Bihar Board Class 10 Science Solutions Chapter 8 How do Organisms Reproduce?

BSEB Bihar Board Class 10 Science Solutions Chapter 8 How do Organisms Reproduce? Textbook Questions and Answers.

Bihar Board Class 10 Science Solutions Chapter 8 How do Organisms Reproduce?

Bihar Board Class 10 Science Chapter 8 How do Organisms Reproduce? InText Questions and Answers

In-text Questions (Page 128)

Question 1.
What is the importance of DNA copying in reproduction?
Answer:
The DNA copying is important because:

• it ensures the transmission of characteristics from parents to their offsprings.
• variations are created during DNA copying which increases the chances of survival of the species and in the evolution of new life forms.

Question 2.
Why is variation beneficial to the species but not necessarily for the individual?
Answer:
The variations which arise during the process of reproduction enable the organisms to survive under adverse conditions. The variations which arise in an individual are beneficial only if they are inherited by the offsprings of the individual for several generations. So, we can say that variations are not necessarily beneficial for the individual unless they are transmitted to the other members of the species.

In-text Questions (Page 133)

Question 1.
How does binary fission differ from multiple fission?
Answer:
Binary Fission:

1. The parent cell divides/splits equally into two daughter cells.
2. It occurs under favourable conditions. For example, Amoeba

Multiple Fission:

1. The parent cell splits into many daughter cells.
2. It occurs under unfavourable conditions.
   For example, Plasmodium (Malarial parasite)

Question 2.
How will an organism be benefited if it reproduces through spores?
Answer:
The spores have a thick wall which help them to tide over and survive under unfavourable conditions. Spores germinate on the return of favourable conditions. So, spores benefit the organism to ensure its survival.

Question 3.
Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Answer:
Multicellular organisms consist of specialised cells which form the various tissues and the organs of the body of the organism present at different locations in the body of the organism. This makes it difficult for cell by cell division of the organism. So, multicellular animals need a complex method of reproduction and cannot give rise to new individuals through regeneration.

Question 4.
Why is vegetative propagation practised for growing some types of plants?
Answer:
Vegetative reproduction is practised for growing some types of plants because

• some plants have lost the ability to form seeds and can be propagated by vegetative reproduction. For example, Banana, rose, orange, jasmine, etc.
• it helps in creating genetically identical plants.
• plants which take a longer time to grow and mature can be grown by this method.
• it can be used to grow such plants which require more care during early stages of their development.

Question 5.
Why is DNA copying an essential part of the process of reproduction?
Answer:
DNA copying is an essential part of the process of reproduction because:

• it helps in the transmission of characteristics from the parents to their offsprings.
• the variations are created during copying which increases the chances of the survival of the members of the species under adverse conditions.
• it helps in the evolution of the species over time by creating variations during copying of DNA.

In-text Questions (Page 140)

Question 1.
How is the process of pollination different from fertilisation?
Answer:
Pollination:

1. The transfer of pollen grains from the anther to stigma of a flower.
2. It is of two types-Self-pollination and cross pollination
3. It is a physical process.
4. It occurs only in the plants.

Fertilisation:

1. The process of fusion of male and female gamete to form a zygote is called fertilisation.
2. It is of two types-Internal fertilisation and external fertilisation.
3. It is a bio-chemical process.
4. It takes place both in the plants as well as in animals.

Question 2.
What is the role of the seminal vesicles and the prostate gland?
Answer:
Seminal vesicles- The sperms are stored in the seminal vesicles. It also provides nutrition to the sperms.
Prostate gland- The secretions of this gland make the transport of the sperms easier.

Question 3.
What are the changes seen in girls at the time of puberty?
Answer:
The changes which occur in the girls at the time of puberty are:

• Increase in the breast size.
• Growth of hair in the armpits and the pubic region.
• Menstruation and ovulation begin.
• Excess fat gets deposited in various parts of the body like hips and thighs.

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 figner-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 special tissue Placenta is nutrients. Also, there is special tissue placenta is embedded in the uterine wall. The embryo receives oxygen and nutrients from the mother’s blood through 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, copper-T are placed in the uterus to prevent pregnancy. They can cause side effects due to irritation of the uterus.

Bihar Board Class 10 Science Chapter 8 How do Organisms Reproduce? Textbook Questions and Answers

Question 1.
Asexual reproduction takes place through budding in
(a) Amoeba
(b) yeast
(c) Plasmodium
(d) leishmania
Answer:
(b) A sexually 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 is not a part of the female reproductive system in human beings.

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:
Sexual reproduction is more advantageous than asexual reproduction because:

• variations are caused during sexual reproduction which increases the chances of survival of an organism under adverse conditions.
• the progeny obtained by asexual reproduction is genetically identical to the parents and does not lead to evolution of the organism. The variations caused during the sexual reproduction leads to accumulation of variations which can lead to the evolution of new species.

Question 5.
What are the functions performed by the testis in human beings?
Answer:
Testis perform the following functions in the human beings:

• They are the sites for sperm production.
• They provide a suitable temperature required for the sperm formation.
• Male sex hormones are released by the testes.

Question 6.
Why does menstruation occur?
Answer:
Menstruation is a process which occurs when the egg is not fertilised by the sperm. The lining of the uterus prepares itself by becoming thick and spongy every month for receiving the fertilised egg and nourish the growing embryo. If the egg does not get fertilised then this lining breaks and comes out through the vagina along with blood by the process called menstruation.

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 methods to avoid pregnancy are called as contraceptive methods. The different methods are:
Physical Methods: Prevent union of sperm and egg. For example, Condoms, diaphragm and cervical caps.

Chemical Methods: Act by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur. They may have side-effects too. For example, Oral pills.

Surgical Methods:

• Vasectomy: The vas deferens of male is blocked to prevent sperm transfer.
• Tubectomy: The fallopian tube of female is blocked to prevent egg to reach uterus.
• Copper-T or loop is placed in uterus to prevent pregnancy.

Question 9.
How are the modes for reproduction different in unicellular and multicellular organisms? [CBSE2016]
Answer:
Unicellular organisms usually reproduce by fission or budding as they have only one cell and there is no separate tissue for reproduction.

Multicellular organisms have different modes of reproduction like sexual and asexual methods because they have special reproductive tissues and systems for the process of reproduction.

Question 10.
How does reproduction help in providing stability to populations of species?
Answer:
Reproduction provides stability to population of species as it helps in maintaining a balance between the birth rate and death rate in a population.

Bihar Board Class 10 Science Chapter 8 How do Organisms Reproduce? Textbook Activities

Activity 8.1 (Textbook Page 129)

The budding process of yeast may be seen as the yeast multiply by the process of budding.

Activity 8.2 (Textbook Page 129)

The slice of bread would be seen covered with a white cottony mass of fungal threads called hyphae, belonging to the fungus Rhizopus. Rhizopus reproduces by spores formed in the sporangia borne on the hyphae.

Activity 8.3 (Textbook Page 129)

Amoeba has no definite shape, has cytoplasm and a nucleus in a flexible cell membrane. During binary fission Amoeba undergoes nuclear division and forms two nuclei. The two nuclei formed by division move to opposite directions in the parent cell. Ultimately, the cell divides and forms two daughter cells.

Activity 8.4 (Textbook Page 130)

Spirogyra is a filamentous alga found as slimy filamentous green masses in clean water, ditches and ponds. Its filaments come to the surface of water and form dense green coloured structures on it. It has unbranched chains of cylindrical cells having spiral chloroplasts. It occurs as a slimy, green ‘blanket weed’ in ponds.

Activity 8.5 (Textbook Page 132)

Only the pieces of potato having the notch or the bud give rise to fresh green shoots whereas those pieces which do not have the notch or bud are not able to reproduce. This is so because the reproductive buds are present in the potato at the regions called as eyes form where the buds arise to form new plants. Potato is a stem.

Activity 8.6 (Textbook Page 132)

Only the portions which have at least one leaf will be able to form new plants because the leaves arise from the nodes. Nodes are the regions where reproductive buds are present in most of the plants. So, new plants will arise from the reproductive buds present at nodes in plants having at least one leaf, whereas the portion between two leaves known as the internode will not be able to form new plants.

Activity 8.7 (Textbook Page 135)

The seeds when cut open will show two large cotyledons attached to the middle of the embryonal axis. The cotyledons have reserve food material to nourish the developing embryo. The portion above the cotyledon is the future shoot called as plumule and the portion below the cotyledons is the future root called as the radicle.