reproduction
Vegetative reproduction in the "air plant". (Image by Eric Guinther, GNU)

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Reproduction

REPRODUCTION

A woman's right to determine whether she will give birth was not legally recognized until the 1960s and 1970s, when U.S. Supreme Court decisions established that right. Until that time, women in the United States were denied access to birth control and to legal abortions by state criminal laws. Since the 1970s, there has been ongoing controversy over legalized abortion, with the Supreme Court allowing states to impose restrictions on obtaining the procedure. In addition, medical science has developed techniques of artificial insemination and in vitro fertilization that enable pregnancy. These advances, in turn, have created opportunities for surrogate motherhood, opening up even more legal issues dealing with reproductive rights. Because of the cultural importance placed on motherhood and the intersection of religious beliefs and public policy, the debate over reproductive rights has been contentious.

Historical Background

In the nineteenth century, the average size of the U.S. family declined dramatically. A white woman in 1800 gave birth to an average of seven children. By the end of the century, the average was three-and-a-half children. In part, the decline was caused by the dissemination of scientific information on birth control. Many of the nineteenth-century proponents of family planning were radical social reformers who offended church and community leaders with their graphic descriptions of human reproduction.

Conservatives sought to curtail this information on birth control and abortion. The most prominent conservative watchdog was Anthony Comstock, a New York businessman who led a national reform effort against obscene materials. His work resulted in the federal comstock law of 1873, which criminalized the transmission and receipt of "obscene," "lewd," or "lascivious" publications through the U.S. mail. The law specified that materials designed, adapted, or intended "for preventing conception or producing abortion" were included in the list of banned items. Some states passed "little Comstock laws" that prohibited the use of contraceptives.

Until the second half of the nineteenth century, few states had criminal laws against abortion. Women in colonial times had used abortion to dispose of the offspring of rape or seduction. Abortion was not illegal under the common law as long as it was performed before "quickening," the period at about four months when the fetus begins to move in the womb.

State legislatures passed laws in the first half of the nineteenth century that adopted the quickening rule, and a few states allowed abortion after quickening to save the life of the mother. Abortions increased markedly in the 1850s and 1860s, especially among middle-class white women.

Religious leaders began to denounce abortion, but the american medical association (AMA) proved to be the most successful in ending legalized abortion. The AMA was formed in 1847, and the all-male professional group (women were not allowed to become doctors) made abortion law reform one of its top priorities. The AMA saw abortion reform as a way to increase its influence and to drive out unlicensed practitioners of abortion. By the 1880s, medical and religious leaders had convinced all-male state legislatures (women were not allowed to vote) to impose criminal penalties on persons performing abortions and, in some states, on the women who had abortions. The laws were based on the states' police power to regulate public health and safety. This had some justification because abortion procedures of the time were dangerous, subjecting women to sterility and, in many cases, death. In response, women turned to birth control and to illegal abortions. The legal restrictions on birth control and abortion that were created in the late nineteenth century were not be removed until the 1960s and 1970s.

Restricting Antiabortion Protests

The legalization of abortion resulted in the creation of many groups opposed to the medical procedure. Some groups have sought to take away this reproductive right by lobbying Congress and state legislatures, and others have picketed outside clinics that offer abortion services. In the 1990s, groups such as Operation Rescue sought to prevent abortions by organizing mass demonstrations outside clinics and blockading their entrances, as well as confronting and impeding women seeking to enter the clinics.

Clinics responded by obtaining court injunctions that restricted how close abortion protestors could get to clinic property. Abortion protestors claimed that these court orders violated their first amendment rights of assembly and free speech.

The U.S. Supreme Court, in Schenck v. Pro-Choice Network of Western New York, 519 U.S. 357, 117 S. Ct. 855, 137 L. Ed. 2d 1 (1997), clarified what types of restrictions a judge could impose on abortion clinic protests. The Court upheld an injunction provision that imposed a fixed buffer zone around the abortion clinic. In this case the buffer zone affected protests within 15 feet from either side or edge of, or in front of, doorways or doorway entrances, parking lot entrances, and driveways and driveway entrances. Chief Justice william h. rehnquist ruled that the government had an interest in ensuring public safety and order, promoting free flow of traffic, protecting property rights, and protecting a woman's freedom to seek pregnancy-related services.

The Court did strike down a provision concerning floating buffer zones. These zones, which prohibited demonstrations within 15 feet of any person or vehicle seeking access to or leaving abortion facilities, "burdened more speech than was necessary" to serve the government interests cited in support of fixed zones. Thus, protestors were free to approach persons outside the 15-foot fixed buffer zone.

In 2000, though, the Court again considered the issue of a buffer zone in Hill v. Colorado, 530 U.S. 703, 120 S. Ct. 2480, 147 L. Ed. 2d 597 (2000). The Court upheld Colorado's 1993 statute, which prevented anyone from counseling, distributing leaflets, or displaying signs within eight feet of others without their consent whenever they are within 100 feet of a health-clinic entrance. The Colorado law was enacted, according to attorneys for the state, after abortion patients complained of being spat on, kicked, and harassed outside clinics. Those who challenged the law claimed it was a violation of their freedom of speech under the First Amendment. The court found sufficient public and state interest to uphold the restriction.

further readings

Briant, Keith. 1962. Marie Stopes: A Biography. London: Hogarth.

Korn, Peter. 1996. A Year in the Life of an Abortion Clinic. New York: Grove/Atlantic.

cross-references

Abortion; Roe v. Wade.

Birth Control

In the early twentieth century, a group of reformers sought to legally provide birth control information. The most prominent of these reformers was margaret sanger, who coined the term birth control. Sanger challenged state laws restricting birth control information, seeking to draw public support. Though the courts generally rebuffed her efforts, Sanger helped build a national movement. In 1921, she founded the American Birth Control League, which, in 1942, became the Planned Parenthood Federation of America.

Renewed legal challenges to restrictive state laws began in the 1950s. By 1960, almost every state had legalized birth control. Nevertheless, laws remained on the books that prevented the distribution of birth control information and contraceptives. A specific target was the 1879 Connecticut little Comstock law that made the sale and possession of birth control devices a misdemeanor. The law also prohibited anyone from assisting, abetting, or counseling another in the use of birth control devices.

The Supreme Court reviewed the Connecticut law in griswold v. state of connecticut, 381 U.S. 479, 85 S. Ct. 1678, 14 L. Ed. 2d 510 (1965). Estelle Griswold was the director of Planned Parenthood in Connecticut. Just three days after Planned Parenthood opened a clinic in New Haven, Griswold was arrested. She was convicted and fined $100. The Connecticut courts upheld her conviction, rejecting the contention that the state law was unconstitutional.

The Supreme Court struck down the Connecticut birth control law on a vote of 7 to 2. In his majority opinion, Justice william o. douglas announced that the law was unconstitutional because it violated an individual's right to privacy. Douglas asserted that "specific guarantees in the bill of rights have penumbras, formed by emanations from those guarantees that help give them life and substance. Various guarantees create zones of privacy." Thus, these "penumbras" (things on the fringe of a major region) and "emanations" added up to a general, independent right of privacy. In Douglas's view, this general right was infringed by the state of Connecticut when it outlawed birth control. He said that the state cannot be permitted "to search the sacred precincts of marital bedrooms for telltale signs of the use of contraceptives."

The Griswold decision invalidated the Connecticut law only insofar as it invaded marital privacy, leaving open the question of whether states could prohibit the use of birth control devices by unmarried persons. In Eisenstadt v. Baird, 405 U.S. 438, 92 S. Ct. 1029, 31 L. Ed. 2d 349 (1972), the Court reviewed a Massachusetts law that prohibited unmarried persons from obtaining and using contraceptives. William Baird was arrested after giving a lecture on birth control to a college group and providing contraceptive foam to a female student. The Court struck down the law, establishing that the right of privacy is an individual right, not a right enjoyed only by married couples. Justice william j. brennan jr., in his majority opinion, stated, "If the right of privacy means anything, it is the right of the individual, married or single, to be free from unwarranted governmental intrusion into matters so fundamentally affecting a person as the decision whether or not to beget a child."

With Griswold and Eisenstadt, state prohibition of birth control information and devices came to an end. These decisions also enabled schools to give more information to students concerning sex education. Some schools even dispense contraceptives.

In 1997, the food and drug administration (FDA) approved the use of emergency contraceptive, known popularly as the "morning-after pill." Developed by Canadian professor Albert Yuzpe and known as the Yuzpe Regimen, the pill contains heavy dosages of hormones that can prevent pregnancy if taken 72 hours after sexual intercourse. Proponents, including pro-choice advocates in the abortion debate, claim that it is a safe and effective method of birth control. Pro-life advocates and others denounce the pill as a form of abortion. Some critics in the medical field also claimed that repeated use of the pill could have unknown long-term effects due to its high level of hormones.

Abortion

The establishment in Eisenstadt of an individual's right to privacy soon had dramatic implications for state laws that criminalized abortions. Until the 1960s, abortion was illegal in every state, except to save the mother's life. The growth of the modern feminist movement in the 1960s led to calls for the legalization of abortion, and many state legislatures began to amend their laws to permit abortion when the pregnancy resulted from a rape or when the child was likely to suffer from a serious birth defect. However, these laws generally required that a committee of doctors approve the abortion.

State legislation was swept away with the Supreme Court's controversial decision in roe v. wade, 410 U.S. 113, 93 S. Ct. 705, 35 L. Ed. 2d 147 (1973). A class action lawsuit challenged the state of Texas's abortion law. sarah weddington, the attorney for "Jane Roe," argued that the Constitution allows a woman to control her own body, including the decision to terminate an unwanted pregnancy.

The Supreme Court, on a 7โ€“2 vote, struck down the Texas law. Justice harry a. black-mun, in his majority opinion, relied on the prior right to privacy decisions to justify the Court's action. Blackmun concluded that the right to privacy "is broad enough to encompass a woman's decision whether or not to terminate her pregnancy." More importantly, he stated that the right of privacy is a fundamental right. This meant that the state of Texas had to meet the strict scrutiny test of constitutional review. Texas showed a compelling state interest because it had a strong interest in protecting maternal health that justified reasonable state regulation of abortions performed after the first trimester (three months) of pregnancy. However, Texas also sought to proscribe all abortions and claimed a compelling state interest in protecting unborn human life. Though the Court acknowledged that this was a legitimate interest, it held that it does not become compelling until that point in pregnancy when the fetus becomes "viable," capable of "meaningful life outside the mother's womb." Beyond the point of viability, the Court held that the state may prohibit abortion, except in cases in which it is necessary to preserve the life or health of the mother.

The Court rejected the argument that a fetus is a "person" as that term is used in the Constitution and thus possesses a right to life. To find a fetus to be a person would make any abortion a homicide, which would prevent a state from allowing abortions in cases of rape or in which the pregnancy endangers the life of the mother.

The Roe decision elicited a hostile reaction from opponents of abortion. The creation of a "pro-life" movement that sought to overturn Roe was immediate, becoming a new fixture in U.S. politics. Pro-life forces sought a constitutional amendment to undo the decision, but it fell one vote short in the U.S. Senate in 1983. Over time, as the composition of the Supreme Court has changed, the Court has modified its views, without overturning Roe.

In the 1970s, a majority of the Court resisted efforts by some states to put restrictions on a woman's right to have an abortion. In Planned Parenthood of Central Missouri v. Danforth, 428 U.S. 52, 96 S. Ct. 2831, 49 L. Ed. 2d 788 (1976), the Court struck down a Missouri law that required minors to obtain the consent of their husbands or parents before obtaining an abortion. In 1979, in Bellotti v. Baird, 443 U.S. 622, 99 S. Ct. 3035, 61 L. Ed. 2d 797, the Court invalidated a similar Massachusetts law. Both opinions emphasized the personal nature of abortion decisions and the fact that the state cannot give someone else a veto over the exercise of one's constitutional rights.

In Akron v. Akron Center for Reproductive Health, 462 U.S. 416, 103 S. Ct. 2481, 76 L. Ed. 2d 687 (1983), the Court struck down a city ordinance that required that all abortions be performed in hospitals; a twenty-four-hour waiting period must pass before an abortion could be performed; certain specified statements be made by a doctor to a woman seeking an abortion to ensure that she made a truly informed decision; and all fetal remains be disposed in a humane and sanitary manner. The Court held that these requirements imposed significant burdens on a woman's exercise of her constitutional right without substantially furthering the state's legitimate interests.

Opponents of abortion were successful, however, in preventing the payment of public funds for abortions not deemed medically necessary. In Maher v. Roe, 432 U.S. 464, 97 S. Ct. 2376, 53 L. Ed. 2d 484 (1977), the Court upheld a Connecticut state regulation that denied medicaid benefits to indigent women seeking to have abortions, unless their physicians certified that their abortions were medically necessary. The Court found the law permissible because poor women were not a "suspect class" entitled to strict scrutiny review and because the regulation did not unduly burden the exercise of fundamental rights. In 1980, the Court upheld a provision of federal law, commonly known as the Hyde amendment, forbidding federal funds to support nontherapeutic abortions (Harris v. McRae, 448 U.S. 297, 100 S. Ct. 2671, 65 L. Ed. 2d 784).

During the 1980s and 1990s, the conservative majority on the Court showed more deference to state regulation of abortions. In webster v. reproductive health services, 492 U.S. 490, 109 S. Ct. 3040, 106 L. Ed. 2d 410 (1989), the Court upheld a Missouri law restricting abortions that contained the statement, "the life of each human being begins at conception." On a 5โ€“4 vote, the Court upheld a law that forbids state employees from performing, assisting in, or counseling women to have abortions. It also prohibited the use of any state facilities for these purposes and required all doctors who would perform abortions to conduct viability tests on fetuses at or beyond 20 weeks' gestation.

In 1991, the Court upheld federal regulations imposed by the Reagan administration that barred birth control clinics that received federal funds from providing information about abortion services to their clients (Rust v. Sullivan, 500 U.S. 173, 111 S. Ct. 1759, 114 L. Ed. 2d 233). The Supreme Court found the regulation to be a legitimate condition imposed on the receipt of federal financial assistance.

The Court appeared to be ready to overturn the Roe precedent, but it surprised observers when it upheld Roe in Planned Parenthood v. Casey, 505 U.S. 833, 112 S. Ct. 2791, 120 L. Ed. 2d 674 (1992). The Pennsylvania law restricting abortions required spousal notification, parental consent in cases of minors, and a 24-hour waiting period before the abortion could be performed. Similar requirements had been struck down by the Court before.

On a 5โ€“4 vote, the Court reaffirmed the essential holding of Roe that the constitutional right of privacy is broad enough to include a woman's decision to terminate her pregnancy. Though there was no majority opinion, the controlling opinion by Justice anthony m. kennedy, joined by Justices sandra day o'connor and david h. souter, defended the reasoning of Roe and the line of cases that followed it. However, the joint opinion abandoned the trimester framework and declared a new "undue burden" test for judging regulations of abortion. Using this test, the joint opinion upheld the parental consent, waiting period, and record-keeping and reporting provisions, but invalidated the spousal notification requirement.

Pregnancy and Medical Developments

Artificial insemination, in vitro fertilization, and embryo transplants have created new opportunities for conceiving children. With artificial insemination, sperm from a donor is introduced into the vagina or through the cervix of a woman by any method other than sexual inter-course. Originally this technique was used when a husband was sterile or impotent, but it is now available to women regardless of whether they are married. For example, a lesbian couple could

use artificial insemination to start a biological family.

The technique of in vitro fertilization gained international attention with the 1978 birth in England of Louise Brown, the first child conceived by in vitro fertilization. This technique involves the fertilization of the egg outside the womb. The embryo is then transferred to a woman's uterus.

Because sperm and eggs can be frozen and stored indefinitely, there are occasional legal disputes over the rights to these genetic materials when a husband and wife divorce. For example, in Kass v. Kass, 696 N.E. 2d 174 (N.Y. 1998), the New York Court of Appeals determined that the custody of five frozen embryos should be determined by the terms of a contract signed by a couple with a hospital that stored the embryos. The couple had sought to become pregnant through in virto fertilization, but, after several failed attempts, decided to divorce. The husband and wife initially agreed to the terms of a consent decree with the hospital whereby the hospital could retain the right to keep the embryos for research purposes. The wife later changed her mind and wanted custody of the embryos. The court held that the consent agreements constituted valid contracts and must be enforced. The court ruled that under the terms of the contract, the hospital should be awarded the embryos for use in research.

Other courts have considered disputes whereby one spouse wishes to use embryos for the purpose of procreation while the other wants the embryos destroyed. Several state supreme courts have held that the right of a spouse who wishes to avoid procreation is superior to the wishes of spouse who wishes to procreate. In J. B. v. M. B., 783 A. 2d 707 (N.J. 2001), for example, the New Jersey Supreme Court determined that a husband's right to procreate was not disturbed by its ruling that remaining frozen embryos from the husband and wife be destroyed according to the wishes of the wife.

Developments in in vitro fertilization led to surrogate motherhood, which has caused legal battles as well. In these cases, a woman agrees to be either artificially inseminated by a spermdonor father or have a fertilized ovum inserted into her uterus. After giving birth, the surrogate mother legally surrenders the infant to the person or couple who will adopt and rear the child. The idea of surrogate motherhood is attractive to some couples because a child born of a surrogate mother will share half or all the genetic material of the parents who will raise the child.

One of the most publicized cases regarding surrogate motherhood is that of Baby M. In 1985, Mary Beth Whitehead agreed to be inseminated with the sperm of William Stern and, upon the birth of the child, relinquish her parental rights to Stern. But once the child was born, Whitehead found that she did not wish to give up the child, a girl who she named Sara. A court battle ensued, during which Stern, along with his wife, Elizabeth, were granted temporary custody of the child they had named Melissa. The court decided that Whitehead's parental rights were to be terminated, and Elizabeth Stern was granted the right to immediately adopt the child. The New Jersey Supreme Court overturned this verdict in part on February 2, 1988, restoring Whitehead's parental rights and invalidating Elizabeth Stern's adoption, but granting William Stern custody of the infant.

Many surrogate mothers are close friends or relatives of the childless couple. However, the practice of commercial surrogate arrangements has increased greatly since the late 1980s. Many major cities have surrogate agencies, which are often run by doctors and lawyers who maintain lists of potential surrogate mothers and help match a woman with a couple wanting to have a baby. Commercial surrogate agencies typically charge a fee of $10,000 or more to make the arrangements, which is in addition to the surrogate mother's expenses and fees, which may range from $10,000 to $100,000.

Commercial surrogate arrangements are not legal in all states, and there is little case law on the subject. Some states declare surrogacy contracts null, void, and unenforceable because they are against public policy. Opponents of commercial surrogacy believe that such arrangements exploit the surrogate mother and turn children into a commodity. They also are concerned that if a child is born with a disability, the adoptive parents may decline to take the child. Finally, there is the issue of the surrogate mother who may not wish to surrender the child after birth.

Other medical developments have also stirred controversy. In 1997, scientists successfully cloned the first adult animal, leading to speculation that the process could be used to clone human beings. Scientists first successfully inserted DNA from one human cell into another human egg, but they do not expect successful human cloning to be possible for several years. The issue has caused heated debates focusing on the scientific, moral, and religious concerns over the possibility that an adult human could be cloned.

Reproductive Hazards in the Workplace

Legal disputes have arisen when employers have barred pregnant women and women of childbearing age from jobs that pose potential hazards to the fetus. The Supreme Court, in United Auto Workers v. Johnson Controls, 499 U.S. 187, 111 S. Ct. 1196, 113 L. Ed. 2d 158 (1991), ruled that a female employee cannot be excluded from jobs that expose her to health risks that may harm her fetus. The Court found that the exclusion of the women violated Title VII of the civil rights act of 1964 (42 U.S.C.A. ยง 2000e et seq.) because the company policy only applied to fertile women, not fertile men. Justice Blackmun, in his majority opinion, noted that the policy singled out women on the basis of gender and childbearing capacity rather than on the basis of fertility alone. Concerns about the health of a child born to a worker at the plant were to be left "to the parents who conceive, bear, support, and raise them [the children] rather than to the employers who hire those parents."

further readings

"Genetics, Reproduction, and the Law." 1999. Trial 35 (July).

Hollinger, Joan Heifetz. 1985. "From Coitus to Commerce: Legal and Social Consequences of Noncoital Reproduction." University of Michigan Journal of Law Reform 18 (summer).

"In re Baby M" (colloquy). 1988. Georgetown Law Journal 76 (June).

"In re Baby M" (symposium). 1988. Seton Hall Law Review 18 (fall).

Levy, Stephanie. 2001. "Whose Embryo Is It Anyway? Courts Wrestle with Issues of High-tech Reproduction." Trial 37 (December).

Rahman, Anika. 1995. "Toward Government Accountability for Women's Reproductive Rights." St. John's Law Review 69 (winter-spring).

Ridder, Stephanie, and Lisa Woll. 1989. "Transforming the Grounds: Autonomy and Reproductive Freedom." Yale Journal of Law and Feminism 2 (fall).

Robertson, John A. 1988. "Procreative Liberty And The State's Burden Of Proof In Regulating Noncoital Reproduction." Law, Medicine & Health Care 16 (spring-summer).

cross-references

Abortion; Adoption; Fetal Rights; Fetal Tissue Research; Genetic Engineering; Husband and Wife; Penumbra; Sex Discrimination; Wattleton, Alyce Faye; Women's Rights.

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Reproduction

REPRODUCTION

CONCEPT

The term reproduction encompasses the entire variety of means by which plants and animals produce offspring. Reproductive processes fall into two broad groupings: sexual and asexual, the latter being the means by which bacteria and algae reproduce. Many plants reproduce sexually by means of pollination, and some plants alternate between sexual and asexual forms of reproduction. Other creatures, such as bees and ants, reproduce through a form of reproduction called parthenogenesis, which is neither fully sexual nor asexual.

HOW IT WORKS

Asexual Reproduction

Asexual reproduction involves only one organism, as opposed to two in sexual reproduction. It occurs when a single cell divides to form two daughter cells that are genetically identical to the parent cell. This process is known as fission, and it may take the form either of binary fission, in which two new cells are produced, or multiple fission, which results in the creation of many new cells. Since there is no fusion of two different cells, the daughter cells produced by asexual reproduction are genetically identical to the parent cell. Asexual reproduction usually takes place by mitosis, a process during which the chromosomes in a cell's nucleus are duplicated before cell division. (Mitosis, chromosomes, and many other topics referred to in this essay are discussed in considerably more detail in Genetics.)

Whereas sexual reproduction is extremely complexand human sexual reproduction is much more so, freighted as it is with degrees of meaning that go far beyond mere biologyasexual reproduction is a fairly simple, cellular process. Of course, nothing in nature is really simple, and, in fact, the dividing and replication of DNA (deoxyribonucleic acid, the genetic blueprint material found in each cell) is a complicated subject; however, that subject, too, is discussed in the essay Genetics. DNA is located at the cell nucleus, which is the cell's control center, and the nucleus is the first part of the cell to divide in asexual reproduction. After the nucleus splits, the cytoplasm, or the cellular material external to the nucleus, then divides. The result is the formation of two new daughter cells whose nuclei have the same number and kind of chromosomes as the parent.

The adaptive advantage of asexual reproduction is that organisms can reproduce quickly and by doing so colonize favorable environments rapidly. (See Evolution for more about the importance of adaptation and environment in shaping species.) For example, some bacteria can double their numbers every 20 minutes. In addition to bacteria, which are discussed in more detail in Infection, other life-forms that reproduce asexu-ally include protozoa (varieties of which are examined in Parasites and Parasitology), blue-green algae, yeast, dandelions, and flatworms.

Sexual Reproduction

Sexual reproduction involves the union of two organisms rather than the splitting of one. Like asexual reproduction, it is a process that takes place at the cellular level. In sexual reproduction it is not binary fission that occurs, but the fusion of two cells. Nor are the two cells identical; rather, the cellsknown as gametescan be identified as either male or female according to the makeup of their chromosomes. The male gamete is called a sperm cell, and the female gamete is termed an egg cell. In sexual reproduction, the sperm cell fuses, or bonds, with the egg cell to produce a cell that is genetically different from either of the parent cells. This process of fusion is known as fertilization, and the fertilized egg is called a zygote. Gametes are produced in the male testes and female ovaries by a splitting process called meiosis. (Meiosis and other terms mentioned briefly in these paragraphs are discussed in much more detail in Genetics.)

Meiosis produces haploid cells, or ones that have half the number of chromosomes as are in a normal cell for that species. When the haploid sperm and egg cells fuse at fertilization, however, the chromosomes from both combine, so that the normal number of chromosomes appears in the zygote. The shuffling of the parents' genetic material that happens during meiosis allows for new gene combinations in offspring that account for variations between offspring (which is why you don't look just like your siblings) and which, over time, can improve a species' chances of survival.

REAL-LIFE APPLICATIONS

Examples of Asexual Reproduction

As we noted earlier, bacteria, blue-green algae, most protozoa, yeast, and flatworms all reproduce asexually, as do mosses and starfish. (The last actually reproduce both sexually and asexually by means of alternation of generations, discussed later.) The products of asexual reproduction are known as clonesan example of the fact, discussed in Genetic Engineering, that cloning and the concept of clones are not as new as one might imagine. (See that essay for much more about artificial cloning.) A starfish can regenerate and eventually produce a whole new organism from a single severed appendage, while flatworms divide in two and regenerate to form two new flatworms. This formation of a separate organism is obviously much more complex than the simple splitting of single bacteria cells, but it is still a form of asexual reproduction.

VEGETATIVE PROPAGATION.

Strawberries reproduce by forming growths called runners, which grow horizontally and generate new stalks. At some point, the runner decomposes, leaving a new plant that is a clone of the original. This is an example of vegetative propagation, a term for a number of processes by which crop plants are produced asexually. Vegetative propagation is used for such crops as potatoes, bananas, raspberries, pineapples, and some flowering plants. Its advantage to farmers is that the crops will be more uniform than those grown from seed. Furthermore, some plants are difficult to cultivate from seed, and the vegetative propagation of those plants makes it possible to grow crops that otherwise would not be available for commercial marketing.

In reproducing potatoes through vegetative propagation, farmers plant the so-called eyes to produce duplicates of the parent. With banana plants, the farmer separates the suckers that grow from the root of the plant and plants them. The farmer raising raspberry bushes bends the branches and covers them with soil, whereupon a process not unlike that of the runner growth of mosses takes place: the branches eventually grow into a separate plant, with their own root system, and ultimately can be detached from the parent plant.

Between Asexual and Sexual

The example of vegetative propagation suggests that there is not a sharp dividing line between sexual and asexual reproductionthat is, that many organisms can reproduce either way. This is true even of humans, who, in theory, could be cloned, though the technology to do solet alone resolution of the ethical issues of the procedurelies in the far distant future. (See Genetic Engineering for more on this subject.) Even humans, however, can use external fertilization, which is sexual reproduction without sexual intercourse (see Sexual Reproduction).

Plants go through a process known as alternation of generations, in which they alternate as sexual and asexual reproducers, or gametophytes and sporophytes, respectively. In the asexual stage, the sporophyte produces diploid reproductive cells called spores, which develop into gametophytes. These gametophytes produce haploid gametes, which then unite sexually to form a diploid zygote that grows into a sporophyte. In plain English, this means that the asexual "grand-parent" generates a sexually reproducing "child," which in turn produces a "grandchild" that is asexual, like its grandparent.

At one phase in the alternation of generation for mosses, for instance, male and female moss plants grow from spores. Male moss plants produce sperm cells, which, when the moss receives rainfall, are able to propagate because they have a medium (water) in which to move. They fertilize the female plants, producing zygotes. The zygote grows on top of the female moss plant, which helps to store moisture and thus provides a hospitable environment in which the zygote can develop. The zygote eventually produces haploid spores, which it releases into the air. These tiny spores, carried by the wind, float away from their point of origin until they come to rest, and soon the cycle begins once again.

PARTHENOGENESIS.

There are also organisms, including bees, ants, wasps, and other insects, that reproduce in a way that is neither fully sexual nor asexual. This is parthenogenesis, a type of reproduction in which a gamete develops without fertilization. In other words, a sex cell is reproduced without actual intercourse between male and female. The gamete is almost always femalea fact indicated in the name itself, which comes from parthenos, Greek for "maiden."

The Parthenon in Athens, like the city itself, is named after the goddess Athena (also called Minerva), who was known by the nickname Parthenos. She is said to have been born fully formed, having sprung from the head of her father, Zeus, dressed in armor and ready for battle. Thus, her own birth was a form of parthenogenesis, a word whose second half (a name well known from the Bible) means "beginning."

Pollen and Pollination

Pollen is a fine, powdery substance consisting of microscopic grains containing the male gametophyte of certain plants that reproduce sexually. These plants include angiosperms, a type of plant that produces flowers during sexual reproduction, and gymnosperms, which reproduce sexually through the use of seeds that are exposed and not hidden in an ovary, as with an angiosperm. Pollen is designed for long-distance dispersal from the parent plant, so that fertilization can occur. Pollination is the transfer of pollen from the male reproductive organs to the female reproductive organs of a plant, and it precedes fertilization. In other words, pollination is the equivalent of sexual intercourse for seed-bearing plants. Actually, cross-pollination, or the transfer of pollen from one plant to another, would perhaps be analogous to sexual intercourse in animals. Pollination occurs in seed-bearing plants, as opposed to the more primitive spore-producing plants, such as ferns and mosses. Gymnosperms, such as pines, firs, and spruces, produce male and female cones, whereas angiosperms produce flowers containing a male organ called the stamen and a female organ called the pistil. Both types of plants rely on insects and other creatures to aid in the pollen transfer.

DARWIN'S MOTH.

The German physician and botanist Rudolf Jakob Camerarius (1665-1721) was the first scientist to demonstrate that plants reproduce sexually, and he pioneered the study of pollination. One of the scientists influenced by his work was the English naturalist Charles Darwin (1809-1882), who discussed the subject in The Various Contrivances by which Orchids Are Fertilized by Insects (1862). Darwin wrote this book partly to support the ideas on evolution presented in his much more well known book Origin of Species (1859). In Various Contrivances, he suggested that orchids and their insect pollinators evolved by interacting with one another over many generations.

As an example, he discussed Angraecum sesquipedale, an orchid native to Madagascar. Darwin had not seen the plant in its native habitat, however; he had looked only at its dried leaves. The white flower of this orchid has a foot-long (30 cm) tubular spur with a small drop of nectar at its base, and from observing this, he hypothesized that the orchid had been pollinated by an insect with a foot-long tongue. This hypothesis, he wrote, "has been ridiculed by some entomologists," or scientists who study insects. After all, no such creature had been found in Madagascar. But then, around the turn of the nineteenth centurysome two decades after Darwin's deathit was found. A Madagascan moth was discovered that had a foot-long tongue that uncoils to sip the nectar of A. sesquipedale as it cross-pollinated the flowers.

PLANTS AND THEIR POLLINATORS.

Angiosperms and gymnosperms are discussed in Ecosystems and Ecology, where each is compared in terms of its degree of adaptation to its environment. Angiosperms seem to be the hands-down winner: by enlisting the aid of insects and other pollinators, they manage to pollinate much more efficiently than gymnosperms, which have to produce vast quantities of pollen for each grain that reaches its target. Typically, pollination benefits the animal pollinator by supplying it with sweet nectar and, of course, benefits the plant by providing direct transfer of pollen from one plant to the pistil of another plant. For this reason, specific plant and animal species have developed a relationship of mutualism, a form of symbiosis in which each participant reaps benefits (see Symbiosis). In many cases, plant and pollinator have evolved together, and it is possible to determine which animal pollinates a certain flower species simply by studying the morphologic features (shapes), color, and odor of the flower.

For example, some flowers are pure red, or nearly pure red, and have very little odor. In most such situations, the pollinator is a bird species, since birds have excellent vision in the red region of the spectrum but a rather undeveloped sense of smell. It so happens that Europe, which has no pure red native flowers, also has no bird-pollinated native flower species. Not all bird-pollinated flowers are red, but they are all characterized by striking, and sometimes contrasting, colors that readily catch the eye. Examples of plants pollinated by birds include the cardinal flower, the red columbine, the hibiscus, the eucalyptus, and varieties of orchid, cactus, and pineapple.

Some flowering plants have a very strong odor but are very dark, or at least drab, in color. These flowers and plantsexamples include the saguaro cactus, century plant, or cup-and-saucer vineare often pollinated by bats, which have very poor vision, are typically active during the night, and have a very well developed sense of smell. The flowers of many plant species are marked with special pigments called flavonoids, which absorb ultraviolet light and appear to direct the pollinator toward the pollen and nectar. These pigments are invisible to humans and most animals, but bees' eyes have special ultraviolet photoreceptors that enable the bees to detect patterns and so pollinate these flowers.

WHERE TO LEARN MORE

"Asexual Reproduction Lab." Lester B. Pearson College of the Pacific (Web site). <http://www.pearson-college.uwc.ca/pearson/biology/asex/asex.htm>.

Canine Reproduction (Web site). <http://www.labbies.com/canine_reproduction_table_of_con.htm>.

CRES: The Center for Reproduction of Endangered Species/ San Diego Zoo (Web site). <http://www.sandiegozoo.com/conservation/cres_home.html>.

Elia, Irene. The Female Animal. New York: Henry Holt, 1988.

"Flowering Plant Reproduction." Estrella Mountain Community College (Web site). <http://gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookflowers.html>.

Kevles, Bettyann. Females of the Species: Sex and Survival in the Animal Kingdom. Cambridge, MA: Harvard University Press, 1986.

Kimball, Jim. "Asexual Reproduction ." Kimball's Biology Pages (Web site). <http://www.ultranet.com/~jkimball/BiologyPages/A/AsexualReproduction.html>.

Maxwell, Kenneth E. The Sex Imperative: An Evolutionary Tale of Sexual Survival. New York: Plenum, 1994.

The Pollination Home Page (Web site). <http://pollinator.com/>.

Reproduction (Web site). <http://www.factmonster.com/ce6/sci/A0841565.html>.

Topoff, Howard R. The Natural History Reader in Animal Behavior. New York: Columbia University Press, 1987.

Walters, Mark Jerome. The Dance of Life: Courtship in the Animal Kingdom. New York: Arbor House, 1988.

KEY TERMS

ALTERNATION OF GENERATIONS:

A process whereby plant generations alternate as sexual and asexual reproducersgametophytes and sporophytes, respectively.

ASEXUAL REPRODUCTION:

One of the two major varieties of reproduction (along with sexual reproduction), In contrast to sexual reproduction, which involves two organisms, asexual reproduction involves only one. Asexual reproduction occurs when a single cell divides through mitosis to form two daughtercells, which are genetically identical to the parent cell.

BINARY FISSION:

The process in asexual reproduction whereby a single cell divides to form two daughter cells that are genetically identical to the parent cell.

CLONE:

A cell, group of cells, or organism that contains genetic information identical to that of its parent cell or organism.

CLONING:

A specialized genetic process whereby clones are produced. Cloning is a form of asexual reproduction.

CHROMOSOME:

A DNA-containing body, located in the cells of most living things, that holds most of the organism's genes.

CROSS-POLLINATION:

The transfer of pollen from one plant to another.

CYTOPLASM:

The material inside a cell that is external to the nucleus.

DIPLOID:

A term for a cell that has the basic number of doubled chromosomes.

DNA:

Deoxyribonucleic acid, a molecule in all cells, and many viruses, that contains genetic codes for inheritance.

EGG CELL:

A female gamete.

ENZYME:

A protein material that speeds up chemical reactions in the bodies of plants and animals without itself taking part in or being consumed by those reactions.

FERTILIZATION:

The process of cellular fusion that takes place in sexual reproduction. The nucleus of a male reproductive cell, or gamete, fuses with the nucleus of a female gamete to produce a zygote.

GAMETE:

A reproductive cellthat is, a mature male or female germ cell that possesses a haploid set of chromosomes and is prepared to form a new diploid by undergoing fusion with a haploid gamete of the opposite sex. Sperm and egg cells are, respectively, male and female gametes.

GAMETOPHYTE:

In alternation of generations, a gametophyte is a plant that reproduces sexually.

GERM CELL:

One of two basic types of cells in a multicellular organism. In contrast to somatic or body cells, germ cells play a part in reproduction.

HAPLOID:

A term for a cell that has half the number of chromosomes that appear in a diploid or somatic cell.

MEIOSIS:

The process of cell division that produces haploid genetic material. Compare with mitosis.

MITOSIS:

A process of cell division that produces diploid cells, as in asexualreproduction. Compare with meiosis.

NUCLEUS:

The control center of a cell, where DNA is stored.

OVARY:

Female reproductive organ that contains the eggs.

OVULE:

Female haploid gametophyte of seed plants, which develops into a seed upon fertilization by a pollen grain.

PARTHENOGENESIS:

A type of reproduction that involves the development of a gamete without fertilization. In other words, a sex cell (usually female) is reproduced without actual intercourse between male and female.

POLLEN:

Male haploid gametophyte of seed plants (including angiosperms and gymnosperms), which unites with the ovule to form a seed. Pollen is a fine, powdery substance consisting of microscopic grains.

POLLINATION:

The transfer of pollen from the male reproductive organs to the female reproductive organs of a plant. Pollination precedes fertilization. See also cross-pollination.

REGENERATION:

A biological process among some lower animals whereby a severed body part is restored by the growth of a new one.

SEXUAL REPRODUCTION:

One of the two major varieties of reproduction (along with asexual reproduction). In contrast to asexual reproduction, which involves a single organism, sexual reproduction involves two. Sexual reproduction occurs when male and female gametes undergo fusion, a process known as fertilization, and produce cells that are genetically different from those of either parent.

SOMATIC CELL:

One of two basic types of cells in a multicellular organism. In contrast to germ cells, somatic cells (also known as body cells) are not involved in reproduction; rather, they make up the tissues, organs, and other parts of the organism.

SPERM CELL:

A male gamete.

SPOROPHYTE:

In alternation of generations, a sporophyte is a plant that reproduces asexually.

ZYGOTE:

A diploid cell formed by the fusion of two gametes.

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Reproduction

Reproduction

BIBLIOGRAPHY

Reproduction in anthropology refers to the processes by which new social members are producedspecifically, the physiological processes of conception, pregnancy, birth, and child-raising. In its larger sense, reproduction encompasses the processes by which societies are reproduced for the future. The term is thus fraught with biological, cultural, and political meanings; power is a central focus in reproductive studies, as those who have the power to influence the process of reproduction can control both individual and large populations for better or for worse.

The maturation of the field of the anthropology of reproduction was marked by the publication of Conceiving the New World Order: The Global Politics of Reproduction (1995), edited by Faye Ginsburg and Rayna Rapp. This collection expanded the meaning of reproduction into the political arena and generated the interface of reproductive studies with wider issues in the politics of womens health care. From a study of anti-abortion policies in Romania, to Chinas one-child policy, to the displacement of thousands of women in India and Pakistan to purify the national bodies of both countries, the chapters in this volume called attention to the impact of national and global processes on everyday reproductive experience, most especially through the notion of stratified reproduction, which points to transnational reproductive inequalities based on gender, race, and class. In addition, Rapps long-term fieldwork on amniocentesis illustrates racial, class, and religious differences in how women make choices about this technology, and demonstrates the linguistic power of genetic counselors to influence these choices in favor of the culturally approved choice of abortion for genetically defective babies.

Since the 1990s, most anthropological studies of reproduction have focused on what have come to be called the new reproductive technologies (NRTs)technologies designed to intervene in human reproduction. From the birth of the worlds first test-tube baby in 1978 to the cloning of a higher vertebrate from an adult cell in 1997, the rapid expansion of the NRTs in the latter half of the twentieth century dramatically redefined the parameters of biological reproduction. The NRTs include, among many others: birth control technologies such as intrauterine devices (IUDs) and the birth control pill; assisted conception technologies such as artificial insemination and in-vitro fertilization (IVF); screening technologies such as ultrasound, amniocentesis, and blood testing; reparative technologies such as fetal surgeries performed in utero; labor and birth technologies such as electronic fetal monitoring, synthetic hormones for labor induction and augmentation, and multiple types of anesthesia; and postnatal technologies such as infant surgeries and high-tech treatment of babies in neonatal intensive care units. All of these technologies are increasingly affected by developments in biotechnology, such as genetic engineering, which have major implications for the control and management of human fertility.

Like the obstetrical forceps developed by the Chamberlen brothers in the sixteenth century, the NRTs have double-edged implications for women and their offspring. While those early forceps did save the lives of babies who otherwise might have died, their overzealous and ill-informed application during childbirth by male midwives and obstetricians often left the mother and baby severely damaged. The NRTs have been equally problematic, often creating as many problems as they solve and causing as much damage as they repair. For example, maternal mortality as a result of ovarian hyperstimulation, and increased congenital abnormality because of multiple births, are but two examples of the downside of in-vitro fertilization (IVF).

Reproductive technology has affected every facet of the reproductive process, from preconception onward. To an extent, these developments respond to specific impediments to fertility: IVF, for example, was originally used to assist women with blocked ovarian tubes. Feminist critics, however, have rightly pointed to other, less woman-centered influences shaping the development of these technologies. For example, Robert Edwards, the research scientist who helped to develop IVF, was trained in embryology and foresaw tremendous research potential from the ability to manipulate the human embryo ex vivo. This potential was extensively exploited in the rapid expansion of human embryo experimentation in the 1980s and the 1990s.

The encounter between a largely male medical and scientific establishment and womens reproductive capacity is very pointed in the context of IVF, which is often represented as being a response to the desperate desires of infertile women but can as readily be interpreted as a response to the irresistible scientific urge to unveil and indeed to redesign the facts of life. The tremendous value of early embryonic cellsboth commercially and in terms of researchhas made IVF an important source of human embryonic stem cells. This fact exists in uneasy tension with womens demands for improved reproductive services. As in other historical periods, the neglect of womens reproductive needs is most evident in terms of which kinds of services will be developed and prioritized.

While new embryo therapies are used to detect, and even to eliminate, genetic disease, other reproductive priorities remain devalued and underfunded. For example, while ever more sophisticated technologies are developed to deal with the complications of labor and birth, the normal physiological needs of laboring women remain understudied and unfulfilled. The scientific evidence that does exist supports simple technologies like eating and drinking during labor, woman-centered, supportive care, and upright positions for delivery as being of far more help to birthing women than high-tech machines. Nevertheless, the hegemonic global influence of what Davis-Floyd (2004) calls the technocratic model of birth has resulted in rapidly rising cesarean rates in many countries and has simultaneously precluded adoption of more humanistic and physiologic techniques for supporting normal birth. A growing body of anthropological literature reveals the systematic deconstruction of traditional birthing systems around the world. These systems are being replaced by biomedical care that disregards womens individual needs in favor of standardized approaches (DeVries et al. 2001), and that, in the developing world, often suffers from such drastic underfunding that basic supplies, clean facilities, and sufficient numbers of trained caregivers are regularly unavailable (Allen 2002; Davis-Floyd and Sargent 1997; Feldman-Savelsberg 1999; Hunt 1999; Luckere and Jolly 2002; Ram and Jolly 1998; Van Hollen 2003).

Two major influences continue to shape the development of reproductive technology in ways that are not in womens interests. One is the continuing, and indeed worsening, effects of global inequality that are borne most heavily by women and young children, especially infants. Adequate, or indeed any, access to basic contraceptive technology remains out of reach of the majority of the worlds female population (despite concerns about population growth, and largely as a result of U.S. anti-abortion policy). Consequently, resource-intensive and largely private fertility care is provided to a predominantly wealthy world elite. Meanwhile, enduring tragedies of high maternal and infant mortality from preventable causes such as malnutrition and lack of a clean water supply, inadequate access to safe abortion and contraceptives, and limited, nonexistent, or ineffective reproductive health care are the main issues affecting the majority of the worlds women. In sum, proper sanitation, adequate nutrition, improved vaccination programs, access to culturally appropriate forms of birth control, access to community midwives backed by adequate transport systems, and above all increased literacy and education rates among women remain the most important and lifesaving reproductive technologies.

At the other end of the spectrum, at the cutting edge of twenty-first-century medical science, is the resurgence of a new genetic essentialism. Reproductive technology is shifting its focus in the direction of germline gene therapies (therapies that can be genetically transmitted because they modify reproductive cells). Annexed to the project of mapping the human genome, reproductive science and medicine are increasingly aimed at both the elimination of genetic pathology and the effort to reengineer the genomes of humans and other life-forms. In addition to existing means of technologically assisting conception, the effort to alter human genealogy is the single most important influence on contemporary reproductive technologies. This effort is driven by enormously competitive economic forces and by an if we can do it, we must do it technocratic mentality, resulting in rapidly escalating and largely unregulated technological innovation.

While some commentators argue that reproductive technologies such as the freezing of eggs, cloning by nuclear transfer, germline gene therapy, and embryo biopsy will have a radical effect on gender roles and kinship definitions, the majority of evidence demonstrates a reverse effect: the restabilization of traditional and conservative family ideologies in the face of their potential disruption. At the same time, other influences, such as the lesbian and gay movement, the increase in transnational adoption, rising divorce rates, and greater economic independence for women, have proven more influential in the redefinition of family and parenthood. Consequently, although some uses of reproductive technology have created more parenting options, such as the use of artificial insemination by lesbians, the overwhelming pattern of access to NRTs is defined by the goal of enhancing conventional parenting arrangements by married, heterosexual, and middle-class couples.

Feminist concern about reproductive technologies in the twenty-first century will increasingly overlap with the criticisms of biotechnology and genetic engineering raised by environmentalists and the general public. Concern about genetically modified organisms in the food chain and in medical applications will increase, particularly as the human-animal border becomes ever more permeable. The extensive feminist literature on NRTs anticipates with great precision many of the profound social, ethical, and political concerns surrounding new forms of genetic and biological determinism arising out of the attempt to alter the human genome. In addition to the effort to redefine medical and scientific priorities in relation to womens reproductive health worldwide, feminist anthropological scholarship will continue to insist upon the primacy of fully informed reproductive decision making, in its widest sense, as a fundamental component of human rights.

SEE ALSO Abortion; Abortion Rights; Anthropology; Birth Control; Childlessness; Demography; Fertility, Human; Genetic Testing; Limits of Growth; Malthusian Trap; Marriage; Multiple Births; Population Growth; Reproductive Rights; Sexual Orientation, Social and Economic Consequences; Women’s Movement

BIBLIOGRAPHY

Allen, Denise Roth. 2002. Managing Motherhood, Managing Risk: Fertility and Danger in West Central Tanzania. Ann Arbor: University of Michigan Press.

Davis-Floyd, Robbie. 2004. Birth as an American Rite of Passage, 2nd ed. Berkeley: University of California Press.

Davis-Floyd, Robbie, and Carolyn Sargent. 1997. Childbirth and Authoritative Knowledge: Cross-Cultural Perspectives. Berkeley: University of California Press.

Davis-Floyd, Robbie, and Joseph Dumit. 1998. Cyborg Babies: From Techno-Sex to Techno-Tots. New York: Routledge.

DeVries, Raymond, Edwin van Teijlingen, Sirpa Wrede, and Cecilia Benoit, eds. 2001. Birth by Design: Pregnancy, Maternity Care and Midwifery in North America and Europe. New York: Routledge.

Feldman-Savelsberg, Pamela. 1999. Plundered Kitchens, Empty Wombs: Threatened Reproduction and Identity in the Cameroon Grassfields. Ann Arbor: University of Michigan Press.

Franklin, Sarah, and Helene Ragoné. 1997. Reproducing Reproduction: Kinship, Power, and Technological Innovation. Philadelphia: University of Pennsylvania Press.

Ginsburg, Faye, and Rayna Rapp, eds. 1995. Conceiving the New World Order: The Global Politics of Reproduction. Berkeley: University of California Press.

Hunt, Nancy Rose. 1999. A Colonial Lexicon of Birth Ritual, Medicalization, and Mobility in the Congo. Durham, NC: Duke University Press.

Luckere, Vicki, and Margaret Jolly, eds. 2002. Birthing in the Pacific: Beyond Tradition and Modernity. Honolulu: University of Hawaii Press.

Ram, Kalpana, and Margaret Jolly. 1998. Maternities and Modernities: Colonial and Postcolonial Experiences in Asia and the Pacific. Cambridge, U.K., and New York: Cambridge University Press.

Taylor, Janelle, Linda Layne, and Danielle Wozniak, eds. 2004. Consuming Motherhood. New Brunswick, NJ: Rutgers University Press.

Van Hollen, Cecilia. 2003. Birth on the Threshold: Childbirth and Modernity in South India. Berkeley: University of California Press.

Robbie Davis-Floyd

Sarah Franklin

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Reproduction

REPRODUCTION

Reproduction is the process by which offspring are formed and genetic material is passed on from one generation to the next. In humans, reproduction is sexual.

FERTILIZATION

Gametes are produced by the reproductive glands, or gonads. Female gonads (ovaries) produce ova and male gonads (testes) produce sperm. Both ovum and sperm are haploid, which means that they contain half the normal (diploid) amount of genetic material (DNA) of the adult. During coitus, about 100 million sperm are deposited in the vagina, but only a few hundred reach the site of fertilization in the fallopian tube. One sperm penetrates the ovum during a process that leads to the fusion of the sperm and ovum nuclei, which contain the DNA. This fusion restores the diploid chromosome number, so that offspring inherit about half of their genes from each parent.

The fertilized ovum, now called the zygote, undergoes repeated cell divisions as it moves toward the uterus and implants in the endometrium. Only 20 to 25 percent of fertilized ova result in successful pregnancies. The rest fail to divide, fail to implant, or miscarry. Many of these unsuccessful pregnancies are genetically abnormal.

PREGNANCY

During the first trimester of pregnancy, the conceptus differentiates various specialized structures and organs, a process called embryogenesis. At the completion of this period, the embryo becomes a fetus. During the second and third trimesters, the fetus continues to grow and mature. By the ninth month, the fetus should be able to breathe on its own and maintain a normal body temperature. Survival rates are greater than 99 percent for babies born in most developed countries. Infant mortality is an important measure of public health and is influenced by many factors, including the proportion of births that occur prematurely or with birthweight that is too low. Other factors, such as the availability of services to ensure safe delivery and good health for mother and fetus, also influence infant mortality.

About 3 percent of infants have major congenital anomalies that are apparent in the first year of life. Such birth defects are the most frequent causes of infant mortality in many developed countries. Some congenital anomalies result from chromosomal abnormalities or mutations of single genes or gene pairs, but the cause of most birth defects is unknown. Many congenital anomalies appear to result from combinations of genetic and nongenetic factors that have not yet been identified.

Supplementation of the mother's diet with folic acid around the time of conception reduces the occurrence of neural tube defects and certain other birth defects. Reducing the occurrence of birth defects by folic acid dietary supplementation or food fortification is an important but largely unfulfilled public health opportunity.

Teratogenic exposures are thought to be responsible for about 10 percent of congenital anomalies. A variety of infections, medications, alcohol, and other agents can adversely affect embryonic or fetal development under certain exposure conditions. The embryo is most sensitive to damage from most teratogenic exposures between two and ten weeks after conception. Teratogenic exposures are an especially important cause of birth defects because they are potentially preventable.

CONTRACEPTION

Contraception is the process or means used to prevent pregnancy. Contraceptive options include abstinence, spermicide, male condoms, female condoms, hormonal methods, diaphragm, intra-uterine devices (IUDs), and surgical sterilization. Different methods of birth control have different degrees of effectiveness against pregnancy and of protection against sexually transmitted diseases (STDs). Each method has specific advantages, risks, and limitations.

The most effective method of birth control is abstinence. This method is 100 percent effective against pregnancy and has a decreased risk of contracting STDs. For sexually active people, the effectiveness for pregnancy prevention by surgical sterilization or hormonal contraceptive methods, when properly used, is about 99 percent. IUDs and condoms with spermicide can provide protection against pregnancy that is almost as good, although inconsistent use is often a limiting factor in practice with methods such as condoms. Condoms can also provide protection against STDs.

The use of effective contraceptive methods has led to fewer unwanted pregnancies and possibly a decrease in the spread of STDs in industrialized countries. Declining infant mortality has produced a growing population and a greater need for family planning measures in most of the world, but the overall reproductive health of women has often received less attention. This is evidenced by high rates of maternal mortality and STDs. It is estimated that about 600,000 maternal deaths occur each year, with the overwhelming majority in developing countries. Close to 80 percent of these deaths are direct results of complications rising during pregnancy, delivery, or the post-partum period. The remaining 20 percent are due to preexisting maternal conditions that worsen during pregnancy, such as HIV/AIDS (human immunodeficiency virus/acquired immunodeficiency syndrome), malaria, heart disease, or hepatitis. Maternal mortality is highest in south and southeast Asia, sub-Saharan Africa, and Latin America.

One possible consequence of STDs is pelvic inflammatory disease (PID), a major cause of damage to female reproductive organs that can lead to death if untreated. Barrier contraceptive methods that decrease the risk of contracting STDs may also protect against PID. Oral contraceptive use is also associated with a decreased risk of PID, although the mechanism of this protection is unknown. IUDs are believed to increase the risk of PID, especially in women who are at an increased risk for STDs. PID currently affects about 1 million American women, most of whom are from lower socioeconomic classes.

Since no method of birth control except for complete abstinence is 100 percent effective, unwanted pregnancies do occur. In these cases, induced abortion may be used to terminate the pregnancy. Induced abortion has important ethical, psychological, and medical drawbacks when used as a substitute for contraception. Physical complications are frequent when abortions are done without proper sterile technique or by individuals who lack the necessary training and skills. Complications may include severe pain, infection, uterine perforation, hemorrhage, and death. Unsafe abortion is a major cause of death and illness for women of childbearing age. It is estimated that complications of unsafe abortions are responsible for 13 percent of maternal deaths. In some parts of the world, one-third or more of all maternal deaths are associated with unsafe abortions.

INFERTILITY

Infertility is an inability to have children. In medical practice, infertility is diagnosed when a couple has been unable to conceive after one year of unprotected intercourse timed to coincide with ovulation. If the woman is over thirty-five years of age or has been unable to carry a pregnancy to term, this time is reduced to six months. Infertility affects 5.3 million Americans. Approximately 40 percent of infertility is due to female factors, 40 percent to male factors, and 20 percent to either combined or unknown factors. STDs and PID are two conditions that can lead to infertility in women. Therefore, educating the public about the risks of these infections is important in preventing infertility and improving women's health.

Conventional treatments for infertility depend on the cause and may include hormonal therapy and surgical procedures. In cases in which conventional methods fail, more advanced assisted reproductive technologies (ARTs) may be used. Current use of ARTs other than artificial insemination by donor is restricted because of limited availability, expense, and relatively low success rates.

PRENATAL DIAGNOSIS AND SCREENING

A variety of prenatal diagnostic techniques are available for couples at increased risk of having a child with certain genetic or developmental abnormalities. These tests include amniocentesis and chorionic villous sampling (CVS). Such invasive techniques are associated with small risks of inducing pregnancy loss or fetal damage and require skilled operators and sophisticated ultrasonography equipment. Ultrasound examination and maternal serum screening tests, which are not associated with any known fetal risks, are used for routine pregnancy screening in some jurisdictions. These techniques can identify many, but not all, fetuses with Down syndrome or serious structural abnormalities such as spina bifida. Because very few fetal abnormalities can be treated effectively before delivery, prenatal screening or diagnosis may raise serious ethical and social issues related to the abortion of fetuses considered to be less than perfect.

Increased availability and public support of reproductive medical care and related educational and prevention initiatives in most developed countries have had an important beneficial effect on the health of women and young children. However, such services are not readily available in all parts of the world, and maternal and infant mortality as well as death and illness from STDs are far too frequent. Providing public health interventions to deal with these problems in an appropriate cultural, social, and religious context remains an urgent and often very challenging priority.

Jan M. Friedman

Roxana Moslehi

(see also: Abortion Laws; Contraception; Maternal and Child Health; Population Growth; Population Policies; Pregnancy; Prenatal Care; Sexually Transmitted Diseases; Teratogens; Women's Health )

Bibliography

Carr, B. R., and Blackwell, R. E. (1998). Textbook of Reproductive Medicine. Stamford, CT: Appleton & Lange.

Enkin, M.; Keirse, M.; Neilson, J. et al. (2000). A Guide to Effective Care in Pregnancy and Childbirth, 3rd edition. New York: Oxford University Press.

Evans, A. T., and Niswander, K. R. (2000). Manual of Obstetrics, 6th edition. Philadelphia, PA: Lippincott Williams and Wilkins.

Frederiksen, M. C. (2000). Rypins' Intensive Reviews: Obstetrics and Gynecology. Philadelphia, PA: Lippincott Williams and Wilkins.

Friedman, J. M.; Dill, F. J.; Hayden, M. R.; and McGillivray, B. C. (1996). National Medical Series for Independent Study: Genetics. Philadelphia, PA: Lippincott Williams & Wilkins.

Hildt, E., and Graumann, S., eds. (1999). Genetics in Human Reproduction. Burlington, VT: Ashgate Publishing.

Killick, S. R. (2000). Contraception in Practice. London: Martin Dunitz Publishers.

Lambeau, N. C.; Morse, A. N.; and Wallach, E. E. (1999). The Johns Hopkins Manual of Obstetrics and Gynecology. Philadelphia, PA: Lippincott Williams and Wilkins.

World Health Organization (1999). AIDS Epidemic Updated: December 1999. Geneva: Author.

(1999). Reduction of Maternal Mobility. Geneva: Author.

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Friedman, Jan M.; Moslehi, Roxana. "Reproduction." Encyclopedia of Public Health. 2002. Retrieved July 27, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3404000731.html

reproduction

reproduction, capacity of all living systems to give rise to new systems similar to themselves. The term reproduction may refer to this power of self-duplication of a single cell or a multicellular animal or plant organism. In all cases reproduction consists of a basic pattern: the conversion by a parent organism of raw materials from the environment into offspring—or into cells that develop into offspring (see meiosis; mitosis)—of a constitution similar or potentially similar to that of the parent. The reproductive process always includes the transmission of hereditary material (see nucleic acid) from the parents so the offspring too can reproduce themselves. Although the methods and complexity of the reproductive process vary tremendously, two fundamental types may be distinguished; asexual reproduction, in which a single organism separates into two or more equal or unequal parts; and sexual reproduction, in which a pair of specialized reproductive (sex) cells fuse.

Asexual Reproduction

Asexual reproduction is advantageous in allowing beneficial combinations of characteristics to continue unchanged and in eliminating the often vulnerable stages of early embryonic growth. It is found in most plants, bacteria, and protists and the lower invertebrates. In one-celled organisms it most commonly takes the form of fission, or mitosis, the division of one individual into two new and identical individuals. The cells thus formed may remain clustered together to form filaments (as in many fungi) or colonies (as in staphylococci and Volvox). Fragmentation is the process in filamentous forms in which a piece of the parent breaks off and develops into a new individual. Sporulation, or spore formation, is another means of asexual reproduction among protozoa and many plants. A spore is a reproductive cell that produces a new organism without fertilization. In some lower animals (e.g., hydra) and in yeasts, budding is a common form of reproduction; a small protuberance on the surface of the parent cell increases in size until a wall forms to separate the new individual, or bud, from the parent. Internal buds formed by sponges are called gemmules.

Regeneration is a specialized form of asexual reproduction; by regeneration some organisms (e.g., the starfish and the salamander) can replace an injured or lost part, and many plants are capable of total regeneration—i.e., the formation of a whole individual from a single fragment such as a stem, root, leaf, or even a small slip from such an organ (see cutting; grafting). F. C. Steward showed (1958) that single phloem cells from a carrot plant, when grown on an agar medium, would form a complete carrot plant. Among animals, the lower the form, the more capable it is of total regeneration; no vertebrates have this power, although clones of frogs (1962) and mammals (1996) have been produced in the laboratory from single somatic cells. Closely allied to regeneration is vegetative reproduction, the formation of new individuals by various parts of the organism not specialized for reproduction. In some plants structures that form on the leaves give rise to young plantlets. Rhizomes, bulbs, tubers, and stolons are other forms of vegetative reproduction.

Sexual Reproduction

Sexual reproduction occurs in many one-celled organisms and in all multicellular plants and animals. In higher invertebrates and in all vertebrates it is the exclusive form of reproduction, except in the few cases in which parthenogenesis is also possible. Sexual reproduction is essentially cellular in nature, i.e., it involves the fertilization of one sex cell (gamete) by another, producing a new cell (called a zygote), which develops into a new organism. The union of two isogametes (structurally identical but differing physiologically) is called isogamy, or conjugation, and occurs only in some lower forms (e.g., Spirogyra and some protozoa). Heterogamy is the fusion of two clearly differing kinds of gametes, distinguished as the ovum and the sperm.

Multicellular plants alternate sexually reproducing, or gametophyte, and asexually reproducing, or sporophyte, generations. The gametophyte produces gametes, and the union of gametes results in the growth of a sporophyte; the sporophyte produces spores that give rise to a gametophyte. The prominent generation in lower plants (e.g., mosses, liverworts) and the complex fungi is the gametophyte; in the vascular plants (ferns, conifers, grasses, and flowering plants) it is the sporophyte. The less prominent generation may be an independent plant, as is the small inconspicuous gametophyte of ferns, or a reduced organism consisting of only a few cells and dependent for survival on the prominent form, like the pollen grain, which is the male gametophyte of seed plants.

Many organisms exhibit special reproductive mechanisms to ensure fertilization; among higher plants the process of pollination may involve extremely complex interaction between the flower and the pollen-bearing agent (e.g., the yucca plant and the yucca moth). Among land-dwelling animals internal fertilization (copulation) is necessary in order to provide the fluid environment essential to fertilization.

Sexual reproduction is of great significance in that, because of the fusion of two separate parental nuclei, the offspring inherit endlessly varied combinations of characteristics that provide a vast testing ground for new variations that may not only improve the species but ensure its survival. This probably explains the predominance of sexual reproduction among higher forms. Even in those microorganisms that reproduce asexually (e.g., bacteria) exchanges of hereditary material take place; in the hermaphroditic plants and animals (e.g., the earthworm) self-fertilization is almost always prevented by anatomical specializations or by differing maturation times for male and female gametes.

See also genetics, recombination, and sex.

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Reproduction

Reproduction

Reproduction is the process by which plants and animals produce offspring. Reproduction may be asexual or sexual. Asexual reproduction occurs when a single cell divides to form two daughter cells that are genetically identical to the parent cell. Sexual reproduction involves the union of an egg (female sex cell) and sperm (male sex cell) to produce a cell that is genetically different than the parent cells.

Asexual reproduction

Asexual reproduction usually occurs by mitosis, a process in which the chromosomes in a cell's nucleus are duplicated before cell division. (Chromosomes are structures that organize genetic information in the nuclei of cells. Genes are units of hereditary information that control what traits are passed from one generation to another.) After the nucleus divides, the cytoplasm of the cell splits, forming two new daughter cells having nuclei with the same number and kind of chromosomes as the parent. Asexual reproduction occurs rapidly and can produce many individuals in a short amount of time. For example, some bacteria that reproduce in this way double their numbers every 20 minutes.

Bacteria, algae, most protozoa, yeast, dandelions, and flatworms all reproduce asexually. Yeasts reproduce asexually by budding, a process in which a small bulge, or bud, forms on the outer edge of a yeast cell and eventually separates, developing into a new cell. Flatworms and starfish can regrow an entire new organism from a piece of their body that is broken off, a process called fragmentation.

Words to Know

Budding: A form of asexual reproduction in which a small part of the parent's body separates and develops into a new individual.

Chromosome: Structures that organize genetic information in the nuclei of cells.

Cytoplasm: The semifluid substance of a cell containing organelles and enclosed by the cell membrane.

Diploid: Having two sets of chromosomes.

Fragmentation: The regeneration of an entire individual from a broken off piece of an organism.

Gamete: A male or female sex cell.

Gene: A section of a chromosome that carries instructions for the formation, functioning, and transmission of specific traits from one generation to another.

Haploid: Having a single set of unpaired chromosomes.

Meiosis: Process of cell division by which a diploid cell produces four haploid cells.

Mitosis: Process of cell division resulting in the formation of two daughter cells genetically identical to the parent cell.

Zygote: A diploid cell formed by the union of two haploid gametes.

Sexual reproduction

In plants and animals, sexual reproduction is the fusion of a sperm and egg, called gametes, from two different parents to form a fertilized egg called a zygote. Gametes are produced in the male testes and female ovaries by a process called meiosis. Meiosis is a type of cell division in which the number of chromosomes in a diploid cell (a cell having two sets of chromosomes in its nucleus) are reduced by half following two successive cell divisions. The four daughter cells that are produced are each haploid, having only half the number of chromosomes as the original diploid cell.

In males, all four daughter cells produced by meiosis become sperm, while in females, only one daughter cell develops into an egg. When an egg and sperm fuse at fertilization, the normal number of chromosomes are restored in the zygote. The shuffling of the parents' genetic material that occurs during meiosis allows for new gene combinations in offspring that over time can improve a species' chances of survival.

Alternation of generations. Plants go through two stages in their life cycle, called alternation of generations. One is the diploid stage, in which cells undergoing meiosis produce haploid reproductive cells called spores. During the haploid stage, the spores develop into gametophytes (or gamete-producing plants) that produce haploid gametes (eggs and sperm) by mitosis. The gametes unite to produce a diploid zygote that grows into a sporophyte (spore-producing plant), thus completing the cycle.

Hermaphroditism. Hermaphroditism is a form of sexual reproduction in which an organism has both male and female organs. Thus, hermaphrodites

produce both male gametes (sperm) and female gametes (eggs). In some animals, the male and female organs develop at different times. Some hermaphrodites, such as the tapeworm, are capable of fertilizing their own eggs with their own sperm. Most hermaphrodites, however, engage in cross-fertilization, meaning that two organisms of the same species inject sperm into the eggs of the other.

[See also Chromosome; Nucleic acid ]

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reproduction

reproduction Process by which living organisms create new organisms similar to themselves. Reproduction may be sexual or asexual, the first being the fusion of two special reproductive cells from different parents, and the second being the generation of new organisms from a single organism. Asexual reproduction is the more limited, found mainly in protozoan, some invertebrates, and in many plants. By contrast, almost all living organisms have the capacity for sexual reproduction. In the majority of cases, the species has two kinds of individuals – male and female – with different sex functions. Male and female sex cells (in animals, sperm and egg) fuse to produce a new cell, the zygote, which contains genetic information from both parents, and from which a new individual develops. Advances in human reproduction include artificial in vitro fertilization (IVF) in which a woman's ovaries are fertilized in the laboratory and then inserted into her uterus. A controversial reproduction method for animals has produced clones from a single original parent. Some organisms are hermaphrodites, each individual of the species having male and female functions, so that when two of them mate each individual fertilizes the other's eggs. Sexually reproducing plants (or generations) are called gametophyte; ones which reproduce asexually, sporophyte. See also alternation of generations; pollen

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reproduce

re·pro·duce / ˌrēprəˈd(y)oōs/ • v. [tr.] produce again: a concert performance cannot reproduce all the subtleties of a recording. ∎  produce a copy or representation of: his works are reproduced on postcards and posters. ∎  create something very similar to (something else), esp. in a different medium or context: the problems are difficult to reproduce in the laboratory. ∎  (of an organism) produce offspring by a sexual or asexual process: bacteria normally divide and reproduce themselves every twenty minutes | [intr.] an individual organism needs to avoid being eaten until it has reproduced. ∎  [intr.] be copied with a specified degree of success: you'll be amazed to see how well halftones reproduce. DERIVATIVES: re·pro·duc·er n. re·pro·duc·i·bil·i·ty / -ˌd(y)oōsəˈbilətē/ n. re·pro·duc·i·ble adj. re·pro·duc·i·bly / -əblē/ adv.

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reproduction

re·pro·duc·tion / ˌrēprəˈdəkshən/ • n. the action or process of making a copy of something: the cost of color reproduction in publication is high. ∎  the production of offspring by a sexual or asexual process. ∎  a copy of a work of art, esp. a print or photograph of a painting. ∎  [as adj.] made to imitate the style of an earlier period or of a particular artist or craftsman: reproduction French classical beds. ∎  the quality of reproduced sound: the design was changed to allow louder reproduction. DERIVATIVES: re·pro·duc·tive / -ˈdəktiv/ adj. re·pro·duc·tive·ly / -ˈdəktivlē/ adv. re·pro·duc·tive·ness / -ˈdəktivnis/ n.

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reproductive

reproductive A fertile male or female member of a colony of social insects. In ants, bees, and wasps the male (drone) dies soon after insemination, leaving the queen as the colony reproductive. In termites the male (king) lives with the queen, periodically inseminating her. Supplementary reproductives, present in termite colonies, take over colony reproduction if the founding king and queen (the primary reproductives) die.

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MICHAEL ALLABY. "reproductive." A Dictionary of Ecology. 2004. Encyclopedia.com. 27 Jul. 2016 <http://www.encyclopedia.com>.

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reproductive

reproductive Fertile male or female member of a colony of social insects. In ants, bees, and wasps the male (drone) dies soon after insemination, leaving the queen as the colony reproductive. In termites the male (king) lives with the queen, periodically inseminating her. Supplementary reproductives, present in termite colonies, take over colony reproduction if the founding king and queen (the primary reproductives) die.

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MICHAEL ALLABY. "reproductive." A Dictionary of Zoology. 1999. Encyclopedia.com. 27 Jul. 2016 <http://www.encyclopedia.com>.

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reproduction

reproduction The production of new individuals more or less similar in form to the parent organisms. This may be achieved by a number of means (see sexual reproduction; asexual reproduction) and serves to perpetuate or increase a species.

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Reproduction

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"Reproduction." International Encyclopedia of Marriage and Family. 2003. Encyclopedia.com. 27 Jul. 2016 <http://www.encyclopedia.com>.

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reproduce

reproduce create anew XVII; repeat in a copy, etc. XIX. f. RE- + PRODUCE vb.
So reproduction XVII.

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T. F. HOAD. "reproduce." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 27 Jul. 2016 <http://www.encyclopedia.com>.

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