Bilateria

The Bilateria are those animals which have a body composed of three different germ layers, called the endoderm, mesoderm, and ectoderm. These animals are also called triploblastic.

Basically, the Bilateria include all animals that are (more or less) bilaterally symmetrical and, except for a few flatworms, have an internal body cavity (coelom or pseudocoelom) with a mouth at one end and an anus at the other. The Bilateria include the majority of animals, with the cnidarians and sponges being the principal exceptions.

The two divisions of the Bilateria are Deuterostomes (echinoderms, chordates, hemichordates, Chaetognatha and Vetulicolia) and Protostomes (arthropods, annelid worms, molluscs and many more groups). They are distinguished by how the coelom develops, in particular whether the first body opening to form in larval growth becomes the anus (deuterostomes) or mouth (protostomes). Another distinguishing characteristic is how the third set of cells to form after egg fertilization orient themselves during cleavage. Protostomes have spiral cleavage, while deuterstomes have radial cleavage.



In the News

Thanksgiving Recipes From America's Past
Find recipes for mince pie (1832), chestnut stuffing (1891), roast turkey with truffle gravy (1905), and a variety of pies and other holiday dishes. Recipes are accompanied by vintage illustrations. From the Pilgrim Hall Museum (Plymouth, Massachusetts).

Study Shows Acrylamide In Baked And Fried Foods Does Not Increase Risk
Researchers from the Harvard School of Public Health and the Karolinska Institute in Stockholm, Sweden, have found no association between acrylamide intake in foods and risk of breast cancer among Swedish women. The findings appear in the March 16, 2005 issue of the Journal of the American Medical Association.

Guarded Hope for Dope Reform
Democratic victory doesn't necessarily spell a new dawn of "San Francisco values" on the drug front, but some things might change. By Randy Dotinga

Skin Color Evolution In Fish And Humans Determined By Same Genetic Mac
Despite the vast evolutionary gulf between humans and the three-spined stickleback fish, the two species have adopted a common genetic strategy to acquire the skin pigmentation that helps each species thrive in new environments.

Stem-Cell Fix for Diabetic Ulcer?
Facing almost certain amputation, an Indian woman with a nasty-looking leg wound undergoes an experimental treatment using bone-marrow stem cells. Two months later, she's all better. Scott Carney reports from Chennai, India.

[Funny] A referee has sent himself off in an English amateur league ma
Andy Wain had to abandon the Sunday league match between Peterborough North End and a Royal Mail side in the 63rd minute after throwing down his whistle and marching up to confront North End's keeper.

[Ironic] An Italian pensioner committed suicide after his wife fell in
Recalling the end of Romeo and Juliet, the 70-year-old man, Ettore, who had sat by his wife's bedside for four months after she slipped into a coma followinga heart attack, finally gave up hope and gassed himself in the garage of his family home.Less than a day later, his wife, Rossana, woke up in her hospital bed in Padua and immediately asked for him.

U.S. Airspace Classes
Provides definitions of Class A, B, C, D, and E controlled airspaces and Class G (uncontrolled) airspace. Includes charts showing the features of each airspace, such as entry requirements, minimum pilot qualifications, and two-way radio communications. From the Federal Aviation Administration (FAA).

Toward New Medications For Iron-overload Diseases
Scientists report progress in developing much-needed new medications for hemochromatosis and other iron-overload diseases. In these conditions, excess amounts of iron accumulate in the liver, heart, pancreas and other organs and eventually cause serious damage.

How Hormones Achieve Their Effects
New insights into the cellular signal chain through which pheromones stimulate mating in yeast have been gained by scientists at the European Molecular Biology Laboratory. Similar signal chains are found in humans, where they are involved in many important processes such as the differentiation of nerve cells and the development of cancer. A sophisticated microscopy technique allowed the researchers to observe for the first time the interplay of signalling molecules in living yeast cells.


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