Class 10 Science • Complete Chapter Notes
Reproduction is a biological process through which organisms produce new individuals of their own kind. It is not essential for the survival of an individual organism, but it is essential for the continuity of a species.
Reproduction also provides opportunities for variations to arise. Such variations can become important when populations face changing environmental conditions.
Organisms reproduce to maintain the continuity of their species from one generation to the next.
During reproduction, genetic material is copied and passed to the offspring. The copying process is not always perfectly accurate, so small variations may arise.
Asexual reproduction generally involves a single parent and does not involve the fusion of male and female gametes.
It is usually simpler and faster than sexual reproduction and often produces offspring that are very similar to the parent.
In binary fission, one parent cell divides to form two daughter cells.
The genetic material is copied and the cell then divides into two parts.
Amoeba commonly reproduces by binary fission.
In multiple fission, one parent cell produces many daughter cells through repeated nuclear division followed by division of the cytoplasm.
Plasmodium is a commonly cited example of an organism showing multiple fission.
During budding, a small outgrowth called a bud develops on the parent organism. The bud grows and may eventually detach to form a new individual.
In fragmentation, an organism breaks into two or more pieces, and each piece can grow into a complete organism under suitable conditions.
Spirogyra commonly reproduces through fragmentation.
Regeneration is the ability of an organism or a body part to form missing structures through cell division and differentiation.
In some simple organisms, a body fragment can develop into a complete individual and thus function as a mode of reproduction.
Planaria is a commonly studied example.
Some organisms produce specialised reproductive structures called spores. Spores can remain protected under unfavourable conditions and germinate when suitable conditions return.
Rhizopus, commonly known as bread mould, reproduces through spores formed inside sporangia.
Vegetative propagation is a form of asexual reproduction in plants in which new plants arise from vegetative parts such as roots, stems or leaves.
Sexual reproduction involves the formation of male and female gametes and their fusion to form a zygote.
Since genetic material comes from two gametes, sexual reproduction generally produces greater genetic variation than asexual reproduction.
The flower is the reproductive structure of flowering plants. It contains male and female reproductive parts.
The stamen consists of anther and filament. The anther produces pollen grains containing the male reproductive cells.
The pistil or carpel consists of stigma, style and ovary. The ovary contains ovules.
Pollination is the transfer of pollen grains from the anther to the stigma.
Transfer of pollen to the stigma of the same flower or another flower on the same plant.
Transfer of pollen from one plant to the stigma of a flower on another plant of the same species.
After pollination, the pollen grain germinates on the stigma and forms a pollen tube. The pollen tube grows through the style towards the ovule.
The male gamete ultimately fuses with the egg cell, resulting in formation of the zygote.
Humans reproduce sexually. The male and female reproductive systems contain specialised organs responsible for formation of gametes, transport of gametes and successful reproduction.
Puberty is the stage during which the body undergoes physical and hormonal changes leading towards reproductive maturity.
The testes produce sperm and the male sex hormone testosterone.
The testes are located in the scrotum, outside the main body cavity, where a slightly lower temperature supports sperm formation.
The vas deferens transports sperm from the testis towards the urethra.
Secretions from glands such as the seminal vesicles and prostate contribute to seminal fluid, which supports sperm movement and nutrition.
The penis is the external reproductive organ. The urethra is a passage through which semen is released and, separately, urine is expelled from the body.
The ovaries produce ova and female sex hormones including oestrogen and progesterone.
The fallopian tubes carry the ovum from the ovary towards the uterus. Fertilisation usually occurs in a fallopian tube.
The uterus is the organ where the embryo implants and develops during pregnancy.
The cervix forms the lower narrow part of the uterus and connects it with the vagina.
The vagina is the muscular canal leading from the cervix to the outside of the body.
In the reproductive years, the female reproductive system undergoes a cyclic sequence of changes associated with maturation of an ovum and preparation of the uterine lining.
If fertilisation does not occur, the thickened uterine lining is shed as menstrual bleeding.
Ovulation is the release of a mature ovum from an ovary. The ovum is then available for possible fertilisation.
Fertilisation occurs when a sperm fuses with an ovum, forming a zygote.
The zygote undergoes repeated cell division as it develops into an embryo.
After early development, the embryo reaches the uterus and becomes attached to the uterine lining. This process is called implantation.
After implantation, the embryo continues to develop in the uterus. The placenta develops as an important interface between the mother and developing embryo.
The placenta helps in transfer of oxygen and nutrients to the developing embryo and removal of carbon dioxide and certain wastes.
In humans, females generally have XX sex chromosomes and males generally have XY sex chromosomes.
The ovum normally carries an X chromosome, while sperm may carry either an X or a Y chromosome.
Reproductive health includes physical, mental and social well-being related to the reproductive system and its functions.
Contraceptive methods are used to reduce the probability of pregnancy.
| Method Category | General Principle |
|---|---|
| Barrier Methods | Prevent sperm from reaching the ovum. |
| Hormonal Methods | Alter hormonal conditions to prevent ovulation or fertilisation. |
| Intrauterine Devices | Devices placed in the uterus under appropriate medical guidance. |
| Surgical Methods | Permanent procedures that block reproductive ducts. |
Sexually transmitted infections, or STIs, are infections that can be transmitted through sexual contact.
| Feature | Asexual | Sexual |
|---|---|---|
| Number of Parents | Usually one | Involves male and female gametes |
| Gamete Fusion | Absent | Present |
| Genetic Variation | Usually lower | Usually greater |
| Complexity | Generally simpler | Generally more complex |
Students should also consult the official NCERT textbook and current CBSE Academic resources for curriculum-aligned preparation.
NCERT Class 10 Science Textbook → CBSE Academic Curriculum 2026-27 → CBSE Assessment Resources →