RBSE Solutions for Class10 Science Chapter 7 How Do Organisms Reproduce?

 The chapter How do organisms reproduces explains the different methods of reproduction in different organisms. These solutions have been prepared by experienced teachers.

If you are preparing for RBSE class 10 board exams, then these solutions of intext and end exercise questions will help you a lot.

These solutions cover a complete syllabus and will let you solve homework and assignments in an easy way.

 

Board	RBSE
Subject	Science
Chapter	How Do Organisms Reproduce?
No. of Intext questions	12
No. of End exercise questions	11
Prescribed Book	NCERT Science

 

How Do Organisms Reproduce?

 

Answers of Questions on Page 114

Q.1 What is the importance of DNA copying in reproduction?

Answer      

Environment is not stable; it changes continuously so the

particular species will not be able to survive in changed

environment. Reproduction is a process in which an

organism produce young one similar to itself. In this

process characters are transmitted by DNA copying.

          

DNA copying has following importance in reproduction

i.        1)Maintains the characteristics of species.

ii.       2)Maintains the continuous survival of life

iii.     3)The characteristics of organisms are transmitted to their progeny.

iv.      4)It produces variations in organisms which is the basis of evolution of new species.

 

Q.2 Why is variation beneficial to the species but not necessarily for the individual?

Answer    

The variations are beneficial to a species and enable them

to survive in a changed environment. A favorable

variation in a species makes them survive in a changed

environment. In a changed environment individual

organism would die but their offsprings with variations

survive in a changed environment. So we can say that

variations are beneficial to a species but not for the

individual. 

 

Answers of Questions on Page 119

Q.1 How does binary fission differ from multiple fission?

Answer 

Binary fission: - In this method; nucleus divides into two

parts and by division of cytoplasm, two daughter

organisms are formed.

 Multiple fission: - In this method; nucleus divides in

several parts and each nuclear part getting some

cytoplasm forms a daughter organism.

           

Q.2 How will an organism be benefited if it reproduces through spores?

Answe   

An organism is benefited if it reproduces through spores,

in the following ways:

(i)         Spores are formed in a large number.

(ii)     Spores have an outer thick wall that protects them in

adverse conditions, when conditions become favouable

(Proper moisture) , they can  to grow.

 

Q.3Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

Answer    

More complex organisms cannot give rise to new

individuals through regeneration because they have

specialized cells, tissues, organs and organ systems to

perform different functions. So multicellular organisms

have high body organization. That’s why they cannot

reproduce though regeneration.

 

Q.4 Why is vegetative propagation practiced for growing some type of plants?

Answer     

Vegetative propagation practiced for growing some type

of plants because of following reasons-

(i)       Some plants such as banana, orange and rose do not

produce seeds so the vegetative propagation is practiced

to grow them.

(ii) Vegetative propagation is a fast method for developing

new plants earlier.

(iii)  Plants raised by vegetative propagation bear flower

and fruits earlier than those produced from seeds.

(iv) Seedless fruits are produced by the process 

vegetative propagation.

(v) Desired characters can be maintained in variety of

species by this method.

 

Q.5 Why is DNA copying an essential part of the process of reproduction?

Answer 

DNA copying is an essential part of the process of

reproduction because so that the characteristics of the

parent organisms are transmitted to its offspring and in

this process some variations are also produced in the

offspring. 

These variations lead to some changes in

offsprings that provide an organism the capability to

survive in changing conditions.

 

 

Answers of Questions on Page 126

Q.1 How is the process of pollination different from fertilisation?

Answer   

Pollination: - In this process pollen grains (male

gametes) are transferred from the anther of a flower to

the stigma of same or other flower.

Fertilisation:-  In this method ; pollen grains (male

gametes) fuses with female gamete (egg cell) to form

zygote.

 

Q.2 What is the role of the seminal vesicles and the prostate gland?

Answer

Seminal vesicle and prostate gland secrete fluids which

forms a part of the semen. The fluid secreted from

seminal vesicle forms 60% of semen. It makes the

transport of sperms smooth.

 This fluid protects the sperms from the acids present in

the urethra and provides nutrition to sperms in the form

of fructose, calcium and some enzymes.

 

Q.3 What are the changes seen in girls at the time of puberty?

Answer    

The various changes occur in girls at puberty are:

1. Breast  size increases and mammary gland develop.

2. Hair grows under armpits and pubic region.

3. The hips broaden.

4. Deposition of fat in various parts of body like hips and thighs.

5. Fallopian tube, uterus and vagina enlarge.

6. Ovaries start to release eggs.

7. Menstruation cycle starts.

 

Q.4 How does the embryo get nourishment inside the mother’s baby?

Answer   

In mother’s body, the embryo gets nutrition from the

mother’s blood with the help of placenta.  Placenta is

formed by foetal and maternal tissue. Placenta contains

villi. 

There are empty spaces in mother’s tissues that

cover the villi. Villi provide a large surface area for the

transfer of glucose, oxygen and other substances from

the mother to the embryo.

 

Q.5 If a woman is using a copper-T, will it help in protecting her from sexually transmitted diseases?

Answer     

No , If a woman is using a copper-T, it will not help in

protecting her from sexually transmitted diseases.

 

Answers of End Exercise Questions on Page

Q.1 Asexual reproduction takes place through budding in

    (a)amoeba               

    (b)yeast

    (c)plasmodium              

     (d)leishmania

 

Answer    (b)  yeast

 

Q.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

 

Q.3 The anther contains

    (a)sepals                         

    (b)ovules

    (c)carpel                         

     (d)pollen grains

 

Answer      (d)  pollen grains

 

Q.4What are the advantages of sexual reproduction over asexual reproduction?

Ans.      

(i) In sexual reproduction the offspring are similar to

their parents, but not identical to them or to one another.

This is because the offspring receive genes from two

different parents. So these genes mix in various different

combinations. Due to this all of the offspring have

genetic variations.

 So in sexual reproduction, due to different variations

offsprings  have  adaptations to their surroundings and

they can survive.

 

(ii).In asexual reproduction, the offspring are almost

identical to their parent because they have the same

genes as their parent. So, much genetic variation is not

possible in asexual reproduction. So in asexual

reproduction due to less genetic variations, this inhibits

the evolution of the organism.

 

Q.5What are the functions performed by the testes in human beings?

Answer   

Functions of testes are as follows

(i)Sperms are formed in testes.

(ii)They secret the hormone testosterone which regulates the formation of sperms and brings changes in appearance of boys at the time of puberty.

 

Q.6Why does menstruation occur?

Answer     

At puberty in girls or female, ovaries release eggs(ovum) regularly and at the same time lining of uterus starts thickening to receive fertilized egg but if the egg(ovum) does not get fertilized due unavailability of sperm then the thick and soft inner lining of uterus is no longer needed and hence it breaks.

 So, the thick and soft inner lining of uterus along with the blood vessels and the dead eggs comes out of the vagina in the form of blood called menstruation. Menstruation occurs after the interval of every 28 days.

 

Q.7Draw a labeled diagram of the longitudinal section of a flower.

 Answer

Q.8What are the different methods of contraception?

Answer    

Following are the different methods of contraception- 

(i) Chemical method: In this method a woman uses oral   pills which are hormonal preparations and suppress the release of ovum in fallopian tube. These are called oral contraceptives.

On the other hand vaginal pills/ creams are spermicidal. The chemicals in these kill the sperms during their journey in the vaginal tract.

(ii) Barrier method: condom, diaphragm and cervical caps are used in this method which prevents the entry of sperms in the female genital tract during sexual intercourse.

(iii) Intrauterine contraceptive devices: Intrauterine contraceptive devices such as copper-T are placed safely in the uterus at hospitals. It prevents the sperms to reach the uterus.

(iv) Surgical method : In this method, a small part of vas deferens of male and fallopian tube of female is cut or tied by surgery. It is called vasectomy in males and tubectomy in females.

 

 

Q.9How are the modes for reproduction different in unicellular and multicellular organisms?

Answer

In unicellular organisms reproduction takes place by

binary fusion or multiple fission (asexual reproduction)

while in multicellular organisms reproduction takes place

by budding (hydra), vegetative propagation asexual

methods and  fusion of male and female gametes (sexual

reproduction).

 

Q.10How does reproduction help in providing stability to population of species?

Answer 

Population of a particular species decreases due to death

or other reasons but reproduction add new individuals to

the species. Reproduction also helps to generate copies

of individuals which are suited to a particular

environment.

Q.11What could be the reasons for adopting contraceptive methods?

Answer    

Contraceptives are adopted due to the following reasons

(i)         For prevention of unwanted pregnancy.

(ii)     To control the birth rate and prevent the increase in

population

(iii)  These methods prevent sexually transmitted disease.