Q24 of 26 Page 1

Human female is not fertile after menopause whereas males can produce gametes at any age after puberty. Analyse the statement and schematically represent a comparison between gametogenesis in males and females.

OR


A village health worker was taking a session with women. She tells the women that one has to be very careful while using oral pills as method of birth control. Wrong usage can actually promote conception.


(a) Analyze the statement and compare the merits and demerits of using oral pills and surgical methods of birth control.


(b) Village women were confused as to how a thin metallic Copper loop can provide protection against pregnancy. Justify the use explaining the mode of action of IUDs.


(a)


PUBERTY:


Before a girl reaches puberty her reproductive system is not developed .Hence Ovulation does not take place. After girl reaches puberty at the age of around 13-14 years, her reproductive system develops. Ovulation starts taking place and secondary sexual characteristics also develops.


MENSTRUATION:


1. Bleeding takes place, when the ova released at the time of ovulation do not get fertilized. This process is called Menstruation.


2. If at the time of ovulation ova gets fertilized then a woman becomes pregnant.


MENOPAUSE:


It marks the end of the reproductive phase in a woman’s life. The woman does not remain fertile and the circulating female hormones like estrogen and progesterone also decreases.


Whereas when a male reaches puberty, he produces numerous sperms which increase the chances of fertilization of the ova. These sperms are produced till the lifetime of a male.


GAMETOGENESIS:


SPERMATOGENESIS


In males, gametogenesis is also termed as spermatogenesis. It is the process of formation of haploid spermatozoa from the germ cells.



OOGENESIS:


In females, gametogenesis is also termed as oogenesis.It is the process of formation of Ovum or the female gamete.





OR


(a) Oral Pills:


These are birth control pills which are used to avoid unwanted pregnancies. These pills are a combination of hormones estrogen and progesterone.


Merits:


1. It is a reversible method.


2. It has lesser side effects.


3. It also prevents various infections of the ovaries, fallopian tubes and uterus etc.


4. It also prevents certain cancers.


De-merits:


1. Can have side effects in the longer run.


2. If not taken at the right time may promote conception.


SURGICAL METHODS:


These are permanent birth control methods. In females the fallopian tubes are tied called as Tube ligation.In males this process is known as Vasectomy.


Merits:


1. It is a highly effective method.


2. It is a quick procedure with lesser side effects.


De-merits:


1. It cannot be reversed.


2. If performed under unhygienic conditions could lead to several health conditions.


(b)IUD’S are Intra uterine devices, these are thin coils or a T-shaped device which is inserted in a women’s uterus to prevent unwanted pregnancy. The most commonly used IUD is Copper- T.


These IUD’S work in the following ways:


1. Increase the phagocytosis of sperms in the uterus.


2. The release of copper ions suppresses sperm motility and fertility.


3. Hormones released by IUD’S make uterus hostile for the sperms.


More from this chapter

All 26 →
22

Rajesh was doing gel electrophoresis to purify DNA fragments. Given below is the sketch of the observations of the experiment performed by him.


(a) At which end he would have loaded the samples and where?


(b) Analyse the reason for different positions taken up by the DNA bands.


(c) Elaborate the step he would have followed to visualize DNA bands.


23

Mohit and Sumit want to buy a new car for their company. Mohit insisted on buying a CNG car with a better mileage but Sumit insisted on buying a diesel version of a high end car with better music system and A.C but relatively low mileage.

(a) Being a responsible citizen of Delhi, how will Mohit convince Sumit about his decision in the wake of rising pollution levels?


(b) What qualities of personality are being exhibited by Mohit in doing so?


(c) Suggest two more measures which can help in reducing vehicular pollution.


25

Observe the representation of genes involved in the lac operon given below –


(a) Identify the region where the repressor protein will attach normally.


(b) Under certain conditions repressor is unable to attach at this site. Explain.


(c) If repressor fails to attach to the said site what products will be formed by z, y and a?


(d) Analyze why this kind of regulation is called negative regulation.


OR


Transcription in eukaryotes is more complex process than in prokaryotes. Justify and compare the initiation, elongation and termination in bacterial cells with eukaryotes.


26

The graph below shows species –area relationship.


(A) If b denotes the relationship on log scale


i) Describe a and b.


ii) How is slope represented? Give the normal range of slope. iii) What kind of slope will be observed for frugivorous birds and mammals in a tropical forest?


(B) Species diversity of plants (22%) is much less than that of animals (72%). Analyze the reasons for greater diversity of animals as compared to plants.


OR


(a) Which of the above represents the increase or decrease of population?


(b) If N is the population density at time t, then what would be its density at time? Give the formula.


(c) In a barn there were 30 rats. 5 more rats enter the barn and 6 out of the total rats were eaten by the cats. If 8 rats were born during the time period under consideration and 7 rats left the barn, find out the resultant population at time.


(d) If a new habitat is just being colonized, out of the four factors affecting the population growth which factor contributes the most?