Unravel the Mysteries of How Organisms Reproduce with Future Classes
Organisms reproduce in various ways, such as asexual and sexual reproduction. Asexual reproduction is a process in which an organism can produce offspring without the involvement of another organism. Sexual reproduction, on the other hand, requires two organisms of different sexes to produce offspring. As per CBSE class 10 Science NCERT chapter 7 notes, asexual reproduction involves the division of a single organism into two or more new organisms, while sexual reproduction involves the fusion of two gametes. The process of sexual reproduction involves different stages like fertilization, meiosis, and gamete formation.
Our website offers a free PDF download of CBSE Class 10 Science Chapter 7 - How Do Organisms Reproduce from NCERT. This PDF will provide students with comprehensive knowledge on the various types of reproduction in different organisms. It will also cover topics such as sexual and asexual reproduction, modes of reproduction in plants and animals, and the role of pollination in reproduction. Download this PDF today to get started on understanding the fundamentals of reproduction in organisms.
Chapter 8 How do organisms reproduce?
The process by which living organisms produce their own kind of individuals to maintain the continuity of species is called reproduction.
The Fundamentals of Reproduction
The process of reproduction involves the formation of DNA copy and other cellular apparatus required by the cells of an individual. DNA is the blueprint of all the basic design of organisms.
Variations
DNA copying during cell division always causes some or other type of variations in newly formed cell. This brings the differences found in the morphological and physiological features of an organism.
Types of Reproduction
Reproduction is mainly of two types, i.e., asexual reproduction and sexual reproduction.
Asexual Reproduction
It is a rapid mode of multiplication in which one parent (either male or female) is involved. The new individuals produced are identical to their parents.
Sexual Reproduction
In this process, the gametes from parents of opposite sex (male and female) fuse together to form a zygote. This zygote develops further and gives rise to new offspring. The individual produced by this method exhibits variation.
Modes of Asexual Reproduction
Asexual reproduction occurs in unicellular organisms by fission, budding, spore formation, fragmentation, regeneration (in animals) and vegetative propagation (in plants). It occurs in multicellular organisms by budding and regeneration. These are as follows
Fission
The process where a unicellular organism splits itself into two or more daughter cells. It is of two types, i.e.
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Binary Fission In this process, parent cell divides into two identical daughter cells, e.g., Amoeba, Leishmania.
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Multiple fission in this process, parent cell divides into many identical daughter organisms simultaneously, e.g., plasmodium.
Fragmentation
The parent body on maturation breaks up into two or more small fragments, which later grow into a completely new organism, e.g., Spirogyra.
Regeneration
In this process, all fragments or parts that are separated from the body develop in new animals, e.g., sponge, Planaria, Hydra, etc.
Budding
A daughter organism is formed from a small projection known as bud. It develops as an outgrowth due to repeated cell divisions of the parent body. When fully grown, it detaches to grow into a new independent individual, e.g., Hydra.
Vegetative Propagation
The process of obtaining complete plant from any vegetative part of plant is called vegetative propagation. This is mainly of two types
Natural Vegetative Propagation
The vegetative propagation that occurs automatically in plants is called natural vegetative propagation. It can be achieved by root, stem, leaf, etc., e.g., Bryophyllum.
Artificial Vegetative Propagation
The artificially made vegetative propagules in plants by humans, is called artificial vegetative reproduction, e.g., cutting, layering, grafting, etc.
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Grafting A small part of stem from one plant without roots (scion) is attached to the part with root (stock) of another plant.
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Layering The development of roots on a stem, while the stem is still attached to the parent plant is called layering.
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Tissue culture It is a technique used for growing new plants using living tissues (like flower buds, stems, growing tips, leaves, etc.) in vitro in an artificial culture medium.
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Using this technique, large number of plants can be developed from a single parent.
Spore Formation
It is a type of asexual reproduction where blob-like structures called sporangia are involved. These cells or spores have the ability to germinate under favorable conditions forming new plants, e.g., Rhizopus.
Modes of Asexual Reproduction
In this type of reproduction, both sexes, i.e., male and female are involved. Sex cell or gamete of one parent (male) fuses with the sex cell or gamete of another parent (female). This results in production of a new cell called zygote.
Vegetative Propagation
Flowering plant bear the reproductive parts within the flower and their seeds are enclosed in a fruit. Most plants have both male and female reproductive organs in the same flower and are known as bisexual flowers. While others have either male or female reproductive parts in a flower known as unisexual flowers.
A flower comprises of four main parts, i.e., sepals, petals, stamens and carpels. Stamens and carpels are the reproductive parts of a flower.
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Stamen It is the male reproductive part of the flower.
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Anther It is a bilobed structure containing two pollen sacs present at tip of stamen. These produce pollen grains that are yellowish in colour.
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Carpel (Pistil) It is the female reproductive part, which is present in the center of the flower. It comprises of three parts
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Stigma It is the terminal part of carpel which may be sticky. It helps in receiving the pollen grains during pollination.
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Style It is the middle-elongated part of carpel. It helps in the attachment of stigma to the ovary.
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Ovary it is the swollen bottom part of carpel. It contains ovules having an egg cell (female gamete).
Pollination
The transfer of pollen grains from the anther of the stamen to the stigma of a flower is termed as pollination. The pollen grains can be transferred by various agents like wind, water, insects and animals.
Pollination usually occurs in two ways
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Self-pollination The pollen from the stamen of a flower is transferred to the stigma of the same flower or another flower of same plant.
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Cross-pollination The pollen from the stamen of a flower is transferred to the stigma of another flower of different plant of the same species.
Fertilization
It is the process of fusion of male and female gametes. It gives rise to a zygote. As soon as the pollen lands on suitable stigma, it reaches the female germ cells in ovary. This occurs via pollen tube. The pollen tube grows out of the pollen grain, travels through the style and finally reaches the ovary.
After fertilization, ovule develops a rough coat around itself and gets converted to seeds and ovary ripens as fruit.
The seed contains future embryo that grows under suitable conditions (germination). The fertilization in the flowering plant is shown in the given figure.
Human Reproductive System
The system of organs required by males and females for the process of sexual reproduction is called reproductive system.
Male Reproductive System
​It includes parts which produce the germ cells and those which deliver these cells at the site of fertilization.
Part and details of the male reproductive system
Part
Detail
Testes
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Paired, oval-shaped male sex organs.
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Consist of seminiferous tubules, where the sperms are produced.
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Produce a male sex hormone called testosterone, which brings about changes in appearance of boys at puberty.
Scrotum
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Small pouch that contains testis.
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Present outside the abdominal cavity. As sperms are formed here, this requires a lower temperature than the normal body temperature.
Vas deferens
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Tube-like structure which connects testis to the urethra deferens in order to allow the passage of semen.
Urethra
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Common passage for both the sperms and urine. It never carries both of them at the same time.
Prostate gland and seminal vesicles
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Secretes seminal fluid and nutrients.
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Fluid and nutrients combine with sperm to form semen. seminal Milky, viscous fluid contains fructose, proteins and other vesicles chemicals for nourishing and stimulating sperms.
penis
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External male genital organ.
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Transfers sperms into the vagina of the female during copulation.
sperms
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Tiny and motile bodies that use their long tail to move through the female reproductive tract.
Female reproductive system
It includes internal and external sex organs that function in reproduction of new offspring. In human, female reproductive system is immature at birth and develops to maturity at puberty to be able to produce gametes, and to carry a foetus.
Parts and Details of the Female Reproductive System
Part
Detail
ovaries
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Paired, oval-shaped organs located in the abdominal cavity near the kidney.
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Produce thousands of ova or egg cells.
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Secrete female sex hormones like oestrogen and progesterone.
Oviduct
(Fallopian tube)
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It has a funnel-shaped opening near the ovary.
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Carries ova or egg from ovary to the uterus. It is the site of fertilization.
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These open into the uterus from both the sides.
Uterus (womb)
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Hollow, pear-shaped, bag-like structure.
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The growth and development of foetus takes place.
cervix
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​It is the lower and the narrower portion of uterus which opens into the vagina.
Vagina
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Receives the sperms from the male partner.
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Serves as a birth canal.
Fertilization and Post-Fertilization Changes
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Fusion of sperm with ovum is called fertilization. It results in the formation of zygote. This process takes place in the oviduct or Fallopian tube. The formation of embryo is the result of growth in zygote.
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The embryo sinks downward, reaches into the soft uterine lining and gets embedded. This process is known as implantation.
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A disc-like structure called placenta grows between the uterine wall and embryo. It has finger-like projections called villi, which provide surface area for the exchange of nutrients, oxygen and waste products between the embryo and the mother.
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Childbirth (after a gestation period of approximately 9 months) occurs by strong rhythmic contractions of uterine muscles.
Menstruation
In the absence of fertilization, the uterine lining which becomes thick and spongy to receive a fertilized egg, is no longer required. It sheds out as blood and mucus which lasts for about 2-8 days and occurs every month. This phase is known as menstruation.
Reproductive Health
It can be defined as the state of physical, mental and social fitness to lead a healthy reproductive life. Good reproductive health provides both male and female with
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the fertility control methods.
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awareness about how to limit their family size.
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protection from infection and sexually transmitted diseases.
Sexually Transmitted Diseases (STDs)
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Many diseases can be sexually transmitted such as:
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Bacterial: Gonorrhoea and syphilis
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Viral: Warts and HIV-AIDS
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Use of condom prevents these infections to some extent
Contraception
It is the avoidance of pregnancy, can be achieved by preventing the fertilisation of ova.
Methods of contraception
Physical barrier
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To prevent union of egg and sperm.
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Use of condoms, cervical caps and diaphragm.
Chemical methods
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Use of oral pills
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These change hormonal balance of body so that eggs are not released.
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May have side effects.
Intrauterine contraceptive device (IUCD)
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Copper-T or loop is placed in uterus to prevent pregnancy
Surgical methods
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In males the vas deferens is blocked to prevent sperm transfer called vasectomy.
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In females, the fallopian tube is blocked to prevent egg transfer called tubectomy.
Female Foeticide
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The practice of killing a female child inside the womb is called female foeticide.
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For a healthy society, a balanced sex ratio is needed that can be achieved by educating people to avoid malpractices like female foeticide and prenatal sex determination.
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Prenatal sex determination is a legal offence in our country so as to maintain a balanced sex ratio.