexual characteristics like facial hair, deep voice, and muscle growth.
18. Why does menstruation occur?
Ans: If the egg released by the ovary is not fertilized, it disintegrates after about one day.
The uterus prepares a thick and spongy lining every month to nourish a fertilized egg.
When fertilization does not occur, this uterine lining is no longer needed.
The lining breaks down and is expelled through the vagina as blood and mucus.
This monthly cycle is called menstruation.
19. Draw a labeled diagram of the longitudinal section of a flower.
Ans :
20. What are the different methods of contraception?
Ans: Different Methods of Contraception:
Natural Method:
Avoids the meeting of sperm and ovum.
Sexual activity is avoided from the 10th to 17th day of the menstrual cycle when ovulation occurs.
Barrier Method:
Prevents fertilization using physical barriers like condoms (for males and females).
Condoms are thin rubber coverings for the penis (males) or vagina (females).
Oral Contraceptives:
Tablets or drugs are taken orally.
Contain hormones that prevent the release of eggs, thus avoiding fertilization.
Implants and Surgical Methods:
Copper-T or loops: Placed in the uterus to prevent pregnancy.
Surgical Methods:
Vasectomy: Blocking of vas deferens to stop sperm transfer (males).
Tubectomy: Blocking of fallopian tubes to prevent egg movement (females).
21. How are the modes of reproduction different in unicellular and multicellular organism?
Ans: Difference in Modes of Reproduction in Unicellular and Multicellular Organisms:
Unicellular Organisms:
Reproduce through asexual methods like cell division (binary fission) or cell fusion.
Example: Amoeba, Bacteria.
Multicellular Organisms:
Simple Body Organization: Reproduce through asexual methods like budding (Hydra) or fragmentation (Spirogyra).
Complex Body Organization: Reproduce primarily through sexual reproduction.
Example: Humans, Animals, and Flowering Plants.
22. How does reproduction help in providing stability to populations of species?
Ans: DNA Consistency: Reproduction ensures accurate DNA copying, maintaining body design and features essential for survival.
Survival in a Niche: Stable body designs help organisms adapt to and survive in specific environmental conditions (niches).
Population Stability: By producing new individuals, reproduction maintains population size, ensuring species’ continuity over generations.
What could be the reasons for adopting contraceptive methods?
Reasons for Adopting Contraceptive Methods:
Prevent Unwanted Pregnancy: To avoid pregnancy when a woman is not physically, mentally, or financially ready.
Health Protection: Pregnancy places significant demands on a woman’s body, and contraception helps avoid health risks.
Prevent STDs: Methods like condoms reduce the risk of sexually transmitted diseases (STDs) like HIV/AIDS.
Family Planning: Helps in controlling the timing and number of children for a stable and planned family life.