REPRODUCTION IN ANIMALS

1. Reproduction:It is one of the important life process, which ensures the continuation of similar kinds of individuals generation after generation.
 
2. Modes of Reproduction:There are two modes by which animals reproduce. These are              (i) Sexual reproduction and (ii) Asexual reproduction.
 
3. Sexual Reproduction

i. The process of reproduction in which the fusion of male and female gametes takes place is called sexual reproduction.

ii. Male Reproductive Organs:
Male reproductive organs are a pair of testis, sperm ducts, and a penis (Fig. 9.1) 
 

 
 
 
 

Fig. 9.1 Male reproductive organs in humans
 
iii. Sperms:
The testes produce the male gametes called sperms (Fig. 9.2). 
 
 
 
 
 
 
 
 
 
 Fig. 9.2.Human sperm
 
iv. Female Reproductive Organs:
The female reproductive organs are a pair of ovaries, oviducts (fallopian tubes) and the uterus (Fig. 9.3). 
 
 
 
 Fig. 9.3. Female reproductive organs in humans
 
v. Ova:
Ovary produces females gametes called ova (Fig. 9.4). 
 

 
 
 
 

Fig. 9.4Human ovum
 
vi. In human beings, a single matured egg is released into the oviduct by one of the ovaries every month.

vii. Uterus
is the part of female reproductive system where development of the embryo takes place.

viii. Both sperm and ova are single celled.

ix. Fertilisation:
The fusion of ovum and the sperm is called fertilisation (Fig. 9.5). 

 
 
 
 
 
Fig. 9.5.Fertilisation
 
 x. Zygote: During fertilisation, the nuclei of the sperm (n) and the egg (n) are fused to form a single nucleus (2n). This fertilised egg is called zygote (Fig. 9.6). 
 
 
 
 
 

Fig. 9.6.    Zygote

xi. Internal Fertilisation:
Fertilisation that takes place inside the female body that is in aquatic medium is called internal Fertilisation. This is observed in human beings and other animals such as hens, cows and dogs.

xii. External Fertilisation:
Fertilisation that takes place outside the female body that is in equatic medium is called external fertilisation. This is observed in frogs, fish, starfish, etc.

xiii. Embryo:
The zygote divides repeatedly to give rise to a ball of cells. The cells begin to differentiate into various tissues. This developing structure is called an embryo.






Fig. 9.7.

(a) Zygote formation and development of an embryo from the zygote;
(b) Ball of cells (enlarged);
(c) Embedding of the embryo in the uterus (enlarged)
 

xiv. The embryo gets implanted with in the wall of the uterus for further development.

xv. Foetus:
The stage of the embryo in which all the body parts are identifiable is called a foetus (Fig. 9.8). 
 
 
 
 
 
 

Fig. 9.8.Foetus in the uterus

xvi. Viviparous:
Animals such as human beings, cows and dogs which give birth to young ones are called Viviparous animals.

xvii. Oviparous:
Animals such as hen, frog and butterfly which lay eggs are called Oviparous animals.

xviii. Metamorphosis:
The drastic change which transforms a larva into an adult is called Metamorphosis. 
 
 
4. Asexual Reproduction

i. The type of reproduction in which only a single parent is involved is called Asexual reproduction

ii. Budding:
In hydra, new individuals develop from buds. This method of asexual production is called budding.

Fig. 9.9.Budding in Hydra
iii. Bud:A lateral outgrowth from the parent body that assumes the shape of parent. 
 
iv. Binary Fission: Amoeba reproduces by simply dividing itself into two. This type of asexual reproduction is called Binary fission.



 
 
 
 
 
 

Fig. 9.10.(a) (b) (c) (d) Binary fission in Amoeba
 
 
 

 
Q. 1. Explain the importance of reproduction in organisms.

Ans.
Reproduction is very important for the organisms because it ensures the continuity of the species, generation after generation.
 
Q. 2. Describe the process of fertilisation in human beings.

Ans.
The first step in the process of reproduction is the fusion of a sperm and an ovum. For this to happen, millions of sperms from the male are transferred into the female body. The sperms swim upto the oviduct with the help of their tails and reach the egg. When they come in contact with the egg, one of the sperms may fuse with the egg. Such fusion of the egg and the sperm is called Fertilisation. During Fertilisation, the nuclei of the sperm and the egg fuse to form a single nucleus. This results in the formation of a fertilised egg or zygote.
 
Q. 3. Choose the most appropriate answer:

(a) Internal fertilisation occurs

        (i) in female body.                  (ii) outside female body.
      (iii) in male body.                    (iv) outside male body.
Ans. (i) in female body.
 
(b)A tadpole develops into an adult frog by the process of
         (i) fertilisation.                            (ii) metamorphosis.
       (iii) embedding.                            (iv) budding.
Ans. (ii) metamorphosis.
 
(c)The number of nuclei present in a zygote is
         (i) none                                       (ii) one
       (iii) two                                        (iv) four.
Ans. (ii) one.
 
Q. 4. Indicate whether the following statements are True (T) or False (F):
  1. Oviparous animals give birth to young ones                                                  (   )
  2. Each sperm is a single cell.                                                                          (   )
  3. External fertilisation takes place in frog.                                                        (   )
  4. A new human individual develops from a cell called gamete.                             (   )
  5. Egg laid after fertilisation is made up of a single cell.                                       (   )
  6. Amoeba reproduces by budding.                                                                  (   )
  7. Fertilisation is necessary even in asexual reproduction.                                   (   )
  8. Binary fission is a method of asexual reproduction.                                        (   )
  9. A zygote is formed as a result of fertilisation.                                                (   )
  10. An embryo is made up of a single cell.                                                          (   )
 
Ans. (a) False             (b) True         (c) True             (d) False
        (e) True               (f) False        (g) False            (h) True
         (i) True               (j) False.
 
Q. 5. Give two differences between a zygote and a foetus.
Ans.
 
ZygoteFoetus
1. It is single celled.
2. Zygote is formed by the fusion of male and female gametes
1. It is multicellular.
2. Foetus is formed by the repeated division of embryo and differentiation.
 
Q. 6. Define asexual reproduction. Describe two methods of asexual reproduction in animals.
Ans.The type of reproduction in which only a single parent is involved is called asexual reproduction. Asexual reproduction may occur in many ways e.g.
  1. By Budding In hydra, new individuals devolop from buds. This process of asexual reproduction is called budding.
  2. By Binary Fission: Amoeba reproduces by simply dividing itself into two. This type of asexual reproduction is called binary fission.
 
Q. 7. In which female reproductive organ does the embryo get embedded?
Ans.Uterus
 
Q. 8. What is metamorphosis? Give examples.
Ans.The drastic change that transforms a larva into an adult is called metamorphosis. Frog, Silk Worm, Honeybee, are some animals in which metamorphosis occurs.
 
Q. 9. Differentiate between internal fertilisation and external fertilisation.
Ans.
 
Internal fertilisationExternal Fertilisation
1. Takes place inside the body of the female.
2. Female lays either fertilized eggs or a
    complete individual is born
1. Takes place outside the body of the female.
2. Female lays unfertilized eggs.

 
Q. 10. Complete the crossword puzzle using the hints given below:
           Across
           1. The process of the fusion of the gametes.
           6. The type of fertilisation in hen.
           7. The term used for bulges observed on the sides of the body of hydra.
           8. Eggs are produced here.
           Down
          2. Sperms are produced in these male reproductive organs.
          3. Another term for the fertilised egg.
          4. These animals lay eggs.
          5. A type of fission in amoeba.
 



Ans.
 
 
 
 
 
 
 
 
 
 
 
 
 
 

ADDITIONAL IMPORTANT QUESTION
 
Q. 1. Give two examples of oviparous animals.
 Ans. Hen., frog, butterfly.
 
Q. 2. What do you know by oviparous animals?
 Ans.Animals which lay eggs are called oviparous animals.
 
Q. 3. Give two examples of viviparous animals.
 Ans.Human beings, cows, dogs.
 
Q. 4. What are viviparous animals?
Ans.Animals which give birth to young ones are called viviparous animals.
 
Q. 5. Name the male and female gametes produced by the testes and ovaries.
Ans.Testes produce sperms and ovaries produce ova.
 
Q. 6. What is Fertilisation?
Ans.The fusion of ovum and sperm is called fertilisation.
 
Q. 7. What is the other name of the fertilized egg?
Ans.Zygote.
 
Q. 8. What is the internal fertilisation?
Ans.If the process of fertilisation occurs inside the body of the female is called internal fertilisation.
 
Q. 9. Give the names of two animals in which internal Fertilisation occurs.
Ans.Human beings, Dog.
 
Q. 10. Define metamorphosis.
Ans.The drastic change which transforms a larva into an adult is called metamorphosis.
 
Q. 11. Give the names of two animals in which external Fertilisation occurs.
Ans.Fish, frog, starfish.
 
Q. 12. How a zygote is changed into an embryo?
Ans.The zygote divides repeatedly to form an embryo.
 
Q. 13. What is foetus?
Ans.The stage of the embroyo in which all body parts are identifiable is called foetus.
 
Q. 14. Define external fertilisation.
Ans.When the process of fertilisation occurs outside the body of the female is called external Fertilisation.
 
Q. 15. Name the female reproductive organs of the human beings.
Ans.The reproductive organs in female are-a pair of ovaries, a pair of oviducts and uterus.
 
Q. 16. Name the male reproductive organs of human beings.
Ans.The male reproductive organs are-a pair of testis, a pair of sperm ducts and penis.
 
Q. 17. What is sexual reproduction?
Ans.Reproduction resulting from the fusion of male and female gametes is called sexual reproduction.
Q. 18. Name the two modes by which animals reproduce.
Ans.(i) Sexual reproduction.
       (ii) Asexual reproduction.
 
Q. 19. What is asexual reproduction?
Ans.The type of reproduction in which only a single parent is involved is called Asexual reproduction.
Q. 20. What is binary fission?
Ans.Splitting of an organism into two-half is called fission. Amoeba reproduces by simply dividing itself into two. This type of asexual reproduction is called binary fission.
 
Q. 21. Nametwoorganisms which reproduce by two types of asexual methods. What are the methods?
Ans.Amoeba and hydra reproduce by separate forms of asexual methods of reproduction. Amoeba reproduces by binary fission while hydra reproduces by budding.
 
Q. 22. Define the following terms:
             (i) Fission      (ii) Multiple Fission
Ans.
  1. Fission:When an unicellular organism divides itself into two, then this is called fission.
Multiple Fission: The cell divides many times within the cyst to produce many daughter cells and this process is called Multiple fission.
  1. Multiple Fission:The cell divides many time within the cyst to produce many daughter cells and this process is called Multiple Fission
 
Q. 23. Why aquatic organisms produce a large number of sperms and eggs?
Ans.This is because the eggs and sperms get exposed to water movement, wind and rainfall. Also, there are other animals in the pond which feed on eggs. All these factors prevent the sperms from reaching the eggs. Thus, production of large number of eggs and sperms is necessary to ensure internal fertilisation of at least a few of them.
 
Q. 24. Name some of the young ones by completing table 9.1 as shown for example in SI. No. 1 and 5.
 
Table 9.1
SI  No.AnimalYoung one
1.    Human    Baby
2.    Cat
3.    Dog
4.    Butterfly
5.    Hen    Chick
6.    Cow
7.    Frog
 
Ans.
 
SI  No.AnimalYoung one
1.    Human    Baby
2.    Cat    Kitten
3.    Dog    Puppy
4.    Butterfly    Caterpillar
5.    Hen    Chick
6.    Cow    Calf
7.    Frog    Tadpole
 
 
Q. 25. Which part of the body (a) produces sperms? (b) produces ova? (c) passes  sperm from a man to a woman?
Ans. 
  1. Sperms are produced by primary sex organ i.e., called testes.
  2. Ova are produced by sex organ called ovaries.
  3. In sexual reproduction passes sperm from a man to woman, through penis (male reproductive organ) to vagina (woman reproductive organ). When sperm enters an egg (ova). The fertilisation of both the sex cells takes place and a zygote.is formed, this is called fertilisation.
 
Q. 26. What is sexual reproduction?
Ans.When the individual uses its sex cells or reproductive cells (gametes) to produce new individuals of its own type, the reproduction is said to be sexual reproduction. Male individual produces male gamete or sperm, which female individual produces female gamete or ovum. Sperm is a small cell with a flagellum for movement. Ovum is a larger cell with more cytoplasm.  
 


Fig. 9.11. Fertilisation of ovum with sperms
 
Sperms move to ovum and fuse with it to form a zygote. This fusion of two dissimilar gametes to form a zygote is known as Fertilisation. Zygote undergoes various developmental changes to form a new individual. Figure 9.11 shows Fertilisation of ovum with sperm.
 
Q. 27. What is budding?
Ans. Budding:Budding is a type of asexual reproduction. An organism form small projections or out growth on its body. These outgrowths are called buds. Each bud grows in to an independent individual which may or may not separate from parent's body. If separated, it behaves as a free organism and if not separated, the whole mass of organisms behave like a colony. For example, hydra, yeast and sponges. In hydra the buds separate from parents body while in sponges, the buds remain attached on parents body and form a colony (Fig. 9.12).
 
 

 
 
Q. 28. In how many ways, the new individuals are produced by their parents?
Ans.New individuals are produced by their parents in following ways:
1. Some individuals hatch out of egg, like chicks and snakes.
2. Some individuals are born from their mother like kittens, puppies and human beings.
3. Some individuals grow out of the parent's body or its parts e.g., hydra, yeast and onions.
4. Some individuals split into two or more individuals, e.g., amoeba and many bacteria.
 
Q. 29. What are test tube babies?
Ans.This is one of the technique, which is applicable for those female, whose oviducts are blocked. These women are unable to bear babies because sperms cannot reach the egg for Fertilisation. In such cases, doctors collect freshly released egg from female and sperms from male and keep them together for a few hours for in vitro fertilisation (Fertilisation outside the body). After the formation of zygote develops for about a week, it is placed in the mother's uterus. Complete development takes place in the uterus and the baby is born like any other baby. Babies born through this technique are called ‘test-tube babies’. This is a misnomer (wrong name) and is misleading because babies cannot grow in test tubes.
 
Q. 30. Draw the various stages in the life-cycle of frog.
Ans.
 
 

 
 
 
 
 
 
 
 
 

Fig. 9.13 Life-cycle of frog
 
Q. 31. What is cloning? Discuss in brief the-history of cloning.
Ans.Cloning is the production of an identical cell of any other living part, or a complete organism. Cloning of animal was successfully performed for the first time by Ian Wilmut and his colleagues at the Roslin Institute in Edinburgh, Scotland. They cloned successfully a sheep named Dolly [Fig. 9.14. (c)]. Dolly was born on 5th July, 1996 and was the first mammal to be cloned.
 

        (a) Finn Dorsett sheep              (b) Scottish blackface ewe                           (c) Dolly
Fig. 9.14
 
 
 
            During the process of cloning Dolly, a cell was collected from the mammary gland of a female Finn Dorsett sheep [Fig. 9.14. (a)]. Simultaneously, an egg was obtained from a Scottish blackface ewe [Fig. 9.14. (b)]. The nucleus was removed from the egg. Then, the nucleus of the cell from the Finn Dorsett sheep was inserted into the egg of the Scottish blackface ewe. The egg thus produced was implanted into the Scottish blackface ewe. Development of the egg followed normally and finally Dolly was born. Though Dolly was given birth by the Scottish blackface ewe, it was found to be identical to the Finn, Dorsett sheep from which the nucleus was taken. Since the nucleus of the Scottish blackface ewe was removed, Dolly did not show any character of the Scottish blackface ewe. Dolly was a health clone and produced several offspring’s of her own through normal sexual means. Unfortunately, Dolly died on 14th February, 2003 due to a certain lung disease.
                 Since Dolly, several attempts have been made to produce cloned mammals. However, many die before or die soon after birth. The cloned animals are also found to be born with severe abnormalities.
            .
 
OBJECTIVE TYPE QUESTIONS
 
Q. 1. Fill in the blanks with appropriate words:
  1. Coke is formed when coal is heated in………….. of air.
  2. The process of ............. ensures continuity of life on earth.
  3. The male and female gametes in human being are called ............ and ………., respectively.
  4. In…………... reproduction, one individual can make many new individuals from its body parts.
  5. ………… grow throughout life, but …………… grow only up to a certain age.
  6. A multicellular animal starts its life from a ………….. through sexual reproduction.
  7. An animal having both male and female reproductive organs is called ….………
  8. Stamens and carpels are found in ............. flowers.
  9. Budding is a type of ............ reproduction.
 
 
Q. 2. Match the following items given in Column ‘A’ with that in Column ‘B’. 
 
Column ‘A’Column ‘B’
  1. Sperm
  2. Ovary
  3. Cell
  4. Fertilised egg
  5. Dog
  6. Frog
  7. Budding
  1. Female Organ
  2. Growth
  3. Male Gamete
  4. Oviparous animal
  5. Asexual reproduction
  6. Viviparous animal
  7. Zygote
 
 
           
Q. 3. State whether the statements given below are True or False:
  1. Two individuals are needed for asexual reproduction.
  2. Humans can develop lost parts.
  3. Internal Fertilisation occurs in humans.
  4. The mass of similar cells is called a clone.
  5. Sperms are produced by ovaries.
  6. Cow and dogs are viviparous animals.
  7. The fusion of. ovum and sperm is called fertilisation.
  8. Amoeba reproduces by simply dividing itself into two.
 
 
Q. 4. Choose the correct option in the following questions:
 
(i) Which of the following does not have external fertilisation?
         (a) Frog                                   (b) Woman
         (c) Hydra                                 (d) Fishes
 
(ii) Which. one is not the part of female reproductive organ?
         (a) Ovary                                 (b) Uterus
         (c) Oviduct                              (d) Sperm
 
(iii) The drastic change that transforms a larva into an adult is called
       (a) binary fission                        (b) metamorphosis
      (c) Asexual reproduction            (d) budding
 
(iv) Which is not the oviparous animals?
      (a) Hen                                       (c) Frog
       c) Butterfly                               (d) Dog
 
(v) Which one of the following is the viviparous animals?
      (a) Cow                                       (b) Hen
      (c) Frog                                       (d) Fish
 
(vi) Hydra reproduces by
      (a) fragmentation                     (b) budding
      (c) spore formation                  (d) binary fission
 
(vii) Tadpole is the developing stage of
       (a) humans                               (b) fish
       (c) frog                                     (d) cow
 
(viii) The fusion of ovum and sperm is called
        (a) fertilisation                        (b) fission
        (c) metamorphosis                 (d) osmosis
 
(ix) Sheep cloned name is
       (a) Jolly                                (b) Holly
       (c) Dolly                               (d) Molly
 
(x) A hormone secreted in a female body only is
       (a) testosterone                    (b) progestrone
       (c) adrenalin                        (d) thyrocin
 
(xi) The organisms having both the male and female sex organs present in the same body are called
       (a) unisexual                        (b) multisexual
       (c) hermaphrodites              (d) asexual
 
(xii) The hormone, Insulin is secreted by which gland?
      (a) Pancreas                         (b) Ovary
      (c) Thyroid                          (d) Adrenal
 
(xiii) The process of fusion of the gametes in plants and animals is called
       (a) development               (b) fertilisation
       (c) fission                         (d) fusion
 
(xiv) Which combination of chromosomes leads to birth of a boby girl?
        (a) XX                             (b) XY
        (c) X                                (d) Y
 
(xv) Out of these, which one is developed by grafting technique?
           (a) Sugar cane             (b) Mango
           (c) Jasmine                  (d) Cactus
 
ANSWERS TO OBJECTIVE QUESTIONS
 
Q. 1. Fill in the blanks:
   (i) reproduction                                (ii) sperm, ova
(iii) asexual                                        (iv) Plants, animals
  (v) single cell (fertilised egg)           (vi) hermaphrodite.
(vii) bisexual                                    (viii) asexual.
 
Q. 2. Match the items under Column ‘A’ with Column ‘B’:
Column ‘A’Column ‘B’
  1. Sperm
  2. Ovary
  3. Cell
  4. Fertilised egg
  5. Dog
  6. Frog
  7. Budding
  1. Male Gamete
  2. Female Organ
  3. Growth
  4. Zygote
  5. Viviparous animal
  6. Oviparous animal
  7. Asexual reproduction
 
Q. 3. True or False:
     i) False                 ii) False                iii) True                  iv) True            
    v) False                vi) True                vii) True                viii) True
 
Q.4. Choose the correct option:
      (i) (c)                   (ii) (d)                  (iii) (b)                (iv) (d)                   (v) (a)
     
    (vi) (b)                 (vii) (c)                 (viii) (a)               (ix) (c)                   (x) (b)
 
    (xi) (c)                 (xii) (a)                 (xiii) (b)              (xiv) (a)                 (xv) (b).