Conclusion

There is not going to be any research here, just an overview on what I have done. I had 2 topics. Reproduction and Issues on sex. Under reproduction, I had two questions. 1) Describe in detail how sexual reproduction takes place in humans. 2) Describe reproduction in other organisms other than mammals. Under Issues on sex, I had the question on whether premarital sex is right or wrong and what are it's consequences.

Reproduction in plants

To round up my final question of research (organisms other than mammals that reproduce), the topic on reproduction and the biojournal in general, I will end off with the topic of research on reproduction in flowering plants. This is my only post where I will talk about something out of the animal kingdom.



Well, firstly we must understand that the flowering plant has male and female organs too. Male organs are collectively called the androecium. The parts include the stamen, which consist of the filament which supports the anthers. The anther contains four microsporangia within which microspores (pollen) are produced by meiosis. Inside the pollen are two (or, at most, three) cells that comprise the male gametophyte. The tube cell (also referred to as the tube nucleus) develops into the pollen tube. The germ cell divides by mitosis to produce two sperm cells.
Female organs are collectively known as the Gynoecium. The gynoecium consists of the stigma, style, and ovary containing one or more ovules. These three structures are often termed a pistil. The stigma functions as a receptive surface on which pollen lands and germinates its pollen tube. The style serves to move the stigma some distance from the ovary. The ovary contains one or more ovules, which in turn contain one female gametophyte, also referred to as the embryo sac.
So for the stigma to even get pollens and reproduce, something known as pollination must occur. This is accomplished by a variety of methods. Entomophyly is the transfer of pollen by an insect. Anemophyly is the transfer of pollen by wind. Other pollinators include birds, bats, water, and humans. Some flowers (for example garden peas) develop in such a way as to pollinate themselves. Flower color is thought to indicate the nature of pollinator: red petals are thought to attract birds, yellow for bees, and white for moths. Wind pollinated flowers have reduced petals, such as oaks and grasses.
The process of pollination being accomplished, the pollen tube grows through the stigma and style toward the ovules in the ovary. The two sperm cells will move down the pollen tube. Once the tip of the tube reaches the micropyle end of the embryo sac, the tube grows through into the embryo sac through one of the synergids which flank the egg. One sperm cell fuses with the egg, producing the zygote which will later develope into the next-generation sporophyte. The second sperm fuses with the two polar bodies located in the center of the sac, producing the nutritive triploid endosperm tissue that will provide energy for the embryo's growth and development.
After fertilization, the zygote divides mitotically. The product of this repeated nuclear division and cell multiplication is an embryo. The seed will now develop. The development consists of a conversion of the integument of the ovule into a resistant seed coat, the development of the endosperm, and the development of the embryo. All these events take place within the original ovary.
A section through a nearly mature seed will reveal an embryo consisting of two large cotyledons with a small epicotyl between them attached to the hypocotyl. Most or all of the endosperm has been absorbed by the cotyledons and the integuments of the ovule have grown into a seed coat. The basal portion of the embryo is termed the radicle. The epicotyl develops into the above ground structures of the plant (stem, leaves, flowers). The radicle develops into the true root system while the hypocotyl develops into the transition zone between root and stem.
The seed will usually lay in the ovary wall which has been devloped into a fruite. The seed will then disperse by either wind, air, animals or water and germinate themselves.
I thank http://io.uwinnipeg.ca/~simmons/lb4pg12.htm and http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookflowers.html for the info

Amphibian reproduction

Now on reproduction of amphibians. For the purpose of reproduction most amphibians are bound to have fresh water. They need to be laid in damp places because of their jellylike characteristic and because there is no shell which means the eggs would quickly dry out and the young would die before they even had a chance to develop if not in water. When the eggs are laid, the male releases sperm over the female's eggs as they are laid. During this time, the male is in a posture called Amplexus which may be inguinal (male grasping the female in front of the her back legs) or axillary (male grasping the female in front of the her hands).
Several hundred frog species in adaptive radiations (e.g. Eleutherodactylus), however, do not need any water whatsoever. They reproduce via direct development, an ecological and evolutionary adaptation that has allowed them to be completely independent from free-standing water. Almost all of these frogs live in wet tropical rainforests and their eggs hatch directly into miniature versions of the adult, passing through the tadpole stage within the egg.
Several species have also adapted to arid and semi-arid environments, but most of them still need water to lay their eggs. Symbiosis with single celled algae that lives in the jelly-like layer of the eggs has evolved several times. The larvae (tadpoles or polliwogs) breathe with exterior gills.
Other kinds of fertilisation include those by salamanders whereby the male deposits a packet of sperm called a spermatophore onto the ground. The female then pulls it into her cloaca where fertilization occurs internally. Some caecilians and tailed frogs use internal fertilization where the male deposits sperm directly into the female's cloaca via an intromittent organ.
Amphibians laying their eggs in water normally leave them alone, but those laying eggs on land usually watch over them to protect them from predators. A few have developed strange ways to guard their eggs until they have hatched. The Surinam toad (Pipa pipa) of South America carries its eggs in pockets of skin on its back until the froglets hatch three months later. The gastric brooder (Rheobatrachus silus) of Australia no sooner lays its eggs than it swallows them! The eggs incubate in the frog's stomach where acid production ceases until the froglets hatch and crawl out through their mother's mouth.
Once hatched, the larva feed on yolk from their egg until they are able to find food for themselves. Then, they start to transform gradually into the adult's appearance. This process is called metamorphosis. Typically, the animals then leave the water and become terrestrial adults.
I thank http://www.eoearth.org/article/Amphibian_morphology_and_reproduction and wikipedia for the information.

Reproduction in fish

Let us move on to fish. Well, most fishes are egg-layers. They lay eggs that are then fertilized by the male when the males spray semen on them, some species lay their eggs on a substrate like a rock or on plants, while others scatter their eggs and the eggs are fertilized as they drift or sink in the water column. Some fish species use internal fertilization and then disperse the developing eggs or give birth to live offspring. The eggs contain yolk which supplies the embryo with food, and albumen - a protein- which protects it. The embryo obtains its oxygen from the water by diffusion, and the young fish, or larvae, hatch after a few days.

Yet many fish also bear live young. Live-bearing fishes may be ovoviviparous, in which the eggs essentially simply hatch within the female, or viviparous, in which the unborn young are supplied nourishment through the mother's tissues.

In some ovoviviparous fishes the embryo develops in the egg while the egg is still within its follicular covering within the ovary, and ovulation (or release of the egg) and birth occur at the same time. In other ovoviviparous forms the eggs are released from the protective follicles into the cavity of the hollow ovary, where development continues.

In some viviparous fishes the walls of the egg follicle are in intimate contact with the embryo, supplying it with nourishment. In the viviparous sharks, a part of the oviduct, or egg channel, is developed into a uterus, where the modified yolk sacs of the young are closely joined to pockets within the uterus. In live-bearing fishes and in some egg-layers, fertilization occurs internally, and methods have been evolved for introducing the sperm into the female's body. In sharks the pelvic fins of the male are modified into intromittent organs called myxoptergia, and in the male topminnows the anal fin is modified into a similar-functioning intromittent organ called the gonopodium.

At least three modes of reproduction--heterosexual, hermaphroditic, and parthenogenetic--are found in fishes. In the most common form, heterosexual reproduction, there are separate male and female parents, but even here there is considerable variation. In some live-bearing fishes, the female is able to store sperm for up to 8 or even 10 months, and this sperm is used to fertilize new batches of eggs as they develop. In some cases, a female may carry sperm from several males at once.

In hermaphroditic reproduction, a single fish is both male and female, produces both eggs and sperm (either at the same time or at different times), and mates with other similar hermaphroditic fishes. External self-fertilization occurs in one hermaphroditic fish, which sheds egg and sperm simultaneously. In another, internal self-fertilization may occur. In certain fishes there is a time sequence of hermaphroditism, young fishes reversing their sex as they grow older.

In parthenogenetic reproduction, unfertilized eggs develop into embryos. This is known to exist in at least one fish species, Poecilia formosa, of the Amazon River; however, even though development proceeds without fertilization in some of these females, mating with a male is still required to stimulate egg development.

Parental care also shows great diversity. Some fishes, like the Atlantic herring, form huge schools of males and females and freely shed their eggs and sperm (milt), and then abandon the eggs. Other fishes build nests and care for both the eggs and newly hatched young. Others have evolved methods of carrying the eggs with them, commonly in their mouths, but also in gill cavities or in special pouches on the body.

I thank www.lookd.com/fish/reproduction.html for the info

Reptile reproduction

Ok, having dealt with birds, let me move on to reptiles. Firstly, most reptiles lay eggs. Reptiles that lay eggs are called oviparous. Some reptiles bear live young, and the term for this is viviparous. We will focus more on oviparous reptiles.

Males and females possess different reproductive organs. The male possesses two testicles, housed inside the body. The male also has a copulatory organ, either a single penis (turtles and tortoises, crocodilians) or a pair of hemipenes (lizards, snakes) that can often be seen as two bulges behind the cloaca at the base of the tail. The penis or hemipenis is not connected to the urinary tract, and is strictly an organ of reproduction. A female has ovaries which store eggs.

For fertilization, a male reptile inserts either one of his two hemipenes into the female's cloaca, or the single penis is inserted. Before actual copulation, the pair usually engages in some type of ritualized courtship. After copulation, sperm can be stored for up to six years, and this stored sperm can fertilize subsequent clutches without additional contact by a male.
Using the green iguana as an example, even without a male present to fertilize eggs, a healthy adult female may begin developing eggs. The process begins with the ovaries, where eggs are stored. Follicles begin developing in the ovaries. Each follicle is composed of a tiny egg and a sac filled with yolk. The follicles then detach and move into the oviducts where the egg white is added, and then a shell is placed around the yolk and white. The female usually will not eat for three to six weeks prior to laying her eggs.

A gravid female would naturally dig a large burrow in moist soil (often along a riverbank) in the wild when she wants to lay her eggs. Then, she will deposit the eggs and completely cover the hole, hiding any evidence of her activities.

Female pythons are one of only a few groups of reptiles to care for her eggs after oviposition. A female will coil around her eggs until they hatch, protecting the eggs and providing temperature regulation, as well. Crocodilians also assist the hatchlings as they emerge from their nests, and will guard them for a while after hatching.

In the species that give birth to live young, some species show a degree of maternal care. Some skinks will assist the neonates by helping them escape from their birth sacs. The Solomon Island skink gives birth to one very large offspring after a long gestation period and while pregnant, she will eat very little. Snakes, such as the boas and garter snakes also give birth to live young.

Now back to egss. In captivity, eggs are usually removed and placed in an incubator. Vermiculite is moistened with bottled water and the eggs are buried halfway. Eggs should be handled carefully, and care should be taken to not change the position that they were in when deposited.

The eggs of some species are hard (turtles, tortoises, crocodilians and some lizards, especially geckos), and those of others are more leathery (snakes and most lizards) Incubation time can vary from about 45 days (in small lizards) to over a year (for some tortoises).
When it is time for the baby to hatch, the neonate uses its egg tooth (also called caruncle) to cut through the eggshell. The baby will usually remain in the egg for 12-48 hours after it pokes its head through the egg. During that time, any remaining yolk still attached to the hatchling will be absorbed.
Babies hatched from eggs, as well as those that are born alive from the female, are able to fend for themselves as soon as they are up and walking around/slithering.

I thank www.exoticpetvet.net/reptile/rerepro.html for the information

Animal reproduction

Ok, sadly, I'm out of ideas for the topic on premarital sex and its consequences, so let us go back to my initial topic, on sexual reproduction. So I will now formulate a third question, describe sexual reproduction in other organisms other than mammals.

So, let us first deal with verterbraes. I will begin with birds. Birds reproduce by sexual reproduction, males having paired testes lying in the bodity cavity, and females having only a functional left ovary and oviduct. Firstly, a stimulus occurs weeks in advance of the breeding season in the birds. This ensures the male arrives on the breeding grounds with the testes fully developed and the female has enlarged of the female reproductive organs, development of eggs in the ovaries, formation of the brood patch, and so on. These enlarged testes secrete greater amounts of male hormones that may brighten skin colors and stimulate singing and courtship behavior.

After mating, copulation occurs, in which the male mounts the female from behind. Both sexes hold their tails to the side and turn back the feathers around the cloaca (the common opening of the bird's alimentary canal and excretory and reproductive systems), so that the swollen lips of the male's and female's cloacae can come into contact. In some birds, such as geese and ducks there is a grooved, erectile penis inside the male's cloaca that guides the sperm, which have been stored in a nearby sac, into the female. In passerines, there is no penis, and copulation amounts to a brief "cloacal kiss" during which the sperm are transferred out of the testis, into the vas deferens and into the female
Once transferred, the sperm remain for a while in storage at the lower end of the oviduct, and then swim to the upper end of that duct to fertilize the egg. Consequently, there is considerable variation among species in the frequency of copulations, how long it takes for the egg to be laid and how many eggs are actually laid. But in order for an egg to form, the sperm must meet the egg in the oviduct before the layers of the egg form.

The birds will be laid in nests that vary from burrows(penguins) to leaf piles(turkeys). When eggs are laid, all birds will incumbate their eggs by supplying heat from their bodies. That heat may be considerable, since the normal temperature of a bird is around 100 to 112 Fahrenheit. Once incubation begins the bird seldom leaves the nest, and then not long, because the eggs will not hatch if they get too cold. During incubation the eggs have to be turned once or twice a day so that they will be heated evenly and the membranes of the embryo will not adhere to the shell.

So now a bit more about a bird egg. The egg cell of a bird is really what we call the yolk. The yolk is the food supply for the developing embryo. The nucleus of the bird's egg can be found in the middle of a white spot which is found on top of the yolk. The egg that female bird lays is covered in layers of albumen (a material like jelly), two membranes and a hard shell. The shell and the membranes protect and support the egg. The albumen feeds the developing embryo with water and protein. The albumen, membranes and shell are added to the yolk layer-by-layer as it passes down a tube called the oviduct inside the hen's body.

When the egg actually hatches, the characteristics again vary species to species. Some hatch naked, while others hatch with their full feathers. Some are blind, others can already move. Thus, there is a lot of difference which makes bird reproduction very fascinating.

I thank www.stanford.edu/group/stanfordbirds/text/essays/Copulation.html, http://www.saburchill.com/chapters/chap0034.html and www.newton.dep.anl.gov/natbltn/400-499/nb456.htm for the info.

Abortion

Having shown you the contraceptive methods available to prevent unwanted pregnancies I will elaborate on what to do if you have them. One way is through abortion. This is a very controversial topic because it involves human lives. It also involves women's rights so one must consider both parties involved. In most countries, this is only done in the first trimester of pregnancy when people don't consider the fetus a life. So I shall not dwell on the moral aspects, but more on the scientific part of abortion itself.

Intentional abortion is also known as Induced abortion. There are 2 main methods, surgical and medical.

Surgical methods include suction-aspiration or vacuum abortion during the first 12 weeks. Manual Vacuum aspiration (MVA) abortion, consists of removing the fetus or embryo by suction using a manual syringe. MVA can be used in very early pregnancy, and does not require cervical dilation. Electric vacuum aspiration (EVA) abortion uses an electric pump.

Surgical techniques are sometimes referred to as 'Suction (or surgical) Termination Of Pregnancy' (STOP). From the 15th week until approximately the 26th, dilation and evacuation (D&E) is used. D&E consists of opening the cervix of the uterus and emptying it using surgical instruments and suction.
Dilation and curettage (D&C), the second most common method of abortion. Curettage refers to cleaning the walls of the uterus and embryo with a curette. The World Health Organization recommends this procedure when MVA is unavailable.
Other techniques must be used to induce abortion in the second trimester. Premature delivery can be induced with prostaglandin; this can be coupled with injecting the amniotic fluid with caustic solutions containing saline or urea.

After the 16th week of gestation, abortions can be induced by intact dilation and extraction (IDX), which requires surgical decompression of the fetus's head before evacuation. IDX is sometimes called "partial-birth abortion," which has been banned in the United States.

A hysterotomy abortion is a procedure similar to a caesarean section, and is performed under general anesthesia because it is considered major abdominal surgery. It requires a smaller incision than a caesarean section and is used during later stages of pregnancy.
From the 20th to 23rd week of gestation, an injection to stop the fetal heart can be used as the first phase of the surgical abortion procedure to ensure that the fetus is not born alive.

The second type of abortion is medical, in which only drugs is used to induce abortion. The first wave of drugs is usually either an injection of methotrexate or a dose of mifepristone in tablet form.
Mifepristone binds to the progesterone receptor to block progesterone. Progesterone is necessary for pregnancy maintenance. Mifepristone also softens and dilates the cervix, and causes decidual necrosis (which leads to placental detachment).
Methotrexate blocks an enzyme necessary for DNA synthesis, thus inhibiting the growth of rapidly dividing placental trophoblastic cells.

Both drugs are then followed up by A prostaglandin analog--a dose of misoprostol in tablet form, or gemeprost. Misoprostol works by softening and dilating the cervix, and binding to myometrial cells to cause strong uterine contractions. Contractions cause expulsion of the embryo.

Having shown you all the methods of abortion if you have an unwanted pregnancy, I would end my topic on issues of sex here.

I thank wikipedia and wikimedia for the info and pics

Contraceptives

Having talked about STDs, let me move on the the other important complication of premarital sex. That is of unwanted pregnancies. To prevent this, one must use contraceptives. Contraeptives are mechanisms, devices, or medications that are intended to reduce the likelihood of a sperm cell fertilizing the egg which will deliberately prevent or reduce the chances of pregnancy or childbirth. Effectiveness varies depending on method.
The methods are mainly:
Abstinence - simply means no sex, 100% effective
Birth Control Pill -They contain two hormones, an estrogen and a progestin. They work by stopping ovulation and by inhibiting the movement of sperm. Quite effective when used consistently
Cervical Cap -It is a small cap made of soft latex which is placed by a doctor up into her vagina and onto her cervix. Suction keeps the cap in place so sperm cannot enter the uterus. The woman can also put spermicide in the cap. Women should obtain a new cap yearly. 9% accidental pregnancy. Can also prevent STDs
Condom -(refer to last post).
Contraceptive Film/ suppositories -These are medications with a chemical that kills sperm (a chemical called nonoxynol-9). It is placed on or near the cervix (the opening of the womb). It dissolves in seconds. Quite ineffective and does not work against STDs.
Contraceptive Sponge -It acts as a barrier to prevent semen from entering the cervix. Ineffective, but can prevent STDs because it is a barrier.
Contraceptive Implant -Implanon is an implant inserted into the upper arm. They give off small amounts of a hormone like the progesterone that stops the releasing of the egg. This effectively prevents pregnancy (but not STDs) for 3 years.
Diaphragm - It is a latex disc a woman places into her vagina. It blocks a man's semen from entering the cervix (the opening to the womb). A spermicide placed onto the diaphragm kills sperm. Quite effective
Fertility Awareness Method(the "rhythm" method) -It is a understanding a woman's reproductive cycle by observing and writing down fertility signs that determine when she can become pregnant. The signs are then used to decide when best to have sex.
Injectable Contraception (most commonly known as Depo-Prevera) -A shot given every three months. It is provides a hormone like the progesterone that stops the woman's ovaries from releasing an egg and have other contraceptive effects. Very effective but no STD protection.
Intrauterine Contraception (IUD) -It is a small device which is placed into the uterine cavity. the IUD gives off copper into the uterine cavity which stops sperm from making their way up through the uterus. Very effective, inexpensive and can last for long time.
The Patch -It is a patch that can be pasted anywhere on the body. The hormones it gives out is like that of a pill and it has the same effect. Quite effective and can last for 7 days.
The Ring -NuvaRing is a small, flexible device that a woman inserts into her vagina once a month. The ring releases combined hormones (estrogen and progestin) to protect against pregnancy. Same effect as a pill.
Withdrawal -It is the act of a man pulling his penis out before ejaculation into the vagina. Not very effective as pre-ejaculate fluid can also contain semen.
So from today, I have researched through the various methods of contraceptions. Though different, we see that the methods require consistency to work. Couples should consult each other before deciding on their method to prevent unwanted pregnancies. Remember that no method (other than abstinence) is perfect.
I thank http://www.advocatesforyouth.org/youth/health/contraceptives for the info.

Preventions and cures

According to http://microbiology.suite101.com/article.cfm/sti_and_std, the main ways to prevent STDs are Abstaining from sexual intercourse unless it is with a long-term monogamous relationship; Consistent, correct usage of latex condoms during sexual intercourse. You can also go for annual STD, such as chlamydia, testing which does not cure STDs, but give you an idea of whether you are infected so you can receive early treatment.
The first prevention need not be further explained. So I'll move on to the second. How do condoms work? A condom is a sheath made from latex, polyurethane, or lamb intestines which is designed to cover the penis, creating a barrier between sexual partners and thus preventing the exchange of bodily fluids, which include STDs and semen, between two sexual partners. This prevents partners to be infected with STDs and prevents the female from getting pregnant. Many condoms also include spermicide, to ensure that any semen which may escape will perish before it reaches an egg. Some companies also manufacture insertable female condoms that can be worn by female sexual partners. To use a condom properly, it must be put on in the beginning stages of sexual intercourse, because pre-ejaculate can still infect a partner or cause pregnancy. Roll the condom all the way down the shaft of the penis, adding lubricant to the outside if necessary. Make sure to use a water based, latex friendly lubricant. After ejaculation, the condom should be disposed of properly. In addition to using condoms correctly for maximum efficiency, it is also important to never use expired condoms. Ultimately, if used consistently, condoms shouldn't break and is 97% of the time effective.
So let me move on to the informative, rather than preventive measure, that on tests for STDs. Well, these tests are usually done as a blood, urine, cell or visual examination and there are different procedures for each infection. Some prominent ones include the HIV antibody test which involves a blood sample where doctors check for HIV antibodies. Sometimes, there will be a cervical swab (like a pap smear) like in Chlamydia and Trichomoniasis where doctors examine under the microscope for traces of the parasite or bacteria. Some tests like the one for Syphilis may even require collection of spinal fluid.
Done with prevention, let me move on to cures for STDs. Well, most STDs are relatively easy to cure. In fact, there have even been vaccines created like the one for HPV (genital warts). In most cases antibiotics can cure bacterial STDs. For example, to cure syphilis, a single intramuscular injection of penicillin, an antibiotic, is usually effective if the person has had syphilis for less than a year. Antibiotics are not, however, effective in fighting viral infections such as herpes and HIV. Instead, these viruses can be treated. For instance, HIV can be treated through the use of antiretroviral drugs. For Herpes, drugs, like acyclovir, work to hasten the healing of herpes sores and can also work to suppress an outbreak. However, the above drugs for viruses cannot prevent transmission and are not cures.
Thus the best way to protect oneself would still be protected sex or abstinence in general.
I thank http://www.epigee.org/health/std_testing.html and http://chirkut.blog.co.in/2008/06/23/how-do-condoms-work/ for the info.

Premarital sex consequences

So, now we established that premarital sex is actually harmful, let us look at the practical remifications. Well, they include unwanted pregnancies and STDs, but today I will focus on the latter. Yes, admittedly, while STDs can be transmitted even with sex after marriage, we still must understand that at that stage, the couple is ready to accept the consequences of their action, do teens who participate in premarital sex do? Thus, STDs is a much more pressing issue on the uninformed teen who practises unprotected sex.
Well, STDs are diseases that are mainly passed from one person to another during oral, anal or vaginal sex. There are at least 25 different sexually transmitted diseases with a range of different symptoms. STD symptoms are soreness, unusual lumps or sores, itching, pain when urinating, and/or an unusual discharge from the genitals. STDs can also affect fetuses as the infection spreads through the placenta and cause problems like stillbirth or other complications.
As, I cannot talk about all the STDs, I will just touch on the more common ones today.
First up-Chlamydia. It is one of the most commonly reported bacterial sexually transmitted diseases. It is caused by the Chlamydia trachomatis bacterium. It infects the urethra, rectum and eyes in both sexes, and the cervix in women. If left untreated, long-term infection can lead to fertility problems in women.
Next-Pubic Lice. They are small crab-shaped parasites that burrow into the skin to feed on blood. They live on coarse body hair, predominantly pubic hair. The lice use their crab-like claws to grip hair strands.
Next-Genital warts. They are caused by some sub-types of Human Papillomavirus (HPV). They can appear on the skin anywhere in the genital area as small whitish or flesh-coloured bumps. They are unlikely to cause pain but may itch and can be difficult to spot.
Next-Gonorrhea. It is an infection that can infect the urethra, cervix, rectum, anus and throat. Symptoms include a burning sensation when urinating and abnormal discharges from genitals or the anus.
Next-Herpes. It is caused by two strains of the herpes simplex virus, type 1 (HSV-1) and type 2 (HSV-2). HSV-2 is more common and usually manifests itself in the genital and anal area. Symptoms include blisters, itching sensations and flu-like symptoms.
Next-Molluscum contagiosum (also known as water warts). It is a common viral infection resulting in a skin disease that presents itself as small bumps, often in clusters. They are filled with a gungy white fluid that is very contagious. The bumps usually appear on exposed skin such as the torso, thighs, genitalia and anus.
Next-Scabies. It is an intensely itchy, contagious skin infestation of the parasitic mite Sarcoptes scabiei. Female mites burrow into the outer layer of the skin (stratum croneum) to lay eggs. This causes intense itching
Next-Syphilis. It is a bacterial infection caused by Treponema pallidium. Symptoms include ulcers and flu-like symptoms. If left untreated, it can affect organs like the heart.
Next-Trichomoniasis (also known as Trich). It is caused by the single-celled organism Trichomonas vaginalis, which is transmitted through sex. It can infect the vagina and the male and female urethra. Often this STD presents no visible symptoms.
Next-HIV (human immunodeficiency virus). It is a virus that kills your body’s "CD4 cells." CD4 cells (also called T-helper cells) help your body fight off infection and disease. This leads to another disease called AIDS. There is no cure to HIV and symptoms are hard to detect.Next-Hepatitis B. It is a virus attacks your liver. It can cause permanent damage and even liver cancer.
Having shown you the dire consequence one can have from unprotected premarital sex. I will show you later ways to prevent it.
I would like to thank avert.org and http://www.pamf.org/teen/sex/std/ for the information.

Premarital sex ban

At first, I wanted to write about benefits about premarital sex, but I realised very few people truly believe premarital sex is right, they just do it for impulse and curiousity. Then they regret it. But if there is such a consensus, why isn't the government banning it?
The biggest argument that is stopping a ban of premarital sex in liberal democracies today is the fact that people have freedom of choice and that if they want to engage in sexual acts, they should know the consequences, accept it and the government should not intervene. In fact if the government intervenes, the people may feel their rights infringed and may rebel even more, since it is impossible to suppress curiousity, which drives premarital sex.
But then again, if the government does not ban it, is it right? That is a weird question as many people view the government as a moral beacon and model. The message it sends when it does not ban premarital sex seems to lean towards the advocation of it. Yet, if we take a step back and look at the numeroues health campaigns, sex education classes that the government has sponsored, we ask ourselves, maybe even the government is against such acts. The thing is, the government cannot make a firm decision on whether or not this is right or wrong because society has evolved so much that the current day trend is as influential as religion, thus, if any law were to be passed, we would disatisfy the people and the trend.
So the government is hindered in deciding what is right or wrong because it is accountable to the people. They have left premarital sex in a very debatable grey area. Thus, it is up to you to decide. Do you want to have premarital sex? Are you ready for it? Do you want to follow the crowd? Ultimately, no one can decide for you, only yourself.

premarital sex

Now that we have answered the first question (how is reproduction possible?), let us move on to the second on issues on sex - Is premarital sex right or wrong and what are its consequences?
Now this is a prominent issue, according to the 1974 National Survey data in US, adults, 25 years of age, 97% of men and 81% of women had premarital sex. Thus addressing it should prove important and beneficial.
Well, right now, I will discuss why it may be wrong. Now in a moral perspective, religion has always looked down on premarital sex. The Bible refers to premarital sex as fornication. Premarital sex is just as much of a sin as adultery and all other forms of sexual immorality. They all involve having sexual relations with someone you are not married to. Most people believe that something sacred like virginity should be kept for the person you truly love. Sadly, most youths in fact have sex based on impulse and emotions. They do it out of peer pressure, curiousity and recreation, rather than love. This is because they have not matured. Thus, morally it is incorrect.
But deeper in, practical remifications of premarital are also plentiful. Firstly, the youth is unprepared for a deep relationship so should anything happen, like unwanted pregnancies, the youths will not be able to support each other. Even if they do love each other, their age will hinder them as they cannot earn a living to support their family, thus abortions usually occur. Other than that, premarital sex usually cause the couple to feel guilty and depressed after the act and this affects their emotional health. This is because they never truly loved each other and is regretful. Lastly, chances of gainng STDs is also high as much premarital sex is on impulse so most people don't know about the health condition of their partners.
But ultimately, do these problems deter society from having premarital sex? Why not? I will elaborate further.

Pregnancy

So after going through fertilisation, let us look more in depth into pregnancy (also known as gestation). Well, Pregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the uterus of a female. Childbirth usually occurs about 38 weeks from fertilization. Pregnancy is typically broken into three periods, or trimesters, each of about three months. While there are no hard and fast rules, these distinctions are useful in describing the changes that take place over time.
The beginning of pregnancy may be detected in a number of ways, including various pregnancy tests which detect hormones generated by the newly-formed placenta. The tests are known as Human Chorionic Gonadotrophin (HCG). Clinical blood and urine tests can detect pregnancy soon after implantation, which is as early as 6-8 days after fertilization. The tests are usually carried out on the day where a woman's monthly menstruation period is due.
After fertilisation and during the first trimester, the developing embryo becomes implanted into the endometrial lining of a woman's uterus. The embryo is a blastocyst which secretes a hormone named human chorionic gonadotropin which in turn, stimulates the corpus luteum in the woman's ovary to continue producing progesterone. This acts to maintain the lining of the uterus so that the embryo will continue to be nourished. The glands in the lining of the uterus will swell in response to the blastocyst, and capillaries will be stimulated to grow in that region. This allows the blastocyst to receive vital nutrients from the woman. During this time, the fetus is still developing by division via mitosis in the female
Months 4 through 6 of the pregnancy are called the second trimester. Most women feel more energized in this period. Although the fetus begins moving and takes a recognizable human shape during the first trimester, it is not until the second trimester that movement of the fetus, can be felt. The placenta is now fully functioning and the fetus is making insulin and urinating. The teeth are now formed inside the fetus's gums and the reproductive organs can be recognized, and can distinguish the fetus as male or female.
In the third trimester, movement of the fetus becomes stronger and more frequent and via improved brain, eye, and muscle function the fetus is prepared for ex utero viability. The woman can feel the fetus "rolling" and it may cause pain or discomfort when it is near the woman's ribs and spine. This period of her pregnancy can be uncomfortable, causing symptoms like weak bladder control and back-ache. It is also during this time that a baby born prematurely may survive.
I thank wikipedia again for the information.

Fertilisation

So now that we have covered how the sperms and eggs prepare for fertilisation, let us go in depth on how fertilisation actually takes place. So firstly, sexual intercourse must take place and the male must ejaculate sperms into the female's vagina. As ovulation approaches, the cervical mucus becomes watery allowing the sperm to swim up the vagina through the cervix. Only about 2,000 sperm will be strong enough to reach the uterus and the fallopian tube.
So to begin, sperms must penetrate the cell membrane of the oocyte. To reach the oocyte, the sperm must pass through the corona radiata and the zona pellucida; two layers covering and protecting the oocyte from fertilization by more than one sperm. When the sperm reaches the zona pellucida, which is an extra-cellular matrix of glyco-proteins, a special complementary molecule on the surface of the sperm head then binds to a ZP3 glyco-protein in the zona pellucida. This binding triggers the acrosome to burst, releasing enzymes that help the sperm get through the zona pellucida.
When the sperm penetrates the zona pellucida, the cortical reaction occurs. Cortical granules inside the secondary oocyte fuses with the plasma membrane of the cell, causing enzymes inside these granules to be expelled by exocytosis to the zona pellucida. This in turn causes the glyco-proteins in the zona pellucida to cross-link with each other, making the whole matrix hard and impermeable to sperm. This prevents fertilization of an egg by more than one sperm.
So with the fusion of cell membranes of the sperm and opcyte, both the oocyte and the sperm also go through transformations, preparing for the fusion of their genetic material.
For the oocyte, it completes its second meiotic division. This results in a mature ovum. The nucleus of the oocyte is called a pronucleus in this process, to distinguish it from the nuclei that are the result of fertilization.
The sperm's tail and mitochondria degenerate with the formation of the male pronucleus. This is why all mitochondria in humans are of maternal origin.
The pronuclei migrate toward the center of the oocyte, rapidly replicating their DNA as they do so to prepare the new human for its first mitotic division.
The male and female pronuclei don't fuse, although their genetic material do so. Instead, their membranes dissolve, leaving no barriers between the male and female chromosomes. During this dissolution, a mitotic spindle forms around them to catch the chromosomes before they get lost in the egg cytoplasm. By subsequently performing a mitosis, the cell gathers genetic material from the male and female together. Thus, the first mitosis of the union of sperm and oocyte is the actual fusion of their chromosomes.
Each of the two daughter cells resulting from that mitosis have one replica of each chromatid that was replicated in the previous stage. Thus, they are genetically identical. These cells will continue to divide so the fetus can develop

I thank wikipedia for the information and pictures.

Menstrual cycle

Now unlike the male sperms, female eggs need not be formed because they are already present in the ovaries at birth. Instead, during puberty, girls will release their eggs in a process known as ovulation during a menstrual cycle which starts at puberty. The process ends at around the age of 51 (termed as menopause) and the woman can no longer reproduce. The average menstrual cycle is 28 days long. The purpose of the menstrual cycle is to prepare the body for pregnancy each month
So, the first part of the cycle is menstruation. Menstruation is the shedding and breaking down of the uterine lining which occurs because estrogen and progesterone levels decreased at the end of the previous cycle. This results in menstrual blood flows from the uterus through the small opening in the cervix, and passing out of the body through the vagina. Most menstrual periods last from three to five days. To contain the blood, many women use tampoons or pads.
About this time, the follicle-stimulating hormone level increases slightly, stimulating the development of several ovarian follicles. Each follicle contains an egg. Later, as the follicle-stimulating hormone level decreases, only one follicle continues to develop. This follicle produces estrogen.
The ovulatory phase begins with a surge in luteinizing hormone and follicle-stimulating hormone levels. Luteinizing hormone stimulates egg release (ovulation) of the dominant follicle that ruptures the ovaries. After the egg has left the ovary it travels through the fallopian tube to the uterus. Hormone levels rise and help prepare the uterine lining for pregnancy. A woman is most likely to get pregnant during the three days before ovulation or on the day of ovulation.
During the luteal phase, luteinizing hormone and follicle-stimulating hormone levels decrease. The ruptured follicle closes after releasing the egg and forms a corpus luteum, which produces progester-one. During most of this phase, the estrogen level is high. Progesterone and estrogen cause the lining of the uterus to thicken more, to prepare for possible fertilization. If the egg is not fertilized, the corpus luteum degenerates and no longer produces progesterone, the estrogen level decreases, the top layers of the lining break down and are shed, and a new menstrual cycle begins.
This is a video on the menstrual cycle

Because of the taxing nature of the mestrual cycle, some women experience pre-menstrual syndrome. The three most prominent symptoms are irritability, tension, and dysphoria. Physical symptoms also include cramps and headaches. Treatment is mostly counselling and recommendations to change lifestyle and diet.
I would like to thank wikipedia and www.merck.com/mmhe/sec22/ch241/ch241e.html for the info.

female reproductive system

Now before we move on to the sperm meeting the egg, let us first examine the organs that create and contain the egg. This is the female reproductive system.

Unlike the male, the human female has a reproductive system located entirely in the pelvis. The external part of the female reproductive organs, between the legs is called the vulva. Located between the legs, the vulva covers the opening to the vagina and other reproductive organs located inside the body.
The fleshy area located just above the top of the vaginal opening is called the mons pubis. Two pairs of skin flaps called the labia surround the vaginal opening. The clitoris, a small sensory organ, is located toward the front of the vulva where the folds of the labia join. Between the labia are openings to the urethra which iscthe canal that carries urine from the bladder to the outside of the body. Once girls become sexually mature, the outer labia and the mons pubis are covered by pubic hair.
A female's internal reproductive organs are the vagina, uterus, fallopian tubes, and ovaries.
The vagina is a muscular, hollow tube that extends from the vaginal opening to the uterus. It can become wider or narrower to let the vagina to accommodate something as slim as a tampon and as wide as a baby. The vagina's muscular walls are lined with mucous membranes, which keep it protected and moist. The vagina has several functions: for sexual intercourse, as the pathway that a baby takes out of a woman's body during childbirth, and as the route for the menstrual blood (the period) to leave the body from the uterus.
A thin sheet of tissue with one or more holes in it, called the hymen, partially covers the opening of the vagina. Most women find their hymens have stretched or torn after their first sexual experience.
The vagina connects with the uterus, or womb, at the cervix. The cervix has strong, thick walls. The opening of the cervix is very small, but it can expand to allow a baby to pass.
The uterus is shaped like an upside-down pear, with a thick lining and muscular walls . These muscles are able to expand and contract to accommodate a growing fetus and then help push the baby out during labor.
At the upper corners of the uterus are the ovaries. The ovaries are two oval-shaped organs that lie to the upper right and left of the uterus. They produce, store, and release eggs into the fallopian tubes in the process called ovulation. The ovaries also produce female sex hormones such as estrogen and progesterone.
There are two fallopian tubes, each attached to a side of the uterus, which connect the uterus to the ovaries. When an egg pops out of an ovary, it enters the fallopian tube. Once the egg is in the fallopian tube, tiny hairs in the tube's lining help push it down the narrow passageway toward the uterus.
I would like to thank http://upload.wikimedia.org/ for the picture and http://kidshealth.org/teen/sexual_health/changing_body/female_repro.html for their info.