News tagged with fossil
Related topics: dinosaurs , fossil record , bone , teeth , proceedings of the national academy of sciences
Fossils (from Latin fossus, literally "having been dug up") are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record. The study of fossils across geological time, how they were formed, and the evolutionary relationships between taxa (phylogeny) are some of the most important functions of the science of paleontology. Such a preserved specimen is called a "fossil" if it is older than some minimum age, most often the arbitrary date of 10,000 years ago. Hence, fossils range in age from the youngest at the start of the Holocene Epoch to the oldest from the Archaean Eon several billion years old. The observations that certain fossils were associated with certain rock strata led early geologists to recognize a geological timescale in the 19th century. The development of radiometric dating techniques in the early 20th century allowed geologists to determine the numerical or "absolute" age of the various strata and thereby the included fossils.
Like extant organisms, fossils vary in size from microscopic, such as single bacterial cells only one micrometer in diameter, to gigantic, such as dinosaurs and trees many meters long and weighing many tons. A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous exoskeletons of invertebrates. Preservation of soft tissues is rare in the fossil record. Fossils may also consist of the marks left behind by the organism while it was alive, such as the footprint or feces (coprolites) of a reptile. These types of fossil are called trace fossils (or ichnofossils), as opposed to body fossils. Finally, past life leaves some markers that cannot be seen but can be detected in the form of biochemical signals; these are known as chemofossils or biomarkers.
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People with higher levels of cadmium in their urine—evidence of chronic exposure to the heavy metal found in industrial emissions and tobacco smoke—appear to be nearly 3.5 times more likely to die of liver disease than ...
Surgery May 09, 2013 | not rated yet | 0
Genomics and African queens: Diversity within Ethiopian genomes reveals imprints of historical events
Researchers have started to unveil the genetic heritage of Ethiopian populations, who are among the most diverse in the world, and lie at the gateway from Africa. They found that the genomes of some Ethiopian populations ...
Genetics Jun 21, 2012 | 4.5 / 5 (2) | 1 |
A partial, duplicate copy of a gene appears to be responsible for the critical features of the human brain that distinguish us from our closest primate kin. The momentous gene duplication event occurred about two or three ...
Genetics May 03, 2012 | 3.7 / 5 (3) | 2 |
Prenatal exposure to combustion-related pollutants leads to anxiety, attention problems in young children
Mothers' exposure during pregnancy to a class of air pollutants called polycyclic aromatic hydrocarbons (PAH) can lead to behavioral problems in their children. PAH are released to air during incomplete combustion of fossil ...
Health Mar 22, 2012 | not rated yet | 0 |
Efforts by some in Congress to dismantle clean air laws are a threat to public health, experts warn in a "Current Issues" article published online today in the American Journal of Preventive Medicine.
Health Nov 01, 2011 | 1 / 5 (1) | 4
Pesticides and pollutants are related to an alarming 450 percent increase in the risk of spina bifida and anencephaly in rural China, according to scientists at The University of Texas at Austin and Peking ...
Health Oct 19, 2011 | 5 / 5 (1) | 0 |