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CBSE Class 12th Biology Notes: Reproduction in Organisms

Jun 24, 2016 17:25 IST

    Find CBSE Class 12th Biology notes for the chapter Reproduction in Organisms. Every concept is followed by the solved and unsolved questions. You can also find the various categories questions like short, very short and long answer type.

    Some important terminologies and concepts are given below:

    Reproduction-As a biological process in which an organisms gives rise to young ones similar to itself.

    Clone-Morphologically and genetically similar individuals is called clone.

    Binary Fission-Many single celled organisms reproduce by binary fission, where a cell divides in two halves and each rapidly -grows into adult.

    e.g. Amoeba, Paramecium and yeast.

    Vegetative Propagation-In plant the formation of vegetative propagation does not evolve two parent, the process Involved in a sexual so is called vegetative propagation.

    Monoceious - Homothelics like cucurbits, Bisexual Coconut, Chara.

    Dioecious - Heterothelic and Unisexual Papaya, date Palm, marchantia.

    Parthenogenesis - When the female gamete undergoes development to form new organisms without fertilization, This Phenomenon is called parthenogenesis e.g. Rotifers, honeybees, lizards and birds (turkey).

    Gametogenesis - The process of formation of the two type of gametes male and female. The male gamete is called the aniherozoid or sperm; and female gamete is called egg or ovum.

    Spermatogenesis - lt is the process of formation of haploid spermatozoa from diploid male germ cells of the testes.

    A spermatogonium produces four spermatozoa (sperms).

    Oogenesis - It is the process of formation of haploid ova from the gamete' mother cells (oogania) in the ovany. An oogonium form only one ovum.

    Also Read: CBSE Class 12th Solved Question Papers PCMB - eBook

    Lets discuss some unanswered questions from this chapter

    Q1.Explain – in asexual reproduction a part of organism separates and forms a new organism?

    Q2.Name the  parasite which causes black fever

    Q3 .How does reproduction take place by multiple fission?

    Q4. What do you understand by the term daughter nuclei?

    Q5.Colonies of yeast do not multiply in water but they do multiply in sugar solution. explain

    Q6.How does bread mould formation takes place

    Q7.Regeneration and its function. Why complex organisms cannot reproduce though regeneration?

    Lets discuss 2 marks long answer questions from this chapter

     Q. 1. Draw a labelled diagram of conidia of penicillium.


    Q. 2. Diagrammatically represent the asexual reproduction in yeast.


    Q. 3. What is fission ? Name the type of fission.

    Ans. Fission : It is a type of sexual reproduction in which a fully grown parental organism divides into two or more than two daughters.

    It is of two types.

    (i) Binary fission

    (ii) Multiple fission

    Q. 4. Diagrammatically represent the asexual reproduction in Amoeba ?


    Q. 5. Write the two significance of vegetative propagation ?

    Ans. (i) Characters of the parents plants are preserved. A good variety produced can be     propagated by vegetative propagation?

    (ii) It is easier and cheaper method of propagation.

    Q. 6. When artificial methods of vegetative propagation are utilised ?

    Ans (i) For quick production of new plants.    

    (ii) For combining good qualities of two different varieties.

    Q. 7. Write the Zoological name of given animals.

    Rhesus monkey, Goat, Guinea, Pig, Ascaris.


    Animals Zoological Name      

    (i) Rhesus monkey.
    (ii) Goat

    (iii) Guinea Pig

    (iv) Ascaris

    Maccaca Mulatto

    Copra hircus

    Cavia cubaya

    Ascaris megaloce phala

    Q. 8. Identify each part and write whether it is haploid (n) or diploid (2n) Ovary, Anther, Egg, Pollen, male gamete and Zygote.


    (a) Ovary                       - Diploid (2n)

     (b) Anther                     - Diploid (2n)

    (C) Egg                         - Haploid (n)

    (d) Pollen                      -Haploid (n)

    (e) Male gamete            - Haploid (n)

    (f) Zygote                      - Diploid (2n)

    Q. 9. If the Chromosome numbers in meiocytes of human beings, rat, elephant, rice, butterfly and onion. 46, 42, 56, 24, 380, and 32 respectively. What will be the chromosome number in gametes of these species.

    Rat = 21

    Elephant = 28

    Rice = 12

    Butterfly = 190

    Onion = 16.

    Ans. Human beings = 23

    Also Read: CBSE Class 12th Biology Solved Guess Paper- eBook

    Lets discuss 3 marks answer questions from this chapter

     Q. 1. In extreme summer and winter, certain animals like frogs and hazards abandon active life.

    This is popularly called summer sleep and winter sleep respectively.

    (i) What are the technical terms for summer sleep and winter sleep?

    (ii) State any two changes in the body that occur during the above mentioned dormant stale.

    Ans. Technical terms are as follows :

    Winter sleep - Hibernation

    Summer sleep -- Aestivation

    (i) Rate of metabolism declines

    (ii) Respiration takes place through skin only (Cutaneous respiration).

    Q. 2 Show by a series of diagrams the manner of regeneration in a hydra if it is cut into two pieces transversely at the, middle.


    Show by a series of diagrams the manner of transverse binary fission in Planaria.


    Q. 3. What is vegetative propagation? Give two suitable examples.

    Ans. Vegetative propagation in plants is a, type of asexual reproduction in which new individual appears from any vegetative parts of parents plant.     

    In plants, The units of vegetative propagation such as runner, rhizome, sucker, tuber, offset, bulb are all capable of giving rise to new offsprings.

    Such structures are called vegetative propagules.

    Examples of vegetative propagation are:

    (i) Vegetative propagation by leaves, in Bryophyllum.

    (ii) Vegetative propagation by Stem (rhizome) in Ginger, Turmeric etc.

    Q. 4. Define the following terms:

    (i) Juvenile Phase,

    (ii) Reproductive Phrase

    (iii) Senescent Phase

    Ans. (i) Juvenile Phase- The period of growth and maturity in life when then organisms reproduce sexually. This period of growth is called Juvenil Phase, or Vegetative phase.

    (ii) Reproductive Phase-The end of Juvenile Phase is indicated by many of them showing morphological and physiological changes prior to active reproductive behaviour,

    (iii) Senscent Phase-The end of reproductive phase is one of the parameters of senescene or old stage. At this stage body metabolism is shown down and ultimately this stage leads to death.

    Q. 5. Explain why meiosis and gamete genesis are always Inter linked ?

    Ans. Gametogenesis refers to the process of formation of two types of gametes male and female. Gametes are haploid cells. Gametes in all heterogametic species are of two types i.e., male and female. A haploid parent produced gametes by mitosis.

    But in majority of organisms, Parent body is diploid. Thus meiosis is required by such diploid. Organisms, to produce haploid gametes. In haploid organisms meiocytes undergo meiosis. At the end of meiosis only one set of chromosome is incorporated into each gametes.

    Let’s discuss 5 marks long answer questions from this chapter

    Also Read: CBSE Class 12th Solved Question Papers PCB - eBook

    Q. 1. Define fission, what are two types of fusion?
        Describe multiple .fission irt Amoeba and Binary fission.

    Ans. Fission is a type of sexual reproduction in which a fully grown parental organism divides into two or more than two daughters. It is of two type.

    (i) Binary fission-A type of asexual reproduction in which the Parental Organisms divides in two daughters cells during favourable conditions.

    (ii) Multiple fission-A type of sexual reproduction in which the Parental Organisms Produces many daughter cells simultaneously during unfavourable conditions.

    Q. 2. The- unicellular organisms which reproduce by binary fission are causidered immortal Instify.

    Ans. Asexual reproduction is common among single-celled organisms. Thus in these organisms cell division is itself a mode of reproduction. In binary fission. The parent body divides into two halves and each rapidly growing into an adult. There is no remains of parents body cell and parent cannot be said to have dead. In fact after binary fission, parent continues living as two daughter- individuals. Hence, the unicellular organisms which undergo binary fission are considered immortal. Example-Amoeba and Paramecium.

    There are some small and I marks questions based on this chapter

    Q. 1. What is life Span ?

    Ans. The period between birth to the natural death of an organisms is known as life span.

    Q. 2. Define reproduction.

    Ans. Reproduction is a biological process by which an organisms produces another organisms of its own kind.

    Q. 3. Name two monoecious plants.

    Ans. Cucurbita and Coconuts.

    Q.4. Name two dioecious plants.

    Ans. Papaya and date palm.

    Q. 5. Name one bisexual and one unisexual animal.

    Ans. Bisexual - Earthworm. Unisexual - Cockroach.

    Q. 6. What are post-fertilisation events?

    Ans. The post-fertilisation events included:
    1. Formation of diploid zygote.
    2. Development of embryo from zygote by the process called embryogenesis.

    Q. 7. "Amoeba is immortal". Explain.

    Ans. Amoeba is considered immortal because it does not undergo natural death.

    Q. 8. Which is the most critical event in Sexual Reproduction.

    Ans. Fertilisation of gametes is the most critical event in Sexual Reproduction.

    Q. 9. Give two example which reproduce a sexually by binary fission.

    Ans. Bacteria and Amoeba reproduce by binary fission.

    Q. 10. What are the Vegetative Propagules.

    Ans. In plants, the units of vegetative propagation, such as tuber, bulb, rhizome etc. are called vegetive propagules.

    Q. 11. Why offsprings of Oviperous animals are at a greater risk as compared to offsprings of viviparous animals.

    Ans. Oviparous animals lay eggs in a safe place in the environment. In an open area, the eggs are not always safe and the offsprings are always at a risk.

    Q. 12. How many type of natural vegetative reproduction take place in flowering plants?

    Ans. The natural vegetative reproduction takes place by modified tuberous roots having adventitious buds, under ground modified stems, creeping stems, leaves, balbs and turions.

    Q. 13. Name the artificial means of vegetative reproduction.

    Ans. The artificial means of vegetative reproduction are cutting, layering, grafting and micropropagation.











    Lets discuss 5 marks long answer questions from this chapter

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