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Stephen Jay Gould studied snail fossils and worked at Harvard University in Cambridge, Massachusetts during the latter half of the twentieth century. He contributed to philosophical, historical, and scientific ideas in paleontology, evolutionary theory, and developmental biology. Gould, with Niles Eldredge, proposed the theory of punctuated equilibrium, a view of evolution by which species undergo long periods of stasis followed by rapid changes over relatively short periods instead of continually accumulating slow changes over millions of years.
Victor Jollos studied fruit flies and
microorganisms in Europe and the US, and he introduced the concept of
Dauermodifikationen in the early 1900s. The concept of
Dauermodifikationen refers to environmentally-induced traits that are
heritable for only a limited number of generations. Some scientists
interpreted the results of Jollos's work on Paramecium and Drosophila as
evidence for cytoplasmic inheritance. Jollos was forced to emigrate from
Germany to the United States due to anti-semitic government policies in
Dennis Lo, also called Yuk Ming Dennis Lo, is a
professor at the Chinese University of Hong Kong in Hong Kong,
China. In 1997, Lo discovered fetal DNA in maternal
plasma, which is the liquid component of a pregnant woman's
blood. By 2002, Lo distinguished the DNA differences between pregnant women
and their fetuses, enabling scientists to identify fetal DNA in pregnant
women's blood. Lo used his discoveries to develop several
non-invasive and prenatal genetic tests, including tests for blood
"The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme" (1979), by Stephen J. Gould and Richard C. Lewontin
The Spandrels of San Marco and the Panglossian Paradigm:
A Critique of the Adaptationist Programme, hereafter called
The Spandrels, is an article written by Stephen J. Gould and
Richard C. Lewontin published in the Proceedings of the Royal
Society of London in 1979. The paper emphasizes issues with
what the two authors call adaptationism or the adaptationist
programme as a framework to explain how species and traits evolved. The paper
is one in a series of works in which Gould emphasized the
Theodora Colborn studied how chemicals affect organisms as they develop and reproduce during the twentieth and twenty first centuries in the US. By the 1940s, researchers had reported that chemicals from agricultural and industrial processes affected how wild organisms developed, but in 1991, Colborn organized the Wingspread Conference in Racine, Wisconsin, at which a group of scientists classed these chemicals as environmentally harmful substances. Colborn and her colleagues called those chemicals endocrine disruptors, as they mimic or block the body's endocrine system.
Sir John Bertrand Gurdon further developed nuclear transplantation, the technique used to clone organisms and to create stem cells, while working in Britain in the second half of the twentieth century. Gurdon's research built on the work of Thomas King and Robert Briggs in the United States, who in 1952 published findings that indicated that scientists could take a nucleus from an early embryonic cell and successfully transfer it into an unfertilized and enucleated egg cell.
During the twentieth and twenty-first centuries, Robert Paul Lanza studied embryonic stem cells, tissues,
and endangered species as chief scientific officer of Advanced Cell
Technology, Incorporated in Worcester, Massachusetts. Lanza's team cloned
the endangered species of gaur Bos gaurus.
Although the gaur did not survive long, Lanza successfully cloned
another cow-like creature, called the banteng
javanicus). Lanza also worked on cloning human embryos
to harvest stem cells, which could be used to treat dieases. While
Karl Landsteiner studied blood types in Europe and in the United States in the late nineteenth and early twentieth centuries. Landsteiner won the Nobel Prize in Physiology or Medicine in 1930 for detailing immunological reactions in the ABO blood group system. The ABO blood group system divides human blood into one of four types based on the antibodies that are present on each cell. Landsteiner's work with blood types led physicians to safely perform blood transfusions and organ transplants.
David Edwin Wildt developed and applied assisted reproductive technologies to conserve rare and endangered wildlife species in the US during the twentieth and twenty-first centuries. He advocated genome resource banks to help preserve biodiversity, and he advocated for practical ethics to guide wildlife reproductive biologists when they use technology and environmental planning. Wildt often focused on the cheetah (Acinonyx jubatus), but he researched greater than fifty vertebrate species.
Nikolai Ivanovich Vavilov proposed theories of plant genetic diversity and participated in the political debate about genetics in Soviet Russia in the early twentieth century. Vavilov collected plant species around the world, building one of the first and most comprehensive seed banks, and he spent much of his life researching plant breeding and genetics. Vavilov also developed a theory of the historical centers of origin of cultivated plants. Vavilov spent most of his scientific career in Russia, although he studied abroad and traveled extensively.
The US President's Council on Bioethics was an organization headquartered in Washington D.C. that was chartered to advise then US President George W. Bush on ethical issues related to biomedical science and technology. In November 2001, US President George W. Bush created the President's Council on Bioethics (PCB). Convened during a nationwide cloning and embryonic stem cell research debate, the Council stated that it worked to address arguments about ethics from many different perspectives.
Teratogens are substances that may produce physical or functional defects in the human embryo or fetus after the pregnant woman is exposed to the substance. Alcohol and cocaine are examples of such substances. Exposure to the teratogen affects the fetus or embryo in a variety of ways, such as the duration of exposure, the amount of teratogenic substance, and the stage of development the embryo or fetus is in during the exposure.
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.
In 1830, a dispute erupted in the halls of lÕAcad mie des Sciences in Paris between the two most prominent anatomists of the nineteenth century. Georges Cuvier and tienne Geoffroy Saint-Hilaire, once friends and colleagues at the Paris Museum, became arch rivals after this historical episode. Like many important disputes in the history of science, this debate echoes several points of contrasts between the two thinkers.
Sprayed extensively by the US military in Vietnam, Agent Orange contained a dioxin contaminant later found to be toxic to humans. Despite reports by Vietnamese citizens and Vietnam War veterans of increased rates of stillbirths and birth defects in their children, studies in the 1980s showed conflicting evidence for an association between the two. In 1996, the US National Academy of Sciences reported that there was evidence that suggested dioxin and Agent Orange exposure caused spina bifida, a birth defect in which the spinal cord develops improperly.
This image shows a chicken (Gallus gallus) embryo undergoing gastrulation in stage four (18-19 hrs after laying) according to the Hamburger-Hamilton staging series. At this point in time the chicken embryo is a blastoderm (shown in blue). The first magnification of the embryo shows that the blastoderm cell layers have thickened to form the primitive streak and Hensen's node. The primitive streak extends from the posterior (P) region to the anterior (A) region. The second rectangular magnification shows the blastoderm cross-sectioned through the primitive streak.
A 3-D fate map of the chicken (Gallus gallus) embryo with the prospective point of ingression and yolk. The area where the primitive streak will form during gastrulation is shown. The anterior- posterior axis is shown by labeling the anterior and posterio ends (A) and (P). Different colors indicate prospective fates of different regions of the epiblast after gastrulation.
Illustration of the animal-vegetal gradient in Xenopus laevis ( African clawed frog) eggs after fertilization. During fertilization, the sperm s point of entry determines the future dorsal side (shaded) and ventral side (unshaded) of the embryo. The prospective ventral side of the embryo forms on the side where the sperm enters while the prospective dorsal side forms opposite the sperm s point of entry.
Object is a digital image of Notch signaling between a signaling cell and a receiving cell. Labels indicate the signaling and receiving cells, nuclear membrane, Notch receptor, the ligand, a protease, a transcription factor and a repressor. The image depicts three stages involved in Notch signaling, including the binding of the ligand with the receptor, the action of the protease, and the Notch intracellular domain fragment replacing the repressor in the nucleus.
Mechanism of Notch Signaling: The image depicts a type of cell signaling, in which two animal cells interact and transmit a molecular signal from one to the other. The process results in the production of proteins, which influence the cells as they differentiate, move, and contribute to embryological development. In the membrane of the signaling cell, there is a ligand (represented by a green oval). The ligand functions to activate a change in a receptor molecule. In the receiving cell, there are receptors; in this case, Notch proteins (represented by orange forks).
The Development of the Neural Crest and the Migration of Neural Crest Cells (NCCs) in the Embryos of Various Vertebrates
Object is a digitized image line drawings that depict the formation of neural crest cells in vertebrates. Image has six sub images, which depict six stages, labeled (a) through (f), of the neural plate as it folds to form the neural tube, neural crest cells, and a sheet of extoderm. Arrows between the six subimages indicate developmental processes for different taxa. The path from (a) to (b) to (c) represents the process in rats. The path (a) to (b) to (d) to (f) represents the process in birds. The path (a) to (b) to (e) to (f) represents the process in amphibians.
This diagram shows how NCCs migrate differently in rats, birds and amphibians. The arrows represent both chronology of NCCs migration and the differential paths that NCCs follow in different classes of animals. The solid black portion of each illustration represents the neural crest, and the large black dots in (c) and in (f) represent the neural crest cells. The speckled sections that at first form a basin in (a) and then close to form a tube in (f) represent the neural ectoderm. The solid white portions represent the epidermal ectoderm.
Object is a digital image of an animal triploblastic gastrula. The image labels the three germ layers and some of the fully differentiated cell types that arise from those germ layers. The image shows the egg and sperm germ cells. It also shows and labels the epithelial cells, liver cells, and endothelial cells that develop from endoderm. It also shows the skeletal musclecells, osteoblast cells, cardiac muscle cells, and red blood cells that develop from the mesoderm. It also shows the hair cells, skin cells, and neuron cells that develop from the ectoderm.
From a developing embryos three primary germ layers, ectoderm (green), mesoderm (pink) and endoderm (yellow), a variety of differentiated cell types and organ systems arise, far more than are shown here. The three primary germ layers are shown during the gastrula stage because they become distinct at the gastrula stage. The germ cells (blue) are pre- cursors to sperm and egg cells, and they are set aside early in development, and are thought to arise from the ectoderm.
Felix Anton Dohrn is best remembered as the founder of the Stazione Zoologica di Napoli, the world' s first permanent laboratory devoted to the study of marine organisms. Dohrn was born on 29 December 1840 in Stettin, Pomerania (now Poland), to a wealthy merchant family. Dohrn's paternal grandfather, Heinrich, trained as a surgeon and then established a sugar refinery, while Dohrn's father, Carl August Dohrn, who inherited the family business, became interested in natural history through Alexander von Humboldt, a family friend.
The New York Appellate Court ruled on 11 December 1977 in favor of Steven and Hetty Park and against Herbert Chessin for the wrongful life of the Parks' child. In a wrongful life case, a disabled or sometimes deceased child brings suit against a physician for failing to inform its parents of possible genetic defects, thereby causing harm to the child when born. Park v. Chessin was the first case to rule that medical personnel could be legally responsible for wrongful life. Further cases such as the 1979 case Berman v. Allan and the 1982 case Turpin v.
"Casti Connubii," a papal encyclical given by Pope Pius XI on 31 December 1930, served primarily as a reaffirmation and expansion of the issues discussed in Arcanum, an encyclical written by Pope Leo XIII. It was released to address new threats to marriage and conjugal unity, and indeed is translated "On Christian Marriage" or "On Chastity in Marriage." The document explores the meaning of Christian marriage and emphasizes its threefold purpose as borrowed from St.
First published in 1930 and reprinted in 1972, Edward Stuart Russell's The Interpretation of Development and Heredity is a work of philosophical and theoretical biology. In this book Russell outlines a methodological and philosophical program aimed at reorienting the biological understanding of development and heredity.