Haryana State Board HBSE 10th Class Science Notes Chapter 8 How do Organisms Reproduce Notes.
Haryana Board 10th Class Science Notes Chapter 8 How do Organisms Reproduce
The production of new organisms from the existing organisms of same species is known as reproduction. Organisms do not need to undergo reproduction for maintaining their lives, even though they reproduce so that they may continue the existence of their species. This is the reason why reproduction is vital for the survival of the species.
Do Organisms Create Exact Copies of Themselves?
All organisms of a particular species look similar. For example, dogs look like dogs and a human looks like another. This happens because the designs of their bodies are similar. Hence, the first and foremost task of the reproduction process is to make ‘copies of blueprints of body design’. This is done by creating copies of DNA.
During cell division, a cell divides to give rise to two cells. Although, the two cells will be similar but will not be exactly identical. It is quite obvious that the process of copying the DNA will have some variations. Hence, the generated DNA copies will be similar, but may not be identical to the original.
In conclusion, the cells that survive after the cell division are
- Similar to each other as well as
- different i.e. show variation. This inbuilt tendency for variation during reproduction is the basis for evolution which is useful for the organism to adapt to ever changing environment.
The Importance of Variation
A niche is the role and position a species plays in the environment, how the species meets its needs for food and shelter, how it survives and how it reproduces. Different species of organisms have different niches. For example, the way a lion gathers its food or shelter or reproduces are quite different from that of a crocodile i.e. the niches of two organisms vary.
Modes of Reproduction Used by Sinsle Oreanism
Asexual reproduction: The method of producing a new plant (or animal) without the act of fertilization of gametes is called asexual reproduction.
- Vegetative propagation and
- Spore formation.
Fission: In fission process, a unicellular organism divides to form two or more new organisms.
- Binary fission and
- Multiple fission
Binary fission: In binary fission, the nucleus lengthens and then divides into two parts. After that the cytoplasm divides into two parts. This results in two daughter cells. Example: amoeba and leishmania.
Multiple fission: In multiple fission, the parent organism divides to form many new organisms at the sarrje time. Example: Malarial parasite plasmodium.
The process wherein the body of a multi-cellular organism breaks (fragments) into two or more pieces and on maturing each piece grows to form a complete new organism is known as fragmentation. Example: spirogyra.
In some plants and animals, if some parts of their bodies get cut then such parts have the ability to regenerate and form a complete new organism. This method of reproduction is called regeneration. Example: Planaria.
In budding, a small part of the body of the parent organism grows out as a ‘bud’. It then detaches from parent and becomes a new organism. Example: Hydra and planaria.
In vegetative propagation, new plants are reproduced from the plant parts such as roots, stem and leaves of old plants, without taking help of any reproductive organs. Example: bryophyllum.
When the coat of spore bursts, the spores spread into air. These airborne spores settle on food and under favourable condition, germinate to produce new plants. Example: Production of spores in rhizopus on bread.
- The mode of reproduction that takes place with the help of both male sex cells and female sex cells is known as sexual reproduction.
- Flowering plants belong to the group of angiosperms. The reproductive parts of angiosperms are located in the flower. So, we can say that flower is the reproductive organ of the plant.
The four main reproductive parts of a flower are –
- Petal and
Unisexual flower: If the flower contains only one part out of stamen or pistil then such a flower is called unisexual. For example, papaya and watermelon.
Bisexual flower: If the flower contains both stamen as well as pistil the flower is called bisexual. For example, hibiscus and mustard.
Main processes of sexual reproduction:
- Pollination: The travel of the pollen from stamen to the stigma with the purpose of formation of zygote and hence a new plant is called pollination.
- Fertilization: The process of fusing of male gamete from the pollen grain and the female gamete in the ovary is called fertilization. Fertilization leads to formation of zygote.
- Seed germination: The seed contains the future plant or embryo which develops into a seedling under appropriate conditions. This process is known as germination.
Reproduction in Human Beings
Changes that human body experiences:
- The changes that occur in humans from infancy to childhood, to teenage and finally to fully grown matured body takes place quite slowly over several years. Moreover, neither do all these changes happen together at the same time in one person, nor do they happen at an exact age.
- In some people, the changes happen early and quickly, while in others, they can happen slowly.
- Each change takes its own time to get completed.
The age at which a body starts producing gametes and girls and boys become biologically capable to reproduce is known as puberty. Generally, girls attain puberty at the age of 12 years, while boys reach puberty at the age of 13 to 14 years.
Male Reproductive System
Main reproductive organs: Ureter, Seminal vesicle, Vas deferens, Scrotum, Testes, Bladder, Penis and Urethra
Female Reproductive System
Main reproductive organs:
A pair of ovaries, oviduct, fallopian tube, uterus and vagina. The female reproductive system is more complicated than male because it takes care of fertilization and the development of embryo till the birth.
Sexually transmitted diseases:
The infectious diseases which are spread from an infected person to a healthy person through sexual contact are called sexually transmitted diseases (STDs). These disease can be caused either by bacteria or by virus. Example: Syphilis, gonorrhoea and AIDS.
What is contraception? List out the methods of contraception and explain them.
The method to prevent pregnancy in women is called contraception. Methods adopted to prevent pregnancy are called contraceptive methods.
1. Birth control tools: Under this method, a mechanical barrier is created which prevents the entry of sperm into the genital tract. As a result, fertilization does not occur.
- The tools include condoms, a diaphragm and Copper-T.
2. Birth control pills: There are oral pills that a women can take. These pills change the hormonal balance of the body so that the eggs are not released by the ovaries and fertilization is prevented.
3. Surgical methods: These include vasectomy to prevent the sperms from entering urethra and tubectomy to prevent It will not allow the sperm to reach the uterus.
4. Abortion: Another method is to surgically remove the foetus from the body of pregnant women.