Lesson – How do organisms reproduce

                            Class –X (Bio)

Q1. What is the importance of DNA copying in reproduction?

Ans: DNA copying is an important phenomenon of reproduction through which the organisms pass on their body features to their off springs. It maintains the body design features in different generation of the species. DNA copying also produces variations due to linkage and crossing over. Such variations are useful for the survival of species over time.

Q2. Why is variation beneficial to the species but not necessary for the individual?

Ans: Population of organism normally live and interact with definite kinds of ecological niches. A population, therefore, survives in particular ecological surroundings. If there is an alteration in the ecological conditions of such places, the population of organism will get damaged and may be wiped out. The variants of the organism, however, may have chances of survival. The surviving individuals may reproduce and develop a kind of population which is suited to the changed nitch. Thus, variation is beneficial to the species but not necessary for the individual.

Q3. How does binary fission differ from multiple fission?

Binary fission	Multiple fission
1.When the parent cell produces two daughter cells it is called binary fission.	1.When a parent cell produces more than two daughter cells. It is called multiple fission.
2.The parent nucleus divides into two and goes to two daughter cells.	2. The parent nucleus divides into many daughter nuclei each surrounded by cytoplasm.
3.It is usually during favorable conditions.	3. It is usually during unfavorable conditions in other protozoans.
4. No protective covering is formed.	4.A protective covering cyst is formed.
5.It takes in different patterns as in amoeba and leishmania.	5.No such patterns e.g. plasmodium.

Q4. How will an organism be benefitted if it reproduces through spores?

Ans. 1.Spores are produced in large numbers.so the population will increase soon on their growth.

         2.Spores have a protective coat that helps them to resist unfavourable environmental conditions that are harmful to plant.

        3. spores are carried to long distances by wind. This helps in their distribution and growth.

 Q5. Can you think of reasons why more complex organisms cannot give rise to new individual through regeneration?

Ans: Complex organisms have several kinds of complex organs and organ systems. It is probably not easy to develop such an organism through regeneration.

Q6. Why is vegetative propagation practiced for growing some types of plants?

Ans: : Advantage of vegetative propagation:

1.     Plant parts (vegetative) of certain plants used for the process of reproduction.

2.     It is natural process also can be practiced artificially for agricultural purposes.

3.     Plants that have lost the ability to reproduce by seeds (sexual reproduction) can be reproduces by these methods.

4.     All plants are genetically similar to their parent and other plants produces by the same parent. Hence, they are clones. There is no variation in them/ such plants. Therfore, the quality of the plant is maintained.

Q7. Why is DNA copying is essential part of the process of reproduction?

Ans:The process of reproduction results in the production of offsprings which are exactly similar to parents. The exact blue prints of body design is inherited in the ofsprings  due to DNA replication in parent cell. Thus, DNA copying is essential part of the process of reproduction.

Q8. How is the process of pollination different from fertilization?

Pollination	Fertilization
1.     It is process of transfer of pollen grains from anthers of a flower to stigma of a flower. 2.     It is of two types: i.                   Self pollination ii.                 Cross- pollination 3.     It takes place by various pollinating agencies. 4.     If successful then it results in fertilization.	1.     It is the union or fusion of male and female gamaetes. 2.     It is of one type only. 3.     It takes place by natural/ artificial means. 4.     It results in seed and fruit formation.

Q9. What is the role of the seminal vesicles and the prostate gland?

Ans: Seminal vesicle is the place where sperms are stored temporarily. Here the mucus and a watery alkaline fluid containing the sugar-fructose, mix with the sperms. Prostate gland secretes alkaline fluid comprising up to a third of semen volume. It affects the vaginal pH so that sperms move smoothly inside the vagina.

Q10. What are the changes seen in girls at the time of puberty?

       i.            Pubic hair grows.

     ii.            Mammary gland or breast develops with the darkening of he skin of the nipples.

  iii.            The uterus and other parts of the reproductive system enlarge.

   iv.            The hips widen.

     v.            Periods start

   vi.            Extra fat is laid down in various parts of the body. Ovary starts to release egg or ova.

vii.            The ovaries start making hormone, Oestrogen, which brings about all these changes in girls.

Q11.How does the embryo get nourishment inside the mother’s body?

Ans: The embryos get nourishment from the mother’s blood through placenta. In the placenta, the foetal blood comes very close to the maternal blood. Here the exchange of materials between the mother’s blood and the blood of foetus take place.

Q12. If a women is using a copper-T, will it help in protecting her from sexually transmitted diseases?

Ans: No, using a copper-T will not help in protecting her from sexually transmitted disease.

EXERCISE

Q1. Asexual reproduction takes place through budding in

Ans. Yeast

Q2. Which of the following is not a part of the female reproductive system in human beings?

Ans. Vas deferens

Q3. The anther contains

Ans. Pollen grains

Q4. What are the advantages of sexual reproduction over asexual reproduction

Ans.Sexual reproduction has the following advantages over asexual reproduction

1.     Sexual reproduction involves fusion of male and female gamete coming from the male and female parents. Since the fusing gametes comes from two different individuals, the offsprings exihibit diversity of characters

2.     Meiosis during gametogenesis provides opportunities of new combinations of genes. It plays a prominent role in origin of new species and leads to variations required for evolution.

Q5. What are the functions perform by the testes in human beings?

Ans. Testes are the sites where male gametes i.e. sperms are made. The testes also produce the male sex hormone testosterone that helps in formation of secondary sexual characteristics.

Q6. Why does menstruation occur?

Ans. Menstruation occurs to remove the dead egg/ unfertilized egg, the thick and spongy lining formed on the uterine wall. It marks the end of one cycle to restart the next phase of egg maturation and provide a second chance for fertilization of egg.

Q7. Draw a labeled diagram the longitudinal section of a flower.

Ans.                                                                                                             

 

Q8. What are the different methods of contraception?

Ans.

 1. Barrier methods   eg. Condoms, diaphragm

2.Chemical methods eg. Oral pills, vaginal pills

3. Intrauterine contraceptil device(IUCD) eg. Copper-T

4.Natural methods

5.Surgical methods

(i) Vasectomy

(ii) Tubectomy

Q9. How are the modes of reproduction different in unicellular and multicellular organisms?

Mode of reproduction in            Unicellular organisms	Mode of reproduction in            Multicellular  organisms
1.     The mode of reproduction is simple and involves the division of the parent cell. 2.     Simple modes of reproduction takes place. 3.     No specialized system/tissue/cells are involved. No germs cells/sex cells are formed. 4.     Fertilization process is absent. 5.     No variation in the individuals take place. 6.     Only one individual is involved.	1.     The mode of reproduction is complex and involves the production of specialized cells. 2.     Complex mode of reproduction takes place. 3.     Specialized system/tissue/cells are involved. Germ cells/ sex cells are formed. 4.     Fertilization process in present. 5.     Variation in the individuals produced take place. 6.     Two individuals of opposite sex are involved.

Q10. How does reproduction help in providing stability to population of species?

Ans. Stability to population of species is attained by equalizing the birth and death ratio. Thus, the rate of birth should be approximately  equal to the rate of death.

Q11. What could be the reason for adopting contraceptive methods?

Ans. The contraceptive methods have been advised to avoid pregnancy and control child birth. These methods are generally adopted to prevent unwanted conception and to have sufficient gap between successive births.