"AKC SCIENCE CLASSES"
CLASS 10 TH (CBSE AND MP BOARD)
CHAPTER 08
HOW DO ORGANISMS REPRODUCE?
INTEXT QUESTIONS AND ANSWERS
NCERT INTEXT QUESTIONS (PAGE NO. 128)
Q.01:- What is the importance of DNA copying in reproduction?
Ans:- DNA found in chromosomes in the nucleus of the cells has the information to create proteins which lead to body design of an organism. If the organisms are to make exact copies of themselves, the DNA should replicate to make an exact copy of itself. DNA replicate in the cell with the help of various enzymes and this is accompanied by divisions of the basic unit of every organism i.e., the cell.
Q.02:- Why is variation is beneficial to the species but not necessarily for the individual ?
Ans:- Variations are useful for the survival of species in changed environmental situations. For example, if a population of reproducing organisms were suited to a particular niche (well defined place of abode) and if the niche is drastically changed, 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 theme to survive. Thus, if there is a population of bacteria living in temperate waters and if water temperature increases by global warming, most of bacteria would die. But a few variants resistant to heat would survive and grow further variation is thus useful for the survival of species over time.
NCERT INTEXT QUESTIONS (PAGE NO. 133)
Q.01:- How does binary fission differ from multiple fission?
Ans:-
| SL No. | Binary fission | Multiple fission |
|---|---|---|
| 1 | No protective coat or wall or cyst is formed around the cell. | A cyst or a protective coat or wall is formed around the cell. |
| 2 | A fully mature individual cell divides into two producing two daughter individuals. | The cell nucleus divides many times within the cyst to produce many daughter nuclei. Each gathers cytoplasm and forms daughter individuals. |
| 3 | No such phenomenon occurs. | The parent cell breaks away, releasing many individuals at once. |
Ans:- The nuclei in the hypha of fungus like mucor, get surrounded by a bit of cytoplasm and get a thick wall. This wall protects the spores during unfavourable conditions. When the favourable conditions return the spores develop into new hyphae. Thus, spores help the fungus tide over unfavourable conditions.
Q.03:- Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Ans:- The tissues in the complex organisms cannot regenerate a new individual as they are highly differentiated to perform specialised functions. For example, human skin cannot regenerate into a new individual as it is a highly differentiated tissue performing a designated function.
Q.04:- Why is vegetative propagation practised for growing some types of plants?
Ans:- Vegetative propagation is practised in some plants because :-
- It is the only method of reproduction in seedless plants.
- We get fully matured plant in very short time.
- It is a short cut method for rapid multiplication.
- It helps to preserve the type of character that a plant breeder desires.
- It is very easy and economical method for the multiplication of ornamental plants.
Ans:- DNA is the genetic material which makes proteins which in turn give rise physical characteristics of an organism. Copying of DNA results in transfer of informations to form a fully developed organism.
QQAns:- Pollination is the process by which the pollen from another reaches the stigma of the flower of the same species. Fertilization is the process in which the male gamete fuses with the egg to form zygote.
Q.02:- What is the role of the seminal vesicles and the prostate gland?
Ans:- Seminal vesicles secrete a viscous fluid which forms most of the part of semen. It also lubricates the passage through which the sperms travel. This fluid also protects the sperms from the acids normally present in the urethra and female reproductive duct. Prostate gland produces prostatic fluid which is discharged into urethra through more than two dozen fine ducts. There is more secretion during sexual act when they are forcefully ejected by contraction of muscular and elastic tissues.
Q.03:- What are the changes seen in girls at the time of puberty?
Ans:- The females show development of breasts, darkening of nipples, an set of menstruation and growth of pubic hair.
Q.04:- How does the embryo get nourishment inside the mother's body?
Ans:- After fertilisation the lining of uterus thickens and richly supplied with blood to nourish the growing embryo. The embryo gets nutrition from the mother's blood with the help of a special tissue called placenta. This is disc shaped tissue which is embedded in the uterine wall. Placenta contains villi on the embryo's side of the tissue and blood spaces on mother's side surrounding the villi. This provides a large surface area for food and oxygen to pass from mother to the embryo and waste products from embryo to mother.
Q.05:- If a women is using a copper-T , will it help in protecting her from sexually transmitted diseases?
Ans:- Copper-T is a contraceptive method which prevents implantation of the zygote inside the uterus. It cannot prevent a women from sexually transmitted diseases (STDs). STDs are transmitted by contact which cannot be prevented by copper-T.
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