RBSE Class 10 Science Solutions Chapter 8 How do Organisms Reproduce

RBSE Class 10 Science Solutions Chapter 8 How do Organisms Reproduce

RBSE Class 10 Science Chapter 8 How do Organisms Reproduce InText Questions and Answers

Page 128.

Question 1.
What is the importance of DNA copying in reproduction?
Answer:
The creation of DNA copying is a basic event in reproduction. Cells use chemical reactions to build copies of their DNA. This creates two copies of DNA in a reproducing cell. Therefore, DNA copying is accompanied by the creation of an individual cellular apparatus. Then the DNA copies separate and a cell divides to give rise to two cells. In this way in reproduction for making two cells, DNA copying is necessary.

By DNA copying genetical characters goes from parents to new bom (offspring). Sometimes at the time of DNA copying some variations comes in them. So new born cells or offspring are similar but in some types are different from one another. These variations are the basis of evolution and useful in survival of species.

Question 2.
Why is variation beneficial to the species but not necessarily for the individual?
Answer:
In organisms variations are useful for species but not necessary for population. During reproduction in members of Some species some variations develop that allow the organisms to use that particular niche. In niches there may be many changes. If a population of reproducing organisms were suited to a particular niche and if the niche were drastically altered, the population could be wiped out.

However, if some variations were to be present in a few individuals in these populations there would be some chance for them to survive. Thus, if there were a population of bacteria living in temperate waters, and if the water temperature were to be increased by global warming, most of these bacteria would die, but the few variations resistant to heat would survive and grow further. Variation is thus useful for the survival of species over time. But if variations in population would be favouarble’ to environment then it will survive, otherwise die.

Page 133.

Question 1.
How does binary fission differ from multiple fission?
Answer:
Differences between binary fission and multiple fission:

Question 2.
How will an organism be benefited if it is reproduced through spores?
Answer:
Generally spore formation is found in plants. Spores can survive in unfavourable conditions as they have a hard protective layer, spores are light in weight so they are easily dispersed. In favouarable conditions (proper temperature, moisture, food etc.) spores germinate to give the birth to new individuals. Ex. Rhizopus, Mucor etc.

Question 3.
Can you think of reasons why more complex organisms cannot give rise to the individuals through regeneration?
Answer:
In complex multicellular organisms cells are specialised for functions. These cell form the tissues, organs, organ systems and body of organisms. In these, new organism develop only on fusion of sexual cells (male and female gamete). In such organisms any other cell or tissue is not capable to form a new individual.

To its opposite some simple multicellular organisms, as sponge, hydra etc. are capable to form new individuals by regeneration. In this process any cut part of organisms form the new individual. The organisms having complex structure, the capability of regeneration is only limited to fill the wound.

Question 4.
Why is vegetative propagation practised for growing some types of plants.
Answer:
That reproduction in which any vegetative part of the plant develops into new plant, is called vegetative propagation or vegetative reproduction. Roots, stems and leaves of some plants are having the capability of vegetative propagation. Use of vegetative propagation is done due to the following reasons:
(1) In nature some plants do not produce seeds as seedless varieties of banana, orange, grapes and rose etc., can be grown only by this method. This is the only method by which we can keep the availability of these at commercial level.

(2) Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds. It is also not sure that all seeds will germinate and develope into plants while vegetative reproduction is definitely taken place.

(3) Plants obtained from vegetative reproduction are completely similar to the parent plants in respect of fruit and flower character and maintain the desired characters from generation to generation, while the plants develop from seeds are having its low level properties.

(4) Plants developed from vegetative reproduction are having more production capacity.

Question 5.
Why is DNA copying an essential part of the process of reproduction?
Answer:
Organisms look similar because their body designs are similar. If body designs are to be similar, the blueprints for these designs should be similar. Thus, reproduction at its most basic level will involve making copies of the blueprints of body design. The chromosomes in the nucleus of the cell contain information for inheritance of features from parents to next generation in the form of DNA molecules.

The DNA is the cells nucleus is the information source for making proteins. If the information is changed, different proteins will be made. Different proteins will eventually lead to altered body designs. Therefore, DNA copying is an essential part so that the characteristics of species and body organisation remain same generation after generations.

Page 140.

Question 1.
How is the process of pollination different from fertilisation?
Answer:
Difference in pollination and fertilisation:
Transfer of the pollen grains from the anther of a flower to the flower of same species or stigma of

Question 2.
What is the role of the seminal vesicles and the prostate gland?
Ans.
Along the path of the vas deferens, glands like the prostate and the seminal vesicles add their secretions so that the sperms are now in a fluid which makes their transport easier and this fluid also provides nutrition.

Question 3.
What are the changes seen in girls at the time of puberty?
Answer:
At the time of puberty the following changes are observed in females:

• Breast size begins to increase and the front parts of the nipples start to darken.
• Girls begin to menstruate.
• Voice becomes thin (high pitched) and sweet.
• Hair growing in armpits and genital area between the thighs start. They become darker in colour.
• The skin frequently becomes oily and might develop pimples.
• Widening of pelvic regional (hip area) starts and there is deposition of fat in the body.
• Growth in size of uterus, vagina, oviduct and vulva starts.
• Psychological attraction starts towards male.

Question 4.
How does the embryo get nourishment inside the mother’s body?
Answer:
The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall. It contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo. The developing embryo will also generate waste substances which can be removed by transferring them into the mother’s blood through the placenta.

Question 5.
If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?
Answer:
If a woman is using a copper-T it will not protect from sexually transmitted diseases because it is only a device to prevent pregnancy.

RBSE 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) 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) pollen grains.

Question 4.
What are the advantages of sexual reproduction over asexual reproduction?
Answer:
The sexual reproduction is having the following advantages over the asexual reproduction:

• Symtoms of both parents are found in children.
• Sexual reproduction brings varieties in offspring which is very important for evolution.
• Sexual reproduction plays an important role in the formation of new species.
• The organisms develop>ed by sexual reproduction includes the best characters and they also contain more hybrid vigour.

Question 5.
What are the functions performed by the testis in human beings?
Answer:
The human testes are having following functions:

• Hormone testosterone formed by testes by which there is development of secondary sexual characters in inales boys.
• Formation of sperms is also done by testes.
• They also control the sperm hormones.

Question 6.
Why does menstruation occur?
Answer:
Since the ovary releases one egg every month, the uterus also prepares itself every month to receive a fertilised egg. Thus, its lining becomes thick and spongy. This would be required for nourishing the embryo if fertilisation had taken place. Now, however, this lining is not needed any longer. So, the lining slowly breaks and comes out through the vagina as blood and mucous. This cycle takes place roughly every month and is known as menstruation.

Question 7.
Draw a labelled diagram of the longitudinal section of a flower.
Answer:

Question 8.
What are the different methods of contraceptiion?
Answer:
Following are the different methods of contraception:
(i) One category is the creation of a mechanical barrier so that sperm does not reach the egg. Condoms on the penis or similar coverings worn in the vagina can serve this puirpose.

(ii) Another category of contraceptives acts by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur. These drugs commonly need to be taken orally as pills. However, since they change hormonal balances, they can cause side effects too.

(iii) Other contraceptive devices such as the loop or the copper-T are placed in the uterus to prevent pregnancy.

(iv) If the vas deferens in the male is blocked, sperm transfer will be prevented. If the fallopian tube in the female is blocked, the egg will not be able to reach the uterus. In both cases fertilisation will not take place. Surgical methods can be used to create such blocks.

Question 9.
How are the modes for reproduction different in unicellular and multicellular organisms?
Answer:
Difference in mode of reproduction in unicellular and multicellular organisms.

Question 10.
How does reproduction help in providing stability to populations of species?
Answer:
Populations of organisms fill well defined places, or niches, in the ecosystem, using their ability to reproduce. This consistency of DNA copying during reproduction is important for maintenance of body design features that allow the organisms to use that particular niche. Reproduction is therefore linked to the stability of populations of species.

Question 11.
What could be the reasons for adopting contraceptive methods?
Answer:
Following may be the reasons for adopting contraceptive devices:
(i) Since the sexual act is a very intimate connection of bodies, so sexual transmitted diseases in bacterial form can be avoided.

(ii) By adopting the contraceptive devices population can be controlled.

(iii) By these devices pregnancy and child birth can be avoided. Again and again pregnancy causes the bad effect in the body of mother. So by using these devices we can care the health of mother