Welcome to the NCERT Solutions for Class X Science Chapter 8, How do Organisms Reproduce. This chapter explores the fundamental processes of reproduction in living organisms. The chapter delves into the different modes of reproduction, including sexual and asexual reproduction. It also discusses the significance of reproduction for the continuity of species and the evolution of life on earth.
In this chapter, you will learn about the various reproductive structures and their functions, as well as the different stages of reproduction. You will also study the different strategies that organisms use for reproduction, such as parthenogenesis, budding, fragmentation, and regeneration.
The NCERT Solutions for Class X Science Chapter 8 provide detailed explanations and step-by-step solutions to all the questions in the textbook. With the help of these solutions, you can clear your doubts and understand the concepts thoroughly. So, let’s dive into the fascinating world of reproduction and learn how organisms reproduce and propagate their species.

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Answers of Science NCERT solutions for class 10 Chapter 8 How do Organisms Reproduce

Chapter 8

How Do Organisms Reproduce

Intext Questions

Question 1:

What is the importance of DNA copying in reproduction? 

Answer:

DNA (Deoxyribonucleic acid) is the genetic material found in the chromosomes, which are present in the nucleus of a cell. The DNA is the information site for making proteins and each specific type of protein leads to a specific type of body design.

Thus, it is the DNA molecule that determines the body design of an individual. Therefore, it can be concluded that it is the DNA that gets transferred from parents to off springs and makes them look similar.

DNA determines body structure 

Question 2:

Why is variation beneficial to the species but not necessarily for the individual? 

Answer:

Variations are more beneficial to the species than individual because sometimes for a species, the environmental conditions change so drastically that their survival becomes difficult. For example, if the temperature of water increases suddenly, then most of the bacteria living in that water would die. Only a few variants that are resistant to heat would be able to survive. However, if these variants were not there, then the entire species of bacteria would have been destroyed. Thus, these variants help in the survival of the species.

However, all variations are not necessarily beneficial for the individual organisms.

Question 1:

How does binary fission differ from multiple fission? 

Answer:

In binary fission, a single cell divides into two equal halves. Amoeba and Bacteria divide by binary fission.

Binary fission in Amoeba

In multiple fission, a single cell divides into many daughter cells simultaneously. Amoeba and Plasmodium divide by multiple fission.

Multiple fission in Plasmodium

Question 2:

How will an organism be benefited if it reproduces through spores? 

Answer:

There are many advantages, if an organism reproduces through spores.

Advantages of spore formation:

• Large numbers of spores are produced in one sporangium.
• Spores are distributed easily by air to far-off places to avoid competition at one place.
• Spores are covered by thick walls to prevent dehydration under unfavourable conditions.

Question 3:

Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

Answer:

Simple organisms such as Hydra and Planaria are capable of producing new individuals through the process of regeneration. The process of regeneration involves the formation of new organisms from its body parts. Simple organisms can utilize this method of reproduction as their entire body is made of similar kinds of cells in which any part of their body can be formed by growth and development.

However, complex organisms have organ-system level of organization. All the organ systems of their body work together as an interconnected unit. They can regenerate their lost body parts such as skin, muscles, blood, etc. However, they cannot give rise to new individuals through regeneration.

Question 4:

Which of the following is a plant hormone?

1. Insulin
2. Thyroxin
3. Oestrogen
4. Cytokinin 

Answer:

4. Cytokinin is a plant hormone.

Question 5:

Why is DNA copying an essential part of the process of reproduction? 

Answer:

DNA (Deoxyribonucleic acid) copying is an essential part of reproduction as it passes genetic information from parents to offspring. It determines the body design of an individual. The reproducing cells produce a copy of their DNA through some chemical reactions and result in two copies of DNA. The copying of DNA always takes place along with the creation of additional cellular structure. This process is then followed by division of a cell to form two cells.

Question 1:

How is the process of pollination different from fertilization? 

Answer:

Pollination is the process of transfer of pollen from anther to stigma. It occurs with the help of certain pollinators such as air, water, birds, or some insects.

Fertilization, on the other hand, is the fusion of the male and female gametes. It occurs inside the ovule and leads to the formation of zygote.

Question 2:

What is the role of the seminal vesicles and the prostate gland? 

Answer:

The secretions from seminal vesicles and prostate glands lubricate the sperms and provide a fluid medium for easy transport of sperms. Their secretion also provides nutrients in the form of fructose, calcium, and some enzymes.

Question 3:

What are the changes seen in girls at the time of puberty? 

Answer:

Secondary sexual characteristics in girls:

• Increase in breast size and darkening of skin of the nipples present at the tips of the breasts.
• Appearance of hair in the genital area.
• Appearance of hair in other areas of skin like underarms, face, hands, and legs.
• Increase in the size of uterus and ovary.
• Beginning of menstrual cycle.
• More secretion of oil from the skin, which results in the appearance of pimples.

Question 4:

How does the embryo get nourishment inside the mother’s body? 

Answer:

The embryo develops inside the mother’s body for about nine months. Inside the uterus, the outer tissue surrounding the embryo develops finger-like projections called villi.

These villi are surrounded by uterine tissue and maternal blood. They provide a large surface area for exchange of oxygen and nutrients. Also, there is a special tissue called placenta, which is embedded in the uterine wall. The embryo receives the oxygen andnutrients from the mother’s blood via the placenta. The waste materials produced by the embryo are also removed through the placenta.

Question 5:

If a woman is using a copper−T, will it help in protecting her from sexually transmitted diseases?

Answer:

No. Using a copper-T will not provide a protection from sexually transmitted diseases, as it does not prevent the entry of semen. It only prevents the implantation of the embryo in the uterus.

Exercises

Question 1:

Asexual reproduction takes place through budding in

1. amoeba.
2. yeast.
3. plasmodium.
4. leishmania.

Answer:

(b) Asexual reproduction takes place through budding in yeast.

Question 2:

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

1. Ovary
2. Uterus
3. Vas deferens
4. Fallopian tube 

Answer:

(c) Vas deferens is not a part of the female reproductive system in human beings.

Question 3:

The anther contains

1. sepals.
2. ovules.
3. carpel.
4. pollen grains. 

Answer:

4. The anther contains pollen grains.

*Question 4:

What are the advantages of sexual reproduction over asexual reproduction? 

Answer:

Advantages of sexual reproduction:

• In sexual reproduction, more variations are produced. Thus, it ensures survival of species in a population.
• The new formed individual has characteristics of both the parents.

• Variations are more viable in sexual mode than in asexual one. This is because in asexual reproduction, DNA has to function inside the inherited cellular apparatus.

Question 5:

What are the functions performed by the testis in human beings? 

Answer:

The testes are the male reproductive organs that are located outside the abdominal cavity within a pouch called scrotum.

Functions of testes:

• Produce sperms
• Produce a hormone called testosterone, which brings about secondary sexual characters in boys.

*Question 6:

Why does menstruation occur? 

Answer:

Menstruation is a process in which blood and mucous flows out every month through the vagina. This process occurs every month because one egg is released from the ovary every month and at the same time, the uterus (womb) prepares itself to receive the fertilized egg. Thus, the inner lining of the uterus gets thickened and is supplied with blood to nourish the embryo. If the egg does not get fertilised, then the lining of the uterus breaks down slowly and gets released in the form of blood and mucous from the vagina.

Question 7:

Draw a labelled diagram of the longitudinal section of a flower. 

Answer:

*Question 8:

What are the different methods of contraception? 

Answer:

The contraceptive methods can be broadly divided into the following types:

• Natural method→ It involves avoiding the chances of meeting of sperms and ovum. In this method, the sexual act is avoided from day 10th to 17th of the menstrual cycle because during this period, ovulation is expected and therefore, the chances of fertilization are very high.
• Barrier method → In this method, the fertilization of ovum and sperm is prevented with the help of barriers. Barriers are available for both males and females. Condoms are barriers made of thin rubber that are used to cover penis in males and vagina in females.
• Oral contraceptives →In this method, tablets or drugs are taken orally. These contain small doses of hormones that prevent the release of eggs and thus fertilization cannot occur.
• Implants and surgical methods →Contraceptive devices such as the loop or Copper-T are placed in the uterus to prevent pregnancy. Some surgical methods can also be used to block the gamete transfer. It includes the blocking of vas deferens to prevent the transfer of sperms known as vasectomy. Similarly, fallopian tubes of the female can be blocked so that the egg will not reach the uterus known as tubectomy.

*Question 9:

How are the modes for reproduction different in unicellular and multicellular organisms? 

Answer:

In unicellular organisms, reproduction occurs by the division of the entire cell. The modes of reproduction in unicellular organisms can be fission, budding, etc. whereas in multicellular organisms, specialised reproductive organs are present. Therefore, they can reproduce by complex reproductive methods such as vegetative propagation, spore formation, etc. In more complex multicellular organisms such as human beings and plants, the mode of reproduction is sexual reproduction.

*Question 10:

How does reproduction help in providing stability to populations of species?

Answer:

Living organisms reproduce for the continuation of a particular species. It helps in providing stability to the population of species by producing a new individual that resembles the parents. This is the reason why cats give birth to only cats or dogs give birth to only dogs. Therefore, reproduction provides stability to populations of dogs or cats or any other species.

Question 11:

What could be the reasons for adopting contraceptive methods? 

Answer:

Contraceptive methods are mainly adopted because of the following reasons:

1. To prevent unwanted pregnancies.
2. To control population rise or birth rate.
3. To prevent the transfer of sexually transmitted diseases.

Access Answers of Science NCERT Class 10 Chapter 8 How do Organisms Reproduce? ( All intext and Exercise Questions Solved)

Questions Page no: 128

1. What is the importance of DNA copying in reproduction?

Solution:

DNA – Deoxyribonucleic acid is the genetic material that is present in the cells of all organisms. DNA carries genetic information from one generation to the other and this helps in producing organisms of its own types. DNA copying is a must for inheriting the traits from parents. Any variations in DNA copying will give rise to origin of new species.

2. Why is the variation beneficial to the species but not necessarily for the individual?

Solution:

The reason why the variation is beneficial to the species than individuals is because sometimes the climatic changes have a drastic effect on the species, which makes their survival difficult. For examples, if the temperature of the water body increases, then there might be certain species of microorganisms which might die. This may result in disturbance in the environment. So, variation is beneficial to species and not for the individuals.

Questions Page no: 128

1. How does binary fission differ from multiple fission?

Solution:

When a single cell divides into two equal halves, it is known as binary fission. Bacteria and amoeba are the examples of binary fission.

When a single cell divides into multiple daughter cells at the same time, it is known as multiple fission. Algae and sporozoans are the examples of multiple fission.

2. How will an organism be benefited if it reproduces through spores?

Solution:

Following are the ways through which an organism will be benefited if it reproduces through spores:

• Number of spores produced in one sporangium would be large.
• In order to avoid competition at one place, spores can be distributed to faraway places with the help of air.
• In order to prevent dehydration under unfavorable conditions, the spores are covered by thick walls.

3. Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

Solution:

Organisms at higher complex levels cannot give rise to new individuals through regeneration because they have organization of their organs system at different levels. All these organ systems are interconnected and work in full coordination. They can regenerate a few of their lost body parts like skin, blood, muscles, etc. but can’t give rise to new individuals.

4. Why is vegetative propagation practised for growing some types of plants?

Solution:

Following are the advantages of practising vegetative propagation for growing some types of plants:

• Crops like orange, banana, pineapple do not have viable seeds, so vegetative propagation can be used.
• It is a rapid, cheap and easier method to grow crops.
• It can be used in places where seed germination fails.
• A good quality of variety can be preserved.

5. Why is DNA copying an essential part of the process of reproduction?

Solution:

DNA copying is an essential part of the process of reproduction because it carries the genetic information from the parents to offspring. A copy of DNA is produced through some chemical reactions resulting in two copies of DNA. Along with the additional cellular structure, DNA copying also takes place which is then followed by cell division into two cells.

Questions Page No: 140

1. How is the process of pollination different from fertilization?

Solution:

Pollination is defined as the process of transfer of pollens from anther to stigma. The process takes place with the help of pollinators like air, water and some insects.

Fertilization is defined as the fusion of male and female gametes. It takes place in the ovule and leads to the formation of zygote.

2. What is the role of the seminal vesicles and the prostate gland?

Solution:

Lubrication of sperms and providing of a fluid medium for the easy transportation of sperms takes place with the help of secretions from the seminal vesicles and the prostate gland. These secretions also provide nutrients in the form of fructose, calcium and some enzymes.

3. What are the changes seen in girls at the time of puberty?

Solution:

Following are the changes seen in girls at the time of puberty:

• In genital area, hair growth appears.
• Hair growth in other areas like underarms, face, hands and legs.
• The size of uterus and ovary increases.
• The size of the breast increases followed by darkening of the nipple skin that is present at the tip of the breast.
• Beginning of menstrual cycle.
• Appearance of pimples, as the oil secretion is more from the skin.

4. How does the embryo get nourishment inside the mother’s body?

Solution:

The lining of the uterus thickens after fertilization. The blood flow is good so as to nourish the growing embryo. Placenta is a special tissue which is embedded in the uterine wall and helps the embryo get the nourishment from the mother’s tissue. Placenta has villi on the embryo side and blood space on the mother’s side. This spacing provides a large area between the mother and the embryo and also for waste removal.

5. If a woman is using a Copper-T, will it help in protecting her from sexually transmitted diseases?

Solution:

No, because usage of copper-T cannot stop the contact of body fluids. Hence, it cannot protect her from getting sexually transmitted diseases.

Exercises Page no: 141

1. Asexual reproduction takes place through budding in

(a) Amoeba

(b) Yeast

(c) Plasmodium

(d) Leishmania

Solution:

(b) Yeast

Yeast is an example for asexual reproduction taking place through budding. A small protuberance is produced on the parent cell that grows in full size forming a bud. In the parent cell, the daughter nucleus splits and migrates to the daughter cell. By forming a constriction, the bud detaches from the mother’s body at the base. This process of budding continues to form a chain of bud cells. The mother cell is smaller than the daughter cell.

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

(a) Ovary

(b) Uterus

(c) Vas deferens

(d) Fallopian tube

Solution:

(c) Vas deferens

Vas deferens is a part of male reproductive system. It is a long, muscular tube travelling from the epididymis into the pelvic cavity. It is behind the bladder. Its function is to transport the mature sperm to the urethra. It also carries urine to the outside of the body.

3. The anther contains

(a) Sepals

(b) Ovules

(c) Pistil

(d) Pollen grains

Solution:

(d) Pollen grains.

Pollen grains are the microscopic particles that occurs in the pollen giving rise to male gametophyte of a seed plant.

4. What are the advantages of sexual reproduction over asexual reproduction?

Solution:

Following are the advantages of sexual reproduction:

• The offspring has the characters of both the parents.
• The survival of the species is ensured as there are more variations.
• The offspring can easily adapt to environmental changes.
• It also improves the health of humans.

5. What are the functions performed by the testis in human beings?

Solution:

Following are the functions performed by the testis in human beings:

• Apart from the production of sperms, it also produces the male hormone known as androgens.
• They also produce hormone called testosterone, which is responsible for secondary sexual characters in boys.

6. Why does menstruation occurs?

Solution:

Menstruation is the normal bleeding of the vaginal line which starts between puberty and lasts till menopause. During this period, the body prepares itself for pregnancy.

Every month an egg is released from one of the ovaries at the same time where the uterus prepares itself for fertilized egg. The inner lining of the uterus gets thickened and is supplied with sufficient amount of blood for the embryo. Since there is no interaction between the egg and the sperms, the fertilization of egg doesn’t takes place. So when the egg doesn’t get fertilized, the uterus lining breaks down slowly resulting in menstruation.

7. What are the different methods of contraception?

Solution:

Following are the different methods of contraception:

• Natural method: In this method, the main focus is to avoid the meeting of sperms and ovum. This can be achieved by avoiding the mating from 10^th to 17^th day of the menstrual cycle. During this period, there are high chances of fertilization as ovulation is expected.
• Barrier method: In this method, the meeting of sperms and ovum is avoided by using a barrier. These barriers are available for males as well as for females. Condoms for both male and female, diaphragms for female, cervical cap and contraceptive sponge for females.
• Oral contraceptives: In this methods, pills are taken orally. These pills contain small portion of hormones that block the eggs so that fertilization doesn’t takes place.
• Implants and surgical method: In this method, contraceptive devices like copper-T or a loop can be used to block the meeting of sperms and ovum. In surgical method, the fallopian tubes are blocked in females to stop flow of eggs and vas deference is blocked in men to stop the flow of sperms.

8. How are the modes for reproduction different in unicellular and multicellular organisms?

Solution:

The different modes of reproduction in unicellular organisms are fission, budding, etc. Here, the cell divides into two daughter cells and this process of cell division continues.

Whereas, in multicellular organisms there is a different organ system for reproduction. The different modes of reproduction in multicellular organisms are vegetative propagation, spore formation, etc.

In more complex organisms like humans and animals, the reproduction is through sexual reproduction.

9. How does reproduction help in providing stability to populations of species?

Solution:

Reproduction is the process of producing the same kind of species by the existing species. This is done so as to maintain the population of that species and also to take forward their species to next generations. Stability is maintained by keep a check of rate of births and rate of deaths.

10. What could be the reason for adopting contraceptive methods?

Solution:

Following are the reasons for adopting contraceptive methods:

• To control population
• To avoid unplanned pregnancy
• To avoid transfer of sexually transmitted diseases

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NCERT Solutions for Class 10 Science Chapter 8 explains reproduction in various organisms. It also explains the male and female reproductive systems, changes in the body of puberty, examples of asexual reproduction where new generations are created from a single individual. NCERT Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce explains some of the important organisms used in different modes of reproduction depending on their body design. Organisms such as hydra can regenerate if they are broken into pieces.

NCERT Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce?

• NCERT Solutions for Class 10 Science chapter 8 explains the various reproduction modes like

1. Sexual reproduction
2. Sexual reproduction
3. Reproduction in flowering plants

• It explains that reproduction involves the creation by the cell involved in the process of a DNA copy and additional cellular devices.
• Briefs the DNA copying mechanisms
• Explains the body design and how different organisms use different reproductive modes

Key Features of NCERT Solutions for Class 10 Science Chapter 8 How do Organisms Reproduce?

• For CBSE board exams, Science Olympiads and other competitive exams, these solutions will be useful.
• Students can easily understand the language used in NCERT solutions.
• After extensive research on each topic, these solutions are prepared by our subject experts to provide the students with adequate and genuine information.
• Provides fully resolved solutions to all the issues in the respective NCERT textbooks.
• To assist students in their preparations, detailed answers to all questions are provided.

Conclusion

NCERT Solutions for Class X Science Chapter 8, How do Organisms Reproduce, is an important chapter that deals with the fundamental processes of reproduction in living organisms. The chapter explains the different modes of reproduction, including sexual and asexual reproduction, and their significance for the continuity of species and evolution of life on earth.
The chapter also provides a detailed explanation of the different reproductive structures and their functions, including male and female reproductive systems in humans. It also discusses the various stages of reproduction, including fertilization, embryonic development, and birth.
Furthermore, the chapter highlights the different reproductive strategies used by organisms, such as parthenogenesis, budding, fragmentation, and regeneration. It emphasizes the importance of understanding these different modes of reproduction in different organisms and their relevance in different contexts.
Overall, NCERT Solutions for Class X Science Chapter 8, How do Organisms Reproduce, is an essential resource for students who want to gain a comprehensive understanding of the process of reproduction in living organisms. The solutions provided in this chapter help students to clear their doubts and understand the concepts thoroughly. It also provides a strong foundation for further studies in biology and related fields.

List out the topics discussed in the Chapter 8 of NCERT Solutions for Class 10 Science.

The topics discussed in the Chapter 8 of NCERT Solutions for Class 10 Science are –
1. Various reproduction modes like sexual reproduction, asexual reproduction and reproduction in flowering plants are explained in brief.
2. Students can understand that reproduction involves the creation by the cell involved in the process of DNA copy and additional cellular devices.
3. DNA copying mechanisms are explained in brief.
4. The body design and the use of different reproductive modes by different organisms are discussed in this chapter.

Explain the process of Asexual reproduction covered in the Chapter 8 of NCERT Solutions for Class 10 Science.

Asexual reproduction is for lower animals. Gametes are absent in their reproductive cells. Biological features are maintained by genes by transmitting from one generation to another. Students who wish to understand the concepts covered in this chapter are advised to download the PDF of solutions from SWC. The solutions are created by a set of highly experienced subject matter experts with the aim of helping students to score well in the board exams.

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