Chapter-8-How do Organism reproduce ?
Reproduction
Differentiation is a qualitative distinction between the cells, tissues, organs of an organism ,e.g,, xylem cells and phloem cells in plants, muscle cells, nerve cells and blood cells in human beings and higher animals.
Growth:-Growth concerns the permanent and irreversible increase in shape, size and body weight of an organism.It refers to increase in cell size and number or total mass.
Growth is manifestation of a greater construction work at the expense of nutrients. Nutrients are the chemical and that are processed by the organism through two different metabolic routes. In the first route, called catabolism, nutrients are decomposed so that the energy contained in them become available for the other activities. In the second route, called anabolism, they are utilized for the construction of large molecules such as protein, lipids, polysaccharides, and nucleic acid ( all of which go into the building of body components or of protoplasm). Which the construction and the breakdown are in equilibrium, there occurs no growth of the organism. When the construction process (anabolism) outpaces the breakdown process (catabolism), the organism will grow.
Table 1 Comparison of growth between plants and animals
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Plants |
Animals |
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1) A plant continue to grow throughout its life. 2) Only meristem-containing growth regions, such as tips of roots and stems,grow. 3) Growth is due to meristematic tissue. |
1) In animals, the growth is regulated in time. 2) Growth is uniform throughout the animal body. 3) No maristematic tissue is present. |
Diffused growth:- In unicellular organism such as Amoeba, Paramecium, Euglena, algas, fungi and bacteria, growth means an increase in the synthesis of material, proliferation, In the number of cellular organelles and ultimately an expansion in cell size. Cell division is responsible for in increase in their population. This pattern of growth is called diffused growth.
Multiplicative growth:- In higher species( multicellular organism) a zygote is first formed by the fusion of the male and female gametes which are product of meiosis. The intial growth start from a zygote. Zygote divides by the repeated mitotic cell division of cleavage and the number of cells increase but the cell size get smaller. Hence at the end of the cleavage the total mass and size of the organism remains the same, even though cell multiplication, morphogenesis (i.e. ,, mode of development of shape of cells and organs) and differentiation may have occurred.This type of growth is called multiplicative growth.
Localised Growth:- In the higher plants , gowth is confined to certain fixed regions such as meristems of root nad shoot tips so it is called localized growth .
Phases of growth
Cell Division (or Formative pahase) :- The cell frist absorbs water and food and matures. This cell divides and redivides by mitosis to form new cells.
Cell elongation (or Elongation phase). :-In most cases, the cell division is followed by cell elongation and enlargement, which include following two processes:
i. absorption of water which causes stretching of the cell wall due to increased turgor pressure.
ii. Deposition of cell wall material on these stretched walls. This phase also results in appearance of large vacuoles.
Reproduction
Reproduction:- Reproduction is one of the most important and fundamental properties of living organism by which every kind of living organism multiplies to form new individual of its own kind. In this process one generation of living organism gives rise to next generation. This process is not essential to the life of nay individual but is function essential for the life of the species.
In living organism , reproduction is carried out by two methods: asexual and sexual.
Asexual Reproduction:- The type of reproduction involves a single individual which produces new offspring genetically similar to the parents. It does not involve production or fusion of sex cell (gametes) by two sexes , so is called asexual reproduction. Asexual reproduction is performed by involvement of mitosis. Following types of asexual reproduction occur in living organism.
1. Fission:- It is very common reproductive mechanism and occurs in bacteria, blue-green algae and protozoans [e.g. Amobea, Euglena and Paramecium]. When the individual cell is fully-mature, it divides into two.This is called Fission.
2. Budding:- This is an asexual method of reproduction. In the unicellular fungus-yeast, a bulb-like projection is formed on the one-side of the cell, called bud. The nucleus divides and one of the daughter nuclei passes into the bud. The bud is ultimately detached from the parent cell ,goes to full size and becomes a new individual. This process is called budding and it result in the formation of two cells of unequal size.
Some organisms like sponges and corals, the buds remain attached to the parent organism permanently. These buds then grow and produce buds of their own .In this way a colony of sponges and corals is formed.
Spores: Spores are the microscopic ‘asexual reproductive bodies’ which are covered by a hard protective coat. This coat enables them to survive under unfavorable conditions like the lack of food, lack of water and extreme temperature. But when the conditions are favourable (food and water is available, and temperature is suitable), then the spores grow to produce new plants. Thus, spores are a kind seeds of plants.
3. Fragmentation :- Some of the multicellular organism having relatively simple-body organisation can break up easily into smaller pieces (or fragments) on maturing. These pieces or fragments can then grow and form new organism complete in all respects.The breaking up of the body of a simple multicellular organism into two (or more) pieces on maturing, each of which subsequently grows to form a complete new organism, is called fragmentation. Some organism such as Spirogyra break up into two or more pieces or fragment upon masturbation. These fragments grow into new individuals. Some worms, such as, flatworms (Turbellaria, and ribbon-worms (Nemertinea), also reproduce asexually by fragmentation.
4. Spore formation:- Spore formation is the asexual method of reproduction. The reproduction by spore formation takes place to place. In spore formation, the parent plant produces hundreds of microscopic reproductive units called ‘spores’. When the spore case of the plant bursts, then the spores spread into air. When these air-borne spore land on food (or soil) under favourable conditions (like damp and warm conditions), they germinate and produce new plants. Some bacteria and lower plants, such as, fungi (Rhizopus, Mucor), moss fern from spores, each of which is a resting stage in which is the cell resting stage in which the cell is protected by a thick wall that protects the cell from unfavorable conditions, such as, high temperatures, drought high acidity and alkalinity. On return of favourable condition, the thick wall breaks open and the organism reproduces and grows in the usual fashion. Spores of bacteria, such as Clostridium and Bacillus are called endospores.
Note:- The main difference between fission and fragmentation is that in fission, a unicellular organism breaks up to form two (or more) daughter organisms whereas in fragmentation, a multicellular organism breaks up to form tow (or more) daughter organisms.
5. Regeneration:- In some organism (plants as well as animals) small cut parts of their body can grow (or regenerate) to form whole new organism complete in all respects. The process of getting back a full organism from its body parts is called regeneration. The simple animal like Hydra and Planaria show regeneration. These means that in these organism, whole new organism can be reproduced from their cut body parts. The regeneration of an organism from its cut body part occurs by the process of growth and development. This happens as follows : The cells of cut body part of the organism divide rapidly to make a ‘ball of cells’. The cells present in the ‘ball of cells’ move to their proper places within the ball where the ball where they have to form various organs and various parts of organism. The cells then change their shapes (or become specialized) to form different types of tissues. These different tissues form various organs and body parts of the organism. In this way a complete organism is regenerated. Why the complex multicellular organism (like mammals) cannot give rise to complete individuals from their cut body parts through the process of regeneration.
6. Vegetative propagation:- This is a asexual method of reproduction. The reproduction by vegetative propagation occurs only in plants. In vegetative propagation, new plants are obtained from the part of old plants (like stem, roots and leaves), without the help of nay reproductive organs. Vegetative propagation usually involves the growth and development of one (or more) buds present on the old part of the plant. When provided suitable conditions (like moisture warmth etc.),these buds grow to form new plants. vegetative propagation is also called vegetative reproduction.Here is an example of the vegetative propagation (or vegetative reproduction) in grass. The green grass grows in the fields after rains from the dry, old stems of grass plants present in their fields, by the method of vegetative propagation.
Buds are present on the stems as well as the leaves of the Bryophyllum plant which can develop into new plants. So Bryophyllum plants can be using either a piece of its stem or its leaves. Money plant can also be grown by vegetative propagation by using a piece of its stem. A tuber is the thicknied underground stem of a plnat which is swollen with stored food. The tuber has a number of ‘buds’ 9called ‘eyes’). Each bud (or eye) of the tuber grows into a new plant when the old tuber is planted in the soil in the next growing season. The example of tuber is potato. Each potato plant produce more than one tuber and each tuber has more than one bud (which produce more than one new plant. Due to this ,the vegetative propagation method of producing potato plants by tubers is much faster than the production of potato plants from seeds. Examples of plants produced by vegetative propagation are : Bryophyllum, Guava, Potato, Onion, Banana, Garlic, Water hyacinth, Tulip, Mint, Strawberry and Lily.
When a portion of plant body detached and develops into an independent individual, we say the vegetative propagation or reproduction has occurred. There are two types of vegetative propagation:-
1) Vegetative propagation by roots:- Some adventitious roots, e.g. sweet potato, Dahlia, etc., become thick,swollen and tuberous due to storage of food and also bear adventitious buds on them
2) Vegetative propagation by stems:- The stems are very efficient means of vegetative propagation
a) Subaerial stems:- Subaerial stems which develop
as lateral branches from the mother plant and give rise to new individual plants. Examples of such means of vegetative propagation by Subaerial stems are runners( e.g.,. grass), suckers (e.g., mint or pudina, and Chrysanthemum, stolon(Jasmine),offset (e.g. Pisita and water hyacinth or Eichhornia).
b) Underground stem modification:- In certain plants underground stems become modified for storage of food during active phase of vegetative growth.Such modified stems remain dormant indefoliate condition whereas the parent annual plant shrivels up and dies. Under favourable conditions such stem modification give off aerial shoots. Examples :- rhizome (e.g., Canna, banana, ginger and turmeric), tuber (e.g.,Potato), bulb (e.g., Onion, garlic and lilies), and corm (e.g., Colocasia or kachalu, saffron and Gladiolus)
3) Artifical propagation of plants:- The fleshy or succulent leaves of Bryophyllum bear adventitious buds in their notches located on the margins. When the leaf falls on the moist soil, these buds develop into small plants resulting in vegetative propagation. There are 3 method of Artifical propagation of plants
1. Cutting :- It is a most common method of vegetative reproduction . In this method a piece of suitable length of stem is taken from the mother plant.The stem piece (cutting) necessarily has few nodes and internodes. This cutting placed in moist-soil. After sometime roots emerge from nodes of the basal portion of cutting and the bud gives rise to shoot. The plant of rose, sugarcane , pine apple, banana, orange, citrus, Bougainvillea.
2. Layering:- Layering is the development of roots on a stem while it is still attached to parent plant.the stem or branch that develops adventitious roots while still attached to the parents plant is called layer.It is practised in plant such as Magnolia, Rhododendron, Jasminum, rose etc.
(ii) Grafting:- This is a method in which the cut stem of two different plants (one with roots and other without roots) are joined together in such a way that the two stems join and grow as a single plant. In other words you can that in this process are detached part of one plant(i.e., a twig or bud) is inserted into the stem or root system of another plant.
The new plant have the characteristics of the both of the original plants.
(i) The cut stem of a plant (or tree) having roots( and fixed in soil) is called stock . Stock is the lower part of a plnat (or tree) having the roots.
(ii) The cut stem of another plant (without roots) is called scion.Scion is the upper part of a plant which may have leaves on it (but no roots).
In carrying out grafting, two plants (or trees) are chosen which are to be used as scion and stock. The scion is placed over the stock. The cut surface of the scion and stock are fitted together and bound tightly with a piece of cloth and covered properly with polythene sheet ( so as to prevent har ful infection by bacteria or fungus, and loss of water and plant sap from the cut and joined ends of stock and scion) While joining the scion to the stock; care should be taken to make sure that the cambium layer of scion is in contact with the cambium layer of stock (because the cambium layer in the stem is responsible for growth). The cut soon heals and the stock and scion of two plants grow together and become one plant.
Grafting is used to breed fruits tress and flowering bushes. Apple, peach, apricot and pear trees are often grafted. We will now now describe some of the advantage of the grafting method of artificial propagation
1. Grafting enables us to combine the most desirable characteristics of two plants (scion and stock) in its flowers and fruits.
2. By grafting method, a very young scion (shoot part of a plant) can be made to flower and produces fruits quite fast when it is grafted to the stock (stem having roots) of a nature plant.
3. It enables us to obtain flower and fruits having different desired characteristics by grafting scions from different varieties of plants on the same stock. Many varieties of mango have been produced by grafting method.
4. Grafting can be used to produce by varieties of seedess fruits.
Such plants which are produced by by artifical vegetative propagation methods are : Banana, Pineapple, Orange, Grape,Rose etc.
Advantages of artifical vegetative propagation
1. The new plant produced by artificial vegetative propagation will be exactly like the parent plant. Any desirable feature of the parent plant will be replicated in new plants.
2. The fruit trees grown from seeds may take many years before they start to bear fruit. But the fruit trees grown from cuttings or by grafting start to bear fruits much earlier (only after a few growing seasons).
3. The plants grown by vegetative propagation usually need less attention in their early stage than the palnts grown from seeds.
4. =/span>Many plants can be gown from just one parent plant by artificial propagation.
5. We can also get seedless plants by artificial propagation.
Bud grafting:- In this process of bud grating ,a bud is taken along with some portion of bark from a plant and is used as scion. The bud is fixed in a ‘T’ shaped cut made on the stock and is tightened with a tape or covered with grafting wax. After some time the bud gets fixed with the stocks and gives rise to new branches. Examples Roses, leaches, pears, citrus, plums etc.
5. Tissue culture:- This is a modern method of vegetative propagation and is now used in propagation and is now used is propagating plants .The production of new plants from small piece of plant tissue (or cells) removed from the growing tips of a plant in a suitable medium (called culture solution) is called tissue culture. The growth medium (or culture solution) used for growing plant tissues is very important in this process, because it contains various plant nutrients in the f form of ‘jelly’ (called agar) and plant hormones which are necessary for plant growing .the process of tissue culture for producing new plants is carried out as follows:
1. A small piece OF PLANT TISSUE is taken from the growing point of the plant (tip or the plant) and placed on a sterile jelly containing suitable plant hormones make the cell in the plant tissue divide rapidly producing many cells which forma shapeless lump of mass called ‘callus’.
2. The callus is then transferred to another jelly containing suitable plant hormones which stimulates the callus to develop roots.
3. The callus with developed roots is then put on a yet another jelly containing$nbsp; different hormones"nbsp; which stimulated the development of shoots.
4.&lbsp; The callus having roots and shoots seprates into tiny plantlets are produced from just a few original plant cells (or tissue).
5. The plantlets thus produced are transplanted into pots and soil where they can grow to form mature plants.
The tissue culture techniques is "eing used increasingly for the produbtion of ornamental plants like orchids, dahlia, cabnathon, Chrysanthemum..The method of tissue culture is also known as micropropagation (due to the extremely small amount of plant material used.).
Advantages of tissue culture
1. Tissue culture is a very fast technique.Thousandsof plantlets can be produced in a few weeks’time from a small amount of plant tissue.
2. The new palnt produced by tissue culture are diseases free.
3. Tissue culture can grow plants round the year, irrespective of weather or season.
4. Very littile space is needed for developing new plants by tissue culture.
The importance of variations in organism introduced during reproduction is the it helps the species of various organism to survive and flourish even in adverse environment
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such as orchids, chrysanthemums, Asparagus and many other plants. In tissue culture a small piece of tissue is cut from plant and kept in a container with a nutrient medium under proper conditions. The tissue grows out into an unorganised mass called the callus. This callus is used for further multiplication. Small portions of this tissue (i.e., callus) are put in another medium, which induces the differentiation of plantlets .These plantlets are transplanted in pots or soil and raised to maturity.
SEXUAL REPRODUCTION
Sexual Reproduction:-sexual reproduction takes place by the combination of special reproductive cells called ‘sex cells’. Sex calls are of two types: male and female sex cells (which come from two different parent : a male and a female). The sex cells are commonly known as gametes. Thus, the cells involved in sexual reproduction are called gametes. Gametes are of two types male gametes and female gametes. In sexual reproduction, a male gamete fuses with a female gamete to form a new cell called ‘zygote’. This zygote then grows and develops into a new organism in due course of time. Please note that the sex cells or gametes are also sometimes called germ cells.
SEXUAL REPRODUCTION IN FLOWERING PLANTS
The plants in which the sex organs are carried within the flower and the seeds are enclosed in a fruit are called angiosperms. Angiosperms are commonly known as flowering plants. The sex organs (or reproductive organs) of a plant are in its flower., the same flower contains the male and female sex organs. The function of a flower is to make male and female gametes and to ensure that fertilisation will take place to make new seeds for the reproduction of plant.
The sexual reproduction in plants takes place in the following steps:-
1. The male organ of flower called ‘stamen’ makes the male gametes (male sex cells) of the plant. These male gametes are present in pollen grains.
2. The female organ of a flower called ‘carpel’ makes the female gametes (female sex cells) of the plant. These female gametes are present in ovules. The female gametes present in ovules are also called ‘ova’, ‘egg cells’ or just ‘eggs’.
3. The male gametes present in pollen grains fertilise the female gametes or egg cells present in ovules.
4. The fertilised egg cells grow within ovules and become seeds.
5. The seeds produce new lants on germination (under suitable condition of water, warmth, air and light, etc.).
The main parts of flower are:
1. RECEPTACLE:- The base of flower to which all the parts of a flower are attached is called receptacle.
2. SEPAL:- The green leaf-like parts in the outermost circle of flower are called sepals. All the sepals taken together are called ‘calyx’. The function of seplas (or calyx) is to protect the flower in its initial stages when it is in the form of a bud.
3. PETALS:- The colorful parts of a flower are called petals. The petals lie inside the seplas, All the petals taken together are called ‘corolla’. The petals are usually scented. The function of petals (or corolla) is to attract insects (for pollination ) nad to protect the reproductive organs which are the centre of the flower.
4. STAMEN:- The little stalks with swollen tops just inside the ring of petals in a flower are called stamens. Stamen is male reproductive organ of the plant. Stamen produces pollen grains.It is made of two parts : a filament and an anther . The stalk of stamen is called filament and the swollen top of stamen is called anther. Anther makes and stores pollen grains (The pollen grains appear to be yellow, powder- like substance to us). Pollen grains contain the male gametes (or male sex cells) of the plant.
5. CARPEL :- The centre of a flower, there is flask- shaped organ called carpel. Carpel is female reproductive organ of the plant. A carpel is made of three parts : stigma, style and ovary. The top part of carpel is called stigma. Stigma is for receiving the pollen grains.Stigma is sticky so that pollen can stick to it.The middle part of carpel is called style. Style is a tube which connects stigma to the ovary. The swollen part at the bottom of a carpel is called ovary. The ovary makes ovules and stores them. Ovules contain the female gametes (or female sex cells) of the plant. There are usually many ovules in the ovary. Each ovules contains only one female gamete of the plant The female gamete (or female sex cell) of the plant which is present inside the ovule is called ‘ovum’ or ‘egg’. The female organ of plant is known by two name carpel and pistil.
The flower which contain only sex organ , either stamens or carples, are called unisexual flowers. The flowers of papaya and watermelon plants are unisexual flowers. On the other hand, The flower which contain both the sex organs, stamens as well as carpel, are called bisexual flowers. The flowers of Hibiscus and mustard plants are bisexual flowers.
A new seed of the plant is formed when the male gamete present in a pollen grain unites with the female gamete present in the ovule.
6. Pollination:-The transfer of pollen grains from the anther of a stamen to the stigma of a carpel is called pollination. When the pollen grains from the anther of a flower are transferred to the stigma of the same flower ( or another flower on the same plant), it is called self-pollination. When thepollen grains from the anther of a flower on one plant are transferred to the stigma of a flower on another similar plant. It is called cross-pollination.
7. Fertilisation:- Fertilisation occurs when the male gamete present in pollen grain joing with the female gamete (or egg) present in ovule. When a pollen grain falls on the stigma of the carpel, it bursts open and tows pollen tube downwards through the style towards the female gamete in the ovary. A male gamete move down the pollen tube. The pollen tube enters the ovule in the ovary. The tip of pollen tube bursts open nad male gamete cones out of pollen tube. In ovary , the male gamete of pollen combines with the nucleus of female gamete or egg present in ovule to form a fertilised egg (called zygote).
Formation of fruit and seeds
The fertilised egg ( or zygote) divides seraval times to form an embryo within the ovule. The ovule develops a tough coat around it and is gradually converted into a seed (containing a baby plant). In fact, all the eggs in the ovules present I the ovary of a flower get fertilised by male gametes from pollen grains and grow to become seeds. The ovary of flower develops and become a fruit. Some fruits are soft, sweet and juicy like mangoes and oranges . But some fruits are hard, dry and woody like the peanuts and almonds. etc. The seed is the reproductive unit of a plant ( which can be used to grow a new plant. The seed contain the baby plant in seed which develops into root is called radicle. The part of seed which contain stored food for the by plant is called cotyledons. The wheat grains, gram (chana), corn, peas and beans are all seeds. The bay plant present inside a seed is in the inative state (called dormant state).
SEXUAL REPRODUCTION IN ANIMALS
Animals are also have male and female sexes. .Even the plants have male and female sexes. As we will learn after a while being male or female depends on the type of sex cells present in one’s body An animal having male sex cells called ‘sperms’ in its body is called male. On the other hand an animals having female sex cells called ‘ova’ ( or ‘eggs’.) in its body called female.
Gametes:- Sexual reproduction takes place by the combination of special reproductive cells called ‘sex cells’. The cells involved in sexual reproduction are called gametes. The male gamete in animals is called ‘sperm’ and the female gamete in animals is called ‘ovum’ (or ‘egg’).
Fertilisation:-The fusion of gametes gave rise to a single cell called zygote. We can also say that the cell which is formed by the fusion of a male gamete and female gamete is called zygote. The fusion of sperm with an ovum (or egg) to form zygote during sexual reproduction is called fertilisation. The stage of development between zygote (fertilised egg) and newly formed baby is called embryo.
Internal and External fertilisation:-
Internal fertilisation:- The fertilisation which occurs inside the female body is called internal fertilisation. In fertilisation, the female animal’s eggs are fertilised by sperms inside her body. In mammals (including human beings), birds and reptiles, the fertilisation occurs inside.
External fertilisation:- The fertilisation which occurs outside the female body is called external fertilisation. In external fertilisation, the female animal’s eggs are fertilised by sperms outside its body. In amphibians (like frogs and toads) and fishes, the fertilisation of eggs occurs outside the female animal’s body .in other words, in amphibians (like frogs and toads) and fishes external fertilisation takes place.Now we know that there are two different modes of in nature: internal fertilisation and external fertilisation.
The Advantages of sexual fertilisation:- The sexual reproduction has many advantages over asexual reproduction, the offspring are almost identical to their parent because they have the same genes as their parent . So, much genetic variation is not possible in asexual reproduction. This is disadvantage because it inhibits the further evolution of the organism. In sexual reproduction the offspring, although similar to their parents, are not identical to them or to one another. This is because the offspring’s receive some genes from the mother and some from the father. Because of the mixing of genes of mother and father in various combinations, all the offspring has genetic variations. In this way sexual reproduction leads to a greater variety in population.
Why the amount of DNA Does Not GET Doubled During Sexual reproduction:- In sexual reproduction though the genetic material DNA (in the form of chromosomes) from two gametes, male and female gemetes, combine together to form a new cell ‘zygote’ but the amount of DNA in zygote does not get doubled. The gametes are special type of cells called reproductive cells which contain only half the amount of DNA (or half the number of chromosomes) as compared to the normal body cells of an organism.
Q-How sexual reproduction in animals takes place?
Ans:-
1. The male parent produces male gametes (male sex cell) called sperm. The sperm is a small cell with a long tail (flagellum) for movement.
2. The female parent produces female gametes (female sex cell) called ‘ova’ (or ‘eggs’). The ovum (or egg) is a much bigger cell then the sperm, having a lot of cytoplasm.
3. The sperm enters into the ovum (or egg) and fuses with it to form a new cell called ‘zygote’. This process is called fertilisation. So, the zygote is a fertilised ovum (or fertilised egg).
4. The zygote then divides again and again to form a large number of cells (all of which remains together). And ultimately zygote grows and develops to become a new baby.
Puberty:- The age at which the sex hormones (or gametes) begin to be produced and the boy and girl become sexually mature(able to reproduce) is called puberty. Puberty tends to start earlier in female (girls) than in males (boys). Generally boys stain puberty at the age of 13 to 14 years while girls reach puberty at a comparatively lower age of 10 to 12 years. On the attaining puberty, the male gonads called testes start producing male gametes called sperms and the female gonads called ovaries start producing female gametes called ova (or eggs). In addition to producing sex cells (or gametes) male and female gonads (testes and ovaries) also produce and secrete sex hormones with the onset of puberty.
The various changes which occurs in boys at puberty are : Hair grow under armpits in pubic regions (genital region) between the thighs. Hair also grow on other parts of the body like chest and face (moustache, beard, etc.). Body becomes more muscular due to the development of muscles. The voice deepens (or cracks). Chest and shoulder broadens. The penis and testes become larger. The testes start to make sperms. Felling and sexual drives associated with adulthood begin to develop. All these changes in boys are bought about by the male sex hormones ‘testosterone’ made in testes.
The various changes which occurs in girls at puberty are : Hair grow under armpits in pubic regions (This change is the same as in boys). Mammary glands (or breasts) develops and enlarge. The hips and thighs. Fallopian tubes, uterus and vagina enlarge. Ovaries start to release eggs. Menstruation (monthly periods) start. felling and sexual drives associated with adulthood begin to develop. All these changes in girls are bought about y the female sex hormones ‘oestrogen’ and ‘progesterone’ made in ovaries.
Human reproductive System:- The Human use sexual mode of reproduction. The organs associated with the process of reproduction in human males (men) and human females (women) are different which are known as male reproductive system and female reproductive system, respectively. The reproductive system in human beings become functional ( or start functioning ) at a definite age called puberty.
The Male Reproductive System
The human male reproductive system consist of the following organs:-Testes, Scrotum, Epididymis, Vas deferens (or sperm duct), Seminal, vesicles, Prostrate gland, Penis.
Testes are the oval shaped organs which lie outside the abdominal cavity of a man. A man has two testes (singular of testes is testis. Testis are the primary reproductive organs in man (or males). The Function of testes is to make to male sex cells (or male gametes) called sperms and also to make the male sex hormones called testosterone. The testes of a man make the sex gametes (or sperms) from puberty onwards, throughout his life. The testes of a man lie in small muscular pouch called scrotum outside the abdominal cavity. The testes are outside the abdominal cavity of the body (and not deep inside the body), because the sperm formation requires a lower temperature than the normal body temperature Being outside the abdominal cavity, the temperature of scrotum is about 3o C lower than the temperature inside the body. In this way, the testes provide an optimal temperature (most suitable temperature) for the formation of sperms.
The sperm formed in testes come out and go into a coiled tube called Epididymis. The sperms get stored temporarily in Epididymis. From Epididymis, the sperms are carried by a long tube called vas deferens (or sperm duct) which joins with another tube called vrethra coming from the bladder. Along the path of vas deferens, the glands called seminal vesicles & prostrate gland add their secretions to sperms so that the sperms are now in a liquid. This liquid plus the sperms it contains is called semen (which is a thick liquid). The secretion of seminal vesicles and prostrate gland provide nutrition to the sperms and also make their further transport easier. Urethra forms a common passage for sperms for sperms and urine. Urethra carries the sperms to an organ called penis which opens outside the sperms from the man's body into vagina in the woman's body during mating for the purpose of reproduction.
The Female Reproductive System
The human Female reproductive System consist of the following organs : Ovaries, Oviducts (which are also called Fallopian tubes), Uterus and vagina. Ovaries are the oval shaped organs which are inside the abdominal cavity of a woman near the kidneys. A woman has two ovaries. Ovaries are the primary reproductive organ in a woman (or female). The function of ovaries is to make a mature female sex cells (or female gametes called 'ova' or 'eggs', and also to make the female sex hormones (called oestrogen and progesterone). Each ovary is composed of serval thousands follicles (which are a kind of unripe eggs or unripe ova). At puberty these follicles mature to form the ripe eggs or ripe ova (required for fertilisation).
Just above the ovaries are the tubes called oviducts (which are also known as fallopian tubes). The oviducts are not directly connected to ovaries but have funnel shaped openings which almost covers the ovaries. The ovum (or egg cells released by an ovary goes into the oviduct through its funnel shaped opening. The fertilisation of egg (or ovum) by a sperm take place in the oviduct.
The two oviducts connects to a bag like organ called Uterus (or womb) at their other ends. The growth ovum (or fertilised egg) into a baby takes place in the uterus. The uterus is connected through a narrow opening called cervix to another tube called vagina which opens to the outside of the body. Vagina receives the penis for putting sperms into the women's body. Vagina is also 'birth canal' because it is through this passage that the baby is born after the completion of development inside the uterus of the mother.
Fertilisation:- In human beings internal fertilisation takes place. The sperms (or male gametes) made in the testes of man are introduced into the vagina of the women through penis during copulation (or mating). In this way, millions of sperms are released into the vagina at one time> The sperms are highly active and mobile (moving). The sperms move up through cervix into the uterus. From uterus, the sperms pass into the oviducts one of the oviducts contain an ovum (egg cells) released by the ovary during ovulation. Only one sperm fuses with the ovum (or egg) takes place in the oviduct to form a zygote. Thus is called fertilisation. Thus, the fertilisation of the ovum (or egg) takes place in the oviduct. The zygote divides rapidly by mitosis as it moves down slowly in the and forms a hollow ball of hundreds of cells. The hollow ball of cells, now called an embryo, sinks into the soft and thick lining of the uterus and gets embedded in it. The embedding of embryo in the thick lining of the uterus is called implantation.
After implantation, a disc like special tissue develops between the uterus wall (called foetus), which is called placenta (The foetus is connected to placenta in mother body through umibilical cord). It is through placenta that all the requirements of the developing foetus like nutrition, respiration and excretion, etc., are met from the mother's body. The time period from the fertilisation upto the birth of the baby is called gestation. The average gestation period in human (or the average duration of human pregnancy) is about 9 months.
Sexual Cycle in Female:- Menstruation is when a girl child is born, her ovaries already contain many thousands of immature ova (or egg) which are contained in immature follicles. When a girl reaches the age of puberty then one follicle develops at a time to form a mature ovum (or egg) shoots out of the ovary. This is called ovulation. Thus, The release of an ovum (or egg) from an ovary is called ovulation.
In a normal healthy girl (or woman), ovulation take place on the 14th day of the beginning of menstrual cycle of 28 days. In girls ovulation does not take place every day after puberty.
Before every ovulation, the inner lining of the uterus becomes thick and soft with lot of blood capillaries ( or blood vessels) in it. These changes in the uterus are necessary because in case the ovum (or egg) released by the ovary gets fertilised by the sperm, then the uterus has to keep this fertilised ovum (or egg) for further development and supply it with food and oxygen the unfertilised ovum (or egg) dies within a day and the uterus lining also breaks down. Since the thick and soft uterus lining contains a lot of blood vessels, so the breaking (or disintegration) of the uterus lining produces blood along with other tissues. This blood and other tissues come out of the vagina in the form of a 'bledding' we can now say that the break down and removal of the inner thick and soft lining of the blood vessels in the form of vaginal bleeding is called menstrual flower menstruation.
Menstruation occurs if an ovum (or egg) released by the ovary of a woman does not get fertilised due to non-availability of sperm at the time of ovulation. Menstruation occurs every 28 days because ovulation (release of ovum or egg by ovary) occurs every 28 days. In everyday language menstruation is called 'period' the menstrual cycle is controlled by hormones.
Birth Control:- The population of our country is increasing rapidly day to day though our country has sufficient food resources but still many people do not get sufficient food for their large families (having many children) due to poverty. So, every years it is becoming very difficult for our government to provide sufficient food, adequate, clothing good housing and proper education to every citizen of the country. If a couple has less number of children, it can provide good food, good clothes and good education to each child this will make the parents as well as the children happy. So, a small family is happy family.
Family planning can be done by practicing birth control measures. birth control can be done by preventing pregnancy in females (or women)
Birth Control Methods:- The prevention of pregnancy in women (by preventing fertilisation) is called contraception and any device or chemical (drug) which prevents pregnancy in women is called a contraceptive. Three categories of birth control methods.
1)Barrier methods
2)Chemical methods
3)Surgical methods
1. Barrier methods:- In the barrier methods of preventing pregnancy, the physical devices such as condoms and diaphragm (or cap) are used. An important benefit in the use of condom is that it protects a person from the sexually transmitted diseases such as gonorrhoea, syphilis & AIDS.
2. Chemical methods:- In the chemical methods of preventing pregnancy, the female use 2 types of pills: (1)Oral pills and (2)Vaginal pills, which are made of specific drugs. The oral pills contain hormones which stops the ovaries from releasing ovum (or egg) into the oviduct. Oral pills are called oral contraceptives. Some women, however, do experience unpleasant side effect on taking oral pills because they change the hormonal balance in the body. So, it is important that the women on pills have regular check-ups with their doctors. The vaginal pills contains the chemical called spermicides which kills the sperms.(3) Intra-uterine contraceptive device (IVCD):- The use of Intra-uterine contraceptive device called copper-T is also very effective in preventing pregnancy. A copper-T is placed inside the uterus by a doctor or a trained nurse. The IVCD or copper-T prevents the implantation of fertilised egg in the uterus.
3. Surgical methods:- The surgical methods of birth control are available for males as well as females. In males, a small portion of the sperm duct (or vas deferens) is removed by surgical operation and both the cut ends are ligated (or tied). This prevents the sperms from coming out the surgical procedure carried out in males is called 'vasectomy'. In females, a small portion of the oviducts is removed by surgical operation and the cut ends are ligated (or tied). This prevents the ovum (or egg) from entering into the oviducts. The surgical procedure carried out in females is called 'tubectomy'.
Stop Female Foeticide:- Surgical operation can also be used for the termination of pregnancies in woman particularly after and weeks of conception such as surgical termination of pregnancy (or abortion) is allowed by law only in certain circumstances where the once of pregnancy can affect the health of mother or of unborn child garvely.
Sexually transmitted Diseases (STD):- The diseases which are spread by sexual contact with an infected person are called sexually transmitted diseases (or STD). Thus a healthy person can get STD by making sexual contact with an infected person. Some of the common sexually transmitted diseases are:-
1. Gonorrhoea,
2. Syphilis, and
3 AIDS (Acquired Immunal deficiency Syndrome)