DNA is the genetic material present in the cells of all organisms. The genetic information from,generation to generation is carried by DNA .It is therefore possible for the organism to produce organism of its own type due to DNA copying only. For the inheritance of traits of the parent,DNA copying is a must.DNA copying also brings about variation ,which forms the basis for the origin of new species.
Q2) What are the changes seen in girls at the time of puberty?
i) Enlargement of breasts with the darkening of skin of the nipples .
ii) growth of hair in the genital region and in armpits occurs.
iii) onset of menstruation .
Q3) If a woman is using a copper-Twill it help in protecting her from sexually transmitted
No,using copper-T will not protect a woman against catching STD.Copper-T is a device which will only guard her against pregnancy .
Q4)Sexual reproduction is considered advantageous over asexual reproduction? Explain
Sexual reproduction ensures that large number of variations appear in the daughter organism constituting a population. This is made possible by the appearance of many new gene combinations which are contributed by the two parents. Sexual reproduction also ensures that the rate of appearance of new variations is speed up which is not achieved due to asexual reproduction.
Q5) Mention the changes observed in flower after fertilization.
a) ovary ripens and developed into fruit.
b) ovules develop into seed.
c) petals and sepals wither and drop.
d)stigma, style and stamens dry up and fall off.
Q6) Give the advantages of vegetative propagation.
1) it is much easier,lowcost,quicker method compared to sexual reproduction.
2) plants which produce non viable seeds or too few seeds or have lost the ability to produce seeds can be made to reproduce vegetatively to produce daughter organisms.
3) plants produced by vegetatively reproduction are genetically similar to the parent plant and show all the characteristics of the parent.
Q7) What is placenta? Give the significance of placenta
Ans-placenta is a disc like mass of nutritive tissue which develops on the inner wall of uterus where the fertilized egg is implanted.
Placenta performs the following functions:
1)it provides all the nutrients such as glucose,proteins,minerals and vitamins to the foetus.
2)ti provides antibodies through the mother’s blood to the foetus.these antibodies provide immunity to the child after its birth against a number of diseases.
3)it also meets the oxygen requirement of the foetus and removes carbon dioxide and other metabolic waste generated in the body of the foetus. These metabolic wastes are ultimately removed and excreted by mother’s excretory system.
Q8) Why is reproduction essential for a species?
Reproduction is necessary for species in order to increase their numbers otherwise it will become extinct.
Q9) Name an organism which shows binary fission and another that shows multiple fission.
Ans-binary fission-Amoeba, multiple fission-material parasite.e.,plasmodium
Q10) Name a unicellular organism and also a multi-cellular organism that show budding process.
Q11)How do oral contraceptive pills prevent pregnancy?
Ans-oral pills do not allow release of ovum from the follicle to occur, so fertilization does not take place.
Q12)Which is the most effective contraceptive method which will not allow sexually transmitted diseases(STD’s) to spread?
Ans-mechanical barrier by condoms, cervical caps, etc.
Q13)Give one difference between zygote and embryo.
Ans-Zygote is single celled fusion product of sperm and ovum. Embryo is a multicellular product produced by mitotic divisions from zygote.
14)How does the embryo derive nutrition after getting implanted in the walls of uterus?
ans-the embryo derives nutrition after getting implanted in the walls of uterus through a disc like tissues called placenta which has villi like projections on embryo side and blood spaces on mother’s side. This enables transport of materials like amino acids,glucose and oxygen from mother to child.
Q15)What happens if the ovum does not fertilized in female body?
Ans-when the ovum does not get fertilized it lives for one day.As the preparations of the uterine lining are not needed any more, the lining breaks and comes out along with the unfertilized ovum through the vaginal path in form of blood discharge. This is known as menstruation as it happens once in a month and it lasts for 2-8 days.
Q16)What is the function of seminal vesicles and prostate gland in the male body?
Ans-they add their secretions to sperms in order to make the sperms lie in a fluid which makes their flow and transport easier and also provides nutrition to sperms.
Q17)Why are pair of testes located outside the male body?
Ans-the pairs of testes are located outside the body of the males because a temperature of 2-3 degrees C,less than the body temperature is required for production of sperms.
Q18) Give example of two bacterial and two viral diseases which are transmitted through sexual contact?
Ans-bacterial diseases-gonorrhoea and syphilis, viral diseases-AIDS and genital warts.
Q19)What factors have lead to adoption of contraceptive methods? give at least four factors.
1)growing human population.
2)spread of sexually transmitted diseases like AIDS.
3)gap between children in a family so that both mother and child get proper nutrition.
4)maintenance of sexual health.
Q20) How do sperms reach the female genital tract? where does fertilization and implantation of the embryo takes place. For how long does the embryo remain attached to uterine walls.
Ans-sperms travel upwards through uterus to oviduct where they may meet an ovum and hence fertilize it. Fertilization takes place in oviduct to give rise to single celled zygote. The zygote divides to become multicellular embryo which gets fixed in uterus. The embryo remains attached in uterine walls throughout gestation period which is 40 weeks in humans. full post
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