| Class | 10th |
| Subject | Science (NCERT) |
| Category | Important Questions |
How do Organisms Reproduce? Class 10 Science Chapter 7 Important Question Answer
Q1. Which organism cause Kala-azar ?
Ans – Leishmania
Q2. What is Germination ?
Ans – The seed contains the future plant or embryo which develops into a seedling under appropriate conditions. This process is known as germination.
Q3. Describe the process of budding in Hydra. Most Important
Ans – Hydra use regenerative cells for reproduction in the process of budding. In Hydra, a bud develops as an outgrowth due to repeated cell division at one specific site . These buds develop into tiny individuals and when fully mature, detach from the parent body and become new independent individuals.
Q4. Write about spore formation in Rhizopus.
Ans – The tiny blob-on-a-stick structures are involved in reproduction. The blobs are sporangia, which contain cells, or spores, that can eventually develop into new Rhizopus individuals. The spores are covered by thick walls that protect them until they come into contact with another moist surface and can begin to grow.
Q5. Draw a well labelled diagram of Longitudinal section of a flower. Most Important
Ans –
Q6. Why are the testes located outside the abdominal cavity in scrotum ?
Ans – The formation of germ-cells or sperms takes place in the testes. These are located outside the abdominal cavity in scrotum because sperm formation requires a lower temperature than the normal body temperature.
Q7. Name various glands associated with male reproductive system & write their role.
Ans – Various glands associated with the male reproductive system and their roles include:
1. Testes:
- Role: Produce sperm cells (spermatogenesis) and secrete testosterone, a male sex hormone.
2. Vas Deferens:
- Role: Transports mature sperm from the epididymis to the urethra during ejaculation.
3. Prostate Gland:
- Role: Secretes a milky alkaline fluid that enhances sperm motility and helps neutralize acidity in the female reproductive tract.
Q8. Draw a well labelled diagram of human female reproductive system.
OR
Explain human female reproductive system with diagram.
Ans – The female germ-cells or eggs are made in the ovaries. They are also responsible for the production of some hormones. On reaching puberty, one egg is produced every month by one of the ovaries. The egg is carried from the ovary to the womb through a thin oviduct or fallopian tube. The two oviducts unite into an elastic bag-like structure known as the uterus.
Q9. What happens when the egg is not fertilized?
OR
Why does menstruation occur?
Ans – If the egg is not fertilised, it lives for about one day. Since the ovary releases one egg every month, the uterus also prepares itself every month to receive a fertilised egg. Thus its lining becomes thick and spongy. This would be required for nourishing the embryo if fertilisation had taken place. Now, however, this lining is not needed any longer. So, the lining slowly breaks and comes out through the vagina as blood and mucous. This cycle takes place roughly every month and is known as menstruation. It usually lasts for about two to eight days
Q10. Write about the process of fission in various organisms.
Ans – For unicellular organisms, cell division, or fission, leads to the creation of new individuals. Many different patterns of fission have been observed. Many bacteria and protozoa simply split into two equal halves during
cell division. In organisms such as Amoeba, Leishmania (which cause kala-azar) binary fission occurs in a definite orientation in relation to these structures. Other single-celled organisms, such as the malarial parasite, Plasmodium, divide into many daughter cells simultaneously by multiple fission.
Q11. What is Pollination ? Write about self and cross pollination.
Ans – The pollen needs to be transferred from the stamen to the stigma. If this transfer of pollen occurs in the same flower, it is referred to as self-pollination. On the other hand, if the pollen is transferred from one flower to another, it is known as cross pollination.
Q12. In which organism fragmentation occur ? Write about its process.
Ans – In multi-cellular organisms with relatively simple body organisation, simple reproductive methods can still work. In organisms like Spirogyra simply breaks up into smaller pieces upon maturation. These pieces or fragments grow into new individuals. This is not true for all multi-cellular organisms. They cannot simply divide cell-by-cell.
Q13. Discuss the structure of female reproductive part of a flower.
Ans – Pistil is present in the centre of a flower and is the female reproductive part. It is made of three parts. The swollen bottom part is the ovary, middle elongated part is the style and the terminal part which may be sticky is the stigma. The ovary contains ovules and each ovule has an egg cell. The male germ-cell produced by pollen grain fuses with the female gamete present in the ovule. This fusion of the germ-cells or fertilisation gives us the zygote which is capable of growing into a new plant.
Q14. Draw a well labelled diagram of seed germination.
Ans –
Q15. What is the role of the seminal vesicles and the prostate gland?
Ans – Role of Seminal Vesicles – It Produce seminal fluid, a nutrient-rich fluid that nourishes and helps transport of sperm.
Role of Prostate Gland – It Secretes a milky alkaline fluid that enhances sperm motility and helps neutralize acidity in the female reproductive tract.
Q16. How is the process of pollination different from fertilization? Most Important
Ans –
| Pollination | Fertilization |
|
|
Q17. Describe three different methods of contraception.
Ans – Contraception to avoid pregnancy can be achieved by the use of condoms, oral pills, copper-T and other methods.
Q18. What is the name of the process of formation of new individual in Amoeba?
Ans – Binary Fission
Q19. What is function of testis in man?
Ans – Production of Sperm and testosterone hormone.
Q20. What are unisexual and bisexual flowers? Give examples.
Ans – The flower may be unisexual when it contains either stamens or pistil. Examples are papaya, watermelon. The flower may be bisexual when it contains both stamens and pistil. Example – Hibiscus, mustard.
Q21. What is Regeneration ?
Ans – Many fully differentiated organisms have the ability to give rise to new individual organisms from their body parts. That is, if the individual is somehow cut or broken up into many pieces, many of these pieces grow into separate individuals. For example, simple animals like Hydra and Planaria can be cut into any number of pieces and each piece grows into a complete organism. This is known as regeneration.
Q22. What is the function of ovary in human beings?
Ans – The ovaries in human females have two main functions: they produce eggs for reproduction (ovum production) and secrete hormones (estrogen and progesterone) that regulate the menstrual cycle, support pregnancy, and maintain the reproductive system.
Q23. What is vegetative propagation? How is it useful?
Ans – There are many plants in which parts like the root, stem and leaves develop into new plants under appropriate conditions. This property of vegetative propagation is used in methods such as layering or grafting to grow many plants like sugarcane, roses, or grapes for agricultural purposes. Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds. Such methods also make possible the propagation of plants such as banana, orange, rose and jasmine that have lost the capacity to produce seeds. Another advantage of vegetative propagation is that all plants produced are genetically similar enough to the parent plant to have all its characteristics.
Q24. Which organism divides into many daughter cells through multiple fission?
Ans – malarial parasite, Plasmodium,
Q25. Write those changes of puberty that are common to girls and boys.
Ans –
| Changes | Girls during Puberty | Boys during Puberty |
|---|---|---|
| Growth | Significant increase in height. | Significant increase in height. |
| Secondary Sexual Characteristics | Development of breasts, widening of hips, onset of menstruation. | Growth of facial and body hair, deepening of voice. |
| Hormonal Changes | Increase in estrogen levels. | Increase in testosterone levels. |
| Body Hair Growth | Growth of pubic hair and underarm hair. | Growth of pubic hair, facial hair, and body hair. |
| Skin Changes | Changes in skin texture and oiliness. | Changes in skin texture and oiliness. |
Q26. Growth of facial hair and deepening of voice are symptoms of puberty in boys. Which hormone is responsible for it?
Ans – testosterone
Q27. In a flower, pollen tube enters through pistil into ovule. Name that part of pistil.
Ans – Style
Q28. What is difference between binary fission and multiple fission ? Explain with example.
Ans –
| Feature | Binary Fission | Multiple Fission |
|---|---|---|
| Number of Offspring | Two (2) | Multiple |
| Genetic Identity | Offspring are genetically identical to the parent | Offspring may not be genetically identical |
| Process | Single parent cell divides into two equal halves | Single parent cell produces multiple offspring |
| Examples | Bacteria, Amoeba | Plasmodium (malaria parasite) |
Q29. What are different contraceptive methods? How are they important for reproductive health? Most Important
Ans – Contraceptive methods to avoid pregnancy can be achieved by the use of condoms, oral pills, copper-T and other methods. It’s important to note that the choice of contraceptive method depends on individual preferences, health considerations, and lifestyle factors.
Q30. What are the changes seen in girls and boys at time of puberty?
Ans –
| Changes | Girls during Puberty | Boys during Puberty |
|---|---|---|
| Growth | Significant increase in height. | Significant increase in height. |
| Development of Breasts | Breast development and mammary gland growth. | No breast development; growth of chest muscles. |
| Onset of Menstruation | Menarche (start of the menstrual cycle). | No menstrual cycle; reproductive maturity begins. |
| Body Hair Growth | Growth of pubic hair and underarm hair. | Growth of pubic hair, facial hair, and underarm hair. |
| Voice Changes | No significant change in voice pitch. | Deepening of the voice due to larynx enlargement. |
| Hormonal Changes | Increase in estrogen levels. | Increase in testosterone levels. |
| Growth of Facial and Body Hair | No significant growth of facial or body hair. | Growth of facial hair, body hair, and underarm hair. |
Q31. Describe the importance of variation.
Ans – Populations of organisms fill well-defined places, or niches, in the ecosystem, using their ability to reproduce. The consistency of DNA copying during reproduction is important for the maintenance of body design features that allow the organism to use that particular niche. Reproduction is therefore linked to the stability of populations of species. However, niches can change because of reasons beyond the control of the organisms. Temperatures on earth can go up or down, water levels can vary, or there could be meteorite hits, to think of a few examples. If a population of reproducing organisms were suited to a particular niche and if the niche were drastically altered, the population could be wiped out. However, if some variations were to be present in a few individuals in these populations, there would be some chance for them to survive. Thus, if there were a population of bacteria living in temperate waters, and if the water temperature were to be increased by global warming, most of these bacteria would die, but the few variants resistant to heat would survive and grow further. Variation is thus useful for the survival of species over time.
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