12. The Life Cycle SCHOOL SECTION

Transcription

1 12. The Life Cycle 282 SCHOOL SECTION

2 MT EDUCARE LTD. SCIENCE & TECHNOLOGY Q.I (A) Choose the correct alternatives and rewrite the complete sentences : 1. The filament of spirogyra undergoes... resulting in numerous filaments. (a) budding (b) regeneration (c) fragmentation (d) spore formation reproduces from the buds on the leaf margin. (a) Lotus (b) Rose (c) Jasmine (d) Bryophyllum is the receptive organ on which pollen germinates. (a) Style (b) Stigma (c) Anther (d) Ovary 4. The elongated part of carpel bearing stigma at its tip is called.... (a) style (b) stigma (c) anther (d) ovary 5. In plants, male germ cells are produced by.... (a) filament (b) anther (c) pollen grains (d) stamen serves as nutritive tissue for the growing embryo. (a) Embryo sac (b) Endosperm (c) Ovary (d) Fruit 7. The ovule develops into a.... (a) fruit (b) seed (c) flower (d) ovary 8. The ovary develops into a.... (a) fruit (b) seed (c) flower (d) ovule 9. Testes secrete the hormone... which brings about changes in boys during puberty. (a) progesterone (b) estrogen (c) thyroxine (d) testosterone 10. Immature sperms travel to the... for development and storage. (a) vas deferens (b) penis (c) testes (d) epididymis is a passage through which the sperm travels towards the urethra. (a) Vas deferens (b) Penis (c) Epididymis (d) Seminal vesicle 12. The ovaries secrete the hormone... which brings about changes in girls during puberty. (a) progesterone (b) estrogen (c) thyroxine (d) testosterone 13. Planaria reproduces by.... (a) fragmentation (b) budding (c) binary fission (d) regeneration Answers : 1. fragmentation 2. Bryophyllum 3. Stigma 4. style 5. pollen grains 6. Endosperm 7. seed 8. fruit 9. testosterone 10. epididymis 11. Vas deferens 12. estrogen 13. regeneration SCHOOL SECTION 283

3 SCIENCE & TECHNOLOGY MT EDUCARE LTD. Q.I (B) Fill in the blanks : *1. The two main methods of reproduction are... and.... *2. The functional unit in a plant s sexual reproduction is.... *3. The male reproductive part of a flower is.... *4. When the transfer of pollen from an anther to the stigma occurs in the same flower, the process is called.... *5.... give rise to variety and diversity. *6. Hydra uses regenerative cells for reproduction in the process of.... *7. Yeast reproduces by.... *8. During unfavourable conditions, the amoeba secretes a hard covering called.... *9. A basic process in reproduction is the creation of a... copy. * is necessary to maintain the number of individuals of a species. 11. In asexual reproduction the cells divide The... of bread mould (Mucor) are thread like structures. 13. The mould forms spores inside a is the process by which an entire organism is reproduced in a genetically identical manner, from a parent organism enables organisms to adapt and survive in the changing environment. 16. Stamen is made up of... and If pollen is transferred from one flower to the flower of another plant of the same species, it is known as One male gamete fuses with the egg cell to form The second male gamete fuses with the secondary nucleus in the embryo sac to form is a muscular tube that extends from the vaginal opening to the uterus provides the route for the menstrual blood to leave the body during menstruation connect uterus to the ovary. 23. The embryo gets all the nutrients and oxygen from its mother s blood in the oviduct supplied through the The... has prepared guidelines and considered reproductive health as a fundamental human right was the first mammal to be cloned from an adult cell rather than an embryo. 26. As soon as the egg cell (zygote) is fertilized, it begins to divide until it becomes a ball of cells called.... Answers : 1. asexual reproduction, 2. flower sexual reproduction 3. stamen 4. self pollination 5. Variations 6. budding 7. budding 8. multiple 9. DNA 10. Reproduction 11. mitotically 12. hyphae 13. sporangium 14. Animal cloning 15. variation 16. anther, filament 17. cross pollination 18. zygote 284 SCHOOL SECTION

4 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 19. endosperm 20. Vagina 21. Vagina 22. Oviducts 23. umbilical cord 24. WHO 25. Dolly sheep 26. Blastocyst. Q.I (C) Match the following : 1. Column I Column II (i) Penis (a) Site of fertilization (ii) Ovaries (b) Stores sperms (iii) Oviduct (c) Delivers sperms (iv) Testes (d) Produce eggs (v) Epididymis ( e) Produce sperms (f) Provides nutrition (i - c), (ii - d), (iii - a), (iv - e), (v - b). 2. Column I Column II (i) Amoeba (a) Fragmentation (ii) Yeast (b) Vegetative propagation (iii) Bryophyllum (c) Binary fission (iv) Mucor (d) Budding (v) Spirogyra ( e) Spore formation (i - c), (ii - d), (iii - b), (iv - e), (v - a). Q.I (D) State whether the following statements are true or false. If false write the corrected statement : 1. Lack of genetic variation is the advantage of asexual reproduction. False. Lack of genetic variation is the disadvantage of asexual reproduction. 2. DNA copies are identical to the original. False. DNA copies are similar but not identical to the original. 3. Mitosis is a process in which halving the number of chromosomes takes place. False. Mitosis is a process in which the chromosome number is restored. 4. Meiosis is a process in which halving the number of chromosomes takes place. True. 5. Testes secrete the hormone testosterone. True. 6. Immature sperms travel to the vas deferens for storage. False. Immature sperms travel to the Epididymis for storage. 7. Spirogyra reproduces by regeneration. False. Spirogyra reproduces by fragmentation. 8. On reaching puberty, a woman s ovaries usually release thousands of eggs each month. False. On reaching puberty, a woman s ovaries usually release one egg each month. 9. If pollination occurs from one flower to another flower of the same plant, it is called cross-pollination. False. If pollination occurs from one flower to another flower of the same plant, it is called self-pollination. 10. Carpel is the female reproductive part of a flower. True. 11. Cloned animal has the DNA which is identical to parent DNA. True. SCHOOL SECTION 285

5 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 12. Boys become adults at the age of 18. False. Boys become adults at the age of 21. Q.I (E) Find the odd man out : 1. Stigma, Style, Anther, Ovary. Anther. It is the male reproductive part of a flower whereas the others are female reproductive parts of the flower. 2. Vagina, Uterus, Testis, Ovaries. Testis. It is a male reproductive organ whereas the others are female reproductive organs. 3. Bryophyllum, Potato, Sweet potato, Spirogyra. Spirogyra. It reproduces by fragmentation whereas the others reproduce by vegetative propagation. 4. Syphilis, Gonorrhoea, Malaria, AIDS. Malaria. It is not a sexually transmitted disease whereas the others are sexually transmitted diseases. 5. Root, Stem, Leaf, Flower. Flower. It is the reproductive part of a plant whereas the others are vegetative parts of a plant. Q.I (F) Write the correlated terms : *1. Amoeba : Simple binary fission :: Paramoecium :.... Transverse binary fission. *2. Planaria : Regeneration :: Rhizopus :.... Spore formation. *3. Root, Stem, Leaf : Vegetative propagation :: Flower :.... Sexual reproduction. *4. Asexual reproduction : Similarity :: Sexual reproduction :.... Diversity. 5. Testis : Testosterone :: Ovaries :.... Estrogen. 6. Ovule : Seed :: Ovary :.... Fruit. 7. Asexual reproduction : Somatic cells :: Sexual reproduction :.... Germ cells. 8. Spirogyra : Fragmentation :: Planaria :.... Regeneration. Q.II Define the following : *1. Reproduction. The process of production of new individuals of the same species, that is a new generation of the species from an existing individual is called as reproduction. *2. Vegetative propagation. When new plants are produced from the vegetative parts (roots, stems, leaves and buds), it is known as vegetative propagation. *3. Pollination. The process of transfer of pollen grains from anther to stigma is called as pollination. *4. Meiosis. It is a process in which halving the number of chromosomes (2n to n) takes place resulting in the formation of haploid gametes. 5. Mitosis. It is a type cell division occuring in somatic cells leading to growth and development. 286 SCHOOL SECTION

6 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 6. Fertilization. It is a process in which male gamete fuses with the female gamete resulting in the formation of diploid zygote. Q.III (A) Give scientific reasons : 1. DNA copies generated during reproduction are similar but not identical to the original. 1. A basic process in reproduction is the creation of a DNA copy. 2. Cells use chemical reactions to create copies of their DNA. 3. In this process of copying, some variations take place each time. 4. Therefore, DNA copies generated during reproduction are similar but not identical to the original. 2. Daughter cells produced by asexual reproduction are genetically identical to the parent cells. 1. Only one parent is involved in asexual reproduction in which the cells divide mitotically. 2. Since, there is no fusion of two different cells, the daughter cells produced by asexual reproduction are genetically identical to the parent cells. 3. Multicellular organisms show complex ways of reproduction. 1. Multicellular organisms have different cell types which perform different functions. 2. They have special organs, placed at a definite place in the body which are formed by specific tissues. 3. In such organised organisms, method of cell-by-cell division to reproduce is impractical. 4. Therefore, multicellular organisms show complex ways of reproduction. *4. Siberian cranes migrate to Bharatpur during winter. 1. Winter is very severe at Siberia in Russia. 2. Siberian cranes cannot tolerate such extremely low temperatures. 3. In Bharatpur, India, the climate is comparatively warmer and food is available in plenty. 4. Therefore, to escape from the unfavourable climatic conditions, Siberian cranes migrate to Bharatpur during winter. *5. In the absence of honey bees, the yield of sunflower goes down tremendously. 1. Sunflower pollen is heavy and sticky. So it cannot be carried by wind. 2. So, pollen is transferred from one plant to another plant through the agency of honey bees resulting in cross pollination. 3. Cross pollination also increases the yield of seeds. 4. Therefore, in the absence of honey bees, the yield of sunflower goes down tremendously. 6. Testes are located outside the abdominal cavity in the scrotum. 1. Testes are the organs which produce sperms (male germ cells). 2. Formation of sperms requires temperature lower than the normal body temperature. 3. Therefore, testes are located outside the abdominal cavity in the scrotum. 7. Children born to older women may be defective. 1. At birth, the female ovary contains approximately 2-4 million eggs. After birth, new eggs are not added. 2. Out of this eggs, only about 400 are destined to be ovulated, while all others degenerate during development, so that only a few remain by the age of Thus, eggs ovulated near the age of 50 are years older than those ovulated just after puberty. SCHOOL SECTION 287

7 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 4. This ageing of eggs can cause defects in the children born to older women. 8. Regeneration is not the same as reproduction. 1. Regeneration is the reconstruction of entire body from the isolated body cells. 2. Eg. When planaria is cut into many pieces, each piece develops into a whole planaria. 3. This process occurs only if the planarial body gets cut into pieces. 4. But animals cannot wait to be cut to reproduce. 5. Therefore, regeneration is not the same as reproduction. Q.III (B) Answer the following questions in short : *1. What are the advantages of sex ual reproduction over asex ual reproduction? 1. Sexual reproduction promotes diversity of characters in the offsprings. 2. In sexual reproduction, due to genetic variation there is more opportunity for new combination of characters and therefore, it plays a prominent role in the origin of new species. 3. It also leads to variation, which is necessary for evolution. Variation enables the organisms to adapt and survive in the changing environment. 4. It helps to prevent the complete extinction of animal and plant species. *2. Why does menstruation occur? 1. On reaching puberty, a woman s ovaries usually release one egg each month. 2. 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 for three to five days. *3. Explain disadvantages of large family size. 1. There is a strong relation between high national fertility rate and measures of poverty. 2. As the population density increases, decrease in per capita income and natural resources takes place. 3. General health also goes down. 4. It creates an economic burden on the nation. 5. Large families affect both the individual as well as the community life. 6. Economic pressure, mother s poor health, children neglected at home, poor housing, malnutrition, insufficient medical care, lack of better education are some of the disadvantages of large family size. 4. Describe the formation of twins. 1. Sometimes a single fertilized egg may get split and separated into two parts during the early stage of cell division. Each part then develops into a separate individual. As these individuals are produced from a single zygote, they look similar and are called identical twins (either both boys or both girls). 2. Sometimes two eggs are released from ovaries simultaneously and get fertilized to produce two individuals. As these two individuals are produced from different zygote, they are dissimilar (either both boys or both girls or one boy and one girl). 5. What is mitosis? Represent in diagramatically. 1. Mitosis is a type of cell division leading to growth and development. 2. It occurs in somatic cells. 3. Diagramatically it can be represented as : 288 SCHOOL SECTION

8 MT EDUCARE LTD. SCIENCE & TECHNOLOGY Parent cell 2n Two daughter cells 2n (restoring original 2n chromosomal number) 6. What is meiosis? Represent it diagramatically. 1. Meiosis is a type of cell division leading to production of gametes. 2. It is a process in which halving the number of chromosomes (2n to n) takes place resulting in the formation of haploid gametes. 3. It occurs in reproductive cells. 4. Diagramatically it can be represented as : n Mitosis n Parent cell Reduction division 2n n Haploid (diploid) Meiosis n gametes n Mitosis n 7. State the various modes of asexual reproduction in multicellular organisms. The various modes of reproduction in multicellular organisms are : 1. Fragmentation 2. Budding 3. Vegetative propagation 4. Spore formation. *8. What is reproduction? What is its significance? 1. 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. 2. Reproduction is necessary to maintain the number of individuals of a species and to prevent their extinction. 9. Describe asex ual reproduction. Also state its advantage and disadvantage. 1. Only one parent is involved in asexual reproduction in which cells divide mitotically. 2. Since there is no fusion of two different cells, the daughter cells produced by asexual reproduction are genetically identical to the parent cells. 3. Lack of genetic variation is the disadvantage while rapid reproduction is the advantage of asexual reproduction. 10. What is the use of sepals and petals to the flower? 1. Sepals protect the flower when it is in the bud condition. 2. Petals attract the insects for pollination. 3. Petals also protect the inner reproductive parts of the flower i.e., stamen and carpel. 11. Why do some animals reproduce many young ones and some only one? 1. All animals want to make sure that at least some of their young ones reach adulthood and reproduce themselves. 2. Some animals do this by looking after a few young ones until they can fend for themselves. 3. Other animals produce hundreds of eggs which they leave to develop by themselves. Most of them will die, but a few will survive. 12. What are sperms? Give the structure of a sperm cell. 1. Sperms are male germ cells. 2. A sperm cell is composed of a head which carries the genetic information. SCHOOL SECTION 289

9 SCIENCE & TECHNOLOGY 3. It has a middle part which carries mitochondria required for energy production. 4. It has a tail which is like a flagellum to help in movement towards the female germ cells. MT EDUCARE LTD. Head Midpiece Tail 13. What are STDs? How can they be prevented? 1. STDs are sexually transmitted diseases. 2. STDs spread from an infected person to a healthy person by unprotected sexual contact. 3. Syphilis, Gonorrhoea, AIDS are some common sexually transmitted diseases which affect the health of human being. 4. To protect individuals from these STDs, sex education and preventive measures are necessary. 5. Use of condom protects the individual from STDs. Q.III (C) Write short notes for the following : *1. Pollination. 1. The process of transfer of pollen grains from the anther to the stigma is called 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. *2. Regeneration. 1. The capacity to regenerate is very high among some animals. They can reconstruct the entire body from the isolated body cells. 2. Regeneration is carried out by specialised cells. These cells proliferate and make large number of cells which later develop into various cell types and help in production of new organisms. 3. For example, when planaria is cut into many pieces, each piece 290 develops into a whole planaria. 4. This process occurs only if the planarial body gets cut into pieces. But animals cannot wait to be cut to reproduce. So regeneration is not the same as reproduction. 3. Budding in multicellular organisms (Hydra). 1. Organisms such as hydra use regenerative cells for reproduction in the process of budding. 2. When hydra reaches maturity and is well fed, its body wall begins to form a rounded growth from the stalk of the adult. Regeneration in planaria Parent hydra Sperm cell Bud Young hydra SCHOOL SECTION

10 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 3. This growth is called a bud which develops in time into a miniature hydra. 4. The body layers, body cavity and the digestive cavity of the young hydra are continuous with that of the parent hydra. The young hydra gets nourishment from the parent. 5. When the young hydra is sufficiently developed to take up an individual existence, the base of the new hydra seals off and thus allows the new individual to break off from the parent hydra. *4. Vegetative propagation. 1. When new plants are produced from the vegetative parts (roots, stems, leaves and buds), it is known as vegetative propagation. 2. 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. 3. All plants produced by vegetative propagation are similar to the parent, as they are produced from a single parent. 4. Plants produced by vegetative propagation take less time to grow and bear flowers and fruits earlier than those produced from seeds. 5. Spore formation. 1. The hyphae of bread mould (Mucor) are Sporangium thread like structures. Spores 2. The mould forms spores inside the sporangium. 3. When the spores are ready to leave the sporangium, it breaks open. 4. If they land in a moist place, they Hyphae germinate to form new mould. Rhizoids *6. Germination of seeds. 1. After fertilization, the zygote divides several times to form an embryo within the ovule. 2. The ovule develops into a seed and ovary develops into the fruit. 3. The seed contains the future plant. 4. It develops into a seedling under appropriate condition. This process is known as germination. Germination of a seed *7. Multiple fission. 1. During unfavourable condition, the amoeba withdraws its pseudopodia, becomes almost round and secretes a hard covering called cyst. 2. Inside the cyst, the nucleus Cyst Multiple Release of divides into many nuclei by formation fission daughter cells repeated division, followed by the during division of cytoplasm. favourable 3. As a result, many daughter cells are formed. conditions 4. The cyst bursts to release the daughter cells during favourable condition. SCHOOL SECTION 291

11 SCIENCE & TECHNOLOGY MT EDUCARE LTD. *8. Importance of variation. 1. Variation occurs due to sexual reproduction. 2. Variations give rise to variety and diversity. 3. It enables organisms to adapt and survive in the changing environment. 4. It helps to prevent the complete extinction of animal and plant species. Q.IV (A) Distinguish between : 1. Binary fission and Multiple fission. Binary fission 1. In this method, the living cell divides into two equal parts. 2. In this method two daughter cells are formed. 3. It occurs under favourable conditions. Multiple fission 1. In this method, the nucleus divides within the cyst into many nuclei by repeated division. 2. In this method many daughter cells are formed. 3. It occurs under unfavourable conditions. 2. Asexual reproduction and Sexual reproduction. Asexual reproduction Sexual reproduction 1. Only one parent is involved in asexual reproduction. 2. There is no fusion of two different cells. 3. It occurs in somatic cells. 4. Offsprings are identical to the parent. 5. It is a rapid method of reproduction. 1. Two parents are involved in sexual reproduction, one male and the other female. 2. There is fusion of two germ cells. 3. It occurs in germ cells. 4. Offsprings are different from parents. 5. It is a slow method of reproduction. 3. Pollination and Fertilization. Pollination 1. The process of transfer of pollen grains from the anther to the stigma is called as pollination. 2. It occurs only in plants. 3. It requires agents. Fertilization 1. The process in which the male gamete fuses with the female gamete resulting in the formation of a diploid zygote is called fertilization. 2. It occurs in plants and animals. 3. It does not require agents. 4. Self pollination and Cross pollination. Self pollination 1. If the transfer of pollen occurs in the same flower or another flower of the same plant, it is known as self pollination. 2. Offsprings are genetically identical. 3. Variations do not occur in the offsprings. Cross pollination 1. If the transfer of pollen occurs from one flower to the flower of another plant of the same species, it is known as cross pollination. 2. Offsprings are not genetically identical. 3. Variations occur in the offsprings. 292 SCHOOL SECTION

12 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 5. Mitosis and Meiosis. Mitosis 1. Mitosis is a type of cell division leading to growth and development. 2. It occurs in somatic cells. 3. Chromosome number is restored. Meiosis 1. Meiosis is a type of cell division leading to production of gametes. 2. It occurs in reproductive cells. 3. Chromosome number is halved. Q.IV (B) Draw a neat and labelled diagram of the following : *1. Longitudinal section of flower. Stigma Carpel Style Petal Ovary Anther Filament Sepal Stamen *2. Binary fission in amoeba. Parent cell Nucleus dividing Cytoplasm dividing Two daughter cells *3. Spore formation in Mucor. Sporangium Spores Hyphae Rhizoids *4. Human female reproductive system. Oviduct Ovary Uterus Cervix Vagina Endometrium SCHOOL SECTION 293

13 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 5. Human male reproductive system. Bladder Seminal vesicle Prostate gland Vas deferens Urethra Epididymis Testis Penis 6. Budding in yeast. Parent cell Bud Daughter cells Q.V Answer the following in detail : 1. Describe the reproductive parts of a flower. Stigma Carpel Style Petal Ovary Anther Filament Sepal Stamen In plants, flower is the functional unit concerned with sexual reproduction. The parts of the flower which are involved in reproduction are : 1. Carpel : Female reproductive part of a flower present in the centre. It is made up of three parts : stigma, style and ovary. 2. Stigma : It is the sticky terminal part of the style. It is the receptive organ on which pollen germinates. 3. Style : It is the elongated part of carpel bearing stigma at its tip. 4. Ovary : The swollen lower part of carpel containing one or more ovules. Each ovule has an egg cell (female germ cell). 5. Stamen : Male reproductive part of a flower made up of two parts anther and filament. 6. Anther : Usually bilobed and produces pollen grains. 7. Filament : Stalk of anther. *2. Describe sexual reproduction in plants. The process of sexual reproduction in plants involves three processes : 1. Pollination 2. Fertilization 3. Germination. 294 SCHOOL SECTION

14 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 1. Pollination : a (a) The process of transfer of pollen grains from c the anther to the stigma is called pollination. (b) If this transfer of pollen occurs in the same flower or another flower of the same plant, it is known as self pollination. (c) 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. 2. Fertilization : (a) After the pollen grain lands on the stigma, it germinates. (b) The pollen tube grows out from a pollen grain. It travels through the style to reach the ovary. (c) (d) Each pollen tube contains two male gametes and releases them near the egg. One male gamete fuses with the egg cell to form zygote. ( e) The second male gamete fuses with the secondary nucleus in the embryo sac to form endosperm. This is called as double fertilization. (f) 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. 3. Germination : (a) After fertilization, the zygote divides several times to form an embryo within the ovule. (b) The ovule develops into a seed and ovary develops into the fruit. (c) The seed contains the future plant. It develops into the seedling under appropriate conditions. This process is known as germination. *4. Describe the modes of reproduction in unicellular organisms. 1. Binary fission : (a) It is a method of asexual reproduction that is employed by most prokaryotes, some protozoa and some organelles within eukaryotic cells. (b) In this method, the living cell divides into two equal or nearly equal parts which have the potential to grow to the size of the original one. Parent cell (c) The plane of cytoplasmic division is through any plane in amoeba (simple binary fission). (d) However, in some organisms fission occurs through a specific axis (transverse or longitudinal binary fission). Eg. : Paramoecium, Euglena. 2. Multiple fission : (a) Nucleus dividing a, b : Self pollination c : Cross pollination Cytoplasm dividing Pollen grain Stigma Male germ Cells (gamates) Pollen tube Ovary Secondary nucleus Female germ cell (egg cell) During unfavourable conditions the amoeba withdraws its pseudopodia, becomes almost round and secretes a hard covering called cyst. SCHOOL SECTION 295 b Two daughter cells

15 SCIENCE & TECHNOLOGY (b) Inside the cyst, nucleus divides into many nuclei by repeated division, followed by division of cytoplasm. As a result many daughter cells are formed. (c) The cyst bursts to release the daughter cells during favourable conditions. 3. Budding : Parent cell Bud Cyst formation MT EDUCARE LTD. Multiple Release of fission daughter cells during favourable conditions Daughter cells 296 (a) (b) Yeast reproduce by budding in which a small outgrowth is formed on the parental cell. The nucleus of the parental cell divides and one daughter nucleus migrates into the bud. The bud increases in size, separates and grows further. (c) 2. Describe the human male reproductive system. The human male reproductive system consists of : 1. Testis : Produces sperms (male germ cells). As formation of sperms require temperature lower than the normal body temperature, testes are located outside the abdominal cavity in the scrotum. Testes secrete the hormone testosterone which brings about changes in boys during puberty. 2. Epididymis : Immature sperms travel to the epididymis for development and storage. 3. Vas deferens : It is a passage through which the sperm travels towards the urethra. 4. Seminal vesicle and prostate glands : They produce the ejaculatory fluid which helps the sperm in transport and provides nutrition. 5. Penis : It is the portion of the reproductive system that delivers the sperms to the site of fertilization. 6. Sperms : A sperm cell is composed of a head which carries the genetic information, a middle part which carries mitochondria for energy production and a tail which is like a flagellum to help in movement towards the female germ cells. 3. Describe the human female reproductive system. The human female reproductive system consists of main reproductive organs like vagina, uterus, oviduct and ovaries. 1. Vagina : (a) (b) (c) Bladder Seminal vesicle Prostate gland Urethra Epididymis Vas deferens Testis Penis It is a muscular tube that extends from the vaginal opening to the uterus. It provides the route for the menstrual blood to leave the body during menstruation. It is a pathway through which the sperms enter into the woman s body and is a pathway through which a baby comes out of the woman s body during childbirth. SCHOOL SECTION

16 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 2. Uterus : Uterus is a muscular organ. Due to strong muscles and ability to expand and contract, the uterus can accomodate a growing foetus and push the baby during labour. 3. Overies : Ovaries are two oval shaped organs that lie to the upper right and left of the uterus. They develop and release eggs into the oviduct. They secrete hormone oestrogen 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, a woman s ovaries usually release one egg each month. 4. Describe the process of fertilization, development and birth in human beings. 1. The sperms enter through the vaginal passage, travel upwards and reach the oviduct where they may encounter the egg. 2. As soon as it is fertilized, the egg cell (zygote) begins to divide until it becomes a ball of cells called blastocyst. 3. The ball then implants itself in the wall of the uterus. 4. The development of the embryo takes place 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. 5. From nine months onwards, the baby is ready to take birth. It moves down. 6. During birth, the cervix gradually opens and the baby is released through the vagina. 5. Write the functions of the following organs in reproduction. *1. Vagina *2. Stigma *3. Ovaries *4. Seminal vesicles and prostate glands *5. Uterus 6. Epididymis 7. Vas deferens 8. Testis 9. Penis. 1. Vagina : (a) (b) (c) (d) Ovary Uterus Cervix Vagina Oviduct Endometrium It is a muscular tube that extends from the vaginal opening to the uterus. It provides the route for the menstrual blood to leave the body during menstruation. It is a pathway through which the sperms enter into the woman s body. It is a pathway through which a baby comes out of a woman s body during child birth. 2. Stigma : (a) It is the sticky terminal part of the style. (b) It is the receptive organ on which pollen germinates. 3. Ovaries : (a) Ovaries are two oval shaped organs which lie to the upper right and left of the uterus. (b) They develop and release eggs into the oviducts. (c) They secrete hormone estrogen which brings about changes in girls during puberty. (d) When a baby girl is born, the ovaries already contain thousands of immature eggs which remain inactive till puberty. On reaching puberty, a woman s ovaries usually release one egg each month. SCHOOL SECTION 297

17 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 4. Seminal vesicle and prostate glands : They produce ejaculatory fluid which helps the sperms in transport and provides nutrition. 5. Uterus : (a) (b) Uterus is a muscular organ. Due to strong muscles and ability to expand and contract, the uterus can accomodate a growing foetus and can push the baby during labour. 6. Epididymis : Immature sperms travel to the epididymis for development and storage. 7. Vas deferens : It is the passage through which the sperms travel towards the urethra. 8. Testis : (a) (b) Produces sperms (Male germ cells). Testes secrete the hormone testosterone which brings about changes in boys during puberty. 9. Penis : It is the portion of the reproductive system that delivers the sperms to the site of fertilization. 6. Describe the changes that occur in boys and girls from childhood to adulthood. Age From birth to age of years. 11 to age of 18 in girls and 21 in boys (years). Age 18 onwards in girls and 21 onwards in boys (years). Rate of growth Higher Rate of growth slows down and reproductive tissues begin to mature Changes in girls 1. Increase in height. 2. Increase in weight. 3. Acquire and then loose milk teeth and again acquire new ones. 1. Hair grows in armpits. 2. Genital areas become darker in colour. 3. Skin becomes oily and may develop pimples. 4. Breast size begins to increase 5. Begin to menstruate. Body is physically ready to reproduce. Changes in boys 1. Increase in height. 2. Increase in weight. 3. Acquire and then loose milk teeth and again acquire new ones. 1. Hair grows in armpits and genital areas. 2. Genital areas become darker in colour. 3. Skin becomes oily and may develop pimples. 4. Growth of thicker hair on face. 5. Voice begins to crack. Stage Childhood Puberty (Frequent emotional shifts and physical maturation of reproductive system) Adult 298 SCHOOL SECTION

18 MT EDUCARE LTD. SCIENCE & TECHNOLOGY Q.VI Answer the following questions in one sentence each : 1. Which is the basic process in reproduction? A basic process in reproduction is the creation of a DNA copy. 2. Why is reproduction necessary? Reproduction is necessary to maintain the number of individuals of a species and to prevent their extinction. 3. Give one disadvantage and one advantage of asexual reproduction. Lack of genetic variation is the disadvantage while rapid reproduction is the advantage of asexual reproduction. 4. Name some animals and plants that reproduce asexually. Animals such as Amoeba, Paramoecium etc. and plants like Spirogyra, Bryophyllum, Mushroom, Sweet potato etc. reproduce asexually. 5. Name some plants which reproduce by vegetative propagation. Plants which reproduce by vegetative propagation are Potato, Bryophyllum, Sweet potato, etc. 6. What is animal 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. 7. Name the female reproductive part of a flower. Carpel is the female reproductive part of a flower. 8. Name the male reproductive part of a flower. Stamen is the male reproductive part of a flower. 9. Which are the main reproductive organs of the male reproductive system? Testes and Penis are the main reproductive organs of the male reproductive system. 10. Name the main reproductive organs of the female reproductive system. Vagina, Uterus, Oviduct and Ovaries are the main reproductive organs of the female reproductive system 11. What is a blastocyst? As soon as fertilization takes place, the egg cell (zygote) beings to divide until it becomes a ball of cells called blastocyst. 12. Which day is observed and the World Population Day? July 11 is observed and the World Population Day. 13. Give some examples of STDs. Syphilis, Gonorrhoea, AIDS are some of the STDs. 14. Name some contraceptives. Condoms, Oral pills, Copper-T are some of the contraceptives. 15. Name the agents of cross pollination. The agents of cross pollination are wind, water or animals. 16. What is double fertilization? The second male gamete fuses with the secondary nucleus in the embryo sac to form endosperm. This is called as double fertilization. SCHOOL SECTION 299

19 SCIENCE & TECHNOLOGY MT EDUCARE LTD. ACTIVITY BASED QUESTIONS ACTIVITY : 12.1 (a) (b) Observe the above pictures and answer the following questions : Q. Which life process is shown in the pictures? The life process reproduction is shown in the pictures. Q. Is it an essential life process like nutrition, respiration or excretion? Yes. It is an essential life process like nutrition, respiration, excretion because it helps to maintain the number of individuals of a species and to prevent their extinction. ACTIVITY : 12.2 (c) Q. Observe the picture and identify the plants belonging to the same species. (d) (a) (b) (c) (d) (e) (f) Plants (b), (c), (d) belong to the same species as they look alike and have similar structures of roots, stems and leaves. ACTIVITY : 12.3 Q. Observe a permanent slide of amoeba showing binary fission under a compound microscope. 1. Amoeba reproduces by simple binary fission. 300 SCHOOL SECTION

20 \ \\ \ \ MT EDUCARE LTD. SCIENCE & TECHNOLOGY 2. In this method, the parent cell of amoeba divides into two equal or nearly equal parts and each part then grows into a new cell of amoeba. 3. The nucleus divides first followed by the division of cytoplasm by constriction. Q. Allow some aquatic vegetation to decompose in a jar of pond water. In this stagnant bacteria rich environment, paramoecium will often multiply forming a ring just below the water surface. Observe them under a microscope. 1. Paramoecium divides by transverse binary fission. 2. In the parent paramoecium cell, first the macronucleus divides. 3. A new oral groove is formed. 4. The two daughter cells separate. 5. Each daughter cell grows into a new paramoecium. ACTIVITY : 12.4 Q. Observe the following figures and classify them into transverse and longitudinal binary fission. Macronucleus dividing 1. Paramoecium reproduces by transverse binary fission. 2. Euglena reproduces by longitudinal binary fission. ACTIVITY : 12.5 Buy a small packet of dry yeast. Mix 1 gm of yeast, 2 gm of sugar and 25 ml of water in a beaker. Keep the culture in a warm place. After 2-3 hours, put a drop on a slide and observe the reproducing yeast under a compound microscope. 1. Yeast cells show budding which is a method of reproduction. 2. In this method, a small outgrowth is formed on the parent yeast cell. 3. The nucleus of the parent yeast cell divides and one daughter nucleus migrates into the bud. 4. The bud increases in size, separates and grows further. ACTIVITY : 12.6 \\\\\\\ Parent paramoecium New oral groove being formed Daughter paramoecia Binary fission in Euglena Q. Arrange the following plants and animals in ascending order with respect to their structural complexity. Plants : Bacteria, Sunflower, Fungus, Funaria, Spirogyra. Animals : Frog, Amoeba, Planaria, Human being, Hydra. Plants : Bacteria, Spirogyra, Fungus, Funaria, Sunflower. Animals : Amoeba, Hydra, Planaria, Frog, Human being. SCHOOL SECTION 301

21 SCIENCE & TECHNOLOGY MT EDUCARE LTD. ACTIVITY : 12.7 Collect slimy green filaments from a pond. Put one or two filaments on a slide. Q. Observe the slide under the microscope. 1. The filaments are of spirogyra. 2. The filament of spirogyra undergoes fragementation resulting in numerous filaments. 3. With cell enlargement and subsequent mitosis, each fragment grows and develops into a mature filament. ACTIVITY : 12.8 Q. Observe the house lizard. If the tail of a house lizard is cut, the missing part develops again from the remaining part of the tail. 1. House lizard has the capacity of regeneration. 2. Regeneration is carried out by specialised cells in lizard. 3. These cells proliferate and make large number of cells which later develop into various cell types and tissues and help in the production of the remaining part of the tail. Underground branch (a) (b) (c) ACTIVITY : 12.9 Q. Observe the figure and identify parts of the plants involved in reproduction in each picture. 1. Picture (a) shows carrot. In carrot, reproduction occurs through roots. 2. Picture (b) shows leaf of Bryophyllum. In Bryophyllum, reproduction occurs through leaves. 3. Picture (c) shows potato plant. In potato plant, reproduction occurs through stems. ACTIVITY : Take a piece of moist bread or chapati. Leave it in a moist warm place for 2-3 days. Q. Observe the fungus grown on it. 1. The fungus grown on bread is bread mould(mucor). 2. It shows thread like structures called hyphae. 3. The mould forms spores in the sporangium. 4. On maturity, the sporangium breaks open and releases spores. 5. When the spores land in a moist place, they germinate to form new mould. 302 SCHOOL SECTION

22 MT EDUCARE LTD. SCIENCE & TECHNOLOGY ACTIVITY : Complete the following table to get the difference between asexual and sexual reproduction. Characteristics Asexual reproduction Sexual reproduction No. of parents involved Type of cells involved Type of cell division Nature of offspring Rate of reproduction Modes of reproduction One Somatic cells Mitosis Identical to the parent Rapid Single cell divides to form identical daughter cells. Two Germ cells Meiosis at the time of gametogenesis and mitosis after fertilization. Different from parents Slow Two germ cells unite to form zygote which further develops into new offspring. ACTIVITY : Go to your garden and pluck a shoe flower. Bring it to your study room and open it taking care not to destroy its various parts. Carefully take out the petals, stamens, sepals and carpels. Q. Observe each one of them. 1. The petals are five in number. They are red in colour to attract insects for pollination. 2. The stamen is the male reproductive part of a flower. It is made up of two parts, anther and filament. 3. The sepals are green in colour present at the base of the flower. They are together called as calyx. It protects the flower when it is in the bud condition. 4. Carpel is the female reproductive part of the flower. It consists of three parts, the basal swollen portion called ovary, an elongated part called style and a sticky terminal portion called stigma. ACTIVITY : Try this in your garden. You have to shake the anthers of a flower onto the stigma of another flower to induce pollination between flowers of the same plant. This type of pollination is called self pollination. Horticulturists use a special kind of brush to transfer pollen between the flowers of different plants. This type of pollination is called cross pollination. SCHOOL SECTION 303

23 SCIENCE & TECHNOLOGY MT EDUCARE LTD. ACTIVITY : Soak few seeds of green gram in water. After 7-8 hours drain the excess water. Keep the seeds in a wet cloth for a day. Open a seed carefully and observe the different parts. The different parts of the seed are seed coat, cotyledon, radicle and plumule. ACTIVITY : Observe the table showing human developmental stages (Page No. 277) and answer the following questions : Q. During development which changes are common to both boys and girls? The following changes are common to both boys and girls during development : 1. During childhood : (a) Increase in height. (b) Increase in weight. (c) Acquiring and then losing milk teeth and again acquiring new ones. 2. During puberty : (a) Hair grows in armpits and genital areas. (b) Genital areas become darker in colour. (c) Skin becomes oily and may develop pimples. Q. Why has the government of India legally fixed the minimum age of marriage as 18 years for girls and 21 years for boys? The government of India has legally fixed the minimum age of marriage as 18 years for girls and 21 years for boys because at this age girls and boys become adults and their bodies are physically ready to reproduce. 304 SCHOOL SECTION

24 MT EDUCARE LTD. SCIENCE & TECHNOLOGY HOTS QUESTIONS & ANSWERS 1. The reason for having attractive colours and fragrances of the flowers is... (a) to get good price in the market. (b) to give joy to others. (c) to attract insects for the purpose of pollination. (d) to attract human beings. To attract insects for the purpose of pollination. 2. A father gave seeds to four of his sons and told them to convert seeds into plants and bring the grown plants to show him after a period of three months. None of his sons could fulfill his wish. What must be the reason? Seeds develop into seedlings under appropriate conditions. Either the seeds were damaged by boiling before they were given to the sons or the sons did not plant them under appropriate conditions as a result of which the seeds failed to develop into plants. 3. My neighbour gave birth to a twins. To our wonder, both the boys looked similar to each other. How is that so? The sperms reach oviduct and encounter the egg. The egg cell or zygote, in such case, gets split and separated into two parts during the early stage of cell division. Each part then develops into a separate individual. As these individuals are produced from a single zygote, they look similar. 4. Name those parts of the flowers which serve the same function as the following do in the animals : (a) Testes (b) Ovary (c) Eggs (d) Sperms (e) Fallopian tube. (a) Pollen grain. (b) Ovary. (c) Female germ cell or egg cell. (d) Male germ cells or gametes. ( e) Pollen tube. 5. A farmer plotted some seeds of a plant and also few branches of the same plant in soil and provided appropriate conditions for them to grow. Which method must have given the farmer flowers and fruits earlier than the other? Why? Plants produced by vegetative propagation take less time to grow and bear flowers and fruits earlier than those produced from seeds. The branches planted in the soil under favourable conditions must have borne flowers and fruits earlier than the seeds. 6. A fish lays many eggs. A leopard gives birth to 2-3 cubs at a time. Why is the difference? All animals want to make sure that their progeny should survive. Leopard looks after its young ones till they become independent. If the number is limited, it can do so. Fish do not look after their eggs or little ones. Therefore they produce hundreds of eggs and leave them to develop by themselves. Most of them die but because of the large number, a few succeed in surviving. SCHOOL SECTION 305

25 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 7. Population size is an important factor in deciding the success rate of a country. Why? There is undoubtedly a strong relation between high national fertility rate and measures of poverty. As the population density increases, decrease in per capita income and natural resources takes place. General health goes down. It creates an economical burden on the nation. Large families affect both the individual as well as community life. It gives rise to economic pressure, poor health conditions, neglecting children, poor housing, malnutrition, insufficient medical care, lack of better education ultimately affecting the success of a nation. 8. What happens to the following parts of the flower after fertilization? (a) Egg cell (b) Secondary nucleus in the embryo sac (c) Zygote (d) Ovule (e) Ovary. (a) One of the male gametes in pollen tube fuses with the egg cell to form zygote. (b) The second male gamete in the pollen tube fuses with the secondary nucleus in the embryo sac to form endosperm. (c) The zygote develops into embryo. (d) The ovule develops into a seed. ( e) The ovary develops into the fruit. 9. Write the correlated term. Amoeba : Simple binary fission :: Yeast :.... Budding. 10. Describe binary and multiple fission with the help of figures. Binary fission Parent cell Nucleus dividing Cytoplasm dividing Two daughter cells Multiple fission Cyst formation Multiple fission Release of daughter cells during favourable conditions 11. Describe reduction (meiosis) and fertilization (mitosis) and a combination of both with the help of ray diagram. Parent cell 2n 2n 2n Two daughter cells (restoring original chromosomal number) Mitosis 306 SCHOOL SECTION

26 MT EDUCARE LTD. SCIENCE & TECHNOLOGY Parent cell 2n (diploid) Meiosis Reduction division Meiosis n n Mitosis Mitosis n n n n Haploid gametes 12. A scientist created a hen which was replica of a hen in his yard. (a) What is the name of the process? (b) Give scientific reason for the process. (c) Which was the first mammal to be created in this way? (d) Give one advantage of creating human beings in this way. (e) Suggest some other name for this process. (a) Cloning. (b) 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. (c) Dolly sheep. (d) Brilliant or talented human beings could be created is the advantage. ( e) Duplicating, mirroring, replicating, imitating etc. 13. Dolly was the first cloned sheep. She had three mothers but no father. From first mother diploid cell having 2n chromosomes was selected. This cell was from udders of this sheep. From second mother egg was taken out. The haploid nucleus of the egg was removed by microsurgery. Now in this enucleated egg, diploid nucleus from udder s cell was inserted. This egg was then implanted in the uterus of a third sheep which was called the surrogate mother. Then one day Dolly was born. Later calf, monkey, cat, mice, etc. were also cloned. Questions : (a) Who can be called the real mother of Dolly? Why? (b) What is the meaning of surrogate mother? (c) Why had Dolly no father? (d) Which cell nucleus was used in cloning Dolly? (e) Which other animals have been cloned? (a) The sheep from whom the udder cell was taken can be called the real mother of Dolly. Her diploid nucleus was taken, therefore, she is the real mother of Dolly. Moreover, Dolly looked like her. (b) Surrogate mother is the one which uterus is used for raising the foetus. (c) Sperm was not used in cloning Dolly. Therefore, Dolly had no father. (d) The udder s cell nucleus was used in cloning Dolly. ( e) Sheep, calf, monkey, cat, mice, etc. are the other animals which have been cloned. 14. What is the role of testosterone, glands like prostate and seminal vesicles in the male reproductive system? (a) Testosteron is responsible for production of sperms. It is also responsible for the development of secondary sexual characteristics in boys during puberty. (b) The glands like prostate and seminal vesicles produce the ejaculatory fluid which helps in the transport of sperms and also provides nutrition. SCHOOL SECTION 307