Important Questions Class 10 science Chapter 8 How do Organisms Reproduce?

Important Questions Class 10 science Chapter 8 How do Organisms Reproduce?

Question 1:- Write the full expansion of HIV.

Answer:– Human immuno-deficiency virus.


Question 2:- Write the full form of IUCD.

Answer:– Intra-uterine contraceptive device.


Question 3:- Name the type of fission carried out by Amoeba.

Answer:-Binary fission.


Question 4:- What is vegetative propagation ?

Answer:– It is the formation of new plants from vegetative parts (e.g., stem, leaf, root, bud) of a parent plant.


Question 5:-  List two functions performed by ovaries in a human female.

Answer:- Two functions performed by ovaries in a human female are following:-

  1. Formation of ova
  2. Secretion of hormones, estrogen and progesterone.


Question 6:- What is the effect of DNA copying which is not perfectly accurate in the reproductive process ?

Answer:-  It produces mutations which give rise to useful, harmful and neutral variations in the progeny.


Question 7:- Name the hormone, secretion of which is, responsible for dramatic changes in appearance in girls when they approach 10-12 years of age.

Answer:- Estrogen (= oestrogen) produced by growing follicles inside the ovary.


Question 8:- Why is DNA copying an essential part of the process of reproduction ?

Answer:-  Cell multiplication is essential for reproduction either as a means of multiplication in unicellular organisms or as a means of development of multicellular body from a single celled zygote. Cell multiplication cannot occur without DNA replication or DNA copying because each new cell must carry the full DNA complement.


Question 9:- Mention the common mode of reproduction found in

  1. Amoeba
  2. Planaria.

Answer:- Amoeba Binary fission in any plane.

Planaria: Transverse binary fission.


Question 10:- Name any two types of asexual reproduction.

Answer: – Fission, Spore formation.


Question 11. State the method used for growing rose plants.

Answer:– Artificial method of vegetative propagation by stem cuttings and bud grafting.


Question 12:- State what type of method is used for growing jasmine plant.

Answer:-Layering, a type of artificial method of vegetative propagation.


Question 13:- No two individuals are absolutely alike in a population. Why ?

Answer:– Due to presence of variations.


Question 14. “Cell division is a type of reproduction in unicellular organisms”. Justify.

Answer:– In unicellular organisms cell division is a mode of reproduction as it produces two individuals or daughters cells by division of the parent cell.

Question 15:- Name the type of reproduction which
(a) involves gametes
(b) Does not involve gametes.

(a) Sexual reproduction
(b) Asexual reproduction.


Question 16:- Define puberty.

Answer:– It is the beginning of development for sexual maturity which occurs at the age of 10-14 years in girls and 13—15 years in boys. Fully formed primary sex organs start secreting hormones for slow development of secondary sex organs and secondary sex characters.


Question 17:- Name the life process of an organism that helps in the growth of its population.

Answer:– Reproduction.


Question 18:- Name two simple organisms having the ability of regeneration. (CCE 2015)

Answer:– Hydra, Planaria.


Question 19:- Where is DNA found in the cell ?

Answer:– Nucleus, plastids and mitochondria.


Question 20:- Name the type of reproduction mostly seen in unicellular organisms.

Answer:- Asexual reproduction through cell division as binary fission, multiple fission, sporulation, budding.


Question 21:- Define sexual reproduction.

Answer:– It is a mode of reproduction in which offspring are formed by the process of formation and fusion of gametes.

Question 22:- In human female reproductive system where does fertilization occur ?

Answer:– In fallopian tube at ampulla—isthmus junction.


Question 23:- Name the parts where germ cells of a flower are located.

Answer: – Male — in anther of stamen.
Female — in ovule of carpel.


Question 24:- Name the part of Bryophyllum where buds are produced for propagation.

Answer:– Leaf notches.


Question 25:-  What is DNA ?

Answer:- DNA or deoxyribonucleic acid is a self replicating biochemical that is carrier of genetic information for expression of hereditary traits and transfer to the next generation.


Question 26:- What happens when a planaria gets cut into two pieces ?

Answer:- Each piece grows (regenerates the missing parts) to form a complete animal.


Question 27:- Name the method by which Hydra reproduces commonly. Is this method sexual or asexual ?

Answer:– Hydra reproduces commonly by budding (also regeneration). It is a method of asexual reproduction.


Question 28:- List two unisexual flowers.

Answer:– Water Melon, Papaya.


Question 29:- Why is fertilization not possible without pollinatign ?

Answer:– Fertilization requires bringing of male gametes to the female gamete which is possible only when pollen grain is brought from the anther to the stigma in the process of pollination.

Question 30:- What happens when a mature Spirogyra filament attains considerable length ?

Answer:– The elongated mature filament of Spirogyra breaks to form smaller pieces or fragments. The fragments grow to form mature filaments. .


Question 31:- What are those organisms called which bear both the sex organs in the same individual ? Give one example of such organism.

Answer:– Bisexual or hermaphrodite, eg., Mustard, Hydra.


Question 32:- List two functions of ovary of human female reproductive system.


  1. Formation of ova
  2. Secretion of hormones estrogen and progesterone.


Question 33:- Name the method by which Spirogyra reproduces under favourable conditions. Is this method sexual or asexual ?


  1. Fragmentation
  2. Asexual method.


Question 34:- Flow does Planaria reproduce ? Is this method sexual or asexual ?


  1. Transverse binary fission and regeneration
  2. Asexual method.


Question 35:- How does Plasmodium reproduce ? Is this method sexual or asexual?


  1. Multiple fission,
  2. Asexual method.


Question 36:- When a cell reproduces, what happens to its DNA ?

Answer:– DNA replicates and forms its copy at the time of cell reproduction.


Question 37:- Newly formed DNA copies may not be identical at times. Give one reason.

Answer:– Error in DNA copying due to incorporation of wrong nucleotide.


Question 38:- Why is variation important for a species ?

Answer:– Variation provides adaptability to changing environment and increased fitness in the struggle for existence.


Question 39:- Name the organs producing
(i) male germ cells / sperms and
(ii) female germ cells / ova respectively in humans.

(i) Testis
(ii) Ovary.


Question 40:- What is fertilisation ? Where does it occur in a human female ?

Answer:– Fertilisation is the fusion of male and female gametes to form diploid zygote. In human female, it occurs in ampulla part of fallopian tube.


Short Answer Questions

Question 1:- List any two differences between pollination and fertilization.




1.    Definition. It is transfer of pollen grains

from anther to the stigma of a flower.

It is the fusion of male and female gametes.

2.    Step. Pollination precedes fertilization.

Fertilization occurs only after pollination when the pollen grain has germinated and male gametes are carried into ovule.

3.    Purpose. It carries the male gamete producing

pollen grains to the female sex organ.

It actually brings about fusion of gametes.


4.  Process. Pollination is a physical process.

Fertilization is a physico-chemical (biological) process.

5. Occurrence. It occurs only in seed plants.

It occurs in both plants and animals of various types.



Question 2:-  What is reproduction ? Mention the importance of DNA copying in reproduction.

Answer:-  Definition: Reproduction is the process of producing new young individuals of similar type by the mature individuals. Importance of DNA Copying  are following:-

DNA carries hereditary information not only for controlling cellular functions but also all the structural and functional traits of organism. It is because of the latter that single celled zygote is able to form the whole multicellular organism. During reproduction there is formation of new cells which must carry the same amount and type of hereditary information as present in the parent cell. This is accomplished by DNA copying, which occurs prior to each cell division. DNA copying is not error proof. Errors give rise to variations.


Question 3:- Define variations in relation to a species. Why is variation beneficial to the species ?

Answer:- Definition: Variation is differences in structure, physiology and other characters found in the individuals of the same organism.

Benefits of variations to species.

Many of the variations are pre-adaptations which have no immediate benefit to the individuals. However, they remain in the population. Whenever, environment undergoes a drastic change, the pre-adaptations present in some members of the population allow the latter to survive, grow and regain its former size. Therefore, it is not necessary that variations are beneficial to individuals developing them but can prove useful to the species.


Question 4:- Mention the information source of making proteins in the cell. What is the basic event in reproduction ?

Answer:- Information Source: The information source of making proteins in a cell is its DNA.

Basic Event in Reproduction: The basic event in reproduction is replication of DNA, growth of cellular machinery and cell division.


Question 5:- Name one sexually transmitted disease each caused by a bacterial infection and viral infection. How can they be prevented ?

Answer:- Bacterial STD. Gonorrhoea caused by Neisseria gonorrhoeae. Viral STD. Genital warts caused by Human Papilloma virus.

Prevention for stopping STD are following:-

  1. Avoiding multipartner sex
  2. use of condoms
  3. clean toilet habits.


Question 6:- (a) In human body what is the role of seminal vesicles and prostate gland.

(b) List two functions performed by testes in human beings.


(a) Seminal Vesicles:- They secrete 60-70% of semen plasma that is alkaline and viscous having fructose (for nourishing the sperms), fibrinogen, proteins and prostaglandins. Prostaglandins cause movements in the genital tract of the female. Sperms are also activated by secretion of seminal vesicles.

Prostate Gland:- It produces 20-30% of semen plasma. The secretion is alkaline and viscous. It has clotting enzyme and chemical essential for sperm activity.


(b) Function of Testes

Formation of sperms from germinal cells of seminiferous tubules.

Secretion of testosterone by Leydig cells present in the connective tissue in between the seminiferous tubules.


Question 7:- Name the male and female gametes in animals. What is fertilization and where does it take place in human females ?

Answer:- Male Gamete is Sperm and Female Gamete isOvum.

Fertilization: It is the fusion of two compatible gametes (e.g., sperm and ovum) to form diploid zygote during sexual reproduction.

In human females fertilization occurs in fallopian tube.


Question 8:- What is reproduction ? What are the two types ? Which one of the two confers new characteristics on the offspring and how ?

Answer:- Reproduction: Reproduction is the process of producing new young individuals of similar type by the mature individuals.

Types of reproduction are- Asexual reproduction and sexual reproduction.

New Characteristics: New characteristics appear only in sexual reproduction due to Chance separation of chromosomes during meiosis required for gamete formation, Crossing over during meiosis. Chance coming together of chromosomes during fertilization, Mutations or mistakes during DNA replication.


Question 9:- What is binary fission ? Draw a diagram to show binary fission in Amoeba.

Answer:- Binary Fission. It is a mode of asexual reproduction in a mature individual which splits up or divides to form two individuals.