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How to Study SSC 10th - Science - Life cycle?


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How to Study SSC 10th- Science???

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How to Study SSC 10th - Science - Life cycle?

  1. 1. 9011041155 / 9011031155 • Live Webinars (online lectures) with recordings. • Online Query Solving • Online MCQ tests with detailed Solutions • Online Notes and Solved Exercises • Career Counseling 1
  2. 2. 9011041155 / 9011031155 The Life Cycle Reproduction All living organisms produce new individuals of the same species that is a new generation of the species from an existing individual. This fundamental characteristic of living things is known as reproduction. ∙ Plants belonging to same species look similar. A basic process in reproduction is the creation of a DNA copy. In this process of copying, some variations take 2
  3. 3. 9011041155 / 9011031155 place each time. Thus DNA copies generated are similar but not identical to the original. Importance of Variations Variations provide a chance of survival for the species under unfavorable environmental conditions. Plant and animals have different modes of reproduction 3
  4. 4. 9011041155 / 9011031155 Types of asexual reproduction 1 Binary fission 2 Multiple fission 3 Budding 4 Fragmentation 5 Regeneration 6 Vegetative propagation 7 Spore formation 4
  5. 5. 9011041155 / 9011031155 Asexual reproduction Only one parent is involved in asexual reproduction in which cells divide mitotically. Since there is no fusion of two different cells, the daughter cells produced by asexual reproduction is genetically identical to the parent cells. Lack of genetic variations is the disadvantage while rapid reproduction is the advantage Of asexual reproduction. 5
  6. 6. 9011041155 / 9011031155 Binary fission In this method, the living cell is divided into two nearly equal or unequal parts, which have potential to grow to the size of original one. E.g. Binary fission in amoeba, Paramecium. 6
  7. 7. 9011041155 / 9011031155 In paramecium transverse binary fission is observed (fig. a) while in Euglena longitudinal binary fission is observed. (Fig. b) 7
  8. 8. 9011041155 / 9011031155 Multiple fission Multiple fission is observed in amoeba. During unfavorable condition secretes a hard covering called cyst. Inside the cyst nucleus divides into many nuclei by repeated division, followed by division by cytoplasm forming many daughter cells. The cyst bursts to release the daughter cells during favorable conditions. Budding 8
  9. 9. 9011041155 / 9011031155 Budding is observed in yeast cells. 1. Yeast reproduces by budding in which a small outgrowth is formed on the parental cell. 2. The nucleus of the parental cell gets divided. 3. One daughter nucleus migrates into the bud. 4. The bud increases in size, separated and grows further. In unicellular organism, all the life processes 9
  10. 10. 9011041155 / 9011031155 occur in single cell, while multicellular organisms have special tissues, organs, organ system to carry out life processes. In unicellular organism, all the life processes occur in single cell, while multicellular organisms have special tissues, organs, organ system to carry out life processes. ∙ The complexity in reproduction increases with the complexity in structure of organism. 10
  11. 11. 9011041155 / 9011031155 Fragmentation 1. When water and nutrients are available, spirogyra grow and multiply rapidly. 2. The filament of spirogyra undergoes fragmentation resulting in numerous filaments. 3. With cell enlargement and subsequent mitosis, each fragment grows and develops into a mature 11
  12. 12. 9011041155 / 9011031155 filament. Regeneration ∙ Some animals can reconstruct the entire body from the isolated body cells, is called regeneration. ∙ Regeneration is not reproduction. ∙ Regeneration is carried out by specialized cells. These cells proliferate and make large number of cells which later develop into various cell types and tissues and help in production of new organism. E.g. Regeneration in Planaria 12
  13. 13. 9011041155 / 9011031155 1. When Planaria is cut into many pieces, each piece develops into a whole Planaria as shown in above figure. 2. This process occurs only if the planarial body gets cut into pieces 3. But animals cannot wait to be cut to reproduce. So regeneration is not the same as reproduction. 13
  14. 14. 9011041155 / 9011031155 Budding In Hydra, it uses regenerative cells for reproduction in the process of budding. 1. When Hydra reaches maturity and is well fed, its body wall begins to form a rounded growth from the stalk of the adult. 2. This growth is called a bud which develops in time into a miniature hydra. 14
  15. 15. 9011041155 / 9011031155 4. The young hydra gets nourishment from the parent. When the young hydra is sufficiently developed to take up an independent existence, the base of the new hydra seals off and thus allows the new individuals to break off from the parent hydra. 15
  16. 16. 9011041155 / 9011031155 Vegetative Propagation When the plants are produced from the vegetative parts (roots, stems, leaves and buds), it is known as vegetative propagation. For example, new plants of potato develop from eyes (buds on potato), Bryophyllum reproduces from the buds on the leaf margin, the roots of sweet potato give rise to new plants,etc….., 16
  17. 17. 9011041155 / 9011031155 a. In a sweet potato plant vegetative propagation is with the help of roots. b. In figure, vegetative propagation with the help of adventitious buds present in the notches of leaf of Bryophyllum. c. Fig. shows vegetative propagation of potato with the help of stem (underground stem of potato). The adventitious buds present on the potato develop 17
  18. 18. 9011041155 / 9011031155 into new plant. Spore formation In the mucor vegetative propagation is done with the help of spores. 1. The hyphae of bread mould (Mucor) are thread like structures. 2. The mould forms spores inside a sporangium. 18
  19. 19. 9011041155 / 9011031155 3. When the spores are ready to leave the sporangium, it breaks open. 4. If they land in a moist place, they germinate to form new mould. Cloning ∙ Animal cloning is the process by which an entire organism is reproduced in a genetically identical manner, from a single cell taken from the parent organism ∙ This means the cloned animal is an exact duplicate of its parent in every way. Sexual reproduction Two parents are involved in sexual reproduction, one male and the other female. The main two processes involved in sexual reproduction are, 19
  20. 20. 9011041155 / 9011031155 1. Meiosis 2. Fertilization 1. Meiosis: It is a process in which halving the number of chromosomes (2n to n) takes place resulting in the formation of haploid gametes ∙ It is a type of cell division leading to production of gametes. ∙ ∙ It occurs in reproductive cells. Diagrammatically it can be shown as, 2. Fertilization: It is a process in which the male 20
  21. 21. 9011041155 / 9011031155 gamete fuses with the female gamete resulting in the formation of diploid zygote. It restores the number of chromosomes (2n). ∙ Since there is fusion of two germ cells; offsprings produced by sexual reproduction are different from parents. ∙ Variations give rise to variety and diversity. ∙ Variation enables organisms to adapt and survive in the changing environment. ∙ It helps to prevent the complete extinction of animal and plant species. Sexual Reproduction in Plants Flower is functional unit concerned with sexual 21
  22. 22. 9011041155 / 9011031155 reproduction. sepals, petals, stamens and carpels are different parts of a flower. Carpel : Female reproductive part of a flower Present in the centre of flower. Made up of three parts stigma, style and ovary. Stigma : Sticky terminal part of the style. 22
  23. 23. 9011041155 / 9011031155 Receptive organ on which pollen germinates. Style : Elongated part of carpel bearing stigma at its tip. Ovary : The swollen lower part of carpel containing one or more ovules. Each ovule has an egg cell Stamen : Male reproductive part of a flower. Made up of two parts anther and filament. Anther : Usually bilobed and produces pollen grains. Male germ cells are produced by pollen grains. Filaments: Stalk of anther . Pollination 1. The processes of transfer of pollen grains from 23
  24. 24. 9011041155 / 9011031155 anther to stigma is called as pollination. 2. If this transfer of pollen occurs in the same flower or another flower of the same plant, it is known as self pollination. 3. On the other hand, if pollen is transferred from one flower to the flower of another plant of the same species, it is known as cross pollination. The agents of cross pollination are wind, water or animals. Some flowers have attractive colours while some have fragrance, to attract insects and pollination takes place. Like this insects help in pollination. 24
  25. 25. 9011041155 / 9011031155 Fertilization Formation of zygote by fusion of egg and male gametes is termed as fertilization 25
  26. 26. 9011041155 / 9011031155 1. After the pollen grain lands on the stigma, it germinates. The pollen tube grows out from a pollen grain. It travels through the style to reach the ovary. 2. Each pollen tube contains two male gametes and releases them near the egg. 3. One male gamete fuses with the egg cell to form zygote. The second male gamete fuses with the secondary nucleus in the embryo sac to form 26
  27. 27. 9011041155 / 9011031155 endosperm. This is called as double fertilization. 4. The zygote develops into embryo and the endosperm serves as nutritive tissue for the growing embryo. This embryo is capable of growing into a new plant. Germination After fertilization, the zygote divides several times to form an embryo within the ovule. The ovule develops into a seed and ovary develops into the fruit. The seed contains the future plant. It develops into the seedling under appropriate condition. This process is known as germination. 27
  28. 28. 9011041155 / 9011031155 Reproduction in human beings Changes in human girls and boys according to their ages are shown in the table given below: The Male Reproductive System Testis and penis are the main reproductive organs of the male reproductive system. Testis : Produces sperms (male germ cells) As formation of sperms require temperature lower than the 28
  29. 29. 9011041155 / 9011031155 normal body temperature, testis are located outside the abdominal cavity in the scrotum. Testis secretes the hormone testosterone which brings about changes in boys during puberty. Epididymis: Immature sperm travels to the epididymis for development and storage. Vas deferens: It is a passage through which the sperm travels the urethra. 29
  30. 30. 9011041155 / 9011031155 Seminal vesicle and Prostate glands: They produce ejaculatory fluid which helps the sperm in transport and provides nutrition. Penis: It is the portion of the reproductive system that delivers the sperms to the site of fertilization. Sperms: A sperm cell is composed of a head which carries the genetic information, a middle part which carries mitochondria required for energy production and a tail which is like a flagellum to help in movement towards the female germ cells. The female reproductive system Vagina, uterus, oviduct and ovaries are the main reproductive organs of the female reproductive system. Vagina: It is muscular tube that extends from the vaginal 30
  31. 31. 9011041155 / 9011031155 opening to uterus. It provides the route for the menstrual blood to leave the body during menstruation. It is a pathway through which sperms enter into the woman’s body and is a pathway through which a baby comes out of the woman’s body during childbirth. Uterus: Uterus is a muscular organ. Due to strong muscles and ability to expand and contract, the uterus can accommodate a growing foetus and can push the baby during labour. Oviducts: Connect uterus to the ovary. 31
  32. 32. 9011041155 / 9011031155 Ovaries: Two oval shaped organs lie to the upper right and left of the uterus. They develop and release eggs into the oviduct. They secrete hormone estrogen which brings about changes in girls during puberty. When a baby girl is born, the ovaries already contain thousands of immature eggs which remain inactive till maturity. On reaching puberty, women’s ovaries usually release one egg each month. 32
  33. 33. 9011041155 / 9011031155 Menstruation: When the egg is not fertilized, this unfertilized egg along with blood and mucous form a flow which leaves the uterus. This is called menstruation which lasts from three to five days. 33
  34. 34. 9011041155 / 9011031155 Fertilization, development and birth The sperms enter through the vaginal passage, travel upwards and reach the oviduct where they may encounter the egg. As soon as it is fertilized, the egg cell (zygote) begins to divide until becomes a ball of cells called a blastocyst. This ball then implants itself in the wall of the uterus. The development of the embryo takes place 34
  35. 35. 9011041155 / 9011031155 inside the uterus where the embryo gets all the nutrients and oxygen from its mother’s blood in the oviduct supplied through the umbilical cord. From nine months onwards, the baby is ready to take birth. It moves down. During birth, the cervix gradually opens and the baby is released through the vagina. Need for and method of family planning As the population density increases, decrease in per capita income and natural resources takes place. General health also goes down. It creates an economical burden on the nation. Economic pressure, mother’s poor health, children neglected at home, poor housing, malnutrition, insufficient medical care, lack of better education are 35
  36. 36. 9011041155 / 9011031155 some of the disadvantages of large family size. Another problem related to human reproduction is the spread of sexually transmitted diseases (STDs). Preventive measures Sex education Use of condom Contraception (to avoid pregnancy) and to keep sexual health by the use of the condoms, oral pills, copper – T etc. The WHO has prepared guidelines and considered reproductive health as fundamental human right. • Ask Your Doubts • For inquiry and registration, call 9011041155 / 9011031155. 36