NCERT Solutions for Class 10 Science Ch 7: How do Organisms Reproduce?, is given below.
You will get solutions for;
- In-text questions as well as,
- Exercises questions.
So let’s dive into it!
In-text Questions Set-1
1) What is the importance of DNA copying in reproduction?
Solution:
DNA, or Deoxyribonucleic acid, is the genetic material found in the cells of all organisms. It carries genetic information from one generation to the next, ensuring that offspring resemble their parents.
DNA copying is essential for passing on traits. Any variations during this process can lead to the development of new species.
2) Why is the variation beneficial to the species but not necessarily for the individual?
Solution:
Variation is beneficial to a species rather than just individuals because it helps the species survive drastic changes in the environment.
For example, if the temperature of a water body rises, some microorganisms might not survive. This could disrupt the ecosystem.
Therefore, variation within a species increases the chances of survival as a whole, even if some individuals don’t make it.
In-text Questions Set-2
1) How does binary fission differ from multiple fission?
Solution:
When a single cell splits into two equal parts, it’s called binary fission. Bacteria and amoeba reproduce this way.
When a single cell divides into many daughter cells at once, it’s called multiple fission. Algae and sporozoans are examples of this process.
2) How will an organism be benefited if it reproduces through spores?
Solution:
An organism benefits from reproducing through spores in the following ways:
– A large number of spores are produced in one sporangium.
– Spores can spread to distant places through the air, reducing competition in one area.
– Spores have thick walls that protect them from dehydration in unfavorable conditions.
3) Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Solution:
Organisms with more complex structures cannot produce new individuals through regeneration because their organ systems are highly organized and interconnected.
While they can regenerate some lost body parts, like skin, blood, or muscles, they cannot regenerate an entire new individual.
4) Why is vegetative propagation practiced for growing some types of plants?
Solution:
Here are the advantages of using vegetative propagation for growing certain plants:
– Crops like oranges, bananas, and pineapples don’t have viable seeds, so vegetative propagation is ideal.
– It’s a fast, cheap, and easy way to grow plants.
– It works well in areas where seeds fail to germinate.
– It helps preserve good quality varieties.
5) Why is DNA copying an essential part of the process of reproduction?
Solution:
DNA copying is crucial in reproduction because it passes genetic information from parents to offspring. During this process, the DNA is copied through chemical reactions, creating two identical copies. These copies, along with other cell structures, are then divided into two new cells during cell division.
In-text Questions Set-3
1) How is the process of pollination different from fertilization?
Solution:
Pollination is the process where pollen grains are transferred from the anther (the male part of a flower) to the stigma (the female part of a flower). This can happen with the help of wind, water, or animals like insects. Pollination is essential for plants to reproduce but does not involve any fusion of cells.
Fertilization, on the other hand, occurs after pollination. It involves the fusion of a male gamete (from the pollen) and a female gamete (from the ovule) inside the ovule of the flower. This fusion results in the formation of a zygote, which will eventually grow into a new plant.
2) What is the role of the seminal vesicles and the prostate gland?
Solution:
The seminal vesicles and prostate gland secrete fluids that lubricate and provide a medium for the easy transport of sperm. These secretions also supply nutrients like fructose, calcium, and enzymes.
3) What are the changes seen in girls at the time of puberty?
Solution:
Here are the changes that occur in girls during puberty:
– Hair begins to grow in the genital area, underarms, on the face, hands, and legs.
– The uterus and ovaries grow in size.
– The breasts enlarge, and the skin around the nipples darkens.
– The menstrual cycle starts.
– Pimples may appear due to increased oil production in the skin.
4) How does the embryo get nourishment inside the mother’s body?
Solution:
After fertilization, the lining of the uterus thickens to support the growing embryo by increasing blood flow.
The placenta, a special tissue attached to the uterine wall, provides nourishment to the embryo from the mother’s tissue.
The placenta has villi on the embryo’s side and blood spaces on the mother’s side, creating a large area for nutrient exchange and waste removal.
5) If a woman is using a Copper-T, will it help in protecting her from sexually transmitted diseases?
Solution:
No, using a copper-T cannot prevent the exchange of body fluids, so it does not protect against sexually transmitted diseases.
Exercise Questions
1) Asexual reproduction takes place through budding in
(a) Amoeba
(b) Yeast
(c) Plasmodium
(d) Leishmania
Solution:
(b) Yeast
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
3) The anther contains
(a) Sepals
(b) Ovules
(c) Pistil
(d) Pollen grains
Solution:
(d) Pollen grains
4) What are the advantages of sexual reproduction over asexual reproduction?
Solution:
Here are the advantages of sexual reproduction:
– Offspring inherit traits from both parents.
– Greater variation increases the chances of species survival.
– Offspring can adapt more easily to environmental changes.
– It can also enhance human health.
5) What are the functions performed by the testis in human beings?
Solution:
The testis in humans performs the following functions:
– It produces sperm.
– It produces male hormones called androgens, including testosterone, which is responsible for secondary sexual characteristics in boys.
6) Why does menstruation occur?
Solution:
Menstruation is the regular bleeding from the vagina that begins at puberty and continues until menopause. During this time, the body prepares for pregnancy each month.
An egg is released from one of the ovaries while the uterus gets ready to receive a fertilized egg by thickening its inner lining and increasing its blood supply.
If the egg is not fertilized, the lining of the uterus gradually breaks down, leading to menstruation.
7) Draw a labeled diagram of the longitudinal section of a flower.
Solution:
8) What are the different methods of contraception?
Solution:
The different methods of contraception are:
– Natural Method: This involves avoiding intercourse from the 10th to the 17th day of the menstrual cycle, when the chances of fertilization are highest due to ovulation.
– Barrier Method: This method uses barriers to prevent sperm from meeting the egg. Barriers include male and female condoms, diaphragms, cervical caps, and contraceptive sponges.
– Oral Contraceptives: These are pills taken orally that contain hormones to prevent the release of eggs, thereby avoiding fertilization.
– Implants and Surgical Methods: Contraceptive devices like Copper-T or loops can be used to block the sperm and egg from meeting. Surgical methods involve blocking the fallopian tubes in females or the vas deferens in males to stop the flow of eggs or sperm.
9) How are the modes for reproduction different in unicellular and multicellular organisms?
Solution:
Unicellular organisms reproduce through methods like fission and budding, where a single cell divides into two daughter cells, and this process continues.
In contrast, multicellular organisms have specialized organ systems for reproduction. They reproduce through methods like vegetative propagation and spore formation. In more complex organisms, such as humans and animals, reproduction occurs through sexual reproduction.
10) How does reproduction help in providing stability to populations of species?
Solution:
Reproduction is the process by which living organisms produce new individuals of the same species. This helps maintain the population and ensures the species continues into future generations. Stability in the population is achieved by balancing the rates of births and deaths.
11) What could be the reason for adopting contraceptive methods?
Solution:
Here are the reasons for using contraceptive methods:
– To control population growth
– To prevent unplanned pregnancies
– To avoid sexually transmitted diseases
