Why do organisms reproduce? Organisms reproduce for two main things. 1. To maintain the survival of their own species. 2. To introduce genetic variations in their population.
What are genetic variations and why they are important? The genetic variations are very important for the adaptation to changing environment. For example, there is a bacteria existing in the oceans near the poles. where the water is usually cool.
These bacteria produced a variant which can withstand high temperature. Suddenly the temperature of the ocean increases due to global warming. Now this variant which can withstand high temperature survives and the other bacteria becomes extinct. In this way variations help the organisms to survive in a changing environment.
Types of Reproduction Reproduction is of two types. Asexual reproduction and sexual reproduction. First, let us learn about asexual reproduction.
Asexual reproduction means the reproduction that takes place without the fusion of sex cells or gametes. Only one parent is involved in this type of reproduction. So, asexual reproduction is a process that involves a single parent and no fertilization or gamete formation takes place.
Asexual reproduction is observed in both unicellular and in multicellular organisms. First, let us see the different modes of asexual reproduction in unicellular organisms. Binary fission. Binary means two. Fission means splitting.
In this mode of reproduction, one parent organism splits into two daughter organisms. This type of asexual reproduction is observed in single-celled organisms like amoeba, bacteria and euglena. Here we have two unicellular organisms.
This is amoeba and this is leishmania. Leishmania causes Kala Azar disease in humans. Amoeba has no fixed shape to its body.
It can change its body shape. The fission in amoeba can take place in any plane because it has no specific shape. Whereas leishmania splits in a specific direction since it has a specific shape. Multiple fission. Multiple fission means splitting into many.
That means one organism splits into many new organisms. Certain single-celled organisms like Plasmodium reproduce by multiple fission. Next one, Budding. Yeast is an unicellular fungus.
They produce buds on their bodies. These buds get separated and grows into an individual organism. This mode of reproduction is called Budding.
These are the methods of asexual reproduction in unicellular organisms. Now let us see the methods of asexual reproduction in multicellular organisms. 1. Spirogyra is an algae.
It is a multicellular organism with simple body organization. It reproduces by fragmentation. In this method of reproduction, first the organism breaks into fragments.
and each fragment grows into a new organism. Next, Regeneration. Certain multicellular animals have an ability to reproduce from their cut body parts. For example, planaria and hydra. If these organisms are cut into pieces, each piece can grow into a complete individual.
This is called regeneration. Next, Budding. Hydra can reproduce by another sexual method of reproduction called Budding.
Hydras have regenerative cells in their bodies. They use these cells to produce small buds on their bodies. These buds grow in size and becomes big. They get separated from the parent organism and grows into an individual organism.
Vegetative propagation. Flower is the reproductive part of the plant whereas stem, root, branches, leaves and buds are vegetative parts of the plant. If plants reproduce through their vegetative parts, it is called as vegetative propagation. Cutting, layering and grafting are the three major techniques of vegetative propagation.
Sugar canes are grown by stem cuttings. Roses can be propagated by layering. Many fruit plants and trees are grown by grafting techniques. Advantages of vegetative propagation 1. Plants grown through vegetative propagation 2. can flower and fruit sooner than those grown from the seeds.
2. These techniques enable the propagation of seedless plants like bananas, oranges, roaches and jasmine. 3. Plants produced through vegetative propagation exhibit genetic similarity to their parent plant, ensuring they inherit all of its characteristics. Next Reproduction through Leaves In Bryophyllum, certain buds are produced in the notches of their leaves.
These buds are called epiphyllous buds. When these buds touch the soil, they germinate into new plants. Next Spore Formation Rhizopus, a common bread mould, reproduces through a process called sporangiospore formation. Specialized structures known as sporangia develops at the tips of the upright filamentous structures called hyphae.
Inside the sporangia, numerous asexual spores called sporangiospores are produced. As the sporangia matures, it eventually ruptures releasing the spores into the surrounding environment. These spores can then disperse and germinate under suitable conditions, giving rise to new Rhizopus fungi. This is all about the asexual reproduction in organisms. Sexual Reproduction in Plants Flower is the reproductive part of the plant.
These are sepals. These are petals. This is pistil.
This is a plant that is not a plant. Pistil is the female reproductive part of the flower and this is stamen. It is the male reproductive part of the flower.
A flower that has both male and female reproductive parts is called bisexual flower. Example Hibiscus, Mustard. A flower that has only either male or female reproductive parts is called as unisexual flower. Examples Papaya and Watermelon. Now let us study the reproductive parts of the flower.
Stamen has two main parts named as anther and filament. Anther consists of small reproductive units called as pollen grains. If we touch the stamen of a flower, some yellow-colored dust-like material sticks to our fingers.
It is nothing but pollen. These pollen grains carry male reproductive cells in them. Pistil.
It has three main parts-stigma, style and ovary. The top part of the pistil is called stigma. It is sticky in nature.
The middle long tube-like part is the style. The bulged bottom part of the pistil is ovary. Ovules are present inside the ovary. Each ovule has an egg cell in it.
Pollination For the process of fertilization, the pollen grains has to reach from anther to stigma. This transfer of pollen grains from stamens to stigma is called pollination. If the transfer of pollen grains takes place between the stamen of a flower to the stigma of the same flower or another flower on the same plant, it is called self-pollination.
If the transfer of pollen takes place from the stamen of one flower to stigma of another flower on different plant is called cross-pollination. The pollen grains are carried to the pistil by the help of different agents like wind, Water, insects or animals. Fertilization. Once the pollen lands on the sticky stigma, the pollen starts germination and produces a long tube called as pollen tube. This tube travels through this tile and reaches the ovule present inside the ovary.
The male cells from the pollen grain enters the ovule through this tube. The male cell fuses with the egg cell present inside the ovule and forms a zygote. This process is called fertilization.
After fertilization, the zygote divides several times and forms an embryo. The ovule develops a tough covering around it and it turns into seed. The ovary grows in size and gets ripened to become a fruit. That means after fertilization, the ovule of the flower becomes seed and the ovary becomes fruit. Remaining parts like stigma, style, petals, sepals get dried up.
and fall off. The seed contains the embryo and when it gets the necessary conditions then it germinates and grows into a new plant. This is about the sexual reproduction in plants. Now let us learn about sexual reproduction in human beings. Puberty.
Human reproduction is sexual type. For sexual reproduction, sex cells or gametes are required. These gametes are produced by the reproductive organs. Male reproductive organs produce male gametes and female reproductive organs produce female gametes. Boys and girls possess reproductive organs by birth, but they do not produce gametes till they attain certain age.
The maturation of special tissues present in the reproductive organs takes place between 8 to 13 years of age in girls and 9 to 14 years of age in boys. At this age, along with the production of gametes, certain bodily changes also begin to happen in boys and girls. This is called beginning of puberty. During this process of puberty, a child grows into a complete adult.
Puberty ends by 18 to 19 years of age. Puberty is the process of physical changes through which a child's body matures into an adult's body and becomes capable of sexual reproduction. Now let us see what kind of changes takes place in the bodies of boys and girls during puberty.
Changes those are common in both boys and girls. 1. Growth of thick hair on new areas of body parts like in armpits and in genital areas between thighs. 2. The skin in these areas becomes darker in color.
3. Growth of thin hair on hands and legs as well as on the face. 4. The skin becomes oilier and may be prone to acne due to increased sebum production. Acne is the common skin condition during puberty. Changes that takes place 1. only in boys during puberty.
1. The voice becomes hoarse and cracked. The Adam's apple becomes more prominent. 2. Thick hair grows on the face and forms mustache and beard. 3. The penis occasionally becomes enlarged and erect. Changes that takes place only in girls during puberty.
1. Breast size begins to increase. 2. The area near the nipples of the breast becomes darker in color. 3. The hips become wider.
4. Menstruation or periods begin. How do these bodily changes helps in the process of reproduction? Growth of hair on face and body parts acts as an indication for sexual maturity, means a sexually matured animal identifies another sexually matured animal for mating with the help of these indications.
Mating means the joining of male and female bodies for the deposition of male cells into the female's body. The enlargement and erection of penis helps in the deposition of sperm cells in the female reproductive organs while mating. The hips of the females become wider to facilitate pregnancy and delivery of the baby. The breasts grow in size and matures to feed milk to the newborn babies.
This is all about puberty. male reproductive system. Human male reproductive system perform three important functions.
1. Production of male gametes or sperm cells. 2. Secretion of male sex hormone i.e. testosterone. 3. Deposition of gametes in the female reproductive system. There is a pair of testes present in the male reproductive system. The production of male gametes and secretion of male sex hormone is done by testes.
Testes are present outside the body cavity. They are located in an elastic sac-like structure called as scrotum. Testis produces the male sex hormone i.e. testosterone. This hormone helps in the puberty of males.
This hormone is responsible for the bodily changes that takes place during puberty. Why the testis are hanging outside the body cavity? Because testis cannot produce sperms at the body temperature.
They need a low temperature to produce sperms That is why they are present outside the body cavity. The sperm cells produced by the testes are small and motile, means moving cells. Each sperm cell has a head piece, middle piece and a tail.
Now the sperms produced by the testes are to be deposited in the female reproductive system to reach the egg cell. Sperms need some accessory materials for the successful journey to the egg cell. Sperms produced in the testes travel through a duct called as vas deferens. At this point, the secretions from seminal vesicles and prostate gland are added to the sperms.
These secretions and sperms, together called as semen, these secretions make the movement of sperms smooth and easier. They also provide nourishment to the sperms. This semen passes out through this duct called urethra which is present inside the penis. Urethra is the common duct for the passage of sperms and urine. But both do not pass at the same time.
During mating, the semen, sperms and secretions are deposited in the vagina of the female reproductive system. by the pennies of the male reproductive system. Human-female reproductive system Female reproductive system performs four important functions. 1. Production of female gametes or egg cells.
2. Secretion of female hormones i.e. estrogen and progesterone. 3. Providing necessary conditions for the fertilized egg to develop into a baby. 4. Menstruation First let us see the production. of female gametes or egg cells. This task is done by the ovaries of the female reproductive system.
By birth, girls contain a pair of ovaries. Each ovary contains thousands of immature eggs. On reaching puberty, these eggs start maturing and gets released.
Each ovary alternately releases one egg approximately every month. The released egg is collected into a tube called as Fallopian tubule. The sperms deposited by the male in the vagina during sexual intercourse travels through the cervix, uterus and reaches the egg present in the fallopian tubule.
If the sperms fertilize the egg, it becomes zygote. This zygote divides repeatedly and forms an embryo. This embryo moves towards the uterus and get implanted in the wall of the uterus. The lining of the uterus grow new tissues and blood vessels to accommodate the embryo. After implantation, the embryo grows into a fetus.
The embryo gets nutrition from the mother's blood with the help of a special tissue called placenta. This is a disc-like structure embedded in the walls of the uterus. This placenta has blood spaces on the mother's side and villi on the fetus side.
This arrangement provides large surface area for the exchange of materials between the blood of the mother and the blood of the baby. Here the nutrients and oxygen are absorbed and wastes are released into the mother's blood. The development of baby inside the mother's womb takes approximately 9 months. This period is called gestation period.
The delivery of the baby takes place by the rhythmic contractions of the uterus. What happens? if the egg is not fertilized in the fallopian tubule. Every month, the walls of the uterus are get lined by blood vessels and tissues in the anticipation of embryo.
If the egg is not fertilized and the embryo is not formed, then the unfertilized egg leaves for one day. After that, the egg gets dissolved and the tissues formed on the lining of the uterus along with the blood slowly breaks and expels out through the vagina. The loss of blood and mucus from the vagina lasts for 2 to 8 days.
This process is called menstruation. Since this process is periodical and happens for every 28 days, it is called as menstrual cycle or periods. This is all about the female reproductive system.
Reproductive health A boy has got the capability of producing sperm cells and the production of ovum started in a girl. Does it mean that they both are ready for sexual act to produce babies? No.
The mind and body should be completely matured to participate in sexual acts. Otherwise, one needs to face so many complications. Health complications due to sexual acts Sexual act involves the intimate contact of body parts, which may lead to the transmission of certain bacterial diseases like gonorrhea and syphilis. and viral infections such as warts and HIV, AIDS.
For girls, getting pregnant at younger age can adversely affect their health. How to avoid these complications? 1. Participating in sexual acts only when the body and mind are completely matured, i.e. only after crossing 18 years of age.
2. Having sexual relations with a single trustable partner. 3. By using contraceptive devices, and methods. Contraceptive devices and methods.
Condom. Condom is a rubbery covering that is worn on the penis during intercourse to prevent the entry of sperms into the female reproductive system. It also prevents the transfer of germs between the partners and give protection from sexually transmitted diseases.
Copper T. Copper T is the other contraceptive device that is placed in the uterus of the females to prevent The fusion of sperm cell and egg cell. This device may cause irritation in some people. Next, contraceptive pills.
These are the drugs that change the hormonal balance in the female body and stop the release of eggs. The prolonged use of these pills can cause side effects. Next, surgical methods. The vast difference of males is cut and ligated to prevent the release of sperms.
In the same way, the fallopian tubules of females are cut and ligated to prevent entry of eggs. These are the permanent methods. But if the surgery... is not done properly, it may lead to infections.
What if the contraceptives fail and pregnancy happens? Medical termination of pregnancy. Using surgical methods to remove unwanted pregnancy is called medical termination of pregnancy or abortion.
In certain sections of our society, sex-selective abortion of female fetus is practiced. This leads to the disturbance of male-female sex ratio in the population. What did the government do?
to protect the girl child from these false practices. The government has banned the prenatal sex determination to control the misuse of medical termination of pregnancy. Prenatal sex determination means scanning and identification of gender of the fetus. This is all about how organisms reproduce.
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