These comprehensive RBSE Class 10 Science Notes Chapter 8 How do Organisms Reproduce? will give a brief overview of all the concepts.
RBSE Class 10 Science Chapter 8 Notes How do Organisms Reproduce?
→ It is obvious that we notice organisms because they reproduces. If there were to be only, non-reproducing member of a particular kind, it is doubtful that we would have noticed its existence. It is the large number of organisms belonging to a single species that bring them to our notice.
→ Reproduction involves creation of a DNA copy and additional cellular apparatus by the cell involved in the process. The chromosomes in the nucleus of the cell contain information for inheritance of features from parents to next generation in the form of DNA molecule.
→ The basic event in reproduction is the creation of a DNA copy.
→ The consistency of DNA copying during reproduction is important for the maintenance of body design features that allow the organism to use that particular niche. Reproduction is therefore linked to the stability of populations of species.
→ The modes by which various organisms reproduce depends on the body design of the organisms.
→ Fission-For unicellular organisms, cell division, or fission, lead to the creation of new individuals. Amoeba the splitting of the two cells during division can take place in any plane. But in organisms like Leishmania, binary fission occurs in a definite orientation.
→ Multiple fission-Malaria parasite, plasmodium, divide into many daughter cells simultaneously by multiple fission.
→ Regeneration-If the individual is somehow cut or broken up into many pieces, many of these pieces grow into separate individuals. This process is known as regeneration. Example-Hydra and Planaria.
→ Budding-In this type of reproduction, an outgrowth develops on the body of adult, called bud. Bud acts as the unit of reproduction. This bud when fully matures, detaches from the parent body and becomes a new independent individual.
→ Vegetative reproduction Reproduction in which any vegetative part of plant like leaf, stem or root develop into new plant is called vegetative reprdocution. Buds produced in the notches along the leaf margin of Bryophyllum fall on the soil and develop into new plants.
→ In natural form seed is not formed in some plants like banana, orange, grapes and roses etc. These varieties exist only by means of vegetative reproduction.
→ Tissue culture-Using tissue culture, many plants can be grown from one parent in disease-free conditions. This technique is commonly used for ornamental plants.
→ Spore formation-In Rhizopus fungi the erect hyphae consists of rounded structure, called sporangia, which takes part in reproduction. Spores are formed in sporangia. Mature sporangia get burst and spores come out. During favourable condition they come in contact with moist surface and can begin to grow.
→ Sexual reproduction-In sexual reproduction there is the fusion of sperm and egg, a zygote is formed. In such reproductive animals some special type of organ (testis and ovary) found, which forms the sperms and egg.
→ Basic characters of sexual reproduction-Sexual reproduction involves two individuals for the creation of a new individual.
- The fusion of sperm and egg produce child. These structures are sexual cells or gametes.
- Male and female gemate fertilize to form zygote which develop to form new individual.
- As a result two parents genetic material unit.
→ DNA copying mechanisms creates variations which are useful for ensuring the survival of the species. Modes of sexual reproduction allows for greater variations to be generated.
→ Different parts of flower and function.
- Flower stalk or Pedicel-It links the flower to the plant.
- Thalamus-Provides the base to other parts of flower.
- Calyx-Protects the internal organs in the bud stage of flower.
- Corolla-Attracts the insects and birds for pollination.
- Stamen-Formation of pollen grains in anther lobes.
- Carpel-Formation of fruit from ovary and seed from ovule.
→ Unisexual flower-When in flower either stamen or pistil that is only one reproductive organ present, flower called unisexual. Example-papaya and watermelon.
→ Bisexual flower-When stamen and pistil both present in a flower, called bisexual
flower. Example-Hibiscus and mustard.
→ Female reproductive organ (pistil)-Consists of three parts called style, stigma and ovary. Ovules are present inside ovary. Each ovule consists of an egg cell. Male gamete is carried by pollination fuse to egg cell (female gamete). Fertilization or fusion of reproductive cell develops into. zygote and it produces the new plant.
→ Pollination is a process in which the pollen grain liberated from anther lobe reaches to stigma of a flower. It is of two types
(i) Self-pollination-If transfer of pollen grain on the stigma of same flower, then it is called self-pollination.
(ii) Cross-pollination-Pollen grain of a flower transfer on the stigma of other flower is called cross-pollination. It takes place by air, water insects or by any animals.
→ Following changes take place after fertilization
- Embryo develops in ovule and ovule converts into seed.
- Wall of ovary changes into fruit wall and ovary forms fruit.
- Sepal, petal, stamen, style and stigma wither.
Seed germinates in favouarble condition to form new plant.
→ Puberty-In human (male and female) the immature reproductive organ becomes mature and development of reproductive capacity is called puberty. In female puberty starts earlier in comparison to male.
→ Many changes takes place in body during puberty, such as increase in breast size in girls and new facial hair growth in boys, are signs of sexual maturation.
→ Male reproductive system-The organ producing reproductive cell and organ sending the reproductive cells at the site of fertilization combinely form the male reproductive system. These organs are following
- Vas deferens
- Seminal vesicle
- Prostrate gland.
→ Female reproductive system-In female (ladies) following reproductive organs are found (i) ovary (ii) oviduct (iii) uterus (iv) vagina.
→ The sperm enter through the vaginal passage during sexual intercourse. They travel upwards and reach the oviduct where they may encounter the egg. The fertilized egg (zygote) starts dividing and forms a ball of cells or embryo.
→ Placenta-The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall. Placenta supplies nutrition to embryo, respiration and other functional necessities.
→ Menstruation-The process of fertilization takes place in fallopian tube (oviduct). If there is no fertilization the internal thick wall of uterus breaks with blood vessels comes out in form blood secretion, is called menstruation. It usually lasts for about two to eight days and on interval of every 28-30 days menstruation takes place. It is called menstruation cycle.
→ Sexually transmitted disease-The disease developed by sexual contact is called sexually transmitted (STD) disease. Sexually transmitted diseases are-Gonorrhoea, syphilis, wart and AIDS.
→ Birth control methods-Contraception to avoid pregnancy can be achieved by the use of condoms, oral pills, copper-T and other methods.
→ Vasectomy-In male vas deferens are tied up by thread or cut. This process is called vasectomy.
→ Tubectomy-In female oviducts are tied up by thread or cut. This process is called tubectomy.