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

BINARY FISSION	MULTIPLE FISSION
i) In this, parental cell divides and produces two daughter cells.	i) In this, a parental cell divides and produces more than two daughter cells.
ii) The parental nucleus divides into two daughter nuclei.	ii) The parental nucleus divides into many nuclei.
iii) It occurs during favourable conditions. Eg : Amoeba, Bacteria, etc.	iii) It occurs during unfavourable conditions. Eg: Plasmodium, Chlamydomonas etc.

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

Answer

i) Spores are light in weight and get distributed easily to distant places by wind. This helps to avoid competition at one place.

ii) Spores are produced in large numbers, so that large number of organisms are produced.

iii) Spores are covered by protective coat, so that they remain dormant till favourable conditions.

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

Answer:

i) Regeneration is carried out by specialised cells.

ii) Complex organisms do not have specialised cells and they have highly differentiated tissues.

iii) Hence, they cannot give rise to new individuals through regeneration.

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

Answer:

Ans. Vegetative propagation is practiced for growing some types of plants because:

i) it is more rapid, easier and cheaper method.

ii) by this method good quality and variety of plants can be produced.

iii) it helps to introduce plants, in new areas where the seed germination fails to produce mature plant due to changes in environmental factors and the soil.

iv) it is used to grow a plant in which viable seeds are not formed or very few seeds are produced.

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

Ans. DNA copying, also known as DNA replication, is a crucial part of the reproduction process for several important reasons:

1. Passing Genetic Information: DNA carries genetic instructions that determine the traits and characteristics of an organism. During reproduction, it’s vital to pass on this genetic information to the offspring accurately. DNA replication ensures that an identical copy of the genetic material is created, which will be inherited by the new organism.
2. Maintaining Genetic Continuity: DNA copying ensures that the genetic information remains consistent from one generation to the next. This continuity is essential for the preservation of species and the transmission of traits from parents to offspring.
3. Variation: While DNA replication creates an identical copy, there can be occasional errors or mutations in the process. These mutations can lead to genetic variations, which are essential for the evolution and adaptation of species over time.

Class 10 Science Chapter 8 How do Organisms Reproduce

QUESTIONS (Page No. 140) How is the process of pollination different from fertilization?

Answer:

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

Answer:

Seminal vesicles and prostate gland help in:

i) secreting the nutritive fluids.

ii) transportation of sperms.

iii) providing nutrients to the sperms.

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

Answer:

i) Increase in breast size and darkening of skin of the nipples present at the tips of the breasts.

ii) Appearance of hair in the genital area.

iii) Appearance of hair in other areas of skin like underarms, hands and legs.

iv) Increase in the size of uterus and ovary.

v) Beginning of menstrual cycle.

vi) More secretion of oil from the skin, which results in the appearance of pimples.

11. How does the embryo gets nourishment inside the mother’s body?

Answer:

i) The embryo gets nutrients from the mother’s blood with the help of a special tissue called placenta.

ii) Placenta is a disc which is embedded in the uterine wall.

iii) It connects villi on the embryo’s side of the tissue.

iv) On the mother’s side are blood spaces, which surround the villi.

v) This provides a large surface area for glucose and oxygen to pass from the mother to the embryo.

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

Answer:

No, a copper T (also known as an intrauterine device or IUD) does not provide protection against sexually transmitted diseases (STDs). The primary function of a copper T is to prevent pregnancy by creating a hostile environment for sperm inside the uterus. It does not offer any barrier or protection against infections that are transmitted through sexual contact.

Also Check: NCERT Solutions for Class 10 Science

• Chapter 1 – Equations and Chemical reactions
• Chapter 2 – Acids, Bases, and salt
• Chapter 3 – Non Metals and Metals
• Chapter 4 – Carbon and Its Compounds
• Chapter 5 – Periodic Classification Of Elements
• Chapter 6 – Life Processes
• Chapter 7 – Control and Coordination
• Chapter 8 – How do Organisms Reproduce?
• Chapter 9 – Heredity and Evolution
• Chapter 10 – Light Reflection and Refraction
• Chapter 11 – The Human Eye and Colorful World
• Chapter 12 – Electricity
• Chapter 13 – Magnetic Effects of Electric Current
• Chapter 14 – Sources of Energy
• Chapter 15 – Our Environment
• Chapter 16 – Sustainable Management of Natural Resources

Class 10 Science Chapter 8 How do Organisms Reproduce

EXERCISES (Page No. 141)

1. Asexual reproduction takes place through budding in

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

Answer: b. Yeast.

Asexual reproduction through budding is a common method in yeast, where a small bud or outgrowth forms on the parent cell and eventually separates to become a new individual.

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.

The vas deferens is a part of the male reproductive system. It is a duct that carries sperm from the testes to the urethra and is not present in the female reproductive system.

3. The anther contains

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

Answer: d. Pollen grains.

The anther is the part of the flower’s stamen, and it contains pollen grains. Pollen grains are essential for the process of pollination, which is crucial for plant reproduction.

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

Answer:

i) Sexual reproduction provides more chance for genetic variation.

ii) It plays an important role in origin of new species.

iii) It ensures the survival of species in a population.

5. Why does menstruation occur?

Answer: Menstruation occurs to break the lining of the uterus (gradually) so that it comes out through the vagina as blood and mucous. This happens if ovum is not fertilized.

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

Answer:

7. What are the different methods of contraception?

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

i) Natural method : In this method, the sexual act is avoided from day 10 to 17 of the menstrual cycle because during this period, ovulation is expected and therefore, the chances of fertilization are very high.

ii) Barrier method : In this method, barriers (devices) are used to prevent the entry of sperms into female genital tract during sexual intercourse.

Eg: Condoms, diaphragm and cervical cap, copper-T or loop, etc.

iii) Chemical method : In this method, specific drugs are used by females to kill the sperms.

Eg: Vaginal pills, creams, jellies, etc.

iv) Surgical method : It includes vasectomy (blocking of vas deferens) in males, tubectomy (blocking of fallopian tubes) in females.

v) Hormonal method : In this, production of ovum is suppressed by changing the hormonal balance. Eg : Oral pills, i pill, etc.

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

Answer:

i) Reproduction plays role in producing the new individuals of the species that resembles the parents.

ii) Reproduction helps in continuation of the race.

iii) Reproduction replaces the individuals that are dead.

iv) Reproduction introduces new varieties.

v) Hence, reproduction helps in providing stability to populations of species.

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

Answer:

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

Answer: Reproduction ensures species stability by replacing aging individuals, introducing genetic diversity through offspring, allowing natural selection to favor advantageous traits, and maintaining ecological balance within ecosystems.

These factors collectively contribute to the survival and adaptability of a species. System is crucial for ecological balance. Reproduction ensures that species continue to exist, and their interactions with other species contribute to the overall stability of ecosystems.

11. What could be the reasons for adopting contraceptive methods?

Answer:

• Family planning: To control the timing and number of children.
• Health concerns: To prevent pregnancies that may pose health risks to the mother or child.
• Economic considerations: To manage resources and provide for children’s needs.
• Career and education: To pursue personal and professional goals before starting a family.
• Population control: To address concerns related to overpopulation and resource depletion.
• Protection against STIs: Condoms, a form of contraception, also provide protection against sexually transmitted infections (STIs).