NCERT Solutions for Class 10 Science Chapter 7 How Do Organisms Reproduce includes answers to the latest edition of intext & exercise questions. All these NCERT solutions are prepared by expert teachers with detailed explanations of every important topic. The students need to go through these NCERT solutions to get knowledge of the type of questions asked on How Do Organisms Reproduce.
NCERT Solutions for Class 10 Science Chapter 7 Intext Questions
Page No. 114
Question 1: What is the importance of DNA copying in reproduction?
Answer: DNA copying in reproduction is essential because:
- It keeps the species’ traits: By copying DNA, the specific characteristics of a species are passed down to the next generation.
- Allows for variation: Sometimes small changes occur in DNA copying. These variations can lead to differences within a species, which can be important for adapting to new environments.
- Ensures healthy growth: DNA has all the instructions needed for an organism to develop properly. Accurate copying of DNA is key for this.
So, DNA copying is crucial for maintaining species traits, introducing beneficial variations, and ensuring proper development.
Question 2: Why is variation beneficial to the species but not necessarily for the individual?
Answer: Variation is key for a species because it creates a pool of different traits. This diversity helps the species as a whole adapt to changes and survive challenges like diseases or climate change. However, for individual members of the species, certain variations might not be beneficial. For example – giraffes generally have long necks that help them to feed on leaves from tall plants. Now, if due to genetic variations, a giraffe is born with a shorter neck it can not reach the leaves of tall plants which will be disadvantageous for the shorter-necked giraffe.
Thus, these variants help in the survival of the species. However, all variations are not necessarily beneficial for the individual organisms.
Page Number: 119
Question 1: How does binary fission differ from multiple fission?
Answer:
| Binary fission | Multiple fission |
| In this an organism divides into two similar organisms. | In this an organism produces two or more organisms. |
| A cyst or thick layer is not formed around the cell. | A cyst or thick layer is formed around the cell. |
| It generally occurs in favourable conditions Example : Amoeba, paramecium | It can take place in unfavourable conditions too. Example: Malarial parasite. |
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:
- Spores allow reproduction without needing a partner.
- 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 can endure extreme conditions until they find a suitable place to grow.
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 their body parts. Simple organisms can utilize this method of reproduction as their entire body is made of similar kind of cells in which any part of their body can be formed by growth and development.
However, complex organisms have organ-system levels 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?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Answer: (d) Cytokinin.
Question 5: Why is DNA copying an essential part of the process of reproduction?
Answer: DNA copying is essential in reproduction because:
- Genetic Continuity: It ensures the genetic information is passed from parents to offspring, maintaining the species’ characteristics.
- Cell Function: DNA provides the instructions for all cell functions, so copying DNA is crucial for the new organism to develop and function properly.
- Variation: During DNA copying, slight variations can occur, leading to genetic diversity, which is important for the evolution and adaptability of the species.
Page Number: 125
Question 1: How is the process of pollination different from fertilization?
Answer:
| Pollination | Fertilization |
|---|---|
| Pollination is the process of transfer of pollens from anther to stigma. | The fusion of the male gamete with the female gamete inside the ovule is called fertilization. |
| Can occur through wind, water, or animals like bees. | Happens internally inside the ovule. |
| Sets the stage for fertilization but does not involve the actual fusion of gametes. | Results in 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.
OR
The seminal vesicles and the prostate gland play important roles in the male reproductive system:
- Seminal Vesicles:
- They produce a fluid that is a significant component of semen.
- This fluid contains fructose (a sugar) which provides energy for the sperm.
- It also has other substances that help nourish and protect sperm as they travel through the female reproductive system.
- Prostate Gland:
- The prostate gland produces a fluid that mixes with the sperm and fluid from the seminal vesicles to form semen.
- This fluid helps to nourish the sperm.
- It also contains substances that help to protect the sperm and neutralize the acidity of the female vagina, making it a more favorable environment for sperm.
Together, these glands contribute crucial fluids that support sperm mobility, survival, and fertilizing capability.
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 the 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 the exchange of oxygen and nutrients. Also, the embryo gets nourishment inside the mother’s body through the placenta. The placenta is an organ that connects the mother’s blood supply to the embryo through the umbilical cord. It delivers oxygen and nutrients from the mother to the embryo and removes waste products from the embryo’s blood. This process ensures the embryo grows and develops properly during pregnancy.
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 protect from sexually transmitted diseases, as it does not prevent the entry of semen. It only prevents the implantation of the embryo in the uterus.
NCERT Solutions for Class 10 Science Chapter 7 Exercise Questions
Question 1: Asexual reproduction takes place through budding in
(a) amoeba
(b) yeast
(c) plasmodium
(d) 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?
(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube
Answer: (c) Vas deferens
Question 3: The anther contains
(a) sepals
(b) ovules
(c) carpel
(d) pollen grains
Answer: (d) The anther contains pollen grains.
Question 4: What are the advantages of sexual reproduction over asexual reproduction?
Answer: Advantages of sexual reproduction over asexual reproduction are as follows:
- Sexual reproduction creates offspring with different genetic combinations, which can lead to a variety of traits and appearances.
- In sexual reproduction, more variations are produced. Thus, it ensures the survival of species in a population.
- Sexual reproduction can help filter out harmful genetic mutations.
- The mixing of genes of the father and mother allows for new traits and advances in the species.
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 the scrotum.
Functions of testes are as follows:
- They make sperm for reproduction.
- They produce the hormone testosterone, which is important for male characteristics and reproductive functions.
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 fertilized, 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 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 is usually asexual, often through processes like binary fission, where the cell divides into two identical cells. In multicellular organisms, reproduction can be either asexual or sexual. Asexual reproduction in multicellular organisms involves methods like budding or fragmentation, where new organisms grow from a part of the parent. Sexual reproduction involves the fusion of male and female gametes, leading to offspring with genetic material from both parents.
OR
Certainly, here’s a simple table outlining the differences in the modes of reproduction between unicellular and multicellular organisms:
| Unicellular Organisms | Multicellular Organisms |
|---|---|
| Reproduce mostly asexually, like splitting into two (eg., binary fission). | Can reproduce asexually (like plants growing new plants from cuttings) and sexually (like animals using male and female gametes). |
| Single parent cell gives rise to identical offspring | Two parent cells contribute genetic material, leading to variation in offspring |
| Offspring are independent organisms | Offspring often undergo developmental stages within the parent organism |
| Eg: Bacteria, Amoeba, Yeast | Eg: Plants, Animals, Humans |
This table summarizes the basic distinctions in the reproductive modes of unicellular and multicellular organisms.
Question 10: How does reproduction help in providing stability to populations of species?
Answer: Reproduction helps in providing stability to populations of species by following points:
- Reproduction ensures the continuation of species by producing new individuals to replace those that die.
- In sexual reproduction, the combination of different genes leads to genetic diversity, which is crucial for adapting to changing environmental conditions.
- This genetic diversity allows species to evolve over time, developing traits that help them survive in their environment.
- Stable reproduction rates help maintain a balance in ecosystems, ensuring that resources are not overused or depleted.
Overall, reproduction is key to the survival and stability of species in their habitats.
Question 11: What could be the reasons for adopting contraceptive methods?
Answer: Contraceptive methods are mainly adopted because of the following reasons:
- To prevent unwanted pregnancies.
- To control rise or birth rate of population.
- To prevent the transfer of sexually transmitted diseases.