Biology - Continuity of Life - Reproduction - PDF

Biolgy Continuity of life 14 14.1 Reproduction The life process that gives rise to a new generation from an existing generation is referred to as reproduction. Reproduction is a characteristic feature of organisms. It...

Biolgy Continuity of life 14 14.1 Reproduction The life process that gives rise to a new generation from an existing generation is referred to as reproduction. Reproduction is a characteristic feature of organisms. It is essential to maintain the continuity of life. Reproduction is of two types, ² Asexual Reproduction ² Sexual Reproduction ² Asexual reproduction Reproduction that occurs by spores and vegetative parts from a matured organism is known as asexual reproduction. ² Sexual reproduction Reproduction that occurs due to fusion of two gametes produced in sexual structures of male and feamle organisms is known as sexual reproduction. Structures that are adapted for sexual reproduction can be found in evolutionary advanced organisms. ,QSODQWVWKHVWUXFWXUHWKDWLVVSHFLDOO\IRUPHGIRUVH[XDOUHSURGXFWLRQLVÀRZHU In animals, there are male and female reproductive systems. Differences between sexual reproduction and asexual reproduction are given in the table below. Table 14.1- Differences between sexual and asexual reproduction Asexual reproduction Sexual reproduction ² Contributes only one parental ² Contribute two organisms which organism are referred to as maternal and paternal ² Gives rise to offsprings which are ² Gives rise to offsprings with more or less like maternal organism mixed characteristics of parents ² No production of gametes ² Gametes are produced 27 For free distribution  ² Meiosis does not occur ² Meiosis occurs ² New species are not produced ² New species with better adaptation to environment are produced ² A large number of offsprings can ² Increase of the number of offsprings be produced in a short period of is slow time ² Can be seen in primitive plants ² Can be seen in plants and and animals evolutionary advanced animals 14.2 Reproduction of plants Reproduction of plants or the propagation of plants occurs mainly in two ways. 1. Asexual reproduction 2. Sexual reproduction ² Asexual reproduction of plants Vegetative reproduction in plants is an asexual reproduction method. The process of generating new plants from underground or aerial parts of a mother plant is referred to as vegetative reproduction. This gives rise to daughter plants that are identical to mother plant. Vegetative reproduction is of two types. ² Natural vegetative propagation ² $UWL¿FLDOYJHWDWLYHSURSDJDWLRQ ² Natural vegetative propagation Generation of new plants naturally from underground or aerial parts of a mother plant is known as natural vegetative propagation. This occurs from various vegetative parts of a plant. Some examples are given below. ² Roots Eg :- Curry leaves, Bread fruit, Guava, Slime wood, Blue lotus ² Leaves Eg :- Begonia, Akkapana/Sathaikkaraichchan, Queen of the night (Kadupul) ² Suckers Small plants that rise horizontally from the basal part of stem under the soil are known as suckers. Eg :- Paddy, Banana, Pine apple, Chrisanthemum, Hulankeeriya, Kaladuru ² Runners Plant stems that run along the surface of soil connecting the stem to soil by adventitious roots are the runners. Eg :- Gotukola/Vallarai, Sweet potatoes, Maharaavana raevula/Ravanan meesai 28 For free distribution Bulbils 6SHFLDOUHSURGXFWLYHVWUXFWXUHIRUPHGE\DPRGL¿FDWLRQRIDYHJHWDWLYHEXGRUD ÀRZHUEXGLVNQRZQDVDEXOELO Eg :- Pine apple, Jute, Hondala Underground Stems Stems of plants which grow under the soil are known as underground stems. Vegetative propagation, storage of food and spending dormant period in adverse climatic conditions are some functions of underground stems. Underground stems are categorized into four types according to the external features. They are; (I) Rhizome - Eg :- Ginger, Turmeric, Cannas, Araththa (II) Corm - Eg :- Big rooted Taro yam(Habarala/Nersshembu), Cocoyam (Gahala/Shembu),Taro, Elephant foot yam (III) Bulb - Eg :- Red onion, Big onion, Leeks (IV) Stem Tuber - Eg :- Potato, Coleus potato Ginger Habarala Onion Potato Figure 14.1 – Types of underground stems Activity 14.1 ² Observe the plants in your home garden and identify that are propagated by vegetative parts. ² Tabulate those plants and their methods of propagation. ² $UWL¿FLDOYHJHWDWLYHSURSDJDWLRQ 3URGXFWLRQ RI SODQWV YHJHWDWLYHO\ E\ PDQ LV NQRZQ DV DUWL¿FLDO YHJHWDWLYH propagation. This can be done in several ways. ² Rooting of stem cuttings ² Layering ² Grafting ² Tissue culture 29 For free distribution ² Rooting of stem cuttings New plants can be obtained by planting stem cuttings of a mother plant. It is more appropriate to select twigs from a healthy plant that do not bear tender leaves, ÀRZHUVRUIUXLWVDWWKDWWLPH7KLVPHWKRGLVZLGHO\XVHGIRUVRPHSODQWVOLNHRose, SKRHÀRZHUV,[RUD%RXJXLQYLOOHDDQG&URWRQ Assignment 14.1 ² Find out and record various agro-chemicals in the market that are used to promote rooting of twigs. ² Prepare a list of plants that cannot be propagated by stem cuttings. ² Investigate the features of a twig that should be selected quick rooting. ² Layering Initiate rooting while it is still attached to the mother plant is known as layering. Layering is of two types. 1. Ground layering 2. Aerial layering ² Ground Layering Rooting is initiated from a branch of the plant closer to the ground level by this method. First a small cut is made on the underside of the selected twig. Then the twig is bent and burried under the soil. After few weeks, the twig will develop roots. Then the twig is separated from the mother plant and is planted. Eg :- Jasmin, Lemon ² Aerial Layering This method is used for the twigs which are high above the ground. A ring of bark of the twig is removed. a mixture of compost and coir dust is placed round that place and tied with a strip of polythene. After few weeks the twig will develop roots. Then the twig is separated from mother plant and is planted. Eg :- Pomegranate, Lemon Ground layering Aerial layering Figure 14.2 - Types of Layering 30 For free distribution Following are some advantages of layering. ² Plants that do not produce seeds can be propagated successfully. ² Several number of plants can be produced easily. Activity 14.2 Identify a plant in your home garden, which is suitable for ground layering. Follow the process of ground layering properly. After about two weeks, uproot twig and observe how roots are developed. ² Grafting (twig or bud) Connecting a twig or a bud of a plant to a plant of same or closely related species is known as grafting. Two parts of the plants grafted are known as mentioned below. ^1& Stock The rooted part of the plant is known as stock. Following are the characteristics that should be shown by a stock. ” Bearing a strong root system. ” Having a uniform growth. ” Withstanding environmental changes and diseases. ^2& Scion The twig or the bud taken from another plant and grafted to a stock is known as scion. Following are the characteristics that should be shown by a scion. ” Should be a variety of good characteristics ” Should be free from pests and diseases In the process of grafting, stock and scion are fused together by their cambium. Therefore grafting can be done only on the dicotyledonous plants, which have cambium tissues. Grafting can be done in two ways as follows. 1' Bud grafting 2' Twig grafting ² Bud grafting Selecting a plant bud as the scion and grafting it to a stock is known as bud grafting It is done as follows. ² Cutting a live bud (which is located above the leaf scar) using a grafting knife. ² Making a cut on the stock and inserting the bud into the cut. ² Wrapping the place from bottom to top using polythene strips. ² After few days, when the bud is about to emerge, remove the wrap and re-wrap keeping the bud open. ² Cutting the stem of the stock about 15 cm above, from the bud after about three weeks. 31 For free distribution  Figure 14.3 – Steps of bud grafting There are several types of bud grafting according to the shape of the cut on the stock. Eg :- T-bud H-bud V-bud ² Twig grafting In this method, a twig of a plant is taken as the scion. Procedure of grafting is given below. ² Selecting a twig of a fruit-bearing plant (It is more suitable to select a twig ZKLFKKDVQRWHQGHUOHDYHVÀRZHUVRUIUXLWV  ² Cutting the twig without damaging the cut. ² Fixing the twig to the stock, so that the cambium are contacted. ² Wrapping the place from bottom to top using polythene strips. ² Removing the wrap when the twig is observed to be growing. Figure 14.4 – Steps of twig grafting 32 For free distribution According to the shapes of the cuts of the edges of stock and scion several types of twig grafting can be done. Eg :- Arch grafting, Peg grafting Activity 14.3 Try to perform a twig grafting or a bud grafting with the assistance of your teacher. If a grafting knife is not available for this, use any other sharp knife. Following are some advantages of grafting and budding. ” Production of offsprings with characteristics of the scion ” Obtaining of disease resistant plants with strong root systems ” Propagation of plants that do not produce seeds successfully Disadvantages ” Having a short life span ” Not successful with every plant ” Reduce wood value of the trees ” Low seasonal production ² Tissue culture New offsprings, which are identical to the parental plant, can be produced by cultivating any vegetative tissue of a plant in a culture medium under controlled conditions. Offsprings thus obtained are called a clone. Genetically identical clones can be obtained by tissue culture. Generally, tissues are taken from apical buds, lateral buds or root tips for this purpose. Sucrose, mineral salts, vitamins and plant growth substances are included in the culture medium used for tissue culture. Agar is used to solidify the medium. Sterilized conditions and controlling of temperature and light should be practised for the success of tissue culture. ² Following are the principle steps followed in tissue culture ^1& Introducing the part of vegetative tissue, obtained from mother plant, into the culture medium. ^2& Allowing new roots and buds to be developed from the tissue called callus, which is grown from the vegetative tissue introduced. ^3& 6HSDUDWLQJWKHSODQWOHWVDQGSODFLQJWKHPLQWHVWWXEHVRUÀDVNVWRJURZIXUWKHU ^4& Gradually let the new plantlets to get adapted to natural conditions to be FXOWLYDWHGLQWKH¿HOG 33 For free distribution  Figure 14.5- Steps of tissue culture Following are some advantages of tissue culture. ” Production of offsprings which are identical to mother plant. ” Propagating a large number of plants at the same time. ” Production of a large number of plants in a short period of time. ” Propagation of a large number of healthy plants in a limited space. ” Can be obtained a large number of plants using a hybrid tissue with a favourable gene. Assignment 14.2 ² Prepare a list of places, where tissue culture is practising in Sri Lanka, using various sources. ² If possible, visit such a place and study the process of tissue culture. ² Name the plants, which are mostly produced by tissue culture in Sri Lanka. Advantages of vegetative propagation ” Ability of propagating plants that do not produce seeds successfully. ” Ability of having offsprings that are identical to mother plant. ” Propagation of plants that bear fruits early. ” Ability of propagating selected plants which are resistant to diseases and pests. ” Ability of generating plant varieties which withstand harsh environmental conditions. 34 For free distribution Disadvantages of vegetative propagation ” New varieties are not evolved ² Sexual reproduction of plants Seeds are produced by fusion of gametes produced in sexual structures in matured plants. These seeds can grow into new plants. Flower 7KHVWUXFWXUHWKDWEHDUVVH[XDOSDUWVRIDSODQWLVWKHÀRZHU3DUWVRIDÀRZHUDUH DUUDQJHGLQZKRUOVRQWKHUHFHSWDFOHZKLFKLVORFDWHGDWWKHWLSRIWKHÀRZHUVWDON RUSHGLFHO7KHUHDUHIRXUSULQFLSOHSDUWVRIDÀRZHUZKLFKDUHJLYHQEHORZ ” Calyx ” Corolla ” Androecium/Stamen ” Gynoecium/Pistil Stigma Androecium Anther Style Gynoecium Filament Petals Ovary Sepals receptacle )LJXUH±/RQJLWXGLQDOVHFWLRQRIDW\SLFDOÀRZHU ^1& Calyx &DO\[LVFRPSULVHGRIVHYHUDOVHSDOV7KLVLVWKHRXWHUPRVWSDUWRIDÀRZHU&DO\[ LVWKHZKRUORIVHSDOVORFDWHGRQWKHUHFHSWDFOHDWWKHWLSRIWKHÀRZHUVWDON SHGLFHO  7KLVLVJUHHQLQFRORXU7KLVSURWHFWVWKHÀRZHUSDUWVZKHQWKHÀRZHULVLQEXG stage. 35 For free distribution ^2& Corolla Corolla is comprised of a whorl of petals, and is located inner to the calyx. This LVZKLWHRUFRORXUIXO&RUROODSURWHFWVWKHLQQHUÀRZHUSDUWVLQWKHEXGVWDJHDQG DWWUDFWVLQVHFWVIRUSROOLQDWLRQZKHQWKHÀRZHUEORRPV ^3& Androecium/Stamen $QGURHFLXPLVWKHPDOHUHSURGXFWLYHVWUXFWXUHRIDÀRZHU7KLVLVFRPSULVHGRID ¿ODPHQWDQGDQDQWKHU7KHUHDUHSROOHQVDFVLQWKHDQWKHUZKLFKFRQWDLQSROOHQ When matured anther bursts and pollen release. Pollen are the male gamete cells of plants. ^4& Gynoecium/Pistil *\QRHFLXPLVWKHIHPDOHUHSURGXFWLYHVWUXFWXUHRIDÀRZHU7KLVLVFRPSULVHGRI three parts, named stigma, style and ovary. Ovules are located in the ovary. Ovules DUHWKHIHPDOHJDPHWHFHOOVRIDÀRZHU Activity 14.4 ‡ &ROOHFWVRPHÀRZHUV2EVHUYHDQGLGHQWLI\WKHLUSDUWVXVLQJDKDQGOHQV ‡ ,QYHUWDÀRZHUDQGFXWORQJLWXGLQDOO\DFURVVWKHVWDONDQGGUDZDODEHOOHG diagram. ² %LVH[XDOÀRZHUV Flowers that consist of both male and female parts are referred to as bisexual ÀRZHUV (J6KRHÀRZHU3DVVLRQIUXLW&KLOOL.DWKXUXPXUXQJD$JDWKL 8QLVH[XDOÀRZHUV Flowers that consist of either male or female parts are referred to as unisexual ÀRZHUV7KH\DUHRIWZRW\SHV ^1& 6WDPLQDWHÀRZHUV7KHÀRZHUVWKDWKDYHRQO\DQGURHFLXPRUVWDPHQ (J6WHULOHÀRZHUVRIPXPSNLQDSLFDOÀRZHUVRICorn ^2& 3LVWLODWHÀRZHUV7KHÀRZHUVWKDWKDYHRQO\J\QRHFLXPRUSLVWLO (J)UXLWEHDULQJÀRZHUVRIPXPSNLQIUXLWEHDULQJÀRZHUVRICorn ² Monoecious plants 3ODQWV WKDW EHDU ERWK VWDPLQDWH PDOH  ÀRZHUV DQG SLVWLODWH IHPDOH  ÀRZHUV DUH called monoecious plants. Eg:- Pumpkin, Corn, Coconut, Bitter gourd ² Dioecious plants :KHQ VWDPLQDWH ÀRZHUV DQG SLVWLODWH ÀRZHUV DUH ERUQ VHSDUDWHO\ RQ WZR SODQWV they are called dioecious plants. Eg :- Papaw, Vallisneria 36 For free distribution ² Pollination 7KHSURFHVVRIGHSRVLWLQJPDWXUHGSROOHQRIDÀRZHURQWKHVWLJPDRIWKHÀRZHURI the same species is known as pollination. Pollination occurs in two ways. ^1& Self-pollination ^2& Cross-pollination ^1& Self-pollination The process of depositing matured SROOHQ RI D ÀRZHU RQ WKH VWLJPD RI WKH VDPH ÀRZHU LV WHUPHG DV VHOI pollination. ^2& Cross - pollination Figure 14.7 - Self- pollination Process of depositing matured pollen RIDÀRZHURQWKHVWLJPDRIDÀRZHU RIVDPHSODQWRUDÀRZHURIDQRWKHU plant of the same species is termed as cross-pollination. Cross-pollination allows to mix characteristics of two plants. It Figure 14.8 - Cross-pollination helps to give rise to a strong new JHQHUDWLRQZLWKQHZFKDUDFWHULVWLFV7KHUHIRUHVRPHÀRZHUVDUHDGDSWHGWRDYRLG self-pollination and promote cross-pollination. Some of those adaptations are mentioned below.   +DYLQJXQLVH[XDOÀRZHUV %HDULQJRISLVWLODWHÀRZHUVDQGVWDPLQDWHÀRZHUVVHSDUDWHO\ Eg :- Coconut, Corn 2) Self – Sterility )UXLWVDUHQRWGHYHORSHGZKHQSROOHQRIDÀRZHULVGHSRVLWHGRQWKHVWLJPDRIWKH VDPHÀRZHU Eg :- Passion fruit 37 For free distribution 3) Hercogamy 7KLVLVWKHSRVLWLRQLQJRIVWDPHQVDQGVWLJPDRIDÀRZHUDWDGLVWDQFH Eg :- Orchid, Catharanthus 4) Having extrose stamens Here, the stigma is positioned straight while stamens are bent aside or stamens are positioned straight while stigma is bent aside. (J-DVPLQ/HEEHNÀRZHU 3LQQD 5) Dichogamy Here, Stamens are matured earlier than pistil (proterandry) or pistil is matured earlier than stamens (protogyny). Eg:- Corn, Tridax Passion fruit Orchid Jasmin Figure 14.9- Flowers having adaptation to avoid self pollination ² Agents of pollination )DFWRUVWKDWFRQWULEXWHWKHSROOLQDWLRQRIÀRZHUVDUHNQRZQDVDJHQWVRISROOLQDWLRQ There are three principle agents of pollination. 1.Animals 2.Wind 3.Water 1. Animals )ORZHUV SROOLQDWHG E\ DQLPDOV DUH UHIHUUHG WR DV ]RRSKLORXV ÀRZHUV$PRQJ WKH animals, insects contribute much for pollination. Flowers have adaptations to attract insects for the process of pollintation. ” Flowers having a fragrance ” Flowers being large ” &RORXUIXOÀRZHUV ” Having nectaries ” Pollen being sticky ” Stigma being sticky ” Stamens and stigma are located in such a way, that they are easily contacted with animals ” Flowers having shapes that cheat insects 38 For free distribution 6RPHH[DPSOHVIRUÀRZHUVSROOLQDWHGE\DQLPDOVDUHSDVVLRQIUXLWZLQJHGEHDQ Kathurumurunga /Agaththi Kathurumurunga /Agathi Thunbergia Figure 14.10- Flowers pollinated by animals 2. Wind Flowers pollinated by wind are referred to as aerophilous or anemophilous ÀRZHUV6XFKÀRZHUVXVXDOO\ORFDWHVHSDUDWHO\DVVWDPLQDWHDQGSLVWLODWHÀRZHUV $HURSKLORXVÀRZHUVVKRZIROORZLQJDGDSWDWLRQVIRUVXFFHVVIXOSROOLQDWLRQ Ƈ Flowers are born at the apex of the plant Ƈ Large amount of pollen are produced Ƈ Pollen are very small and light Ƈ Stigma is branched Ƈ )ORZHUVDUHLQLQÀRUHVFHQFHV ([DPSOHVIRUÀRZHUVSROOLQDWHGE\ZLQGDUH3DGG\&RUQ*UDVVDQG&RFRQXW Paddy Corn Coconut Figure 14.11-Flowers pollinated by wind 39 For free distribution 3. Water )ORZHUVSROOLQDWHGE\ZDWHUDUHUHIHUUHGWRDVK\GURSKLORXVÀRZHUV6XFKÀRZHUV XVXDOO\ORFDWHVHSDUDWHO\DVVWDPLQDWHDQGSLVWLODWHÀRZHUV:KHQPDWXUHGVWDPLQDWH ÀRZHUVHSDUDWHVIURPWKHSODQWDQGÀRDWVLQZDWHU:KLOHÀRDWLQJLWFRQWDFWVZLWK DSLVWLODWHÀRZHUDQGSROOLQDWLRQWDNHVSODFH([DPSOHIRUDÀRZHUSROOLQDWHGE\ water is Vallisneria. Figure 14.12- Flowers pollinated by water For extra knowledgee $UWL¿FLDOSROOLQDWLRQ 7KHSURFHVVRIGHSRVLWLQJWKHSROOHQRIDÀRZHUDUWL¿FLDOO\RQWKHVWLJPDRI WKHVDPHÀRZHURURQWKHVWLJPDRIDGLIIHUHQWÀRZHURIWKHVDPHVSHFLHVLV NQRZQDVDUWL¿FLDOSROOLQDWLRQ7KLVFDQEHGRQHZLWK¿QJHUVRUZLWKDEUXVK Eg:- Anthurium, Passion fruit Figure 14.13 - PHUIRUPLQJDUWL¿FLDO pollination 40 For free distribution ‡ Fertilization Figure 14.14 - Fertilization of gametes and formation of seeds and fruits of plants ‡ PROOHQDUHGHSRVLWHGRQVWLJPDRIWKHVDPHÀRZHURULQDQRWKHUÀRZHURIWKH same species. ‡ When a pollen grain is deposited on the stigma, it is stimulated by the sugar solution on the stigma and germinates. ‡ Pollen tube grows through the style towards an ovule in the ovary. ‡ The male gamete in the pollen cell fuses with the ovum in the ovary and this phenomenon is known as fertilization. 41 For free distribution ‡ Production of fruits and seeds $IWHUIHUWLOL]DWLRQ]\JRWHGHYHORSVWRIRUPDQHPEU\R7KHÀRZHUXQGHUJRHVVHYHUDO changes after fertilization. ‡ Ovary develops to form the fruit. ‡ Wall of the ovary becomes the pericarp. ‡ Fertilized ovule develops to a seed, and wall of the ovule becomes the testa or the seed coat. ‡ 1RUPDOO\VHSDOVSHWDOVVWDPHQVDQGVWLJPDDUHZRUQRXW%XWLQVRPHÀRZHUV VHSDOVEHFRPHÀHVK\DQGDUHDWWDFKHGWRWKHSHULFDUSDIWHUIHUWLOL]DWLRQ Eg :- Guava, Brinjal, Mangosteen, Rose apple Process of developing fruits without fertilization is known as parthenocarpy. $UWL¿FLDOJURZWKVXEVWDQFHVDUHXVHGWRGHYHORSIUXLWVLQWKDWPDQQHU6XFKIUXLWV are seedless. Eg :- Grapes, Orange, Apple ‡ Dispersal of fruits & seeds Spreading away of the fruits and seeds from the mother plant is referred to as GLVSHUVDO RI IUXLWV DQG VHHGV 3ODQWV IXO¿O WKHLU IROORZLQJ UHTXLUHPHQWV E\ WKDW process. ‡ Competition for essential requirements is minimized ‡ New habitats are found ‡ Diversity is increased ‡ Protection from pests and agents of diseases ‡ Methods of dispersal of fruits and seeds There are four principle methods of dispersal of fruits and seeds, as mentioned below. ‡ %\DQLPDOV ‡ %\ZDWHU ‡ %\ZLQG ‡ %\H[SORVLYHPHFKDQLVP Assignment 14.3 ‡ Identify and name the agent of dispersal of fruits that you come across. ‡ Mention two adaptations that each fruit has for its method of dispersal. 42 For free distribution ‡ 'LVSHUVDORIIUXLWVDQGVHHGVE\DQLPDOV Fruits and seeds that are dispersed by animals may have following adaptations. ‡ 7KHUHDUHVXFFXOHQWHGLEOHSDUWV Eg :- Mango , Papaw ‡ 7KHUHDUHDWWUDFWLYHFRORXUV Eg :- False fruit of Cashew, Banana ‡ 7KHUHDUHKRRNVRUKDLUVDVVLVWWREHDWWDFKHG Eg :- Nagadarana/Maramunthigai, Epala/Amanakku, Love grass (Tuththiri) ‡ 7KHUHDUHVKDSHVDQGSDWWHUQVWRFKHDWDQLPDOV Eg :- Oil castor, Red bead (Madatiya/Manjadi), Olinda/Kunrimani, Bitter gourd Mango False fruit of Cashew Bittergourd Figure 14.15- Fruits and seeds dispersed by animals ² Dispersal of fruits and seeds by wind Fruits and seeds dispersed by wind have following adaptation. ‡ +DYLQJVWUXFWXUHVOLNHWKUHDGVWRÀRDWLQDLU Eg :- Milk weed (Wara/Erukkala), Cotton, Imbul ‡ 3RVVHVVZLQJ±OLNHVWUXFWXUHVWRÀRDW Eg :- Hora/Ennei, Gammalu, Drum sticks. ‡ Fruits and seeds born at the apex of the plant. Eg :- Mahogani, Hora/Ennei ‡ Seeds being very light Eg :- Orchid ‡ Production of fruits and seeds in large numbers. Eg :- Grass, Mahogni, Milk weed (Wara/Erukkalai), Cotton 43 For free distribution  Cotton Hora Mahogani Grass Figure 14.16 - Fruits and seeds dispersed by wind ‡ 'LVSHUVDORIIUXLWVDQGVHHGVE\ZDWHU Fruits and seeds dispersed by water possess following adaptations. ‡ +DYLQJSRURXVRU¿EURXVSHULFDUSV Eg :- Coconut, Ceylon almond, Sea mango (Diya kaduru/ Kalliththi) ‡ 3RVVHVVSHULFDUSVWKDWDUHVXLWIRUÀRDWDWLRQ Eg :- Lotus ‡ +DYLQJDLU¿OOHGVKHOOV Eg :- Water lily Coconut Ceylon almond Lotus Figure 14.17 - Fruits and seeds dispersed by water ‡ Dispersal of fruits and seeds by explosive mechanism Pericarp of the fruit of some plants explodes and the seeds are dispersed far away. Touch, moisture or dry weather conditions can cause explosion. EJ5XEEHU/DGLHV¿QJHUV.RRGDOX5HGEHDG 0DGDWL\D Manjadi) 44 For free distribution  Rubber Madatiya/Manjadi /DGLHV¿QJHUV Figure 14.18- Fruits and seeds dispersed by explosive mechanism Germination of seeds Activation of the embryo in a seed and its development to form a seedling is known as seed germination. Following factors are essential for seed germination. 1) Viability of seed 2) Air (Oxygen) 3) Water or moisture 4) Optimum temperature When a seed is germinating, water activates the enzymes in the cotyledons, and stored complex food is digested to simple nutrients. The nutrients help to develop the radical and the plumule. Dormancy of seeds Sometimes seeds do not germinate, though the essential factors for germination DUHIXO¿OOHG7KLVFRQGLWLRQLVNQRZQDVGRUPDQF\ Seeds show dormancy as an adaptation for adverse environmental conditions. Following factors affect the dormancy of seeds. 1) Embryo being not matured 2) Impermeability of testa for water or oxygen Various methods are practised to remove the dormancy of seeds before germinating them. Some of them are mentioned below. 1) Storing seeds for some period of time 2) Burning the villi on the seed coat or testa of Teak seeds 3) Removing the seed coat of Orange seeds 4) Keeping the seeds of Lead tree (Ipil Ipil) in hot water 5) Gently cracking the seed coat of (Nelli/Nellikai) seeds 45 For free distribution  Activity 14.5 Design a suitable activity to investigate the external factors for seed germination. For extra knowledge Seed germination occurs mainly in two ways. 1) Hypogeal germination 2) Epigeal germination Hypogeal germination Here, when the seed germinates, plumule emerges up from the soil, but cotyledon does not emerge up from the soil. Cotyledon and endosperm supply food for the seedling at its early stage. But colyledon does not produce food by photosynthesis. Most of the monocotyledonous plants show hypogeal germination. Figure 14.19- Hypogeal germination Eg :- Coconut, Corn Epigeal germination Here, when the seed germinates, plumule emerges up from the soil, cotyledons also emerge up from the soil. Moreover, cotyledons produce food by photosynthesis in addition to supply stored food for the seedling Figure 14.20- Epigeal germination in its early stage. Most dicotyledonous plants show epigeal germinaton Eg :- Bean, Tamarind 46 For free distribution 14.3 Reproduction of man ² Puberty (Adolescence) Sexual matuarity or attaining adolescence is referred to as puberty. Secondary sexual characteristcs which differentiate males and females begin to appear from the puberty ² Secondary sexual characters Characters that appear in male and female from puberty are known as secondary sexual characters. ² Secondary sexual characters of males These changes start to appear between the age of 13-16 years. The action of Testosterone hormone is responsible for this. ‡ Pubertal hair grows on face , chest, under arm pits and in genital areas. ‡ Shoulders grow wide. ‡ Larynx enlarges and voice becomes deep. ‡ Bones and muscles grow faster and the growth of body is accelerated. ‡ Testes start to produce sperms. ‡ Genitals start to grow larger. ² Secondary sexual characters of female These changes start to appear between the age of 10-14 years. The action of Oestogen and Progesterone are responsible for this. ‡ Pabertal hair graws on arm-pits and on genital area. ‡ Pubic region widens. ‡ Mammary glands start to grow. ‡ Fat deposits in the subcuticle and body becomes fat. ‡ Bones and muscles grow fast and the growth of body is accelerated. ‡ Releasing of ova from ovaries (menstrual cycle) starts. ² Process of reproduction Reproductive cells or gametes should be produced for the process of reproduction. This occurs in reproductive systems. ² Male reproductive system Main parts of the male reproductive system Ŷ Testes / Testicles A pair of testes which are oval in shape are located in a sac called scrotum or testes sac. Sperms are produced in these structures. A testes is comprised of about 250 testical lobules. There are about 1000 convoluted tubles which are called seminiferous tubules in them. Sperm mother cells are produced in seminferous tubules. 47 For free distribution Ŷ Pair of epididymis All the vas efferenses in a testes emerge out of the testes and are opened to a single convoluted tube called epididymis. Sperms are temporarily stored in it. Ŷ Pair of vas deferenses The tube that brings sperms from epididymis is called vas deferens. The other end of it is joined to the tube coming from seminal vesicles. Ŷ Pair of seminal vesicles, prostrate gland and pair of Cowper's glands These are the glands associated with male reproductive system. These glands secrete DZKLWHÀXLG7KLVVHFUHWLRQLVUHOHDVHGLQWRWKHXUHWKUD7KLVÀXLGLVLPSURWDQWWR SURYLGHQXWULWLRQWRWKHVSHUPVDQGWKHLUWUDQVSRUWDWLRQ6SHUPVDQGWKLVZKLWHÀXLG LVFROOHFWLYHO\NQRZQDVVHPLQDOÀXLGRUVHPHQ Ŷ Penis This is the muscular organ which is important in ejection of semen into female reproductive system. This becomes rigid when blood supply is increased. Urethra opens out through penis. The tip of the penis is called glans penis and it is covered by prepuce or foreskin. Urinary bladder Seminal Vesicle Prostrate gland Urethra Vas deferens Penis Epididymis Testes Scrotum Figure 14.21 - Male reproductive system Functions of male reproductive system Production of sperms begins when a male attains his puberty. Sperms are formed from the sperm mother cells which are in the seminiferous tubules. When sperms are temporarily stored in epididymis. During the copulation, sperms pass through 48 For free distribution vas deferens and are collected to the urethra. At the same time, the secretion of the prostrate gland and Cowper's glands are also mixed with sperms. The secretion PL[HGZLWKVSHUPVLVFDOOHGVHPHQDOÀXLGRUVHPHQ7KHUHDUHPLOOLRQVRIVSHUPV in one milliliter (1 ml) of semen. Sperm cells Epidiymis Cross section of a Seminiferous Sertoli cells seminiferous tubules tubules Figure 14.22 - Structure of seminiferous tubule Process of generating sperms is very sensitive Head to temperature. The temperature in the testes should be lower than body temperature for Neck the production of healthy sperms. That is the Body reason for testes to be in a sac called scrotum out side the body. Matured sperm is motile and consists of three parts named head, body and tail. ² Functions of male reproductive system Ŷ Production of sperm cells Ŷ Ejection of sperms into female reproductive system Tail Ŷ Production of Testosterone Figure 14.23 - Structure of a sperm under electron microscope 49 For free distribution ² Female reproductive system Main parts of the female reproductive system ‡ Ovary There is a pair of ovaries close to the lateral walls of pelvic area in the abdominal cavity. In a cross section of an ovary, there are two zones known as cortex and medulla. Ova are produced in follicles. Each ovary contains primary follicles and YDULRXVVWDJHVRISURGXFWLRQRIRYDVXFKDVJUDD¿FDQIROOLFOHVFRUSXVOXWHXPDQG corpus albicans. Production of ova starts at the birth of a female. ‡ Fallopian tube Ovum that comes out of the ovary enters into long musculer tube called fallopian WXEH7KHHQGRIWKLVWXEHZKLFKLVFORVHWRWKHRYDU\LVIXQQHOOLNHDQGKDV¿QJHU OLNHSURMHFWLRQVFDOOHG¿PEULD7KHVHDUHLPSRUWDQWLQWUDQVIHUULQJWKHRYXPLQWR fallopian tube. ‡ Uterus This is a hollow structure positioned in pelvic area. There are three zones in uterus named as fundus, body and cervix. Two follopian tubes are connected to the zone called fundus. The other end of uterus is cervix. ‡ Vagina or Endocervical canal Vagina starts from the cervix and opens to the exterior from the opening called vulva. Fallopian tube Ovary Uterus Bladder Vagina Urethra Vulva Figure 14.24 - Location of female reproductive system 50 For free distribution  Fallopian tube Fimbria Lumen of uterus Ovary Wall of uterus Uterus Cervix Vagina Figure 14.25 - Female reproductive system Functions of female reproductive system Production of ova in females initiate since foetal stage. At birth each ovary contains 200 000 - 400 000 primary follicles. Nearing puberty, one of the primary follicles GHYHORSV WR IRUP D PXOWLFHOOXODU VWUXFWXUH FDOOHG JUDD¿DQ IROOLFOH ,W UHDFKHV WKH peripheral area of the ovary. :KHQ PDWXUHG JUDD¿DQ IROOLFOH EXUVWV WR UHOHDVH WKH RYXP ZKLFK LV GLUHFWHG WRZDUGVWKHIDOORSLDQWXEHE\¿PEULD7KHQWKHRYXPSDVVHVWKURXJKWKHIDOORSLDQ tube towards the uterus. *UDD¿DQIROOLFOH Primary follicle Corpus albicans Corpus luteum Developing Corpus luteum Released ovum Figure 14.26 - Cross section of an ovary with various stages of ovum 51 For free distribution ² Activities of female reproductive system ² Developing of ova which are the female reproductive cells ² Facilitate the developing of foetus ² Production of hormones Oestrogen and Progesterone ² Menstrual cycle The cyclic process associated with the reproductive systems of sexually matured females as known as menstrual cycle. For one menstrual cycle, it takes appoximately 28 days. Here the pair of ovaries releases the egg cells or ova alternatively. The whole process of menstrual cycle takes place associated with two locations. 1. Changes that take place in the ovary 2. Changes that take place in the uterus 1. Changes that take place in the ovary Development and release of ova, which are the female reproductive cells, are carried out by ovary. Changes that occur in the ovary can be divided into two stages. 1. Follicular phase 2. Luteal phase Follicular Phase 7KLVLVWKHLQLWLDOSKDVH8QGHUWKHLQÀXHQFHRIFollicle Stimulating Hormone (FSH), VHFUHWHGE\SLWXLWDU\DSULPDU\IROOLFOHLQWKHRYDU\GHYHORSVWRIRUPDJUDD¿DQ follicle, which is ready to release an ovum. This takes about 14 days. During this phase, ovary secrets Oestrogen. Luteal Phase 7KLVLVWKH¿QDOSKDVH:KHQJUDD¿DQIROOLFOHLVPDWXUHGLWEXUVWVDQGWKHRYXP LQVLGHLWLVUHOHDVHGIURPWKHRYDU\LQWRWKHIDOORSLDQWXEHXQGHUWKHLQÀXHQFHRI Lutenising Hormone (LH), secreted by pituitary gland. If fertilization does not occur, when the ovum is passing forward through fallopian tube, the remaining part RIJUDD¿DQIROLFOHFKDQJHVWRIRUPFRUSXVOXWHXPDQG¿QDOO\WRFRUSXVDOELFDQVDQG fades off. This whole process occurs during luteal phase and it takes about 14 days, During this phase ovary secrets progesterone. 2. Changes that take place in uterus If an ovum is feritlized, the embryo develops in the uterus. Changes that occur in uterus are divided into three phases. 52 For free distribution 1. Menstrual phase 2. Proliferation phase 3. Secretory phase Menstruation phase Day 0 Day 14 Day 28 Follicuton phase Luteal phase Lutenising Hormone (LH) Follicle Stimulating Hormone (FSH) Primary *UDD¿DQ follicle follicle Ovulation Corpus luteum Corpus albicans Figure 14.27 - Changes in the ovary during menstrual cycle 4 days 14 days 28 days Menstrual Proliferation Secretory phase phase phase Oestrogen Progesterone Figure 14.28 - Changes that take place in uterus 53 For free distribution Menstrual phase This is the initial phase. If fertilization does not take place, level of Progesterone decreases. This causes the degradation of the wall of uterus and it is expelled out IURPWKHERG\WKURXJKYDJLQDZLWKEORRG7KLVLVUHIHUUHGWRDVPHQVWUXDOÀRZDQG occurs for about four days. Proliferation phase This is the second phase. Degraded wall of uterus starts to re-build because of the LQÀXHQFHRIOestrogen. New cell layer and blood capillaries grow on the inner wall of the uterus. It takes about 10 days for this. Secretory phase 7KLVLVWKH¿QDOSKDVH8WHULQHZDOOWKLFNQHVDQGEORRGVXSSO\LVDOVRLQFUHDVHG Glands on the uterine wall are activated and it becomes secretory. This happens EHFDXVHRIWKHLQÀXHQFHRIKRUPRQHProgesterone. It takes about 14 days for this. Body temperature also increases slightly during this period. 370c Day 4 Day 14 Day 28 360c Figure 14.29 - Changes of body temperature during menstrual cycle ² Fertilization and Implantation 'XULQJ WKH FRSXODWLRQ VHPLQDO ÀXLG VHPHQ  LV UHOHDVHG LQWR WKH YDJLQD 6SHUP FHOOVLQVHPHQVZLPPLQJLQWKHÀXLGSDVVWKURXJKXWHUXVWRZDUGVWKHXSSHUSDUW of fallopian tube. Then one of the sperms fuses with the ovum passing down toward the uterus. Here nucleic matter of the ovum and the sperm fuses together. This phenomenon is called fertilization. Figure 14.30 - Fertilization of a sperm and an ovum 54 For free distribution Fertilized ovum is referred to as zygote. While it is rolling towards uterus, it divides to increase the number of cells. Then it is known as morula. Morula distintegrates the tissues of uterine wall, sinks and deposits in the wall. This is known as implantation or interplantation. Day 3 Day 2 (4 cells) Day 4 (2 cells) Day 5 (16 cells) (Morula) Day 1 (zygote) Fertilization Day 7 (Blastula) Figure 14.31- From fertilization to implantation ² Development of foetus After implantation, foetal development occurs with the division of cells. In about six weeks, protective membrances called embryonic membrances develop. There is a ÀXLGLQWKHP)RHWXVLVVXQNLQWKLVÀXLG7KHSODFHWKDWWKHHPEUR\RQLFPHPEUDQHV connect with uterine wall is known as placenta. Material exchange from mother to foetus and foetus to mother occurs through umbilical cord. Umbilical cord is the tissue in placental mammals, through which nutrients and oxygen are exchanged between the mother and the foetus. Though nutrients, oxygen and agents of diseases (some disease causing microoganisms like virus) transfer from mother to foetus, Blood exchange does not occur through umbilical cord. Removal of excretory products and carbondixoide also occurs through umbilical cord. Principle changes in foetal development with time are given in the table below. 55 For free distribution  Table : 14.2- Principle changes of foetus with time Time period Principle changes of foetus with time (Months) 03 Ŷ Takes human form Ŷ Head of foetus is large, with respect to other body parts Ŷ Development of nails starts Ŷ Male and female sex organs are developed 04 Ŷ Development of skeleton starts Ŷ Hair begins to grow 05 Ŷ Foetus is completely covered with hair Ŷ 0RWKHUFDQIHHOWKHPRYHPHQWVRIIRHWXVIRUWKH¿UVW time Ŷ Heart beat of foetus can observe from out side (average rate of heart beat is 120-140 per minute) 06 Ŷ Eyebrows and eyelashes have developed 07 Ŷ Eyelids open Ŷ Skin is in wrinkled nature 08 Ŷ Subcutaneous fat begins to deposit Ŷ Weight of foetus is about 2 1/2 kg 09 Ŷ 1DLOVRI¿QJHUVKDYHFRPSOHWHO\JURZQ Ŷ Testes are positioned in scrotum Ŷ Body shows a full grown nature Ŷ Weight of foetus is about 2 1/2 -3- 1/2 kg 56 For free distribution  Placenta Umbilical Cord Foetus Uterine wall Embryonic membranes Cervix Bladder Vagina Anus Figure 14.32 - Development of foetus in uterus ² Child birth or Parturition When it is close to child birth, head of the foetus in uterus, turns towards vagina. After completion of development for about 280 days, foetus is pushed outside through vagina by the contraction of muscles of uterus. This process is known as child birth or parturition. Further contraction of uterine wall, disconnects the placenta and associated tissues. After parturition the umbilical cord that connected placenta and foetus is cut and tied. Assignment 14.4 ‡ List out the materials that pass from mother to foetus through umbilical cord. ‡ List out the materials that pass from foetus to mother through placenta. Hormonal co-ordination Human reproduction process is completely regulated by hormones. This can be seen in both males and females. Here several hormones such as FSH, LH, Testosterone, Oestrogen, Progesterone, secreted by several endocrine glands are important. 57 For free distribution 14.4 Sexually transmitted diseases Diseases transmit from one person to another, mainly because of a sexual contact and sexual secretions are known as sexually transmitted diseases.These are transmitted due to blood transmission too. Symptoms of such diseases can usually be found on VH[RUJDQV$ERXWRIVXFKGLVHDVHVDUHLGHQWL¿HGVRIDU6RPHRIWKHPZKLFKDUH common , are discussed below. (1) Gonorrhoea This is transmitted by the bacterium called Neisseria gonorrhoeae. Secretions from sex organs, pain, blockage of fallopian tube are some of its symptoms. This disease can be cured and if not treated it will result in blindness and lameness. (2) Syphilis This is transmitted by the bacterium called Treponema pallidum. After about three months of infection, painless blisters appear on sex organs.They are automatically cured. After about six months, fever and pain in throat appears. If treated in early stages this disease can be cured. Pathogens can exist in blood for a long time and can spread to other organs also. (3) Herpes This is transmitted by a virus called Herpes simplex. Highly painful blisters on sex organs are the symptoms. This inactivates the nervous system and is deep-rooted. Though it is not fatal, it has no permanant treatment.  $FTXLUHG,PPXQR'H¿FLHQF\6\QGURPH $,'6  This is transmitted by +XPDQ ,PPXQRGH¿FLHQF\ 9LUXV +,9  Symptoms may appear in about 2- 15 years after infection. This may be fatal and cannot be cured. AIDS is tranmitted by sexual secretions and blood. To keep off from this disease, risk activities and vectors should be avoided. It is possible to avoid sexually transmitted diseases by being responsible during sexual activities. 58 For free distribution  Summary ² Reproduction of organisms is of two types. They are sexual reproduction and asexual reproduction. ² Sexual reproduction is the reproduction, associated with sexual structures and sexual processes. ² The principle method of asexual reproduction in plants is the vegetative propagation. There the plants reproduce by aerial or underground parts. ² Natural vegetative propagation of plants occur by roots, leaves, suckers, runners, bulbils and underground stems ² $UWL¿FLDO YHJHWDWLYH SURSDJDWLRQ RI SODQWV LV FDUULHG RXW E\ PHWKRGV OLNH stem cuttings, layering, grafting and tissue culture ² Flower, which is the sexual structure of plants, consists of calyx, corolla, androecium and gynoecium. ² $QLPDOV ZLQG DQG ZDWHU FRQWULEXWH IRU SROOLQDWLRQ RI ÀRZHUV )ORZHUV have special adaptations for pollination by each agent. ² $IWHUSROOLQDWLRQÀRZHUVSURGXFHIUXLWVDQGVHHGV$QLPDOVZLQGZDWHU and explosive mechanism contribute for dispersal of fruits and seeds. ² Sexual maturity of man is referred to as puberty. Secondary sexual characters appear at this stage. ² Male reproductive system produces sperms and female reproductive system produces ova for sexual reproduction. ² Embryo is developed by the zygote which results in the process of fertilization of a sperm and an ovum. ² The cyclic process that is associated with the reproductive system of sexually matured females is called menstrual cycle. ² Gonorrhoea, Syphilis, Herpes and AIDS are some of the diseases that are sexually trasmitted. 59 For free distribution  Exercises (1) Mention the differences between sexual reproduction and asexual reproduction. Sexual Reproduction Asexual Reproduction (2) State the structures associated with vegetative propagation of plants with examples. (3) Mention some practical problems that you may face in grafting plants. (4) "Vegetative propagation is more suitable than sexual reproduction for a better yield in plants". Clarify this idea.  1DPHWKHPDLQSDUWVRIDÀRZHUDQGZULWHGRZQWKHLUIXQFWLRQV Plant part Functions................................................................................................................................................................................................................................................................................................................................................................................ (6) What are the advantages of cross-pollination when compared with self- pollination? ^7& Write down the problems that may arise if dispersal of fruits and seeds does not occur. ^8& Enlist the changes in males and females during puberty. Changes occur in males Changes occur in females 60 For free distribution (9) Given below is a diagram of a female reproductive system. Name the parts indicated (10) Given below is a diagram of a male reproductive system. Name the parts indicated. 61 For free distribution  $OLQHGLDJUDPRIDW\SLFDOÀRZHULVJLYHQEHORZ1DPHWKHSDUWVLQGLFDWHG A H J B I G C F D E Technical terms Reproduction - m%ckkh - CÚ¨ö£¸UP® Asexual reproduction - w,sx.sl m%ckkh - %‘=2•mͨ %¯}Ëx72ƒ Sexual reproduction - ,sx.sl m%ckkh - %‘=2mͨ %¯}Ëx72ƒ Vegetative propagation - j¾Ol m%pdrKh - xX„mͨ CÚ¨ö£¸UP® Tissue culture - mgl frdamKh - %͜„–¢}{ Pollination - mrd.Kh - P¸UPmhÀ Fertilization - ixfiapkh - 272OJ• Seed - îc iqma;;dj - —\Z72£´ dormancy '¨=5]͐ Zygote - hqla;dKqj - ~P® Foetus - N%EKh - mXi™ 62 For free distribution