Important Questions Class 10 Science Chapter 8

Important Questions Class 10 Science Chapter 8 –  How Do Organisms Reproduce? 

Science is an important subject taught in school. In this chapter, students will study different processes of reproduction. Reproduction is an important activity of the organisms because, in this way, they can increase their population.

There are multiple methods of reproduction. Unicellular living beings produce new living beings by fission. At the same time, multicellular organisms create living beings by other methods based on the system’s complexity. Trees create new living  beings through seeds, which is a developed process of the sexual reproduction system. Developed living beings, including humans, have reproductive organs to form new human beings. Students will study human reproductive systems too. It is an important chapter, and students must solve questions to score better in exams.

Extramarks is a leading company that provides students with all the important study materials. Our experts have prepared the Important Questions Class 10 Science Chapter 8 to help students in practice. They collected the questions from different sources such as the textbook exercise, CBSE syllabus, CBSE sample papers, NCERT exemplars and important reference books. They have solved the questions, and experienced professionals have further checked the answers to ensure the best quality of the content. Thus, the Important Questions Class 10 Science Chapter 8 will help students boost their confidence.

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CBSE Class 10 Science Important Questions 2022-23

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Important Questions Class 10 Science Chapter 8 – With Solutions

Practice is very important to score better in exams. The experts have made the question series to help students solve problems in practice. They collected the questions from different sources, such as the textbook exercise, CBSE sample papers, CBSE past years’ question papers, and important reference books. They have also solved the questions, and experienced professionals have further checked the answers to ensure the best quality of the content. Thus, the Important Questions Class 10 Science Chapter 8 will help students score better in exams. The important questions are-

Question 1: Why is DNA copying important in reproduction?

Answer 1. The information related to the inheritance of characteristics from one parent to the next is stored in the DNA. The blueprint for body design is produced as a result of DNA copying. The characteristic features to be transmitted from one generation to the next are maintained by DNA copying. The useful variations essential for species’ survival over time are related to DNA copying.

Question 2: Variation is beneficial to the species, but it is not necessary for the individual. Give the reason.

Answer 2. In species, many individuals of the same type are included. The organisms of a species have a similar body design and are well adapted to their niche and place. When the variation occurs in the individual, it is not beneficial and may even lead to the individual’s death. But the variation may be helpful when the species faces a drastically altered condition. The population may be completely wiped out in this condition. Still, if the population can survive, it increases the species’ chances of survival, and this variation proves beneficial. For example, if the bacterial species survive in water that is neither too cold nor too hot, and if there is a sudden rise in the temperature of the water, many of the bacteria that live there die, but only those bacteria that are resistant to heat can survive. But if this variation did not exist, then all the species of bacteria would not have survived.

Question 3. Explain the difference between binary fission and multiple fission.

Answer 3: 

Question 4: Mention the benefits of reproduction by spores.

Answer 4: The organisms reproducing through spore formation is beneficial in several ways. They are:

• Spore formation are a simple and faster mode of reproduction.
• They can float in the air as they are light in weight, so the organisms may be dispersed.
• The thick layer of the spore enables them to survive in the atmosphere, which is unfavourable because of extreme temperatures and a lack of food and water.

Question 5: Mention reasons why more complex organisms do not give rise to new individuals through regeneration.

Answer 5. This is because of the following reasons:

• The entire body of simple organisms comprises similar types of cells, so they reproduce through regeneration. The body of complex organisms has a very high degree of organisation.
• The particular organs perform a specific function.
• Labour division occurs in the body of complex organisms.
• Specialised cells are present to carry out regeneration, which is absent in complex organisms.

Question 6: Vegetative propagation is practised for growing some plants. Give a reason and explain why vegetative propagation is important.

Answer 6: The plants that cannot produce seeds or those plants that have non-viable seeds are preferred for vegetative propagation, like, for example, bananas, potatoes, grapes, sugarcane, roses, oranges, etc. The advantages of vegetative propagation are:

• The desired features of the parent plant can be easily replicated in the new plants.
• Using this method, it is very quick and easy for flowers and fruits to be grown in a shorter time
• Banana and rose are two examples of plants raised in this manner.
• The pathogen can eliminate any part of the plant using vegetative propagation.

Question 7: What is the difference between fertilisation and pollination? Explain.

Answer 7:

Question 8: Explain the role of the seminal vesicle and prostate gland.

Answer 8. Seminal vesicles are a pair of the thin-walled, muscular, elongated sacs that secrete fluid to nourish and transport the sperms.

To facilitate sperm transport and provide nutrition, the prostate gland secretes fluid into the urethra and seminal vesicles.

Question 9. Define reproduction. Explain the types of reproduction. Mention the characteristic features of asexual reproduction. What are the advantages of sexual over asexual reproduction?

Answer 9: 

The production of new organisms from the existing organisms of a species that ensures the continuity of the population of that species is known as reproduction. It is of two types:

• Asexual reproduction
• Sexual reproduction.

In asexual reproduction, the offspring is formed from a single parent, and gametes are not fused. The various features of asexual reproduction are:

• Only one organism is involved.
• Different sexes are not involved.
• The cell division occurring is either mitotic or amitotic.
• The individuals produced are genetically identical to their parents. The mode of multiplication is rapid.
• Gamete formation does not take place.
• Fertilisation does not take place.

The process of giving birth to a new offspring or individual through the fusion of male and female gametes is known as sexual reproduction. A diploid zygote is first formed, which develops into a mature organism.

The benefits of sexual reproduction over asexual reproduction are:

• The fusion of male and female gametes occurs between two sexually distinct individuals, and the offspring produced has diverse characteristics.
• Meiosis during gametogenesis provides opportunities for a new combination of genes.
• Origin of new species
• Variation for evolution.

Question 10. What is puberty? Mention the changes that occur in girls and boys during puberty.

Answer 10: Puberty is the period of sexual maturity during adolescence when the reproductive organs become functional.

There is the development of secondary sex organs and secondary sex characters in both males and females.

The changes in males are:

• The penis and scrotum are enlarged.
• Shoulders are broadened.
• Muscle development is increased.
• The larynx is enlarged.
• The voice is deepening due to the thickening of vocal cords.
• Growth of pubic hairs.
• Development of extra hairs on the face, armpits, and chest.

The puberty changes in women are:

• Growth of breast and external genitalia.
• Growth of pubic hair and extra hair in the armpits.
• Hair on the beard, moustache, and chest is absent.
• Pelvis gets broadened.
• Initiation of menstruation and ovulation.
• Fat deposition in various body parts like the thighs, hips, and shoulders.

Question 11. Answer the following questions:

1. What happens to DNA when a cell reproduces?
2. what is the method by which the Plasmodium reproduces?
3. List four modes of asexual reproduction.
4. How does reproduction provide stability?
5. What is the method by which Spirogyra reproduces?
6. In which part of the Bryophyllum is the buds produced for vegetative propagation?
7. What will happen when Planaria is cut into two pieces?
8. What happens when a mature Spirogyra filament attains considerable length?
9. What is the method of reproduction of Hydra? Explain
10. Name two organisms which can regenerate.
11. Which organism causes “Kala-azar” disease, and what is the mode of reproduction of that organism?
12. Which mode of reproduction is exhibited by Rhizopus?

Answer 11:

1. When DNA replication occurs, similar copies of DNA are formed.
2. Plasmodium’s reproduction method is called the multiple fission method, an asexual reproduction method. The parent organism splits to form many new organisms at the same time.
3. The four modes of asexual reproduction are budding, spore formation, regeneration, and fragmentation.
4. The species’ population is stabilised by sexual reproduction. The transfer of specific characters or body design features is essential for an individual to survive in a population; this is possible through reproduction. Variations that occur in the population due to reproduction help the individual survive in a changing niche.
5. Spirogyra reproduces by fragmentation; it is a method of asexual reproduction performed under favourable conditions by Spirogyra.
6. Bryophyllum reproduces vegetatively through buds produced on the margins.7. Planaria undergo regeneration when they are cut into two small pieces. This means that each fragment will grow into a new Spirogyra.
7. When a mature Spirogyra attains considerable length, it breaks into two or more fragments, and each fragment grows into a new Spirogyra.
8. Hydra reproduces by budding, which is the method of asexual reproduction. Hydra is a multicellular organism, and a small protuberance arises from one side of the body. The protuberance grows and gives rise to adult-like structures. At the free end, the hypostome and tentacles are developed. It develops a basal disc at the point of attachment with the parent organism and then gets detached to lead an independent life.
9. Hydra and Planaria are the two organisms that can regenerate.
10. The causative agent of Kala-azar disease is Leishmania. It reproduces asexually by binary fission.
11. The mode of reproduction for Rhizopus is spore formation. There are three favourable conditions for the spore to germinate. They are moisture, a suitable temperature, and food or nutrition.

Question 12. What happens when sporangia burst on maturation?

Answer 12: Many spores are released in the air when the sporangia burst on maturation. When these spores fall on food or soil, and the conditions are favourable, then these spores germinate into new individuals.

Question 13. What are the advantages of vegetative propagation?

Answer 13: This technique is useful for the propagation of those plants that are seedless or do not produce viable seeds.

• For fruit trees and flowering bushes, grafting is a propagation method.
• We can obtain seedless plants by method of artificial vegetative propagation.
• Grafting enables the combination of the most desirable characteristics of two plants.
• Through stem cutting, certain plants, like roses, sugarcane, cacti, etc., can be propagated rapidly.
• Bananas and jasmine are the two plants grown through the vegetative propagation method.
• The new plant produced by vegetative propagation is similar to the parent plant, and the desired feature will be replicated in the new plants.
• Vegetative reproduction can propagate the orange plant that has lost the ability to produce seeds.

Question 14. Explain in brief the following terms:

1. DNA
2. Reproduction
3. Multiple fission.
4. Testis
5. Scrotum
6. Vas deferens
7. Prostate gland
8. Seminal vesicle
9. Prostate gland.

Answer 14:

1. DNA is a polymer of many nucleotide units and is responsible for carrying information from one generation to the next.
2. Reproduction is defined as the life process that helps in the multiplication of an organism and the growth of its population.
3. Multiple fission is a form of asexual  reproduction. In this, the parent organism splits to form many new organisms simultaneously. An example is Plasmodium.
4. The testis is where male gametes or sperm are formed.They also form a male sex hormone called testosterone.
5. The scrotum is the pouch of skin outside, and the two testes lie in their respective scrotal sacs. The scrotum is a thermoregulator that provides the optimum temperature for forming sperm.
6. Vas deferens is a straight tube about 40 cm long, and it carries the sperm to the seminal vesicles, where mucus and watery alkaline fluid containing fructose are mixed with the sperm.
7. Prostate gland is one single large gland that surrounds the urethra and produces a milky and slightly acidic secretion. The secretion of the prostate gland activates and nourishes the sperm so they can swim.8. Seminal vesicles are one pair of sac-like structures located near the bladder’s base. Seminal fluid is a watery, alkaline fluid that contains nutrients such as fructose, which serves as the source of energy for the sperm. Each seminal vesicle releases its content during ejaculation into the ejaculatory duct.
8. Prostate gland is a single large gland that surrounds the urethra. It secretes a slightly acidic and milky fluid that forms 25 % of the volume of semen. The secretion of the prostate gland nourishes the sperm and helps in its motility.

Question 15. When DNA copying is ineffective, what effect does it have on the reproduction process, and how does DNA remain constant through each new generation?

Answer 15: Variation occurs when the copying of DNA is not accurate. This allows a few individuals to survive in the altered niche, and in this way, it becomes the basis of evolution. These are very useful for the survival of the species. The combination of the DNA copies of two individuals, male and female, occurs during the process of sexual reproduction. Meiosis is the reduction division that occurs during gamete formation and halves the chromosome number in both the male and  female gametes. The two gametes fuse during fertilisation, and the original number of chromosomes is restored in the offspring as it was  in the parent. In this way, the amount of DNA in every generation remains constant.

Question 16. How do Leishmania and Plasmodium reproduce, and mention the difference in their modes of reproduction?

Answer 16. Leishmania and Plasmodium reproduce by the process of fission, and this is an asexual mode of reproduction.

Plasmodium reproduces by multiple fission and produces 1000 daughter cells, while Leishmania reproduces by binary fission. The parent cell divides longitudinally in a specific plane, involving the flagellum at its tip, giving rise to the two daughter cells.

Question 17. What are the advantages of spore-forming organisms?

Answer 17: The advantages of spore-forming organisms are:

• It helps the organism  survive in harsh environmental conditions.
• Thick walls cover the spores, so it provides them with protection.
• They come in contact with the moist surface and germinate.
• They are small  and light.
• Wind, water, and animals can easily disperse it.

Question 18. Explain the methods of birth control that deliberately prevent fertilisation in humans. How does using these techniques directly impact the health and prosperity of a family?

Answer 18. The four methods are:

• Barrier methods are the physical devices that prevent the entry of sperm into the female, like, for example, condoms.
• Chemical methods are those that involve the use of oral pills to check ovulation. These are hormonal preparations, and they contain estrogen and progesterone.
• Intrauterine contraceptive devices are implanted in the uterus and include copper T to prevent fertilisation.
• Surgical methods involve removing a small portion of the vas deferens in males and the fallopian tubes in females to prevent fertilisation.

These techniques control the number of children, directly affecting the family’s prosperity. The most common reason for the deterioration of women’s health is frequent conception and childbearing. Controlled childbirth directly affects women’s health and indirectly jeopardises the family’s prosperity.

Question 19. What is the role of testosterone?

Answer 19: The role of testosterone are:

• To play a key role in developing male secondary sex organs such as the prostate.
• To promote secondary sexual characteristics in males.
• Increase muscle mass and bone mass.
• Promote the growth of body hairs.

Question 20. Enumerate the specific characteristics of sexual reproduction.

Answer 20: The specific characteristics of sexual reproduction are:

• The two sexes, male and female, are involved in the process.
• Gametes, which are the special sex cells, are involved in sexual reproduction.
• During fertilisation, gametes can fuse either internally or externallyInternal fertilisation means in the body of the female, and external fertilisation means outside the female body.
• The traits are obtained from both parents, i.e., heredity. They are not clones of their parents and may have some new characteristics.
• Crossing over during meiotic division during gamete formation causes variation.
• There is the emergence of new species as well as variation
• . This gets accumulated over some time, and then it is carried to successive generations.

Question 21. What is the significance of sexual reproduction?

Answer 21: The significance of sexual reproduction is explained below:

• Genetic variation occurs as a result of genetic recombination that occurs during gamete fusion.
• Progenies show a better combination of traits, and they adapt better to their surroundings.
• Genetic recombination, interaction, etc., provide vigour and vitality to the offspring.
• An important role in evolution is due to the variation in genes.

Question 22. Differentiate between self-pollination and cross-pollination.

Answer 22: 

Question 23. Explain the role of testes in human males.

Answer 23: In human males, the testes are the primary reproductive organs and the site of sperm formation. These are also responsible for the production of the male sex hormone testosterone.They are located outside the abdominal cavity, as the formation of sperm requires a lower temperature than the normal body temperature. The temperature of the testes in the scrotum is about 2 to 2.5 degrees Celcius, lower than the normal body temperature. This is the ideal temperature for sperm formation and development. Testosterone develops secondary sexual characteristics during puberty in boys, like the growth of facial hair, the deepening of the voice, scrotum growth, penis growth, muscle mass accumulation, etc., this also regulates the formation of sperm.

Question 24. What are the three contraception methods that can help control the human population?

Answer 24: The three contraception methods are:

• Condoms: The condom is a mechanical barrier that does not allow the sperm and ovum to meet. Hence, it plays a key role in preventing fertilisation.

They are made up of rubber from the latex sheath, which covers the penis in the male and the vagina/cervix in the female just before intercourse. The ejaculated semen is not released into the female reproductive tract.

• Intrauterine devices are devices inserted by the doctor or expert nurses in the uterus through the vagina. They are available as non-medicated IUDs, copper-releasing IUDs, and hormone-releasing IUDs. They are responsible for increasing the phagocytosis of the sperm within the uterus, and the motility of the sperm is suppressed, and its fertilising capacity is reduced. They make the uterus unsuitable for implantation and the cervix hostile to sperm.
• Oral pills contain either progesterone or a combination of estrogen and progesterone alone; they inhibit ovulation, and the uterus becomes unsuitable for implantation, so fertilisation is prevented.

Question 25. What are the steps of sexual reproduction?

Answer 25: The two main steps involved in sexual reproduction are the formation of the male and female gametes, followed by the fusion of the male and female gametes to form a new zygote by the fertilisation process.

Question 26. State the changes that take place in the uterus when: 

(a) Implantation of the embryo has occurred.

(b) Female gamete/egg is not fertilised.

Answer 26: (a) The close attachment of the blastocyst, a young multicellular embryo, or uterine wall is known as implantation. Several developmental changes occur in the thickened wall of the uterus. The intimate connection between the fetal membrane and the uterine wall is called the placenta. This is a disc that is embedded in the uterine wall. The placenta serves as the fetus’s nutritive, respiratory, and excretory functions.

(b) One egg is released by the ovary every month. Every month, uterus prepares itself to receive the fertilised egg, making the lining thick and spongy to nourish the embryo if fertilisation occurs. The lining is not needed when the female egg is not fertilised, so it breaks down and comes out through the vagina as blood and mucus. This cycle takes place every month and is known as the menstrual cycle.

Question 27. Explain the implantation briefly.

Answer 27: The zygote’s implantation refers to the blastocyst attachment to the uterus inner wall. It occurs on the 7th day after fertilisation. The process of implantation is controlled by estrogen, and progesterone.

Question 28. What are fallopian tubes? 

Answer 28: The fallopian tubes are a pair of elongated, ciliated, muscular, and tubular structures extending from the ovaries to the uterus. This is the site of fertilisation and helps conduct the ovum or zygote towards the uterus through ciliary action and peristalsis.

Question 30. Answer the following questions:

1. What is the full form of DNA.
2. Give the location of DNA in the cell.
3. What is the role of DNA in the reproduction process.
4. Give examples of STDs.
5. How STDs can be prevented.
6. Mention the importance of contraception.
7. What are the two modes of pollination.
8. Name two surgical methods that prevent pregnancy.
9. What is the function of semen.

Answer 30:

1. The full form of DNA is Deoxyribonucleic Acid.
2. Through chromosomes, the DNA is located in the cell’s nucleus.
3. DNA plays an important role in the process of reproduction. It contains information on the inheritance of characters from the parents to the next generation. DNA copying is an essential part of reproduction as it makes transmitting one character to another possible from the parents to the offspring in the next generation. The two DNA copies are formed at the time of DNA replication.The creation of additional cellular apparatus accompanies DNA copying, and then the DNA copies separate, each with its own cellular apparatus. Thus, the cell divides to form two daughter cells.
4. Examples of STDs are bacterial infections, including gonorrhoea and syphilis. Viral infections includeAIDS, Genital herpes.
5. Condoms can prevent STDs.
6. Contraception prevents frequent pregnancies and sexually transmitted diseases from supporting a family’s good health and prosperity.
7. The two modes of pollination are self-pollination and cross-pollination.
8. Vasectomy and tubectomy.
9. Semen provides nutrition to the sperm and causes its activation to make transport easy into the vagina of the female during sexual activity.

Question 31. What is the significance of pollination?

Answer 31: The significance of pollination is:

• Seed formation
• Perpetuation of species
• Stimulation of fruit development.

Question 32. Name the flower part that develops into seed and fruit after fertilisation.

Answer 32: After fertilisation, the ovule becomes a seed, and the ovary becomes the fruit.

Question 33. What is tissue culture? Explain its procedure and discuss its advantages.

Answer 33: The method of developing plants from plant cells or small pieces of plant tissue in an artificial medium is known as tissue culture. The process of tissue culture includes the collection of the tissue or the cells from the shoot tip of the desired plant, which are then grown in a nutritive artificial medium where a callus is formed, which is the mass of the identical cells. The callus is then allowed to grow into another medium containing hormones essential for growth and development. When small plantlets develop, they are transplanted into the soil and pots, where they mature and grow into mature plants.

The advantages of  tissue culture are:

• Fast technique.
• Can produce plantlets in a short period.
• Disease-free plants are produced in the tissue culture.
• It can be grown throughout the year and does not depend on the season or the weather.

Question 34. What is a unisexual and bisexual flower?

Answer 34: Unisexual flowers are those flowers that contain only one sex organ, either stamens or carpels. Examples of unisexual flowers include flowers like papaya and watermelon.

When the flower has sex organs, the stamen and the carpel, it is called a bisexual flower—for example, the flower of the hibiscus and the mustard.

Question 35. Name the parts of the flower that serve the same function as the animals.

Answer 35: 

• Testes – anther of stamen
• Sperm – pollen
• Ovary – ovary of the pistil
• Egg – female germ cell present in the ovule.

Question 36. State the functions of the placenta.

Answer 36: The placenta is a disc-shaped structure embedded in the uterine wall and contains villi on the embryo side and the blood spaces on the mother side. The blood spaces surround Villi. The main functions of the placenta are:

• The nutritional elements from the maternal blood pass into the fetus through the placenta.
• Help with respiration.
• Fetal excretory products diffuse into maternal blood through the placenta and are excreted by the mother.
• Placenta also secretes hormones.

Question 37. Answer the following question:

• Name the largest cell in the human body.
• Name the male reproductive parts of a flower.
• Where does the egg develop?
• Fertilisation takes place in which region?
• Where does the fertilised egg get implanted?

Answer 37:

1. Ovum
2. Anther and filament.
3. Ovary
4. Fallopian tube
5. Uterus

Question 38. What is the difference between sperm and eggs?

Answer 38: The sperm has X and Y chromosomes, while the egg has XX. This is the main difference. This is useful in determining the sex of a person and aiding in the maintenance of genetic continuity in organisms.

Question 39. Mention the devices to prevent the spread of STDs.

Answer 39: The spread of STDs can be prevented by:

• By avoiding sexual contact with the infected partner.
• Using condoms.

Question 40. Answer the following questions:

• What does AIDS stand for?
• Name the virus caused responsible for AIDS.
• Give various modes of transmission for HIV.
• How AIDS can be prevented.
• What does HIV stand for?

Answer 40:

1. AIDS stands for Acquired Immune Deficiency Syndrome.
2. Human Immunodeficiency virus is responsible for AIDS.
3. The modes of HIV transmission are:

• Through sexual contact with the infected person.
• Transfusion of infected blood.
• Sharing of infected needles.
• From the mother to the child.

1. AIDS can be prevented by:

• Avoiding sexual contact with the infected partner.
•  Using condoms.
• Avoiding sharing of needles.
• Testing blood before transfusion.

1. HIV stands for Human Immunodeficiency Virus.

Question 41. Mention the significance of reproductive health in society.

Answer 41: The significance of reproductive health in society is given below:

• The mother carrying the child should be physically mature.
• The mother should be mentally fit to take care of the child.
• Between 2 children, there should be a three-year gap.
• Mothers should eat nutritious food during pregnancy and lactation.

Question 42. What impact do contraceptives have on the health and prosperity of the family?

Answer 42: The impact is explained below:

• The use of mechanical barriers prevents sexually transmitted diseases.
• Pregnancy makes demands on the woman’s health, body, both physicallyand mentally. If a woman is not ready for  pregnancy, her health is adversely affected, and such conditions can be avoided.
• The standard of living can be improved with good health.

Question 43. What is spore formation?

Answer 43: When a slice of bread is kept in a moist, dark place for a few days, spores of Rhizopus in the air settle on the bread to form a new fungus plant known as the Rhizopus.A hypha is a fine, thread-like projection found in Rhizopus.These hyphae are non-reproductive structures. Blobs develop at the tip of hyphae and are called sporangia, which have spores. The spores present in sporangia can grow into new Rhizopus.

Question 44. What happens when the egg is not fertilised? Explain 

Answer 44:  The uterus prepares itself every month to receive a zygote. The inner lining of the uterus thickens and becomes spongy with lots of blood capillaries. This is required for the nourishment of the embryo and its development.

When the sperm is unavailable, the ovum’s fertilisation does not occur, and the egg is not fertilised. There is no requirement for a thick and soft uterinelining with lots of blood capillaries. The ovum dies within a day, and the uterinelining breaks down. The breakdown and removal of the uterus inner, thick, and soft lining, along with the blood vessels, in the form of vaginal bleeding is known as menstruation or menstrual flow.

Question 45: Give the role of the gamete and zygote in reproduction.

Answer 45: Gametes are the reproductive cells involved in sexual reproduction, and they have halfof the chromosomes. They carry the variations that are generated during their formation. A male gamete fuses with the female gamete to form a zygote.

The zygote has the normal number of chromosomes and the new combinations of variations expressed in the new generation. Repeated mitotic division occurs in the zygote, which leads to the formation of an embryo that has the potential to develop into a complete individual.

Question 46. Explain reproduction in Hydra.

Answer 46: Hydra is a simple multicellular organism that reproduces by the process of budding, an asexual mode of reproduction. The bud is the first small outgrowth formed on the side of the body by the repeated number of mitotic divisions of the cells. The small hydra is formed when the bud grows by developing mouth tentacles. The tiny new Hydra is finally detached from its parent body, living as a separate organism. This way, a new hydra is formed from the parent hydra.

Question 47. Explain the regeneration in Planaria.

Answer 47: Planaria has a great power of regeneration. If the body of the Planaria gets cut into a small number of pieces, then each piece of the body regenerates into a complete Planaria by growing all the body parts. During this reproduction process, a new organism is formed from the entire parent organism; however, during fragmentation, a fragment of the original parent body grows into the new individual.

Question 48. Why is reproduction important in an organism?

Answer 48: Reproduction is important due to the following reasons:

• Existence and continuity of species.
• Genetic information is passed from one generation to the next.
• Bring variation, which is the basis for evolution.
• Maintains stability of the population.

Question 49. Multiple choice questions:

• Asexual reproduction takes place through budding in:
• Amoeba
• Yeast
• Plasmodium
• Leishmania 

Answer: (b) Yeast

Explanation:

Yeast reproduces asexually by budding.

2. Which of the following is not a part of the female reproductive system in human beings?

• Ovary
• Uterus
• Vas deferens
• Fallopian tube

Answer 2: c) Vas deferens

Explanation: The Ovary, uterus, and the fallopian tube are all parts of the female reproductive system.

3. The anther contains:

• Sepals
• Ovules
• Carpel
• Pollen grains

Answer: (d) pollen grains

Explanation: Anther include pollen grains.

4. In which of the following method of reproduction is there a greater possibility for the evolution of a new species in the organism?

• Binary fission
• Budding
• Fertilisation
• Regeneration 

Answer 4:c) Fertilisation.

5. Pollen grains are produced by:

• Ovary
• Ovule
• Anther
• Corolla 

Answer 5: (c) Anther

• Fertilisation of the human egg by the sperm takes place in 
• Vagina
• Uterus
• Ovary
• Oviduct

Answer 6: (d) Oviduct

7. Many unicellular organisms reproduce through the process of

• Fission
• Ovulation
• Regeneration
• Non-disjunction

Answer 7: (a) Fission

8. Name the primary sex organ in a mammal.

• Ovary
• Vagina
• Uterus
• Mammary glands

Answer: (a) Ovary

1. Which event describes the beginning of the reproductive life of a woman?

1. 1. Menopause
   2. Menarche
   3. Fertilisation
   4. Ovulation

Answer 9: (b) Menarche

10. Which is the site of fertilisation?

• Uterus

• Vagina

• Fallopian tube

• Cervix

Answer 10: (c) Fallopian tube.

Question 50. State true or false

1. Variation helps in the survival of species in an adverse environment.
2. Complex multicellular organisms cannot give rise to new organisms through budding.
3. The primary reproductive organs in man are the testes.
4. An embryo is formed by the growth and development of the fetus.
5. The most important advantage of the barrier method is that it protects against STDs.
6. Foeticide is the killing of an unborn female child.
7. Vasectomy is a surgical procedure carried out in females.

Answer 50:

1. True
2. True
3. True
4. False.
5. True.
6. True
7. False. This procedure is carried out in females.

Question 51. Fill in the blanks:

• Women have two_____________.
• The gestation period in humans is about ______ days.
• __________ is the process of egg release from the ovary.
• The development of foetus inside uterus till birth is called __________
• The attachment of embryo to uterus is called ___________
• __________ is sterilisation in males.
• The ability of cell to divide in several cells during reproduction in Plasmodiumis called ________________
• The kala azar disease is caused by __________
• The spirogyra produces by ___________.
• The fine thread-like structures that spread on the whole surface of a slice of bread in Rhizopus are called ___________.
• _______are primary reproductive organs in men.
• ____________ is the life process that aids in growth of the population.
• ___________ is the most basic event in reproduction.
• DNA is found in the _________ of the cell.
• Planaria reproduces by ___________.
• Amoeba reproduces by __________.
• stage between childhood and adulthood is known as ___________.
• __________ is the liquid which contains semen.
• ____________is the female reproductive organ of the plant.
• Hydra reproduces by ___________.

Answer 51:

1. Women have two X chromosomes.
2. The gestation period in humans is about 280 days.
3. Ovulation is the process of egg release from the ovary.
4. The development of the foetus inside the uterus till birth is called gestation.
5. The attachment of the embryo to the uterus is called implantation.
6. Vasectomy is sterilisation in males.
7. The ability of cells to divide into several cells during reproduction in Plasmodium is called multiple fission.
8. Leishmania causes kala-azar disease.
9. The Spirogyra produces by fermentation.
10. The fine thread-like structures that spread on the Rhizopus whole surface of a slice of bread are called hyphae.
11. Testes are the primary reproductive organs in men.
12. Reproduction is the life process that aids in the growth of the population.
13. Copying of DNA is the most basic event in reproduction.
14. DNA is found in the nucleus of the cell.
15. Planaria reproduces by regeneration.
16. Amoeba reproduces by binary fission.
17. The stage between childhood and adulthood is known as adolescence.
18. Semen is the liquid which contains semen.
19. The carpel is the female reproductive organ of the plant.
20. Hydra reproduces by budding.

Question 52. Match the following

Answer 52:

Question 53. Answer the following questions.

• What are the types of reproduction?

• Name the most basic event of reproduction.

• Which STD damages the immune system of the body.

• Which part of the male reproductive system contributes fluid to semen?

• Give two reasons for variations among progeny in sexual reproduction.

• Give two benefits of the mechanical barrier during the sexual act.

Answer 53:

1. They are of 2 types: sexual and asexual.
2. Creation of a DNA copy.
3. AIDS.
4. The prostate gland and seminal vesicles add fluid to the vas deferens.
5. Two reasons are: two parents have different characters and gene combinations are different in gametes.
6. Pregnancy prevention and non-transmission of infection.

Question 54: Explain the female reproductive system.

Answer 54. The female reproductive system can be explained as follows:

• Ovaries: These are paired and almond-shaped. They are in the lower abdominal cavity, near the kidneys, and are connected by a ligament to the uterus. They are the primary sex organs and have two functions. First is the production of female gametes or ovum, and second is the secretion offemale sex organs like estrogen and progesterone. A mature ovary contains many ova in various stages of development. The formation of ova begins in the female fetus before birth, and at birth, each ovary contains about 2–3 lakh immature ova.Fallopian tubes: These are also known as oviducts. These are the paired tubes originating from the uterus on either side and extending up to the ovary on their respective sides. The terminal part is called the fimbriae and is funnel-shaped. The fimbriae direct the ovum released from the ovary into the fallopian tube.
• The uterus is a single, pear-shaped, highly muscular, hollow structure in the pelvic cavity and lies between the urinary bladder and rectum. This is also known as a wound, as the foetus develops inside it. The cervix is the narrow part of the uterus and leads into the vagina.
• The vagina is about a 7 to 10-cm long tube, where the penis discharges the sperm.It is both the menstrual flow passage and the birth canal.

Question 55. What are the disadvantages of vegetative propagation?

Answer 55: The plants produced by vegetative propagation have the following characteristics:

• Less vigour
• More prone to diseases
• Show no genetic variation.

Question 56. What are fragmentation and regeneration?

Answer 56: Fragmentation is a process in which the parent body breaks into two or more fragments. Each fragment gives rise to a new individual. This occurs in filamentous algae, mycelial fungi, and thalloid bryophytes, e.g. Spirogyra.

image source: MTG CBSE CHAMPION

Regeneration is defined as the ability of an organism to regenerate lost parts of the body that have been removed by injury or autotomy. Many fully differentiated organisms use this ability as a mode of reproduction and give rise to new individual organisms from their body parts, which is more common in Hydra and Planaria.

Question 57. What are the non-essential parts of a flower?

Answer 57: Sepals and petals are the non-essential parts of a flower. Sepals are green, and petals are coloured.

Question 58. What are the essential reproductive parts of a flower? Explain.

Answer 58: Stamens and carpels are the essential reproductive parts of a flower. The stamen, also known as the androecium, is the male reproductive organ that consists of filament and anthers.Anthers produce the pollen grains that contain the male gametes.

image source: MTG CBSE CHAMPION

Carpel is also known as gynecium. It is the female reproductive part of the stigma, style, and ovary. Stigma is primarily responsible for receiving pollen during pollination. The stigma is so sticky that the pollen sticks to it.

The style is the middle part of the carpal and is an elongated tubular structure that connects the stigma with the ovary.

The swollen basal part of the carpal is the ovary. A haploid egg or female gamete is contained in the embryo sac. Each ovule contains only one female gamete from the plant.

Question 59. Name the various pollinating agents.

Answer 59: The various pollinating agents are:

• Entomophily or insect
• Anemophily or wind
• Hydrophily or water
• Ornithophily or birds

Question 60. Explain the post-fertilisation changes.

Answer 60: The repeated mitotic divisions of the zygote cause blastula formation on the 7th day, which descends into the uterus and gets implanted.

Then there is the placenta formation, the mechanical and physiological connection between the mother’s embryo and uterine wall. Through the placenta, the nutrients enter the foetus from the mother’s blood, and the waste products are expelled into the mother’s blood. Gestation is the complete development of the fetus from conception until the birth of the child. The duration of gestation is about 280 days, or 40 weeks, calculated from the first day of the last menstruation.

“Parturition” means the birth of the child. After the gestation period, the fully formed young one is expelled from the mother’s uterusThe influence of oxytocin plays an important role in the contraction of the uterine wall. Relaxin hormone is important in widening the pelvis and vagina for childbirth and is secreted from the ovary.

Question 61. Explain syphilis briefly.

Answer 61: Syphilis is a sexually transmitted disease caused by Treponema pallidum. In this disease, the mucous membrane of the genitals, rectal and oral regions are affected. The primary mode of infection is sexual intercourse, and other ways involve close body contact, kissing, etc. Penicillin and tetracycline can cure this.

Question 62. Explain gonorrhoea briefly.

Answer 62: Gonorrhoea is caused by the bacterium Neisseria gonorrhoeae. This is the inflammation of the mucous membranes of the urino-genital tract, rectum, throat, and eyes. The patient may experience burning sensations and pain during urination. The mode of infection spread is sexual contactThe antibiotics used to cure the disease are Penicillin and Ampicillin.

Question 63. Name the reproductive parts of an angiosperm flower.

Answer 63: The male reproductive part is the stamen, and the female reproductive parts are the carpel or pistil.

Question 64. Name two unisexual flowers.

Answer 64: flowers of papaya and cucumber are unisexual.

Question 65. Name the parts of the flower not directly involved in reproduction.

Answer 65: Calyx and corolla are not directly involved in reproduction.

Question 66. Why are two organisms alike? 

Answer 66: This is due to sexual reproduction as it promotes diversity of characters in the offspring by providing genetic variations.

Question 67. What is binary fission? Explain the process in amoeba.

Answer 67: The division of the adult parental body into two nearly equal daughter cells is known as binary fission.

Amoeba reproduces by binary fission. When the amoeba reaches its maximum size, the length of the nucleus lengthens and divides into two parts. After this, the cytoplasm divides to form two smaller amoeba called the daughter amoeba.

Question 68. The colonies of yeast do not multiply in water, but they multiply in sugar. Explain.

Answer 68: All living organisms require energy, which is provided in the form of sugar by  multiplying yeast. The yeast cells fail to reproduce in water due to inadequate energy, so the yeast colonies multiply in sugar solutions and not in water.

Question 69. What is a chromosome?

Answer 69: A chromosome is a long, thread-like, structure that contains the individual’s genetic information. It is the carrier of the gene, and these are located in the nucleus of the chromosomes.

Question 70. Mention the difference between the bud of Hydra and the bud of Bryophyllum.

Answer 70: The bud of Hydra has special regenerative cells, giving rise to a small bud on the body, which later develops into the new individual after the detachment.

The bud of the Bryophyllum reproduces through vegetative propagation. They are produced in the notches along the teg leaf margin of bryophyllum, fall on the soil, and develop into new plants.

Question 71. The higher the number of chromosomes or cells, the greater the DNA  content. Justify.

Answer 71: Yes, the statement is true because the major component of the chromosome is DNA. If there are more chromosomes in the cells, there is more DNA.

Question 72. Does the chromosome number depend on the size? Justify.

Answer 72: There is no correlation between the size of the individual and the number of chromosomes. The larger organisms do not have more chromosomes.

Question 73. What is a seed? Note down the various parts of the seeds.

Answer 73: The reproductive unit of a plant is known as the seed. The various parts of the seed are:

• The protective covering of the seed is called the seed coat.
• The embryonic leaves that store food for the young plant’s germination are called Cotyledons.
• The part of the embryo that gives rise to the shoot is called the Plumule.
• The part of the embryo that gives rise to roots is known as radicals.

Question 74. What is a clone?

Answer 74: A clone is the exact genetic replica of another individual.

Question 75. Mention the difference between the gamete and the zygote.

Answer 75: A gamete is a germ cell that participates in fertilisation and has two types: male and female gametes. It carries the characteristics of only one parent and is the last cell of its generation. The chromosome number is haploid.

A zygote is the product of fertilisation and has a diploid chromosome number. It has the characteristics of both parents and is the new generation’s first cell.

Question 76.Draw a flowchart to mention the types of asexual reproduction.

Answer 76:

Question 77: How do the modes of reproduction differ in unicellular and multicellular organisms?

Answer 77. The mode of reproduction is different in both unicellular and multicellular organisms. There is only one cell in unicellular organisms, and there is no separate tissue for reproduction. So, there are ways in which they reproduce, like budding, binary or multiple fission, etc.

In multicellular organisms, there are various cells and various systems present which carry out the process of reproduction. There are two methods by which they can reproduce, sexual and asexual reproduction.

Question 78. What is double pollination in plants?

Answer 78. The events taking place in pollination are:

• One male gamete fuses with the female gamete present in the embryo sac.
• The other male gamete fuses with the two polar nuclei which are present in the embryo sac.
• The first fusion leads to the formation of a zygote.
• Endosperm is formed in the second fusion.
• The process by which the fusion occurs twice in the embryo sac is known as double fertilisation.

Question 79. Support the statement: “Reproduction is one of the most important characteristics of living beings.”

Answer 79: The statement can be supported as follows:

• The continuity of the species is maintained by reproduction.
• Reproduction and the stability of the population are linked and the well defined places called niche in the ecosystem are occupied.
• In cases of adverse changes taking place in the environment and the evolution, variations which are created during reproduction are responsible for the survival of the species.

Question 80. What is the difference between sexual and asexual reproduction.

Answer 80: In asexual reproduction, a single parent is involved, and there is neither fusion nor formation of male and female gametes. Also, there is no genetic variation created in the progeny.

In sexual reproduction, two gametes are involved, the male and female gametes. There is formation and fusion of male and female gametes, and there is genetic variation in the progeny.

Question 81. What are the advantages of growing grapes or banana plants through  vegetative propagation.

Answer 81: There are two main advantages to growing grapes or banana plants through vegetative propagation. They are the preservation of the parents’ characteristics and reproduction.

Question 82. Name the germ cells present in  human beings?

Answer 82: The two germ cells present in  human beings are the sperm and the ova.

Question 83. List two points of difference between sperm and ova?

Answer 83:  The differences between sperm and ova are:

• Human sperm contains XY chromosomes, whereas female ova contain XX chromosomes.
• The sperm is long with a tail, and the ova is round in structure.

Question 84. What is the difference between Fragmentation and regeneration.

Answer 84: Fragmentation is that mode of asexual reproduction in which the body of a simple multicellular organism breaks up into two pieces on maturing, each of which subsequently grows to form a complete new organism.

Regeneration is defined as the mode of asexual reproduction in which organisms can grow small, cut parts of their bodies to form a whole new organism in all respects.

Question 85. What is the difference between Fertilisation and germination.

Answer 85: Fertilisation is the fusion of male and female gametes, i.e, sperm and ova, which leads to the formation of a zygote.

Under the right conditions, germination is defined as the first stages of a seed’s development into a seedling.

Question 86. What are the advantages of seed for a plant?

Answer 86: Seeds provide the following advantages to the plant:

• Young embryo is protected by the seeds.
• There are many modes of dispersion which help the spread of the species.
• The formation of seed is more dependable.
• The seeds store  food in order to provide nourishment to the embryo.

Question 87. The male gamete of the tobacco plant has 24 chromosomes. What are the number of chromosomes in the female gamete.

Answer 87: The number of chromosomes in the female gamete of the tobacco plant is 24 chromosomes. The chromosome number in zygote is 48.

Question 88. What is the difference between general growth and sexual maturation.

Answer 88: “General growth” refers to the various types of developmental processes that occur in the body and are related to changes in the height, size, and shape of the body. The reproductive organs are less active during the phase of general growth.

Sexual maturation is defined as the changes that take place in the body at the time of puberty, like the cracking of the voice, a new pattern of hair, breast development in women, etc.

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