Page 174 - Class 10th Biology Chapter "How Do Organisms Reproduce" NCERT Book Questions and Answers


Chapter - How Do Organisms Reproduce

Page : 128

Question 1: 
What is the importance of DNA copying in reproduction? 
Answer : 
DNA (Deoxyribonucleic acid) is the genetic material found in the chromosomes, which are 
present in the nucleus of a cell. The DNA is the information site for making proteins and 
each specific type of protein leads to a specific type of body design. 
Thus, it is the DNA molecule that determines the body design of an individual. Therefore, 
it can be concluded that it is the DNA that gets transferred from parents to offsprings and 
makes them look similar. 



Question 2: 
Why is variation beneficial to the species but not necessarily for the individual? 
Answer : 
Variations are beneficial to the species than individual because sometimes for a species, 
the environmental conditions change so drastically that their survival becomes difficult. 
For example, if the temperature of water increases suddenly, then most of the bacteria 
living in that water would die. Only few variants that are resistant to heat would be able 
to survive. However, if these variants were not there, then the entire species of bacteria 
would have been destroyed. 
Thus, these variants help in the survival of the species. However, all variations are not 
necessarily beneficial for the individual organisms.

Page 133

Question 1: 
How does binary fission differ from multiple fission? 
Answer :  
In binary fission, a single cell divides into two equal halves. Amoeba and Bacteria divide 
by binary fission. 
 


In multiple fission, a single cell divides into many daughter cells simultaneously. Amoeba
and Plasmodium divide by multiple fission. 
 



Question 2: 
How will an organism be benefited if it reproduces through spores? 
Answer :
There are many advantages, if an organism reproduces through spores. 
Advantages of spore formation:
1. Large numbers of spores are produced in one sporangium. 
2. Spores are distributed easily by air to far-off places to avoid competition at one 
place. 
3. Spores are covered by thick walls to prevent dehydration under unfavourable 
conditions.

Question 3: 
Can you think of reasons why more complex organisms cannot give rise to new individuals 
through regeneration? 
Answer :
Simple organisms such as Hydra and Planaria are capable of producing new individuals 
through the process of regeneration. The process of regeneration involves the formation 
of new organisms from its body parts. Simple organisms can utilize this method of 
reproduction as their entire body is made of similar kind of cells in which any part of their 
body can be formed by growth and development. 
However, complex organisms have organ-system level of organization. All the organ 
systems of their body work together as an interconnected unit. They can regenerate their 
lost body parts such as skin, muscles, blood, etc. However, they cannot give rise to new 
individuals through regeneration. 

Question 4: 
Which of the following is a plant hormone? 
(a) Insulin 
(b) Thyroxin 
(c) Oestrogen 
(d) Cytokinin 
Answer :
(d) Cytokinin is a plant hormone. 

Question 5: 
Why is DNA copying an essential part of the process of reproduction? 
Answer : 
DNA (Deoxyribonucleic acid) copying is an essential part of reproduction as it passes 
genetic information from parents to offspring. It determines the body design of an 
individual. The reproducing cells produce a copy of their DNA through some chemical 
reactions and result in two copies of DNA. The copying of DNA always takes place along 
with the creation of additional cellular structure. This process is then followed by division 
of a cell to form two cells.

Page 140

Question 1: 
How is the process of pollination different from fertilization? 
Answer :  
Pollination is the process of transfer of pollens from anther to stigma. It occurs with the 
help of certain pollinators such as air, water, birds, or some insects. 
Fertilization, on the other hand, is the fusion of the male and female gametes. It occurs 
inside the ovule and leads to the formation of zygote. 

Question 2: 
What is the role of the seminal vesicles and the prostate gland? 
Answer :
The secretions from seminal vesicles and prostate glands lubricate the sperms and provide 
a fluid medium for easy transport of sperms. Their secretion also provides nutrient in the 
form of fructose, calcium, and some enzymes. 

Question 3: 
What are the changes seen in girls at the time of puberty? 
Answer : 
Secondary sexual characteristics in girls:
• Increase in breast size and darkening of skin of the nipples present at the tips of 
the breasts. 
• Appearance of hair in the genital area. 
• Appearance of hair in other areas of skin like underarms, face, hands, and legs. 
• Increase in the size of uterus and ovary. 
• Beginning of menstrual cycle. 
• More secretion of oil from the skin, which results in the appearance of pimples.

Question 4: 
How does the embryo get nourishment inside the mother’s body? 
Answer : 
The embryo develops inside the mother’s body for about nine months. Inside the uterus, 
the outer tissue surrounding the embryo develops finger-like projections called villi. These 
villi are surrounded by uterine tissue and maternal blood. They provide a large surface 
area for exchange of oxygen and nutrients. Also, there is a special tissue called placenta, 
which is embedded in the uterine wall. The embryo receives the oxygen and nutrients 
from the mother’s blood via the placenta. The waste materials produced by the embryo 
are also removed through the placenta. 

Question 5: 
If a woman is using a copper−T, will it help in protecting her from sexually transmitted 
diseases? 
Answer : 
No. Using a copper-T will not provide a protection from sexually transmitted diseases, as 
it does not prevent the entry of semen. It only prevents the implantation of the embryo 
in the uterus.

Exercises

Question 1: 
Asexual reproduction takes place through budding in 
(a) amoeba.
(b) yeast. 
(c) plasmodium.
(d) leishmania.
Answer : 
(b) Asexual reproduction takes place through budding in yeast. 

Question 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 is not a part of the female reproductive system in human beings. 

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

Question 4: 
What are the advantages of sexual reproduction over asexual reproduction? 
Answer :
Advantages of sexual reproduction:
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. 

Question 5:
What are the functions performed by the testis in human beings? 
Answer :  
The testes are the male reproductive organs that are located outside the abdominal cavity 
within a pouch called scrotum. 
Functions of testes:
1. Produce sperms 
2. Produce a hormone called testosterone, which brings about secondary sexual 
characters in boys. 

Question 6: 
Why does menstruation occur? 
Answer : 
Menstruation is a process in which blood and mucous flows out every month through the 
vagina. 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.

Question 7: 
Draw a labelled diagram of the longitudinal section of a flower. 
Answer : 



Question 8: 
What are the different methods of contraception? 
Answer : 
The contraceptive methods can be broadly divided into the following types: 
1. 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. 
2. 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.
Condoms are barriers made of thin rubber that are used to cover penis in males 
and vagina in females. 
3. 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. 
4. 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. It includes the blocking of vas deferens 
to prevent the transfer of sperms known as vasectomy. Similarly, fallopian tubes 
of the female can be blocked so that the egg will not reach the uterus known as 
tubectomy.

Question 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. 

Question 10: 
How does reproduction help in providing stability to populations of species? 
Answer :  
Living organisms reproduce for the continuation of a particular species. It helps in 
providing stability to the population of species by producing a new individual that 
resembles the parents. This is the reason why cats give birth to only cats or dogs give 
birth to only dogs. Therefore, reproduction provides stability to populations of dogs or cats 
or any other species. 

Question 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.

Dear Asif Sir