Reproduction In Living Beings Class - 10th
- 2. Reproduction is the process used by living beings to produce offspring of their own kind. Organisms reproduce to continue the continuity of species on this Earth. It is done in order to continue the chain of life, to pass on its genes which are acquired over millennia. There are two kinds of Reproduction:- a. Asexual Reproduction b. Sexual Reproduction What Is Reproduction?
- 3. DNA Copying Organisms look similar because their body designs are similar. Thus, Reproduction involve making copies of the blueprints of body design. The Chromosomes in the nucleus of a cell contain data for inheritance of features from parents to progeny in the form of DNA (Deoxyribose Nucleic Acid). The DNA in the cell nucleus is the information source for making proteins. Different proteins will eventually lead to altered body designs. Therefore, a basic event in reproduction is the creation of a DNA copy.
- 5. How Does Variations Occur? a. Variations refer to the changes that are seen in the case of the genetic makeup of an organism. Variations occur each time when the DNA is copied. As a result, the DNA copies generated will be similar, but may not be identical to the original. b. Some of these variations might be so drastic that the new DNA copy cannot work with the cellular apparatus it inherits. Such a newborn cell will simply die. c. On the other hand, there could still be many other variations in the DNA copies that would not lead to such a drastic outcome. d. Thus, the surviving cells are similar to, but subtly different from each other. e. This inbuilt tendency for variation during reproduction is the basis for Evolution.
- 6. Importance Of Variations The following are a few of the advantages of Variations â a. Variations enable better adaptation of an organism in the changing environment. b. Variations improve the chances of survival of particular species in unfavorable conditions. c. Variations in organisms give rise to the development of new and better fit species in the environment. d. In the case of plants and animals, they help in disease resistance. e. Variation is the major source of species and environmental evolution wherein the more fit organisms replace the less fit organism from the environment they were earlier sharing.
- 7. Asexual reproduction In this, only a single parent is involved and no gamete formation takes place. Variations do not occur in this mode of reproduction. Asexual Reproduction can be further classified into: a. Fission b. Fragmentation c. Regeneration d. Budding e. Vegetative Propagation f. Spore Formation
- 8. Fission is the process of break-down of parent body to form new individuals. The two types of Fission are:- âą Binary Fission â In this, one cell divides and forms two daughter cells. For e.g.: Amoeba {in any plane}, Leishmania {in a definite orientation}. âą Multiple Fission â In this many daughter cells are produced from the Parent Cell. For e.g.: Plasmodium {malarial parasite}. Fission
- 9. FRAGMENTATION Fragmentation is the process in which multi-cellular organisms simply breaks into pieces upon maturation. These pieces or fragments grow into new individuals. For e.g.: Spirogyra, ï This is not true for all multi-cellular organisms. They cannot simply divide cell-by-cell because many organisms are not simply a random collection of cells. Cells are organized as tissues and tissues are organized into organs, which are placed at definite positions in the body. In such a carefully situation, cell-by-cell division would be impractical.
- 10. Regeneration Regeneration is the process in which, fully differentiated organisms give rise to new individuals from their body parts. That is, if the individual is cut or broken into many pieces, these pieces grow into separate individuals. For e.g.: Planaria, Hydra ï Regeneration is carried out by specialized cells. These cells proliferate and make large numbers of cells, which undergo several changes to become tissues to develop into a new organism.
- 11. Budding Budding is the process in which organisms use regenerative cells to reproduce. ï A Bud develops as an outgrowth due to repeated Cell Division at one specific site. These buds develop into tiny individuals and when fully mature, detach from the parent body and become new independent individuals. For e.g.: Hydra, Yeast.
- 12. Vegetative Propagation Vegetative Propagation is an asexual method of plant reproduction that occurs in its leaves, roots and stem. Types of Vegetative Propagation are: âą Natural Vegetative Propagation - New plants may emerge from the roots, stem and leaves of the parent plant, without any human interference. âą Artificial Vegetative Propagation - This is a type of vegetative reproduction carried out by humans in the fields and laboratories. It includes Grafting {Apple}, Layering {Jasmine}, Cutting {Sugarcane}and Tissue Culture.
- 13. Artificial Vegetative Propagation Grafting Layering Cutting Tissue Culture
- 14. Tissue Culture ï In Tissue Culture, new plants are grown by removing tissue or separating cells from the growing tip of a plant. ï The cells are then placed in an artificial medium where they divide rapidly to form a small group of cells or Callus. ï The callus is transferred to another medium containing hormones for growth and differentiation. ï The plantlets are then placed in the soil so that they can grow into mature plants. ï Using tissue culture, many plants can be grown from one parent in disease-free conditions. ï This technique is commonly used for Ornamental Plants.
- 15. Spore Formation âą The thread-like structures that developed on the bread are the Hyphae of the Bread Mould (Rhizopus). They are not reproductive parts. âą On the other hand, the tiny blob-on-a-stick structures are involved in reproduction. The blobs are Sporangia, which contain Spores, that can develop into new Rhizopus individuals. âą The spores are covered by thick walls that protect them until they come into contact with another moist surface and can begin to grow.
- 16. sexual reproduction In this, two parents of same species are involved and gamete formation takes place. Variations occur in this mode of reproduction. âą Why the Sexual Mode of Reproduction? Ans. Sexual reproduction allows the formation of new variants by the combination of the DNA from two different individuals, typically one of each sex. ï§ It involves the fusion of the male and the female gamete to produce variants, which are not identical to their parents and to themselves. ï§ This variation allows the individual to adapt to constantly changing and challenging environments. ï§ Also, it leads to the evolution of better-suited organisms which ensures the greater survival of a species.
- 17. Flowering Plant âą The reproductive parts of Angiosperms are located in the flower. âą Stamens and Carpels are the reproductive parts of a flower which contain the germ-cells. âą Stamen is the male reproductive part and it produces pollen grains that are yellowish in color. âą Carpel is present in the center of a flower and is the female reproductive part. It contains three parts: Style, Stigma and Ovary.
- 18. Flower
- 19. Unisexual And Bisexual Flowers The two types of flowers are:- 1. Unisexual Flowers:- The flower which contains either stamens or carpels. For e.g.:- Papaya, Watermelon, etc. 2. Bisexual Flowers:- The flower which contains both stamens and carpels. For e.g.:- Hibiscus, Mustard, etc. Papaya Mustard
- 20. The process of transfer of pollen grains from an anther to the stigma of the flower is pollination. Two types of pollination are: 1. Self-pollination: The transfer of pollen grains from the anther to the stigma of the same flower or another flower of the same plant. 2. Cross-pollination: The transfer of pollen grains from the anther to the stigma of another flower or another flower of a different plant of the same species. Pollination
- 21. Fertilization: It is the fusion of male and female gamete to form Zygote during sexual reproduction. Pollination is followed by fertilization in plants. The events occur are: âą Pollen Grains land on the stigma of the ovary. âą Pollen tubes grow out of the pollen grains, travel through the style and reach the ovary. âą Pollen tube has two male gametes. Each ovule has two Polar Nuclei and a Female Gamete. âą Pollen tube releases two male germ cells inside the ovule, one of them fuses with female germ cell and forms a zygote which grows into the baby plant, this is known as Syngamy. âą The other male gamete fuses with two polar nuclei, it is known as Triple Fusion. In flowering plants, two fusions take place during fertilization. It is called Double Fertilization. FLOWERING PLANTS
- 23. Post â Fertilization Changes After fertilization, the following changes takes place in the flower. Zygote divides several times and forms an embryo inside the ovule. âą The Ovule develops a tough coat and changes into the Seed. âą The Ovary grows rapidly and ripens to form a Fruit. âą Petals, sepals, stamens, style and stigma shrivel and fall off.
- 24. HUMAN BEINGs âą Human Beings show Sexual Reproduction. âą Male parent produces male gametes called Sperms. Sperms have tail and are therefore, motile. They are produced in large numbers in the testes. âą Female parent produces female gametes called Ova. Ovum is bigger, non-motile and only one ovary produces one ovum in one month. âą There is no food stored in the sperms whereas ova contain stored food. âą Both the gametes are microscopic unicellular and have half the number of chromosomes as compared to the body cells.
- 25. âą Puberty is the period during adolescence when the rate of general body growth begins to slow down and reproductive tissues begin to mature. âą Onset of puberty in human males is between 11 to 13 yrs of age, while in human females is between 10 to 12 yrs. of age. âą Puberty is associated with many physical, mental, emotional and psychological changes in boys and girls which occur slowly over a period of time. These are called Secondary Sexual Characters. âą For e.g.:- Thick dark hair start growing in new parts of the body such as arm pits and genital area between the thighs. Thinner hair appear on legs, arms and face. Skin becomes oily and pimples may appear on the face, etc. Puberty / Adolescence
- 27. Copulation The act of mating between the male and female partner is termed as Copulation. Sexual Reproduction consists of a set of events: 1. Pre-fertilization 2. Gametogenesis of Gamete Formation 3. Transfer of gametes 4. Fertilization 5. Post-fertilization
- 28. The male reproductive system consists of portions which produce the germ-cells and other portions that deliver the germ-cells to the site of fertilisation. o The formation of Sperms takes place in the Testes. These are located outside the abdominal cavity in scrotum because sperm formation requires a lower temperature. Testosterone regulate the formation of sperms and brings about changes in appearance in boys during puberty. o The Sperms are delivered through the Vas Deferens which unites with a tube coming from the Urinary Bladder. The Urethra, forms a common passage for both the sperms and urine. Along the vas deferens, Prostate Gland and Seminal Vesicles add their secretions so that the sperms are now in a fluid which makes their transport easier and provides nutrition. o The Sperms are mainly consist of genetic material and a long tail that helps them to move towards the female germ-cell. Male Reproductive System
- 30. The Eggs are made in the ovaries. They are responsible for the production of some hormones. o When a girl is born, the ovaries contain thousands of immature eggs. On reaching puberty, some of these start maturing. One egg is produced every month by one of the ovaries. The egg is carried from the ovary to the womb through Fallopian Tube. The two oviducts unite into an elastic bag-like structure known as the Uterus. The uterus opens into the Vagina through the Cervix. o The Sperms enter through the vaginal passage during Sexual Intercourse. They travel upwards and reach the oviduct where they encounter the Egg. The Zygote gets implanted in the lining of the uterus, and starts dividing. Hence, the uterus prepares itself every month to receive and nurture the growing embryo. The lining thickens and is richly supplied with blood to nourish the growing embryo. System
- 32. âą The embryo gets nutrition from the motherâs blood with the help of a special tissue called Placenta. âą This is a disc which is embedded in the Uterine Wall. It contains villi on the embryoâs side of the tissue. âą On the motherâs side are blood spaces, which surround the villi. This provides a large surface area for Glucose and Oxygen to pass from the mother to the embryo. âą The developing embryo will also generate waste substances which can be removed by transferring them into the motherâs blood through the placenta. âą The development of the child inside the motherâs body takes approximately Nine Months. The child is born as a result of rhythmic contractions of the muscles in the uterus. Placenta
- 33. Menstrual Cycle Menstruation: It is the loss of blood, along with the unfertilized ovum and the ruptured cells and tissues of the endometrium through the vagina of the female. It is a 28-day cycle which occurs in every reproductively active female (from puberty). The flow of blood continues for 2 to 8 days. ï In case the ovum gets fertilized, then the endometrium becomes thick and spongy for nourishing the embryo and hence menstruation does not occur. ï A lady with a developing embryo in her womb is termed as Pregnant. ï The beginning of menstruation at puberty is known as Menarche. ï The stopage of menstruation when the woman is 45-55 yrs of age is called Menopause.
- 34. Reproductive health A number of diseases occur as a result of sexual intercourse if one of the partners is infected. These are known as Sexually Transmitted Diseases (STDâs). They can be caused by bacteria For Eg; Syphilis, Gonorrhoea; or caused by a virus For Eg; HIV- AIDS, Warts etc. The transmission of these diseases can be avoided by using birth control measures such as wearing a condom during the sexual act. Birth control measures: They can be mechanical, chemical and surgical.
- 35. Contraceptive Measures The following contraceptive measures can be used to prevent Pregnancy:- ï§ Mechanical Methods:- Condoms, Diaphragm and Intra Uterine Contraceptive Device (IUCD) are used to prevent the passage of semen to the fallopian tube. ï§ Chemical Method:- Oral Contraceptive Pills are hormonal pills which are used to prevent ovulation but do not stop menstruation. ï§ Surgical Method:- 1. Tubectomy- It involves cutting and ligating the oviduct in females. 2. Vasectomy- It involves cutting and ligating the vas deferens in males.