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    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 boRead more

    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.

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  2. 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. For more answers visit to website: https://www.tiwariacademy.com/ncert-solutiRead more

    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.

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  3. 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, reproductionRead more

    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.

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  4. 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 meRead more

    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.

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  5. The contraceptive methods can be broadly divided into the following types: • 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 thRead more

    The contraceptive methods can be broadly divided into the following types:
    • 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.
    • 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.
    • 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.
    • 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.

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