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Aristotle (384-322 BCE)

<a href="/search?text=Aristotle" title="" class="lexicon-term">Aristotle</a> (384-322 BCE)Aristotle studied developing organisms, among other things, in ancient Greece, and his writings shaped Western philosophy and natural science for greater than two thousand years. He spent much of his life in Greece and studied with Plato at Plato's Academy in Athens, where he later established his own school called the Lyceum. Aristotle wrote greater than 150 treatises on subjects ranging from aesthetics, politics, ethics, and natural philosophy, which include physics and biology. Less than fifty of Aristotle's treatises persisted into the twenty-first century. In

Julia Barlow Platt (1857-1935)

Julia Barlow Platt (1857-1935)Julia Barlow Platt studied neural crests in animal embryos and became involved in politics in the US during the nineteenth and twentieth centuries. She researched how body and head segments formed in chicks (Gallus gallus) and spiny dogfish (Squalus acanthias). Platt observed that in the mudpuppy (Necturus maculosus), the coordinated migration of neural crest cells in the embryo produced parts of the nervous system, bones, and connective tissues in the head.

The Hedgehog Signaling Pathway in Vertebrates 

The Hedgehog Signaling Pathway in <a href="/search?text=Vertebrates" title="" class="lexicon-term">Vertebrates</a> The hedgehog signaling pathway is a mechanism that regulates cell growth and differentiation during embryonic development, called embryogenesis, in animals. The hedgehog signaling pathway works both between cells and within individual cells. The hedgehog gene (hh) was observed in fruit flies (Drosophila melanogaster) in 1980, and later in vertebrates in 1993. Unlike flies, which have one hh gene, vertebrates have several hh genes. The hedgehog signaling pathway controls a

Mary Coffin Ware Dennett (1872-1947)

Mary Coffin Ware Dennett (1872–1947) Mary Coffin Ware Dennett advocated for social reform in the United States in the early twentieth century, particularly regarding sex education and women's rights to access contraception. Dennett authored several publications on sex education and birth control laws. She also worked to repeal the Comstock Act, a federal law that made it illegal to distribute obscene materials through the US Postal Services. During the early 1900s, Dennett distributed a pamphlet she wrote on sex education called, "The Sex Side of Life," through the post, which triggered a series of legal challenges that contributed to the dismantling of the Comstock Act. Dennett was an advocate for sex

Estrogen and the Menstrual Cycle in Humans

Estrogen and the Menstrual Cycle in Humans Estrogen is the primary sex hormone in women and it functions during the reproductive menstrual cycle. Women have three major types of estrogen: estrone, estradiol, and estriol, which bind to and activate receptors within the body. Researchers discovered the three types of estrogen over a period of seven years, contributing to more detailed descriptions of the menstrual cycle. Each type of estrogen molecule contains a slightly different arrangement or number of atoms

ABO Blood Type Identification and Forensic Science (1900-1960)

ABO Blood Type Identification and Forensic Science (1900-1960)The use of blood in forensic analysis is a method for identifying individuals suspected of committing some kinds of crimes. Paul Uhlenhuth and Karl Landsteiner, two scientists working separately in Germany in the early twentieth century, showed that there are differences in blood between individuals. Uhlenhuth developed a technique to identify the existence of antibodies, and Landsteiner and his students showed that humans had distinctly different blood types called A, B, AB, and O. Once doctors differentiated blood into distinct types, they could use that information to safely perform blood transfusions. Furthermore, forensic scientists can use that information to exculpate people suspected of some types of crimes, and they can use it to help determine the paternity of children.

Kurt Benirschke (1924-)

Kurt Benirschke (1924-)Kurt Benirschke studied cells, placentas, and endangered species in Germany and the US during the twentieth century. Benirschke was professor at the University of California in San Diego, California, and a director of the research department at the San Diego Zoo in San Diego, California. He also helped form the research department of the San Diego Zoo and its sister organization, the Center for Reproduction of Endangered Species.

Methylmercury and Human Embryonic Development

Methylmercury and Human Embryonic DevelopmentMethylmercury (MeHg) is an organic form of mercury that can damage the developing brains of human fetuses. Women who consume methylmercury during pregnancy can bear children who have neurological issues because methylmercury has toxic effects on the nervous system during embryonic development. During the third week of gestation, the human nervous system begins to form in the embryo. During this gestational period, the embryo's nervous system is particularly susceptible to the influence of neurotoxins like methylmercury that can result in abnormalities. Furthermore, the fetal brain can incur damage despite the lack of signs of poisoning in the pregnant woman.

George McDonald Church (1954- )

George McDonald Church (1954-)George McDonald Church studied DNA from living and from extinct species in the US during the twentieth and twenty-first centuries. Church helped to develop and refine techniques with which to describe the complete sequence of all the DNA nucleotides in an organism's genome, techniques such as multiplex sequencing, polony sequencing, and nanopore sequencing. Church also contributed to the Human Genome Project, and in 2005 he helped start a company, the Personal Genome Project. Church proposed to use DNA from extinct species to clone and breed new organisms from those species.

Eugenical Sterilization in the United States (1922), by Harry H. Laughlin

<a href="/search?text=Eugenical%20Sterilization%20in%20the%20United%20States" title="" class="lexicon-term">Eugenical Sterilization in the United States</a> (1922), by <a href="/search?text=Harry%20H.%20Laughlin" title="" class="lexicon-term">Harry H. Laughlin</a>Eugenical Sterilization in the United States is a 1922 book in which author Harry H. Laughlin argues for the necessity of compulsory sterilization in the United States based on the principles of eugenics.

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