How do Organisms Reproduce Class 10 NCERT Solutions

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DNA copying means DNA replication. It ensure that each daughter cell produced at the end of cell division receives an identical amount of DNA.

Transfer of genetic information from parent to the offspring makes the organisms to have similar function.

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When variation occurs in a species group they may be able to cope with the drastic conditions that arise in nature, leaving behind the non-variants. The variation which occurs in an individual may not always be beneficial to it.

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Binary fission is the process by which one cell divides into two halves.

Example: Amoeba

Multiple fission is the process by which a single cell divides into multiple numbers of cells.

Example: Plasmodium

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Advantages of reproduction by spores are:

• The numbers of spores produced are very large
• The can spread to long distances, and
• They have thick outer covering present in them which help them to overcome the harsh environmental conditions

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The reason is the presence of complexity at the organ system level, where all the organs and their functions are interconnected to hold the organism alive.

So it is not possible to completely regenerate the whole individual but some parts such as skin, blood, muscles, etc are regenerated.

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The reason are as follows:

• They are helpful to grow plants which do not produce seeds
• These methods are cheap
• They are helpful to grow plants whose seeds are not able to germinate in the soil
• To preserve the best quality plant and grow its offspring.

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DNA copying is essential because DNA carries genetic information present in an individual.

So when DNA is copied it transfers genetic information from parent to the offspring, which helps in normal growth and functioning of the offspring.

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In pollination, the pollen grains are transferred via a means of transport from the anther to the stigma.

While fertilisation is the fusion of male and female gametes which results in the formation of zygote.

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The seminal vesicles and prostate gland provide lubrication which helps in easy movement of sperms, these glands also provide nutrients to sperms in form of fructose, calcium and enzymes.

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Changes seen in girls at the time of puberty are:

• Growth of hairs in genital parts, face, under arms
• Their hip size increases and body begins to take shape,
• Size of breast increases,
• Size of ovary increases, and
• Menstrual cycle occurs.

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The embryo gets nourishment by the placenta. The walls of the uterus get thick in width and when the embryo gets attached to it, the outer layer of the uterine wall covers the whole embryo. These walls are richly supplied by the blood vessels.

Placenta is a specialised structure present which has villi which helps in transfer of food, waste and gases in and out from mother to embryo.

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No, it won’t protect her from STDs, as the device will not be able to prevent fluid contact.

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B)Yeast

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C) Vas deferens

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D) Pollen grains

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Advantages of sexual reproduction over asexual reproduction are:

• The offspring will have genetic information of both the parent
• The offspring can have variation,
• The offspring can easily adapt to the environmental changes, and
• The offspring will have more advantages as compared to its parents

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Functions of testis are:

• Production of sperms,
• Production of male hormone androgen,
• Production of testosterone, which is important for development of secondary sexual characters in male

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Menstruation is the normal bleeding coming out from the vagina due to degeneration of the uterine wall which was developed over a cycle of around a month, which is important for the fertilized egg to develop into an individual.

When the egg is not fertilized by the sperm the wall of the uterus degenerates and comes out of the vagina, as they have dense blood supply these blood vessels also degenerates which makes the blood like appearance of the degenerated walls.

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Different methods of contraception are:

• Natural methods
• Barrier methods
• Oral contraceptives
• Implants
• Surgical methods

In the Natural method: fertilisation is avoided by avoiding mating from 10th to 17th day, as ovum is released and chances of fusion are very high. Also, the penis is removed just before ejaculation from vagina.

In the Barrier method: fertilisation is avoided by using barriers such as condoms for males, diaphragm for females.

Oral contraceptives are present in tablet forms which are used to avoid fertilisation or may prevent the embryo attachment to the uterine wall. Example: Saheli

Implants are devices which are placed in the female reproductive part to prevent entry of sperm. Example: Copper T

In Surgical methods, the Fallopian tube and vas deferens are cut and tied by surgery to prevent release of egg and sperm

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In unicellular organisms generally, asexual mode of reproduction is used, these are fission, budding, spore formation, etc. Where the offspring produced are identical to the parent.

In multicellular organisms, the sexual mode of reproduction is used. In this method, the male and female reproductive units are developed in separate organs respectively.

These units fuse together to form zygote which later develops into an offspring. The offspring has characters of both the parents and has more ability to cope the harsh environment as compared to its parents

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Reproduction is the process by which new offspring are formed by the existing ones.

As death occurs in a species it is important to add new ones otherwise the population of species will decline and will result in extinction. Thus, reproduction helps in providing stability to the population of species

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The reasons for adopting contraceptive methods are as follows:

• To avoid unplanned pregnancy,
• Maintain age gap between childrens,
• To avoid sexually transmitted diseases,
• Population control