Friday, 25 December 2015

TEXTBOOK ANSWERS AND SOLUTIONS CBSE CLASS X SCIENCE Chapter-8 How do organisms reproduce


1) A sexual reproduction takes place through budding in
(a) amoeba.
(b) yeast.
(c) plasmodium.
(d) leishmania.

ANSWER:-(b) yeast

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

3) The anther contains
(a) sepals.
(b) ovules.
(c) carpel.
(d) pollen grains.

ANSWER:-(d) Pollen grains

4) What are the advantages of sexual reproduction over asexual reproduction?

ANSWER:-Advantages:-
1.    In sexual reproduction, more variations are produced. Thus, it ensures survival of species in a population.
2.    The new formed individual has characteristics of both the parents.
3.    Variations are more viable in sexual mode than in asexual one. This is because in asexual reproduction, DNA has to function inside the inherited cellular apparatus.

5) What are the functions performed by the testis in human beings?

ANSWER:-Functions of testes:
1 .Produce sperms
2. Produce a hormone called testosterone,which brings about secondary sexual characters in boys.

6) Why does menstruation occur?

ANSWER:-This process occurs every month because one egg is released from the ovary every month and at the same time, the uterus (womb) prepares itself to receive the fertilized egg. Thus, the inner lining of the uterus gets thickened and is supplied with blood to nourish the embryo. If the egg does not get fertilised, then the lining of the uterus breaks down slowly and gets released in the form of blood and mucous from the vagina.

7) Draw a labelled diagram of the longitudinal section of a flower.

ANSWER:-



8) What are the different methods of contraception?

ANSWER:-a) Natural method It involves avoiding the chances of meeting of sperms and ovum. In this method, the sexual act is avoided from day 10th to 17th of the menstrual cycle because during this period, ovulation is expected and therefore, the chances of fertilization are very high.

 b) Oral contraceptives In this method, tablets or drugs are taken orally. These contain small doses of hormones that prevent the release of eggs and thus fertilization cannot occur.
c) Barrier method In this method, the fertilization of ovum and sperm is prevented with the help of barriers. Barriers are available for both males and females.
d) Implants and surgical methods
Contraceptive devices such as the loop or Copper-T are placed in uterus to prevent pregnancy. Some surgical methods can also be used to block the gamete transfer.

9) How are the modes for reproduction different in unicellular and multicellular
Organisms?

ANSWER:-In unicellular organisms, reproduction occurs by the division of the entire cell. The modes of reproduction in unicellular organisms can be fission, budding, etc. whereas in multicellular organisms, specialised reproductive organs are present. Therefore, they can reproduce by complex reproductive methods such as vegetative propagation, spore formation, etc. In more complex multicellular organisms such as human beings and plants, the mode of reproduction is sexual reproduction.

10) How does reproduction help in providing stability to populations of species?

ANSWER: - It helps in providing stability to the population of species by producing a new individual that resembles the parents.

11) What could be the reasons for adopting contraceptive methods?

ANSWER:-Contraceptive methods are mainly adopted because of the following reasons:
(i) To prevent unwanted pregnancies.
(ii) To control population rise or birth rate.
(iii) To prevent the transfer of sexually transmitted diseases.



Written By Badal Paul
The author is a passionate blogger, writer and educationalist. This blog is created to ease troubles of the Cbse students. The author holds multiple blogs and the writer of the Novel KALCHAKRA, OOM AND THE CHOSEN FIVE.