CBSE Class 10 Science (2026–27)
Chapter 7: How do Organisms Reproduce?
20 Important Questions and Answers
1. What is reproduction and why is it important for organisms?
Answer:
Reproduction is the biological process by which living organisms produce new individuals of their own kind. It is essential because it ensures the continuity of a species from one generation to the next. Reproduction helps maintain the population of organisms and prevents extinction. It also transfers genetic information from parents to offspring. Through reproduction, variations are introduced in populations, which help organisms adapt to changing environmental conditions. Although reproduction is not necessary for the survival of an individual organism, it is vital for the survival of the species. Thus, reproduction plays a key role in sustaining life on Earth and promoting evolution.
2. Differentiate between asexual and sexual reproduction.
Answer:
Asexual reproduction involves only one parent and does not require the formation or fusion of gametes. The offspring produced are genetically identical to the parent and are called clones. Examples include binary fission in Amoeba and budding in Hydra. Sexual reproduction involves two parents and requires the formation and fusion of male and female gametes. The offspring inherit characteristics from both parents and show variations. Sexual reproduction promotes genetic diversity, which helps species adapt to environmental changes. While asexual reproduction is faster and simpler, sexual reproduction is more complex but beneficial for evolution and long-term survival.
3. Explain binary fission in Amoeba.
Answer:
Binary fission is a common method of asexual reproduction in Amoeba. In this process, the nucleus of the Amoeba first divides into two identical nuclei through mitosis. After nuclear division, the cytoplasm divides, forming two separate daughter cells. Each daughter Amoeba receives one nucleus and sufficient cytoplasm. These daughter cells grow and function independently as new organisms. Binary fission occurs under favorable environmental conditions and helps increase the population rapidly. Since the offspring are genetically identical to the parent, this method produces clones. Binary fission is a simple, efficient, and rapid method of reproduction in unicellular organisms.
4. Describe budding in Hydra.
Answer:
Budding is an asexual mode of reproduction commonly seen in Hydra. In this process, repeated cell division occurs at a specific site on the body of the parent Hydra, forming a small outgrowth called a bud. The bud gradually grows and develops structures such as tentacles and a mouth. As it matures, the bud resembles a miniature Hydra. Once fully developed, it detaches from the parent body and starts living independently. Budding allows Hydra to reproduce rapidly under favorable conditions. Since only one parent is involved, the offspring are genetically identical to the parent and are known as clones.
5. What is regeneration? Give an example.
Answer:
Regeneration is the ability of some organisms to regrow lost or damaged body parts and, in some cases, develop into a complete new organism. This process occurs due to the presence of specialized cells that divide and differentiate into various tissues. An example of regeneration is Planaria, a flatworm. If a Planaria is cut into several pieces, each piece can regenerate the missing parts and form a complete organism. Regeneration is not common in all animals and is generally seen in simple organisms. It helps organisms survive injuries and, in some cases, acts as a method of asexual reproduction.
6. What is vegetative propagation? Mention its advantages.
Answer:
Vegetative propagation is a form of asexual reproduction in plants where new plants are produced from vegetative parts such as roots, stems, or leaves instead of seeds. Examples include potato, ginger, and Bryophyllum. This method has several advantages. It enables rapid multiplication of plants and produces genetically identical offspring. Plants grown through vegetative propagation mature faster and retain desirable characteristics of the parent plant. It is useful for propagating seedless plants such as banana and sugarcane. Farmers and gardeners use this method to obtain large numbers of healthy plants with uniform traits in a short period.
7. What is tissue culture and how is it useful?
Answer:
Tissue culture is a modern technique of plant propagation in which small pieces of plant tissue are grown in a nutrient-rich sterile medium under controlled conditions. The cells divide continuously and develop into complete plants. This method is useful because it allows the production of a large number of identical plants within a short period. Tissue culture helps in conserving rare and endangered plant species. It also produces disease-free plants and is widely used in agriculture, horticulture, and plant breeding programs. Since the plants produced are genetically similar, desired characteristics can be maintained effectively.
8. What are the advantages of sexual reproduction?
Answer:
Sexual reproduction offers several advantages over asexual reproduction. It involves the fusion of male and female gametes, resulting in offspring that inherit characteristics from both parents. This creates genetic variation among individuals. Variations increase the chances of survival in changing environmental conditions and help populations adapt to new challenges. Sexual reproduction contributes to the process of evolution by providing diversity within a species. It also reduces the chances of harmful genetic traits being passed unchanged through generations. Therefore, sexual reproduction plays a significant role in the long-term survival, adaptability, and evolution of organisms.
9. What is pollination? Name its types.
Answer:
Pollination is the process of transferring pollen grains from the anther to the stigma of a flower. It is an essential step in sexual reproduction in flowering plants because it enables fertilization. There are two main types of pollination. Self-pollination occurs when pollen is transferred to the stigma of the same flower or another flower on the same plant. Cross-pollination occurs when pollen is transferred from one plant to the flower of another plant of the same species. Agents such as wind, water, insects, birds, and animals help in pollination. Cross-pollination usually produces greater genetic variation.
10. Explain fertilization in flowering plants.
Answer:
Fertilization in flowering plants occurs after pollination. When a pollen grain lands on the stigma, it germinates and forms a pollen tube that grows through the style toward the ovule. The male gamete travels through the pollen tube and reaches the ovule. Inside the ovule, the male gamete fuses with the female gamete (egg cell) to form a zygote. This process is called fertilization. The zygote develops into an embryo, while the ovule becomes a seed and the ovary develops into a fruit. Fertilization is essential for seed formation and the continuation of plant species.
11. What changes occur in a flower after fertilization?
Answer:
Several changes occur in a flower after fertilization. The fertilized egg develops into a zygote, which grows into an embryo. The ovule transforms into a seed containing the embryo and stored food material. The ovary enlarges and develops into a fruit that protects the seeds. Other floral parts such as petals, sepals, stamens, and stigma usually wither and fall off. The fruit helps in seed dispersal, while the seeds germinate under suitable conditions to produce new plants. These post-fertilization changes ensure the successful reproduction and continuation of flowering plant species.
12. What are the functions of testes in the male reproductive system?
Answer:
The testes are the primary reproductive organs in the male reproductive system. They are located in the scrotum outside the abdominal cavity. The testes perform two important functions. First, they produce male gametes called sperms through a process known as spermatogenesis. Second, they secrete the hormone testosterone. Testosterone is responsible for the development of male secondary sexual characteristics such as facial hair, deep voice, and muscular body structure. It also regulates sperm production and reproductive functions. Thus, the testes play a crucial role in both reproduction and the development of male characteristics during puberty.
13. Explain the role of the ovary in the female reproductive system.
Answer:
The ovaries are the primary reproductive organs in females. There are two ovaries located on either side of the uterus. Their main function is to produce female gametes called ova or eggs. Generally, one mature egg is released during each menstrual cycle through the process of ovulation. The ovaries also produce important hormones such as estrogen and progesterone. These hormones regulate the menstrual cycle, control reproductive functions, and promote the development of secondary sexual characteristics such as breast development and widening of hips. Therefore, the ovaries are essential for reproduction and the maintenance of female reproductive health.
14. What is menstruation?
Answer:
Menstruation is a natural biological process that occurs in females after puberty. Every month, the uterus prepares for pregnancy by developing a thick, blood-rich lining. If fertilization does not occur, the egg released from the ovary degenerates and the uterine lining breaks down. This lining, along with blood and mucus, is discharged through the vagina. This process is called menstruation or the menstrual cycle. It usually occurs every 28 to 30 days and lasts for about three to seven days. Menstruation is a sign that the female reproductive system is functioning normally and preparing for possible pregnancy.
15. What is puberty and what changes occur during puberty?
Answer:
Puberty is the stage of life when a child’s body matures into an adult body capable of reproduction. It usually begins between the ages of 10 and 16 years. During puberty, hormonal changes occur in the body. In boys, facial hair develops, the voice deepens, shoulders broaden, and testes begin producing sperms. In girls, breasts develop, hips widen, and menstruation begins. Rapid growth in height and weight occurs in both sexes. Emotional and psychological changes are also common. Puberty marks the beginning of reproductive maturity and prepares the body for adulthood and reproduction.
16. What is fertilization in humans?
Answer:
Fertilization in humans is the fusion of a male gamete (sperm) and a female gamete (ovum) to form a zygote. This process usually takes place in the fallopian tube. During sexual intercourse, millions of sperms enter the female reproductive tract, but only one sperm successfully fuses with the ovum. The resulting zygote contains genetic material from both parents. The zygote undergoes repeated cell divisions and develops into an embryo. The embryo later implants itself in the uterus and continues developing into a fetus. Fertilization marks the beginning of a new human life.
17. What is the role of the placenta during pregnancy?
Answer:
The placenta is a specialized organ that develops during pregnancy and connects the developing fetus to the mother’s uterus. It serves as a link between the mother and the fetus. The placenta supplies oxygen, nutrients, and essential substances from the mother’s blood to the fetus. It also removes carbon dioxide and waste products produced by the fetus. Additionally, the placenta produces hormones that help maintain pregnancy. Although the blood of the mother and fetus does not mix directly, exchange of materials occurs through the placenta. Thus, the placenta is essential for the growth, nourishment, and protection of the developing fetus.
18. Why is variation important in reproduction?
Answer:
Variation refers to differences in characteristics among individuals of the same species. It is important because it helps organisms adapt to changing environmental conditions. Variations arise mainly during sexual reproduction due to the mixing of genetic material from two parents. Some variations may provide advantages that increase an organism’s chances of survival and reproduction. Over many generations, beneficial variations accumulate and contribute to evolution. Without variation, all individuals would be identical and equally vulnerable to environmental changes, diseases, or disasters. Therefore, variation enhances the survival of species and supports the process of natural selection.
19. What are sexually transmitted diseases (STDs)? Give examples.
Answer:
Sexually transmitted diseases (STDs) are infections that spread primarily through sexual contact with an infected person. These diseases may be caused by bacteria, viruses, or other microorganisms. Common examples include gonorrhea, syphilis, and AIDS caused by the Human Immunodeficiency Virus (HIV). STDs can affect the reproductive system and may lead to serious health complications if left untreated. Symptoms may include pain, discharge, sores, or fever, though some infections may show no symptoms initially. Preventive measures include maintaining personal hygiene, practicing safe sex, avoiding multiple sexual partners, and seeking timely medical advice and treatment.
20. How can reproductive health be maintained?
Answer:
Reproductive health refers to the proper functioning and well-being of the reproductive system. It can be maintained through a healthy lifestyle and awareness. A balanced diet, regular exercise, and personal hygiene are essential for reproductive health. Individuals should be educated about puberty, reproductive processes, and sexually transmitted diseases. Safe sexual practices help prevent infections and unwanted pregnancies. Regular medical check-ups and timely treatment of reproductive disorders are also important. Avoiding harmful habits such as smoking, alcohol consumption, and drug abuse further supports reproductive health. Good reproductive health contributes to overall physical, mental, and social well-being.